Academic literature on the topic 'Voxel-based morphometry (VBM)'

La dystonie est une pathologie du mouvement dont la physiopathologie est mal connue. Jusqu'à présent, les données de l'imagerie IRM classique étaient décevantes, en particulier dans les dystonies primaires. Le développement de nouvelles techniques d'imagerie offre la possibilité d'explorer cette pathologie de façon plus précise avec les techniques d'analyse morphométrique voxel à voxel (VBM) et d'imagerie du tenseur de diffusion (DTI). Dans ce travail, nous avons utilisé une approche IRM multimodale pour étudier la physiopathologie de la dystonie. A l'aide de l'imagerie par résonance magnétique fonctionnelle, nous avons étudié la sélectivité des représentations neuronales dans le striatum des patients atteints de crampe des écrivains avant et après rééducation fonctionnelle. Nous avons recherché des anomalies structurelles à l'aide de la VBM et utilisé la tractographie pour rechercher une atteinte spécifique des fibres cortico - striatales sensorimotrices chez ces patients. Nous avons combiné une approche anatomique et par tractographie pour localiser le territoire fonctionnel des ganglions de la base lésé dans les dystonies secondaires à des lésions ischémiques. L'ensemble de nos travaux souligne le rôle du circuit sensorimoteur cortex - ganglions de la base - cervelet dans la physiopathologie de la dystonie<br>Dystonia is a movement disorder whose pathophysiology is not fully understood. To date, conventional MR imaging was unsuccessful in showing structural abnormality in primary dystonia. New recent imaging techniques, such as voxel based morphometry (VBM) and diffusion tensor imaging (DTI), can be utilized to explore more precisely the pathophysiology of dystonia. In this work, we used several MRI methods to investigate the pathophysiology of dystonia. We used fMRI to determine whether the selectivity of neuronal representation of basal ganglia neurons was altered in the putamen of patients with focal hand dystonia before and after rehabilitation. Using voxel-based morphometry and DTI, we tested the hypothesis that structural or microstructural changes occur in the sensorimotor basal ganglia - cortical circuit in primary focal hand dystonia. Lastly, we combined structural imaging and fiber tracking to determine the functionnal territory of the basal ganglia that is damaged in post stroke dystonia. Overall, our results show that cortico striatal thalamo cerebellar sensorimotor circuit is likely to play a fundamental role in the pathophysiology of the dystonia

Background: The hippocampus and corpus callosum have been shown to be vulnerable in head injury. Various neuroimaging modalities and quantitative measurement techniques have been employed to investigate pathological changes in these structures. Cognitive and behavioural deficiencies have also been well documented in head injury. Aims: The aim of this research project was to investigate structural changes in the hippocampus and corpus callosum. Two different quantitative methods were used to measure physical changes and neuropsychological assessment was performed to determine cognitive and behavioural deficit. It was also intended to investigate the relationship between structural change and neuropsychology at 1 and 6 months post injury. Method: Forty-seven patients with head injury (ranging from mild to severe) had undergone a battery of neuropsychological tests and an MRI scan at 1 and 6 months post injury. T1-weighted MRI scans were obtained and analysis of hippocampus and corpus callosum was performed using region-of-interest techniques and voxel-based morphometry which also included comparison to 18 healthy volunteers. The patients completed neuropsychological assessment at 1 and 6 months post injury and data obtained was analysed with respect to each assessment and with structural data to determine cognitive decline and correlation with neuroanatomy. Results: Voxel-based morphometry illustrated reduced whole scan signal differences between patients and controls and changes in patients between 1 and 6 months post injury. Reduced grey matter concentration was also found using voxel-based morphometry and segmented images between patients and controls. A number of neuropsychological aspects were related to injury severity and correlations with neuroanatomy were present. Voxel-based morphometry provided a greater number of associations than region-of-interest analysis. No longitudinal changes were found in the hippocampus or corpus callosum using region-of-interest methodology or voxel-based morphometry. Conclusions: Decreased grey matter concentration identified with voxel-based morphometry illustrated that structural deficit was present in the head injured patients and does not change between 1 and 6 months. Voxel-based morphometry appears more sensitive for detecting structural changes after head injury than region- of-interest methods. Although the majority of patients had suffered mild head injury, cognitive and neurobehavioural deficits were evidenced by a substantial number of patients reporting increased anxiety and depression levels. Also, the findings of relationships between reduced grey matter concentration and cognitive test scores are indicative of the effects of diffuse brain damage in the patient group.

Cognitive impairment strongly affects people with multiple sclerosis (MS). It comprises multifactorial symptoms and no consistent treatments are available to date. Although cognitive impairment has been observed in all stages of the disease, the majority of studies mainly focused on a specific clinical phenotype (primarily relapsing-remitting MS) or did not differentiate between MS subtypes. Advanced magnetic resonance imaging (MRI) techniques are providing useful measures of functional and structural abnormalities in patients with MS, allowing to overcome the limits of conventional MRI. This thesis wished to improve the understanding of the mechanisms responsible for the accumulation of cognitive dysfunction in patients with relapse-onset MS by combining different advanced structural and functional MRI techniques. First, we applied functional MRI (fMRI) to assess brain functional reorganization in relation to different cognitive tasks (face encoding and N-back) in patients with the main relapse-onset clinical phenotypes. We also explored the relationship between functional network alterations and clinical, cognitive, behavioural and structural MRI measures of disease-related damage. Our results provide new evidence for the debate about adaptive/maladaptive functional reorganization in MS, specifically in relation to the clinical and cognitive characteristics of MS phenotypes. Second, the investigation of resting state default mode network (DMN) functional connectivity enabled us to highlight that different modulations of DMN recruitment lead to different clinical profiles and manifestations. Moreover, functional connectivity of specific DMN areas (hippocampi) was found to be central for the assessment of important cognition-related aspects, such as depression. Finally, by applying voxel-wise MRI methods (VBM and TBSS) we explored the extent and distribution of brain GM atrophy and WM microstructural alterations in adult MS patients according to their age of disease onset, and we made some assumptions about the possible presence of pathophysiological mechanisms related to age of MS onset, that suggests a preserved reserve for structural plasticity that could modulate the structural and functional brain organization, in order to preserve or slow-down MS-related dysfunction. To conclude, the application of advanced MRI techniques allowed us to improve our knowledge on neuropsychological features in patients with relapse-onset MS.

Submitted by PPG Letras (letraspg@pucrs.br) on 2018-04-26T17:05:23Z No. of bitstreams: 1 Tese_Sabrine Cristine Hubner.pdf: 2098756 bytes, checksum: 9b73c0fb004e2143274124c300170dee (MD5)<br>Approved for entry into archive by Sheila Dias (sheila.dias@pucrs.br) on 2018-05-09T12:48:28Z (GMT) No. of bitstreams: 1 Tese_Sabrine Cristine Hubner.pdf: 2098756 bytes, checksum: 9b73c0fb004e2143274124c300170dee (MD5)<br>Made available in DSpace on 2018-05-09T13:29:27Z (GMT). No. of bitstreams: 1 Tese_Sabrine Cristine Hubner.pdf: 2098756 bytes, checksum: 9b73c0fb004e2143274124c300170dee (MD5) Previous issue date: 2018-03-28<br>Conselho Nacional de Pesquisa e Desenvolvimento Cient?fico e Tecnol?gico - CNPq<br>Written and oral text comprehension abilities are indispensable for human experiences. Strokes causing left hemisphere (LH) damage may impact comprehension and textual production. However, little is known about this influence at the textual/discursive level, including the comparison between oral and written modalities in this kind of lesion. This research aimed at investigating text comprehension in two modalities of presentation (read and heard) by left brain damaged individuals (LBD) and healthy controls, comparing their performance in the micro- and macro-structural levels of text comprehension to neuropsychological data and to density of the brain areas involved. In order to do that, we performed two researches, Study 1, with 18 LBD and 10 controls, and Study 2, with 10 LBD and 10 controls, with matched age and education. In both studies, neuropsychological tests assessed working memory, verbal fluency and naming abilities. Comprehension of macro- and microstructural levels was verified by means of six short narratives, presented in oral or written modality. The participants were asked to retell the stories and answer to five interpretation questions. In Study 2, the same method was used, but it included structural magnetic resonance imaging indicating the density of brain regions by voxel-based morphometry (VBM). The results of Study 1 indicated significant differences in narrative comprehension between LBD and controls. The lower performance observed at the macrostructural level of LBD compared to the micro- suggest individuals who had a stroke may face difficulties in the application of macrorules of deletion, construction and generalization, which underlie overall comprehension of a text. The data from Study 2, with a lower number of participants, indicated a tendency to confirm results found in Study 1, with statistical significant differences in benefit of controls at the macrostructural level of oral narratives. We found significant differences between groups regarding the modality of text presentation. In both Study 1 and Study 2, differences were observed between the groups in auditory word span and in naming, with an advantage to controls. The morphometry data of brain regions, related to the participants of Study 2, indicated an integration of areas from left and right hemispheres to process text comprehension in oral and written modalities. In the left hemisphere, precuneus, cerebellum white matter, superior frontal region and medial orbitofrontal region and from the right hemisphere, accumbens and superior temporal sulcus were observed. The right superior temporal sulcus, left precuneus, left cerebellar white matter and superior frontal region are positively correlated among the participants, presenting better performance as the density increases. The left medial orbitofrontal region shows a negative correlation with comprehension. The right accumbens seems to compensate LH demands, showing increased density in the LBD and reduced volume in the controls. The present study intends to contribute to deepen our understanding of the comprehension of texts presented in the oral compared to written modality in the LH lesion, related to neuropsychological and brain data.<br>Compreender um texto, seja ele ouvido ou lido, ? indispens?vel para as experi?ncias humanas. Acidentes vasculares cerebrais (AVCs) ocorridos em especial no hemisf?rio esquerdo (HE) podem impactar na compreens?o e na produ??o textual. No entanto, pouco ainda se sabe sobre essa influ?ncia no n?vel textual/discursivo, incluindo, por exemplo, a compara??o entre a modalidade oral e escrita na compreens?o textual/discursiva nesse tipo de les?o. Esta pesquisa teve por objetivo investigar a compreens?o de narrativas em duas modalidades de apresenta??o (lidas e ouvidas) por indiv?duos com les?o no hemisf?rio esquerdo (LHE) e controles saud?veis, comparando-se seu desempenho nos n?veis micro- e macroestruturais da compreens?o de narrativas a dados neuropsicol?gicos e ? densidade das ?reas cerebrais implicadas. Para tal, realizamos dois estudos, o Estudo 1, com 18 LHE e 10 controles, e o Estudo 2, que contemplou exames de neuroimagem, com 10 LHE e 10 controles (os mesmos do Estudo 1), com idade e escolaridade equiparadas. Em ambos os estudos, testes neuropsicol?gicos avaliaram a mem?ria de trabalho, a flu?ncia verbal e a nomea??o. A compreens?o dos n?veis macro- e microestrutural foi verificada por meio de seis narrativas curtas, divididas na modalidade oral ou escrita. Os participantes realizavam um reconto e respondiam a cinco perguntas de interpreta??o. No Estudo 2 empregou-se o mesmo m?todo, por?m com inclus?o de exame de resson?ncia magn?tica estrutural indicando a densidade das regi?es cerebrais pela morfometria baseada em voxels (VBM). Os resultados do Estudo 1 apontaram diferen?as significativas na compreens?o de narrativas entre LHE e controles. Os preju?zos observados no n?vel macroestrutural dos LHE em detrimento do micro- sugerem falhas na aplica??o das macrorregras de dele??o, constru??o e generaliza??o, subjacentes ? compreens?o global de um texto. Os dados do Estudo 2, com menor n?mero de participantes, indicaram uma tend?ncia a corroborar os resultados encontrados no Estudo 1, observando-se diferen?a significativa em benef?cio dos controles no n?vel macroestrutural das narrativas apresentadas oralmente. Foram encontradas diferen?as entre os grupos quanto ? modalidade de apresenta??o dos textos. Tanto no Estudo 1 quanto no Estudo 2 observou-se diferen?as no span auditivo de palavras e na nomea??o, com vantagem para os controles. Os dados da morfometria das regi?es cerebrais, atinentes aos participantes do segundo estudo, apontam uma integra??o de regi?es do hemisf?rio esquerdo e do direito. Do esquerdo, prec?neus, subst?ncia branca do cerebelo, regi?o frontal superior e regi?o orbitofrontal medial e do direito, accumbens e sulco temporal superior foram observadas. O sulco temporal superior direito, o prec?neus esquerdo, a subst?ncia branca cerebelar esquerda e a regi?o frontal superior correlacionam-se positivamente entre os participantes, apresentando desempenho superior ? medida que a densidade aumenta. A regi?o orbitofrontal medial esquerda apresenta correla??o negativa com a compreens?o. A regi?o do accumbens direito parece compensar as demandas do HE, apresentando sua densidade aumentada nos LHE e reduzida nos controles. O presente estudo pretende contribuir para aprofundarmos nossa compreens?o sobre a compreens?o de narrativas apresentadas na modalidade oral versus escrita na les?o de HE, relacionados a dados neuropsicol?gicos e cerebrais.

The side-effects of chemotherapy treatment are an increasingly important research focus as more cancer patients are reaching survivorship. While treatment allows for survival, it can also lead to problems which can significantly affect quality of life. Cognitive impairments after chemotherapy treatment are one such factor. First presented as anecdotal patient reports, over the last decade empirical evidence for this cognitive concern has been obtained. Much attention has been focused on post-chemotherapy research, yet little attention has been granted to these same patients’ cognition before treatment commences. Breast cancer (BC) patients face many obstacles before chemotherapy treatment such as: surgery and side-effects of anesthesia, increased cytokine activity, stress of a new disease diagnosis and upcoming challenges, and emotional burdens such as depression and anxiety. Many of these factors have independently been shown to affect cognitive abilities in both healthy populations as well as other patient groups. Therefore, the pre-treatment (or baseline) BC patient status warrants systematic study. This would then reduce mistakenly attributing carried-over cognitive deficits to side effects of chemotherapy. As well, it is possible that certain confounding variables may have neural manifestations at baseline that could be exacerbated by chemotherapy agents. The following thesis first presents a review paper which critically describes the current literature examining chemotherapy-related cognitive impairments (CRCIs), as well as possible confound variables affecting this population. Subsequently, three original research papers present pre-chemotherapy data showing significant neuroanatomical and neurofunctional differences in BC patients compared to controls. In particular, these neural differences are present in brain regions that have been reported in post-chemotherapy papers. This, as well as the effects of variables such as the number of days since surgery, depression and anxiety scores and more, support the initiative that research attention should increase focus on these patients at baseline in order to better understand their post-chemotherapy results.

The present thesis comprises three main parts: one theoretical and two experimental. The first part, composed of two chapters, will introduce the clinical and neuropathological features underlying parkinsonian disorders, namely in Parkinson’s disease (PD) as well as in atypical parkinsonisms — multiple system atrophy (MSA) and progressive supranuclear palsy (PSP) (Chapter 1). In this regard, PD and MSA are defined as synucleinopathies due to the presence of synuclein aggregates; while PSP that is characterized by tau protein accumulations, is part of tauopathies. Further, Chapter 2 will provide an overview of the cognitive dysfunctions characterizing these disorders, as well as evidence on the biological mechanisms and structural changes underlying cognitive alterations. The second and third parts are composed by studies I conducted during my doctoral research. Namely, in Chapter 3, I report results of my studies on cognitive screening instruments most sensitive in detecting cognitive alterations in atypical parkinsonisms compared to PD. In the following study, I characterized the progression of cognitive decline in these disorders (Chapter 4). Finally, I investigated with magnetic resonance imaging the structural changes underlying cognitive alterations in PD (Chapter 5), and MSA (Chapter 6). I conclude this thesis by discussing the clinical consequences of these cognitive and imaging findings (Chapter 7). PART I - Theoretical background Chapter 1: Parkinsonian disorders Parkinsonian disorders are characterized by different underlying pathologies. In PD and MSA there are synuclein aggregates respectively in dopamine neurons or in glial cells, while PSP patients present pathological aggregation of the tau-protein, resulting in neurofibrillary tangles formation (Daniel, de Bruin, & Lees, 1995; Dickson, 1999). Clinical manifestations depend by the characteristics of protein aggregation and by the extent of disease spread to cortical and subcortical regions (Halliday, Holton, Revesz, & Dickson, 2011). Thus, the present chapter will overview the underlying pathology of PD, MSA and PSP; and it will describe the different clinical features; and lastly review the most recent diagnostic criteria (e.g., Gelb, Oliver, & Gilman, 1999; Gilman et al., 2008; Höglinger et al., 2017). Chapter 2: Cognitive features and their underlying mechanisms in parkinsonian disorders Non-motor symptoms represent a crucial part of the parkinsonian disorders spectrum; and cognitive dysfunctions, including dementia, are probably the most relevant, since they affect functional independence of patients, increase caregiver burden as well as wield a considerable socioeconomic impact (Keranen et al., 2003; McCrone et al., 2011; Vossius, Larsen, Janvin, & Aarsland, 2011). The first part of this chapter will provide an overview on cognitive dysfunctions in PD, MSA, and PSP. Moreover, the clinical criteria for the diagnosis of mild cognitive impairment and dementia in PD will be reported (Dubois et al., 2007; Emre et al., 2007; Litvan et al., 2012), while so far there are no available criteria to assess cognitive syndromes in PSP and MSA. Lastly, the second and third parts of this chapter will review the evidence on biological mechanisms and structural changes underlying cognitive alterations in these disorders. PART II - Studies on cognitive manifestations in parkinsonian disorders Chapter 3: Montreal Cognitive Assessment and Mini-Mental State Examination performance in progressive supranuclear palsy, multiple system atrophy and Parkinson’s disease There is general agreement that cognitive dysfunctions are common in PD as well as in other parkinsonian disorders (Aarsland et al., 2017; Brown et al., 2010; Gerstenecker, 2017). Brief screening cognitive scales can be adopted in routine care, to support the clinician in the diagnostic process (Marras, Troster, Kulisevsky, & Stebbins, 2014). The Mini-Mental State Examination (MMSE) is the most widely used (Folstein, Folstein, & McHugh, 1975) although MMSE is relatively insensitive in detecting cognitive deficits in parkinsonian disorders mainly because it does not investigate the fronto-executive domain (Hoops et al., 2009). Conversely, the Montreal Cognitive Assessment (MoCA), another brief cognitive screening tool widely used with PD patients (Nasreddine et al., 2005), showed high sensitivity and specificity in the assessment of cognitive dysfunctions in PD (Gill, Freshman, Blender, & Ravina, 2008; Hoops et al., 2009; Zadikoff et al., 2008), as well as also in several neurodegenerative conditions such as Alzheimer’s disease, dementia with Lewy bodies (DLB) and Huntington’s disease (Biundo et al., 2016b; Hoops et al., 2009; Nasreddine et al., 2005; Videnovic et al., 2010). However, MoCA has been poorly investigated in atypical parkinsonisms — especially in PSP and MSA (Kawahara et al., 2015). Thus, this study’s main aim was to determine if MoCA is more sensitive than the commonly used MMSE in detecting cognitive abnormalities in patients with probable PSP and MSA, compared to PD. In this multicenter study across three European institutions, MMSE and MoCA were administered to 130 patients: 35 MSA, 30 PSP and 65 age, and education and sex matched-PD. We assessed between-group differences for MMSE, MoCA, and their subitems and calculated receiver operating characteristic (ROC) curves. Our results show that the mean MMSE is higher than the mean MoCA score in each patient group: MSA (27.7 ± 2.4 vs. 22.9 ± 3.0, p<0.0001), PSP (26.0 ± 2.9 vs. 18.2 ± 3.9, p<0.0001), and PD (27.3 ± 2.0 vs. 22.3 ± 3.5, p<0.0001). Furthermore, MoCA total score as well as its letter fluency subitem differentiates PSP from MSA and PD with high specificity and moderate sensitivity. Namely, a cut-off score of seven words or less per minute would support a diagnosis of PSP (PSP vs. PD: 86% specificity, 70% sensitivity; PSP vs. MSA: 71% specificity, 70% sensitivity). On the contrary, MMSE presented a ceiling effect for most subitems, except for the ‘bisecting pentagons’, with PSP performing worse than MSA and PD patients. These findings suggest that PSP and MSA, similar to PD patients, may present normal performance on MMSE, but reduced performance on MoCA. To conclude, MoCA is more sensitive than MMSE in detecting cognitive dysfunctions in atypical parkinsonisms, and together with its verbal fluency subitem can be a valuable test to support PSP diagnosis. Chapter 4: Prospective assessment of cognitive dysfunctions in parkinsonian disorders Clinical and research evidence suggests cognitive impairments in parkinsonian disorders are progressive. However, there are only a few longitudinal studies in the literature that investigated cognitive progression in PSP and MSA compared to PD (Dubois & Pillon, 2005; Rittman et al., 2013; Soliveri, 2000). In addition, previous studies are based on brief cognitive screening scales or on neuropsychological assessments that do not extensively investigate the full spectrum of cognitive abilities across the five cognitive domains (i.e., attention/working-memory, executive, memory, visuospatial and language). Furthermore, even though clinical criteria for mild cognitive impairment (MCI) and dementia in PD have been formulated (Dubois et al., 2007; Litvan et al., 2012), it remains to be investigated whether similar criteria might be applied also for atypical parkinsonisms (Marras et al., 2014). Based on these observations, the aims of the present study were to: i) assess the severity of cognitive dysfunctions in PSP and MSA patients using PD-criteria for cognitive statuses (i.e., MCI or dementia); ii) investigate the sensitivity of two widely used cognitive screening instruments, the MMSE and MoCA, in differentiating MSA, PSP and PD global cognitive profile; iii) characterize the progression of cognitive decline on the five cognitive domains and behavioral features; and to compare the 15-month follow-up profile across the parkinsonian diseases. Our sample included 18 patients with PSP, 12 MSA; and 30 PD patients, matched for age, education and sex. They were evaluated at baseline and at a mean of 15-month follow-up. Demographic and clinical variables were collected. From the cognitive standpoint, I selected a comprehensive neuropsychological battery specifically designed to target cognitive deficits in PD, according to Level II criteria (Dubois et al., 2007; Litvan et al., 2012; Marras et al., 2014). Thus, I applied these criteria also to MSA and PSP since there are no published criteria for atypical parkinsonisms. Statistical non-parametric analyses were used. I found PSP patients had more severe cognitive decline compared to PD and MSA. Namely, after 15-month follow-up, we noted a marked decline in the executive and language domains in the PSP group. Baseline and follow-up evaluations agreed, showing that PSP had a worse performance than PD and MSA patients: especially, in the Stroop test, verbal fluencies (semantic and phonemic) and MoCA. Assessing the severity of cognitive deficits, I found different percentages of cognitive status (i.e., normal cognition vs. MCI vs. dementia) among the three groups. In particular, the percentage of patients with dementia was higher in PSP compared to MSA (33% vs. no patients with dementia) even if disease duration was similar. Among MSA and PSP patients with multidomain MCI at baseline only PSP converted to dementia at follow-up. Then, although the disease duration was longer for PD patients compared with PSP, the proportion of patients who converted to dementia was lower in the PD group compared to PSP (7% vs. 16%), despite both groups having had similar baseline severity of MCI. Overall, these results suggest more rapid and severe cognitive decline in PSP while MSA patients generally have milder deficits. MoCA showed higher sensitivity than MMSE in detecting cognitive changes, especially in PSP. But MoCA was less sensitive than MMSE in detecting cognitive decline at 15-month in PD, suggesting that MMSE is better if one wants to track cognitive changes in PD. Neuropsychiatric features are more common in PSP than PD patients, especially apathy with accompanying low levels of anxiety and depression. Lastly, analysis of subitems revealed that PSP patients had a ‘clinically significant’ worsening after 15-month in the attentive/executive subitems (Trial Making Test part B and Clock drawing). But it has been observed that some patients also improved in specific subtasks at the follow-up. This improvement could be related to their higher medication dose (although the dopaminergic treatment was not significantly different between the baseline and follow-up). However, noteworthy alterations in performance have been seen for subitems sensitive to motor conditions (such as drawing figures and linking circles with a pen), which could affect cognitive outcome, leading to higher performance at follow-up. These limits of MoCA and MMSE scale have already been reported in PD patients (Biundo et al., 2016b; Hu et al., 2014), and maybe are more pronounced in atypical parkinsonisms. Taken together, these findings show that PSP patients were markedly impaired in comparison to the other parkinsonian disorders (MSA and PD) and six years after first symptoms, 33 percent of patients have dementia. This severe progression is possibly associated with the distribution of tau pathology that involves also cortical structures. On the contrary, the pattern of cognitive impairment in MSA is less severe, possibly due to the predominance of subcortical pathology with cortical involvement occurring only secondary to these abnormalities. Thus, these findings recommend using cognitive assessment to help differential diagnosis in atypical parkinsonisms, and to monitor disease progression. PART III - Neuroimaging studies of synucleinopathies Chapter 5: Amyloid depositions affect cognitive and motor manifestations in Parkinson’s disease Cognitive deficits, particularly executive problems, can be observed early in PD (Aarsland, Bronnick, Larsen, Tysnes, & Alves, 2009). Dysfunction of the frontostriatal dopaminergic system may influence the presence of executive and attention problems (Bruck, Aalto, Nurmi, Bergman, & Rinne, 2005), but so far, evidence from dopamine transporter (DAT) imaging are inconsistent (Delgado-Alvarado, Gago, Navalpotro-Gomez, Jimenez-Urbieta, & Rodriguez-Oroz, 2016). In this regard, the neuropathology underlying cognitive impairment in PD is heterogeneous (Irwin, Lee, & Trojanowski, 2013; Kehagia, Barker, & Robbins, 2010) and amyloid deposit involvement with synuclein pathology remains poorly defined, particularly in the disease’s early stages. Thus, this study’s aims were to investigate the interplay between amyloid depositions in frontostriatal pathways, striatal dopaminergic deficit and brain atrophy rates; and their contribution to cognitive defects (i.e., fronto-executive functions) in early-PD. A multicenter cohort of 33 PD patients from the Parkinson's Progression Markers Initiative underwent [18F]florbetaben positron emission tomography (PET) amyloid, [123I]FP-CIT (see Abbreviations List) single-photon emission computed tomography (SPECT), structural magnetic resonance imaging (MRI), clinical and selective cognitive evaluations. Our results showed that high amyloid levels were associated with reduced dopaminergic deficits in the dorsal striatum (as compared to low amyloid levels), increased brain atrophy in frontal and occipital regions and a tendency to show more frequent cognitive impairment in global cognition (as assessed by MoCA) and fronto-executive tests. Of note, amyloid depositions in frontostriatal regions were inversely correlated with cognitive performance. Overall, our findings suggest that early-PD patients with amyloid burden have higher brain atrophy rates and may experience more cognitive dysfunctions (i.e., executive) and motor impairment as compared to amyloid negative subjects. In this regard, our results seem to be aligned with a recent neuropathological hypothesis that considers synaptic axonal damage and dysfunction as the PD key feature (Tagliaferro & Burke, 2016). Indeed, dopaminergic system neurons are particularly vulnerable to synuclein pathology due to their axonal characteristics — long, thin and unmyelinated. This is also confirmed by imaging studies with DAT-binding PET (Caminiti et al., 2017), suggesting that synuclein aggregations in PD can affect synaptic function, and thus signal transmission from the disease’s very early stages. Our findings suggested a possible interaction between synuclein and the coincident amyloid pathology, wherein amyloid burden may facilitate the spread of synuclein (i.e., Lewy bodies) (Toledo et al., 2016), and we speculate that this interaction can further contribute to axonal vulnerability. Thus, consistently with this hypothesis, we conclude that possibly amyloid depositions act synergistically with synuclein pathology and affect PD clinical manifestations. Chapter 6: Brain structural profile of multiple system atrophy patients with cognitive impairment In contrast to other synucleinopathies (e.g., PD and DLB), presence of dementia is considered a non-supporting feature for MSA diagnosis (Gilman et al., 2008), however there is growing evidence that MSA patients can experience cognitive impairment ranging from executive dysfunctions to multiple-domain cognitive deficits, and in a few cases, also dementia (Gerstenecker, 2017). MMSE is a commonly used global cognitive scale and recently a large multicenter study has suggested using a cutoff score below 27 to increase the MMSE sensitivity in identifying cognitive dysfunctions in MSA (Auzou et al., 2015). Underlying mechanisms of cognitive impairment in MSA are still not understood, and in this regard evidence from MRI studies suggested a discrete cortical and subcortical contribution to explain cognitive deficits (Kim et al., 2015; Lee et al., 2016a), even though these findings were based on a relatively small number of patients at various disease stages as well as being single-center. Thus, the aim of our multicenter study was to better characterize the anatomical changes associated with cognitive impairment in MSA and to further investigate the cortical and subcortical structural differences in comparison to a sample of healthy subjects. We examined retrospectively 72 probable MSA patients and based on the MMSE threshold below 27, we defined 50 MSA as cognitively normal (MSA-NC) and 22 with cognitive impairment (MSA-CI). We directly compared the MSA subgroup, and further compared them to 36 healthy subjects using gray- and white-matter voxel-based morphometry and fully automated subcortical segmentation. Compared to healthy subjects, MSA patients showed widespread cortical (i.e., bilateral frontal, occipito-temporal, and parietal areas), subcortical, and white matter alterations. However, the direct comparison MSA-CI showed only focal volume reduction in the left dorsolateral prefrontal cortex compared with MSA-NC. These findings suggest only a marginal contribution of cortical pathology to cognitive deficits in MSA. Hence, we suggest that cognitive alterations are driven by focal frontostriatal degeneration that is in line with the concept of ‘subcortical cognitive impairment’.<br>La presente tesi è formata da tre parti principali: la prima teorica mentre le due seguenti sono sperimentali. La prima parte, composta di due capitoli, introdurrà le caratteristiche cliniche e neuropatologiche sottostanti ai disturbi parkinsoniani, in particolare nella malattia di Parkinson (PD) e nei parkinsonismi atipici — atrofia multisistemica (MSA) e paralisi progressiva sopranucleare (PSP) (Capitolo 1). Nello specifico, PD ed MSA sono definite come sinucleinopatie per la presenza di aggregati di sinucleina, mentre la PSP che è caratterizzata dall’accumulo di proteina tau rientra a far parte delle tauopatie. Invece, il Capitolo 2 fornirà una panoramica delle disfunzioni cognitive che caratterizzano questi disturbi e fornirà inoltre evidenze circa i meccanismi biologici e i cambiamenti strutturali che sono alla base delle alterazioni cognitive. Nella seconda e la terza parte sono riportati alcuni studi che ho condotto durante il dottorato di ricerca. In particolare, nel Capitolo 3 riporto i risultati dei miei studi sugli strumenti di screening cognitivo più sensibili nel rilevare alterazioni cognitive nei parkinsonismi atipici rispetto ai pazienti con PD. Nel successivo studio invece ho investigato la progressione del declino cognitivo in questi disturbi (Capitolo 4). Infine, ho investigato con studi di risonanza magnetica i cambiamenti strutturali che sottendono le alterazioni cognitive nel PD (Capitolo 5) e nella MSA (Capitolo 6). Seguiranno le conclusioni generali, in cui discuto le conseguenze cliniche dei risultati ottenuti negli studi cognitivi e di imaging (Capitolo 7). PARTE I – Background teorico Capitolo 1: I disturbi parkinsoniani I disturbi parkinsoniani sono caratterizzati da una diversa patologia sottostante. Nel PD ed MSA ci sono aggregati di sinucleina rispettivamente nei neuroni dopaminergici o nelle cellule gliali, mentre i pazienti con PSP presentano delle aggregazioni di proteina tau che determina la formazione di ammassi neurofibrillari (Daniel, de Bruin, & Lees, 1995; Dickson, 1999). Le manifestazioni cliniche dipendono dalle caratteristiche di aggregati proteici e dall’entità di diffusione della malattia nelle regioni corticali e sottocorticali (Halliday, Holton, Revesz, & Dickson, 2011). Quindi, il presente capitolo illustrerà la patologia sottostante nel PD, MSA e PSP, saranno poi descritte le diverse caratteristiche cliniche ed infine, saranno presentati i più recenti criteri diagnostici di questi disturbi (e.g., Gelb, Oliver, & Gilman, 1999; Gilman et al., 2008; Höglinger et al., 2017). Capitolo 2: Caratteristiche cognitive e i sottostanti meccanismi nei disturbi parkinsoniani I sintomi non-motori rappresentano una parte cruciale dello spettro dei disturbi parkinsoniani, in particolare le disfunzioni cognitive, inclusa la demenza, sono probabilmente tra i sintomi non-motori più rilevanti, in quanto influenzano l'autonomia funzionale dei pazienti, incrementano il carico di gestione del caregiver ed hanno un notevole impatto socioeconomico (Keranen et al., 2003; McCrone et al., 2011; Vossius, Larsen, Janvin, & Aarsland, 2011). La prima parte di questo capitolo fornirà una panoramica sulle disfunzioni cognitive nel PD, MSA e PSP. Saranno inoltre riportati i criteri clinici per la diagnosi di declino cognitivo lieve e di demenza nel PD (Dubois et al., 2007; Emre et al., 2007; Litvan et al., 2012), al contrario invece non esistono al momento criteri disponibili per valutare le sindromi cognitive in PSP e MSA. Infine, la seconda e la terza parte di questo capitolo forniranno evidenze sui meccanismi biologici e sui cambiamenti strutturali sottostanti alle alterazioni cognitive in questi disturbi. PARTE II - Studi sulle manifestazioni cognitive nei disturbi parkinsoniani Capitolo 3: Performance al Montreal Cognitive Assessment e Mini-Mental State Examination nella paralisi sopranucleare progresiva, atrofia multisistemica e malattia di Parkinson Vi è un generale consenso nel riconoscere che le alterazioni cognitive siano frequenti nei PD e negli altri disturbi parkinsoniani (Aarsland et al., 2017; Brown et al., 2010; Gerstenecker, 2017). Pertanto, nella pratica clinica possono essere adottate delle scale brevi di screening cognitivo, per supportare il clinico nel processo diagnostico (Marras, Troster, Kulisevsky, & Stebbins, 2014). Il Mini-Mental State Examination (MMSE) è la scala più utilizzata (Folstein, Folstein, & McHugh, 1975), anche se MMSE è relativamente insensibile nell’identificare rilevare disfunzioni cognitive nei disturbi parkinsoniani principalmente perché non indaga il dominio fronto-esecutivo (Hoops et al., 2009). Al contrario, il Montreal Cognitive Assessment (MoCA), un altro strumento di screening cognitivo ampiamente utilizzato nei pazienti con PD (Nasreddine et al., 2005), ha mostrato un’elevata sensibilità e specificità nell’identificazione di alterazioni cognitive nei PD (Gill, Freshman, Blender, & Ravina, 2008; Hoops et al., 2009; Zadikoff et al., 2008), come anche in altre malattie neurodegenerative come l’Alzheimer, la demenza da corpi di Lewy (DLB) e la malattia di Huntington (Biundo et al., 2016b; Hoops et al., 2009; Nasreddine et al., 2005; Videnovic et al., 2010). Tuttavia, vi sono poche evidenze sull’uso del MoCA nei parkinsonismi atipici, in particolare nella PSP ed MSA (Kawahara et al., 2015). Pertanto, lo scopo del presente studio era di determinare se il MoCA fosse più sensibile del comunemente utilizzato MMSE nel rilevare alterazioni cognitive nei pazienti con probabile PSP e MSA, rispetto al PD. In questo studio multicentrico, che ha coinvolto altri tre centri europei, sono state somministrate le scale MMSE e MoCA a 130 pazienti: 35 MSA, 30 PSP e 65 pazienti PD appaiati per età, scolarità e sesso. Sono state valutate le differenze tra i gruppi per MMSE, MoCA, e i loro subitem; infine sono state calcolate le curve ROC (Receiver-Operating Characteristic). Dai risultati emerge che la media del MMSE è superiore al punteggio medio del MoCA in ogni gruppo di pazienti: MSA (27.7 ± 2.4 vs. 22.9 ± 3.0, p<0.0001), PSP (26.0 ± 2.9 vs. 18.2 ± 3.9, p<0.0001), e PD (27.3 ± 2.0 vs. 22.3 ± 3.5, p<0.0001). Inoltre, il punteggio totale MoCA così come il suo subitem di fluenza fonemica è in grado di differenziare la PSP da MSA e PD con un’alta specificità e moderata sensibilità. Specificamente, un punteggio uguale o inferiore a sette parole al minuto sembra supportare una diagnosi di PSP (PSP vs PD: 86% specificità, sensibilità al 70%, PSP vs MSA: 71% specificità, sensibilità al 70%). Al contrario, nel MMSE è stato possibile osservare un ‘effetto-soffitto’ per la maggior parte dei subitem, ad eccezione del subitem dei ‘due pentagoni’, in cui i pazienti con PSP hanno una prestazione peggiore rispetto a MSA e PD. I nostri risultati suggeriscono che PSP ed MSA, similmente al PD, possono presentare una prestazione normale al MMSE ma deficitaria al MoCA. In conclusione, il MoCA è più sensibile del MMSE nel rilevare disfunzioni cognitive nei parkinsonismi atipici ed insieme al suo subitem di fluenza verbale sembra essere un valido test per supportare una diagnosi di PSP. Capitolo 4: Valutazione prospettica delle disfunzioni cognitive nei disturbi parkinsoniani Evidenze in ambito clinico e di ricerca suggeriscono che le disfunzioni cognitive nei disturbi parkinsoniani siano progressive. Tuttavia, in letteratura vi sono pochi studi longitudinali che indagano la progressione cognitiva in pazienti con PSP ed MSA rispetto a pazienti PD (Dubois & Pillon, 2005; Rittman et al., 2013; Soliveri, 2000). In particolare, i precedenti studi si basano solo su scale globali di screening cognitivo, oppure su valutazioni neuropsicologiche parziali che non esaminano l'intero spettro delle abilità cognitive nei cinque domini (i.e., attenzione/memoria di lavoro, esecutivo, mnesico, visuospaziale e del linguaggio). Inoltre, sebbene siano stati formulati criteri clinici per la diagnosi di declino cognitivo lieve (MCI) e di demenza in pazienti PD (Dubois et al., 2007; Litvan et al., 2012), rimane ancora da investigare se tali criteri possano essere applicati anche nei parkinsonismi atipici (Marras et al., 2014). Date tali premesse, gli obiettivi del presente studio sono stati: i) valutare la severità delle alterazioni cognitive in pazienti PSP ed MSA utilizzando i criteri validati nei pazienti PD, per identificare gli stati cognitivi (i.e., MCI o demenza); ii) esaminare la sensibilità di due strumenti di screening cognitivo ampiamente utilizzati, (i.e., MMSE e MoCA), nel differenziare il profilo cognitivo globale di pazienti MSA, PSP e PD; iii) caratterizzare la progressione del declino cognitivo nei cinque domini, il profilo comportamentale e infine confrontare il profilo cognitivo al follow-up tra i vari disturbi parkinsoniani. Il nostro campione includeva 18 pazienti con PSP, 12 MSA e 30 pazienti con PD appaiati per età, scolarità e sesso, che sono stati valutati alla baseline e al follow-up a 15 mesi. Sono stati raccolti dati demografici e clinici; inoltre dal punto di vista cognitivo è stata selezionata una batteria di test neuropsicologici completa, specifica per l’identificazione di deficit cognitivi in pazienti PD, secondo i criteri pubblicati di ‘Livello II’ (Dubois et al., 2007; Litvan et al., 2012; Marras et al., 2014). Abbiamo quindi applicato tali criteri anche a pazienti MSA e PSP, dato che non esistono criteri pubblicati per i parkinsonismi atipici. Infine, sono state utilizzate analisi statistiche di tipo non-parametrico. Dai nostri risultati emerge che i pazienti con PSP hanno un declino cognitivo più severo rispetto a pazienti PD ed MSA. Nello specifico, al follow-up è stato possibile osservare un marcato declino a carico del dominio esecutivo e del linguaggio nel gruppo con PSP. Le valutazioni cognitive alla baseline e al follow-up erano concordanti, ed entrambe confermano che i pazienti PSP hanno una prestazione peggiore rispetto ai pazienti PD ed MSA: in particolare, nello Stroop test, nelle fluenze verbali (semantica e fonematica) e nel MoCA. Valutando la severità dei deficit cognitivi, abbiamo inoltre trovato diverse percentuali di diagnosi cognitive (i.e., profilo nella norma, MCI vs. demenza) tra i tre gruppi. In particolare, la percentuale più elevata di pazienti con demenza era nel gruppo con PSP rispetto ai pazienti MSA (i.e., 33% vs. nessun paziente con demenza), anche se la durata di malattia era simile. Inoltre, tra i pazienti MSA e PSP con un profilo MCI-multidominio alla baseline, solo pazienti con PSP passano ad una diagnosi di demenza al follow-up. Infine nel gruppo di pazienti PD, nonostante avessero una durata di malattia più lunga, la percentuale di soggetti che passano ad una diagnosi di demenza era inferiore rispetto al gruppo con PSP (7% vs. 16%), nonostante entrambi i gruppi avessero una gravità di MCI simile alla baseline. Complessivamente questi risultati suggeriscono un più rapido e severo declino cognitivo in soggetti PSP, mentre i pazienti MSA mostrano generalmente deficit più limitati. La scala globale MoCA sembra essere maggiormente sensibile, rispetto al MMSE, nel rilevare cambiamenti cognitivi, in particolare nella PSP. Tuttavia il MoCA mostra una sensibilità inferiore rispetto al MMSE nell’identificare un declino cognitivo al follow-up in pazienti PD; quindi il MMSE sembra essere uno strumento migliore per monitorare longitudinalmente cambiamenti cognitivi in pazienti PD. Riguardo al profilo comportamentale, i pazienti PSP riportano più comunemente rispetto ai pazienti PD: apatia, ansia e depressione. Infine, l'analisi dei subitem rivela che i pazienti PSP mostrano un peggioramento ‘clinicamente significativo’ dopo 15 mesi soprattutto nei subitem attentivo-esecutivi (Trial Making Test parte B e il disegno di un orologio). Tuttavia è stato possibile osservare che alcuni pazienti hanno anche un miglioramento in specifici subitem al follow-up. Questo miglioramento potrebbe essere attribuibile ad una più elevata dose farmacologica (nonostante il trattamento dopaminergico alla baseline non fosse significativamente diverso al follow-up). Tuttavia, è importante notare che tali alterazioni erano presenti soprattutto in subitem sensibili alle problematiche motorie (i.e., disegno di figure e collegamento di cerchi con una penna) che quindi potrebbero aver alterato la performance. Questi limiti della scala MoCA e MMSE sono già stati osservati in precedenza nei pazienti con PD (Biundo et al., 2016b; Hu et al., 2014), e possibilmente sono ancora più pronunciati nei parkinsonismi atipici. In conclusione i nostri risultati rivelano che i pazienti PSP hanno una performance notevolmente alterata rispetto agli altri disturbi parkinsoniani (MSA e PD), e dopo circa 6 anni di durata di malattia, il 33% dei pazienti PSP ha una diagnosi di demenza. Questa severa progressione è probabilmente associata ad una diffusione di aggregati tau che coinvolge anche strutture corticali. Al contrario, il pattern di compromissione cognitiva in pazienti con MSA è meno severo, e probabilmente è associato ad una predominanza sottocorticale della patologia, con un coinvolgimento corticale solo secondario alle alterazioni sottocorticali. Pertanto, i nostri risultati suggeriscono che la valutazione neuropsicologica può essere utile nella differenziazione dei profili cognitivi nei parkinsonismi atipici e per monitorare la progressione della malattia. PARTE III – Studi di neuroimmagine sulle sinucleinopatie Capitolo 5: Effetti dei depositi di amiloide sulle manifestazioni cognitive e motorie nella malattia di Parkinson Alterazioni cognitive, in particolare deficit esecutivi, possono essere osservati anche nelle prime fasi del PD (Aarsland, Bronnick, Larsen, Tysnes & Alves, 2009). La disfunzione frontostriatale del sistema dopaminergico può influenzare la presenza di problemi esecutivi ed attentivi (Bruck, Aalto, Nurmi, Bergman, & Rinne, 2005), tuttavia al momento le evidenze relative al trasportatore striatale di dopamina (DAT) sono inconsistenti (Delgado-Alvarado, Gago, Navalpotro-Gomez, Jimenez-Urbieta, & Rodriguez-Oroz, 2016). I meccanismi neuropatologici che stanno alla base delle alterazioni cognitive nei PD sono eterogenei (Irwin, Lee, & Trojanowski, 2013; Kehagia, Barker & Robbins, 2010), ed il contributo del deposito di amiloide in aggiunta alla sinucleinopatia rimane ancora poco definito, soprattutto nelle prime fasi della malattia. Pertanto, lo scopo del presente studio è stato quello di indagare l'interazione tra depositi di amiloide nel circuito frontostriatale, deficit dopaminergico striatale, grado di atrofia cerebrale ed il loro contributo nelle alterazioni cognitive (i.e., funzioni fronto-esecutive) nelle prime fasi del PD. Una coorte multicentrica di 33 pazienti con PD ricavata dal ‘Parkinson's Progression Markers Initiative’ è stata sottoposta a una tomografia ad emissione di positroni (PET) con radiofarmaco [18F]florbetaben, tomografia ad emissione di fotone singolo (SPECT) con radiofarmaco [123I]FP-CIT, risonanza magnetica (MRI) strutturale, valutazione clinica e cognitiva. Dai nostri risultati emerge che elevati livelli di depositi di amiloide erano associati ad una riduzione del deficit dopaminergico nello striato dorsale (rispetto ai bassi livelli di depositi di amiloide), ad un aumento dell’atrofia cerebrale in regioni frontali ed occipitali, e ad una tendenza a manifestare più frequentemente alterazioni cognitive globali (come valutato dal MoCA), ed in test fronto-esecutivi. Inoltre, le deposizioni di amiloide nelle regioni frontostriatali erano inversamente correlate alla performance cognitiva. Nel complesso i nostri risultati suggeriscono che pazienti con PD in fase iniziale di malattia e amiloidosi hanno un più elevato grado di atrofia cerebrale e possono esperire maggiori deficit cognitivi (i.e., disfunzioni esecutive) e alterazioni motorie rispetto a soggetti negativi all’amiloide. I nostri risultati sembrano essere in linea con una recente ipotesi neuropatologica che considera il danno e disfunzione assonale a livello sinaptico come un elemento caratteristico del PD (Tagliaferro & Burke, 2016). Infatti, i neuroni del sistema dopaminergico sono particolarmente vulnerabili alla sinucleinopatia a causa delle loro caratteristiche assonali: gli assoni sono lunghi, sottili e non mielinizzati. Questa ipotesi è confermata anche da studi di neuroimmagine PET con traccianti che si legano al DAT (Caminiti et al., 2017), suggerendo che le aggregazioni di sinucleina nel PD possono influenzare la funzione sinaptica e la trasmissione di segnale sin dalle prime fasi della malattia. I nostri risultati suggeriscono quindi una possibile interazione tra depositi di amiloide e sinucleinopatia, in cui la presenza di amiloide può facilitare la diffusione di sinucleina (i.e., corpi di Lewy) (Toledo et al., 2016), pertanto questa interazione può contribuire ulteriormente alla vulnerabilità assonale. In linea con questa ipotesi, i nostri risultati sembrano confermare che le deposizioni di amiloide agiscono sinergicamente con la sinucleinopatia, influenzando le manifestazioni cliniche del PD. Capitolo 6: Profilo neurostrutturale dell’atrofia multisistemica con alterazioni cognitive A differenza di altre sinucleinopatie (e.g., PD e DLB), la presenza di demenza è considerata un criterio di esclusione nella diagnosi di MSA (Gilman et al., 2008), tuttavia vi è una crescente evidenza che pazienti affetti da MSA possano manifestare alterazioni cognitive, che includono disfunzioni esecutive ma anche deficit cognitivi multidominio, e in alcuni casi anche demenza (Gerstenecker, 2017). Il MMSE è una scala cognitiva globale comunemente utilizzata nella pratica clinica, e recentemente uno studio multicentrico ha suggerito l’utilizzo di un cutoff <27 per aumentare la sensibilità di tale scala nell'identificare alterazioni cognitive in pazienti MSA (Auzou et al., 2015). I meccanismi che sottendono le disfunzioni cognitive in soggetti MSA non sono ancora stati identificati ed evidenze da studi di MRI suggeriscono un discreto contributo corticale e sottocorticale per spiegare tali alterazioni cognitive (Kim et al., 2015; Lee et al., 2016a). Tuttavia questi risultati sono basati su un numero relativamente piccolo di pazienti e in vari stadi di malattia, inoltre sono studi basati su singoli centri. Pertanto, lo scopo del nostro studio multicentrico è stato quello caratterizzare i cambiamenti anatomici associati ad alterazioni cognitive in pazienti MSA e di investigare le differenze strutturali corticali e sottocorticali rispetto ad un campione di soggetti sani. Abbiamo quindi esaminato retrospettivamente 72 pazienti MSA, e definito 50 MSA come cognitivamente normali (MSA-NC) e 22 con alterazioni cognitive (MSA-CI) utilizzando il cutoff del MMSE <27. Abbiamo inoltre confrontato direttamente i due sottogruppi di MSA, e comparato l’intero gruppo di MSA ad un campione di 36 controlli sani (HC) utilizzando un’analisi di ‘morfometria basata sui voxel’ che analizzava la sostanza grigia e bianca. Inoltre, abbiamo applicato anche una segmentazione automatizzata dei volumi sottocorticali. Dai nostri risultati emerge che i pazienti MSA, rispetto a soggetti sani, hanno una diffusa atrofia corticale (i.e., che coinvolge bilateralmente aree frontali, occipito-temporali e parietali), sottocorticale ed alterazioni alla sostanza bianca. Tuttavia, nel confronto diretto, i soggetti MSA-CI mostrano solo una focale riduzione del volume a carico della corteccia prefrontale dorsolaterale sinistra rispetto a pazienti MSA-NC. Tali risultati suggeriscono che la patologia corticale abbia un effetto marginale sulle alterazioni cognitive nei pazienti MSA. Suggeriamo quindi che le alterazioni cognitive siano piuttosto determinate da una degenerazione frontostriatale focale, che sembra essere in linea con il concetto di ‘alterazioni cognitive sottocorticali’.

El trastorno por déficit de atención e hiperactividad (TDAH) es un trastorno del neurodesarrollo caracterizado por síntomas de inatención, hiperactividad e impulsividad. Los modelos clásicos acerca de la neuroanatomía del trastorno apuntan a alteraciones en los circuitos fronto-estriado-cerebelares. Los estudios de neuroimagen estructural apoyan parcialmente estos modelos. Sin embargo, casi todos estos estudios se basan en el análisis de regiones seleccionadas a priori (procedimiento que se conoce como ROI, acrónimo inglés de regiones de interés: "region of interest"). Estudios más recientes basados en aproximaciones globales apuntan a que las alteraciones estructurales no se limitan a los circuitos fronto-estriado-cerebelares, sino que también afectan las regiones temporales, parietales y cinguladas.<br/>El objetivo de la presente tesis es el de redefinir y aplicar dos métodos de análisis estructural complementarios para identificar los circuitos cerebrales alterados en el TDAH así como para relacionar dichos circuitos con los diferentes subtipos clínicos. Para tal fin, presentaremos y discutiremos dos estudios de resonancia magnética estructural (Carmona et al. 2005; Tremols et al. 2008). Estos dos estudios representan una novedad y mejora de estudios de TDAH previos, por dos razones principales: a) la aplicación por primera vez un estudios basado en la morfometría de vóxeles para comparar el cerebro de niños con TDAH con el cerebro de niños controles no relacionados familiarmente; b) el diseño e implementación de un nuevo método, fácil de aplicar, de segmentación manual del núcleo caudado.<br/>Los resultados confirman los datos obtenidos en estudios previos acerca de menor volumen cerebral en niños con TDAH, y localizan esta reducción en determinadas regiones de sustancia gris. A parte de confirmar las alteraciones fronto-estriado-cerebelares hayamos reducciones en áreas parietales, cingulares y temporales. En concreto observamos decrementos volumétricos de sustancia gris en la corteza frontal inferior, el estriado dorsal, la corteza parietal inferior y la corteza cingulada posterior, regiones clásicamente relacionadas con problemas de inhibición, deficits de memoria de trabajo y alteraciones en tareas de atención visuoespacial, respectivamente. También observamos reducciones volumétricas en áreas típicamente emocionales, como la corteza orbitofrontal, el estriado ventral y las estructurales temporales mediales deficits que podrían explicar las disfunciones motivacionales así como las alteraciones en el procesamiento del refuerzo. Curiosamente, las reducciones de sustancia gris en áreas relacionadas con el procesamiento emocional son más pronunciadas en el subtipo hiperactivo-impulsivo, algo menos en el subtipo combinado y casi inexistentes en el subtipo inatento. Esta diferente afectación en función de los subtipos va en la línea de teorías neuroanatómicas actuales acerca del TDAH (Castellanos and Tannock 2002). También observamos déficits de sustancia gris en áreas sensorio-motoras (específicamente en la corteza perirrolándica y el área motora suplementaria), y en el cerebelo. Por un lado, los déficits en áreas sensorio-motoras probablemente reflejan los problemas de psicomotricidad fina que presentan muchos de los niños con TDAH. Sin embargo, el hecho de que estas reducciones sean especialmente prominentes en los subtipos combinado e inatento, sugieren la posibilidad de que estas alteraciones estén especialmente relacionadas con los déficits atencionales. En base a esto, hipotetizamos que las alteraciones en estas regiones producirían un déficit para integrar y actualizar la información procedente del mundo exterior y, a su vez darían lugar a un sesgo a favor del procesamiento de los estados internos resultando en inatención. Por otro lado, las reducciones cerebelares (extensamente observadas en la literatura del TDAH) parecen están relacionadas con los déficits cognitivos, los afectivos y los emocionales. Creemos que la implicación del cerebelo en estas disfunciones estaría vehiculada por el papel de esta estructural como moduladora del flujo de información entre los circuitos fronto-estriatales. Finalmente nuestros hallazgos son los primeros en demostrar alteraciones diferenciales en la cabeza y el cuerpo del núcleo caudado en el TDAH. Esta desigual implicación de las diferentes partes del núcleo caudado explicaría en parte la heterogeneidad de los estudios previos. <br/>Como conclusión, las reducciones volumétricas de sustancia gris en áreas cognitivas y emocionales apoyan la implicación de disfunciones en los circuitos fronto-estriatales llamados cool (cognitivos) y hot (emocionales) respectivamente. Hasta la fecha este es el primer estudio neuroanatómico que apoya la existencia de disfunciones tanto cognitvas como emocionales en niños con TDAH. Nuestros hallazgos constituyen la primera evidencia neuroanatómica a favor de los modelos de doble ruta porpuestos por Sonuga-Barke (Sonuga- Barke 2002; Sonuga-Barke 2003).<br/>REFERENCIAS: <br/>1. Tremols V, Bielsa A, Soliva JC, Raheb C, Carmona S, Tomas J, et al. (2008): Differential abnormalities of the head and body of the caudate nucleus in attention deficit-hyperactivity disorder. Psychiatry Res. 163:270-278.<br/>2. Carmona S, Vilarroya O, Bielsa A, Tremols V, Soliva JC, Rovira M, et al. (2005): Global and regional gray matter reductions in ADHD: a voxel-based morphometric study. Neurosci Lett. 389:88-93.<br/>3. Castellanos FX, Tannock R (2002): Neuroscience of attention-deficit/hyperactivity disorder: the search for endophenotypes. Nat Rev Neurosci. 3:617-628.<br/>4. Sonuga-Barke EJ (2003): The dual pathway model of AD/HD: an elaboration of neuro-developmental characteristics. Neurosci Biobehav Rev. 27:593-604.<br/>5. Sonuga-Barke EJ (2002): Psychological heterogeneity in AD/HD--a dual pathway model of behaviour and cognition. Behav Brain Res. 130:29-36.<br>Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disease characterized by symptoms of inattention, hyperactivity and impulsivity. Data from different studies point to ADHD abnormalities in fronto-striatal circuits. Structural neuroimaging studies partially support fronto-striatal abnormalities and suggest an important role of the cerebellum. However, nearly all these studies are based on the analysis of apriori selected regions of interest (known as ROI approaches). Recent studies, using more global approaches, found that ADHD structural abnormalities were not limited to fronto-striatal-cerebellar circuits, but also affect temporal, parietal and cingulate regions.<br/>The aim of the present dissertation is to refine and apply two complementary methods of structural neuroimaging, in order to identify the brain circuits altered in<br/>ADHD and relate them to different clinical ADHD subtypes and to known ADHD neuropsychological deficits. For that purpose, two structural MRI studies will be presented and discussed (Carmona et al. 2005; Tremols et al. 2008). The differential contributions of these studies, which represent a novelty and an improvement of previous ADHD studies, are: a) the application for the first time of<br/>voxel-based morphometry analysis to compare ADHD children with non family related control children; b) the design and application of a new, easy to apply, manual method of caudate nucleus segmentation.<br/>The results confirm previous findings about smaller brain volume in ADHD children, and refine this reduction by attributing it to grey matter (GM) volume. We also confirm abnormalities in fronto-striatal-cerebellar circuits as well as in parietal, cingulate and temporal regions. Specifically, we observed reductions in inferior frontal cortex, dorsal striatum, inferior parietal cortex and posterior cingulate cortex; thus explaining inhibition problems, spatial working memory deficits and visuospatial attentional alterations. We also observed GM volume reductions in emotionally driven areas such as orbitofrontal cortex, ventral striatum and middle temporal structures; thus accounting for dysfunctional delayed reward and motivational deficits. Interestingly, GM volume reductions, related to emotional processes are more prominent in H-I subtype, more preserved in combined subtypes, and relatively undisrupted in inattentive subtypes, which is in agreement with previous ADHD theories (Castellanos and Tannock 2002). We have also found GM deficits in "sensori-motor" areas (specifically in perirolandic cortex and supplementary motor area), and in the cerebellum. On the one hand, deficits in sensori-motor areas probably reflect problems in fine motor coordination. However, the fact that these reductions are especially prominent in combined and inattentive subtypes brings up the possibility that they may be related to attentional dysfunctions.<br/>I hypothesized that deficits in these regions may produce a deficit when integrating and updating information from the external world and, in turn, produce a bias toward internal world focusing, thus, resulting in inattention. On the other hand, cerebellar reductions (which are extensively reported in ADHD literature) seem to be related to all cognitive, affective and sensorimotor deficits. The implication of cerebellum in all these dysfunctions may arise from its role as a modulator of the flow of information between fronto-strital circuits. Finally, our findings are also the first to show caudate head and body differential abnormalities in ADHD, which explain previous heterogeneous results, providing a new and reliable method to study striatal structures.<br/>As a conclusion, GM volume reductions in emotional and cognitive areas support the implication of both hot (emotional) and cool (cognitive) functions, which agrees with most neuropsychological accounts of ADHD. To our knowledge this is the first time that a neuroanatomical study provides support for the existence of both cognitive and emotional dysfunctions in ADHD children. If these findings are replicated, they will constitute critical evidence for Sonuga-Barke's theory (Sonuga- Barke 2002; Sonuga-Barke 2003) about the dual route model.<br/>REFERENCIAS: <br/>1. Tremols V, Bielsa A, Soliva JC, Raheb C, Carmona S, Tomas J, et al. (2008): Differential abnormalities of the head and body of the caudate nucleus in attention deficit-hyperactivity disorder. Psychiatry Res. 163:270-278.<br/>2. Carmona S, Vilarroya O, Bielsa A, Tremols V, Soliva JC, Rovira M, et al. (2005): Global and regional gray matter reductions in ADHD: a voxel-based morphometric study. Neurosci Lett. 389:88-93.<br/>3. Castellanos FX, Tannock R (2002): Neuroscience of attention-deficit/hyperactivity disorder: the search for endophenotypes. Nat Rev Neurosci. 3:617-628.<br/>5. Sonuga-Barke EJ (2003): The dual pathway model of AD/HD: an elaboration of neuro-developmental characteristics. Neurosci Biobehav Rev. 27:593-604.<br/>6. Sonuga-Barke EJ (2002): Psychological heterogeneity in AD/HD--a dual pathway model of behaviour and cognition. Behav Brain Res. 130:29-36.

A polineuropatia inflamatória desmielinizante crônica (PIDC) é uma síndrome caracterizada fundamentalmente pela disfunção do Sistema Nervoso Periférico e que afeta muito a qualidade de vida dos pacientes. O envolvimento da PIDC com o Sistema Nervoso Central tem sido descrito, maiormente como sendo subclínico, porém não há estudos sobre a caracterização deste envolvimento de uma forma ampla e quantitativa. Avaliamos 11 pacientes com PIDC, todos tratados e sem sinais clínicos de alterações centrais, e 11 controles, pareados em gênero e faixa etária de 19 a 69 anos. Foram adquiridas neuroimagens em uma máquina de Ressonância Magnética de alto campo (3T) usando diferentes técnicas de imagens; volumétricas ponderadas em T1, volumétricas de inversão e recuperação com atenuação de fluidos e ponderadas em T2, relaxométricas de cinco ecos para mapas de T2, de transferência de magnetização e por tensor de difusão. As imagens foram processadas em diferentes ferramentas computacionais e foram obtidos resultados para estudos da difusibilidade, volumetria, morfometria, tratometria e conectividade cerebral, além de achados radiológicos para os pacientes. As análises de grupos foram executadas por; 1) testes paramétricos monocaudais de duas amostras pareadas para os resultados da volumetria, da tratometria e conectividade cerebral; 2) mapeamento estatístico paramétrico para os resultados da morfometria baseada em voxel e; 3) estatística espacial baseada em tratos para os resultados da difusibilidade. Foram detectas alterações em todas as comparações. Os principais achados indicam um envolvimento possivelmente caracterizado por uma perda volumétrica encefálica generalizada, sobretudo nas regiões periventriculares associadas a ventrículos proeminentes acrescido de, um aumento da difusibilidade transversa e oblíqua nos maiores tratos de substância branca e, também há uma perda de densidade na substância branca periventricular e um aumento na substância cinzenta em uma região que sinaliza para o espessamento trigeminal bilateral e, uma redução geral da conectividade cerebral estrutural.<br>Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) is a severe disease fundamentally characterized by dysfunction of the Peripheral Nervous System and affects greatly the quality of life of patients. The Central Nervous System (CNS) involvement in CIDP has not been described using recent quantitative neuroimaging techniques. We evaluated 11 patients with CIDP, all treated and without clinical signs of central alterations and 11 controls matched for gender and age group of 19 to 69 years. Magnetic Resonance Imaging were performed on a 3T scanner using different imaging techniques; structural 3D T1-weighted, fluid-attenuated inversion recovery, relaxometry with 5 echoes pulse sequence for T2 maps, magnetization transfer weighted and diffusion tensor imaging. The images were processed on different tools and were obtained results for the studies of diffusivity, volumetry, morphometry, tractometry, brain connectivity, and radiological findings of patients. Different statistical group analyses were performed in the quantitative results: 1) Parametric test for volumetry, tractometry and brain connectivity; 2) Parametric mapping for voxel morphometry; 3) Tract-based spatial statistics (TBSS) for diffusion coefficients. Changes were detected in all comparisons. In the patients, our main findings are: generalized loss brain volume more pronounced in periventricular regions associated with prominent ventricles, increased simultaneously perpendiculars and parallel diffusivity in the major tracts of the TBSS analyze, white matter density loss in the periventricular area, some bilateral trigeminal thickening, and general reduction of the brain connectivity. The CIDP affects the global brain and represents a demyelination in the CNS.