Norovirus-associated neurological manifestations: summarizing the evidence.

Norovirus, a positive-stranded RNA virus, is one of the leading causes of acute gastroenteritis among all age groups worldwide. The neurological manifestations of norovirus are underrecognized, but several wide-spectrum neurological manifestations have been reported among infected individuals in the last few years. Our objective was to summarize the features of norovirus-associated neurological disorders based on the available literature. We used the existing PRISMA consensus statement. Data were collected from PubMed, EMBASE, Web of Science, and Scopus databases up to Jan 30, 2023, using pre-specified searching strategies. Twenty-one articles were selected for the qualitative synthesis. Among these, seven hundred and seventy-four patients with norovirus-associated neurological manifestations were reported. Most cases were seizure episodes, infection-induced encephalopathy, and immune-driven disorders. However, only a few studies have addressed the pathogenesis of norovirus-related neurological complications. The pathogenesis of these manifestations may be mediated by either neurotropism or aberrant immune-mediated injury, or both, depending on the affected system. Our review could help clinicians to recognize these neurological manifestations better and earlier while deepening the understanding of the pathogenesis of this viral infection.

Relationships between neuropsychiatric symptoms and cognitive profiles in Alzheimer's disease and related syndromes.

OBJECTIVES: To investigate the rate of occurrence of neuropsychiatric symptoms (NPS) and their relationship with age, sex and cognitive performance in subjects with Alzheimer's disease and related dementias (Alzheimer's disease and related dementias [ADRD]). METHODS: This is a retrospective matched case-control study. Data from memory clinic patients included demographic information presence of NPS, and cognitive testing of Orientation, Immediate and Delayed Memory, Visuospatial Function, Working Memory, Attention, Executive Control and Language. Participants were Individuals with subjective cognitive impairment (n = 352), mild cognitive impairment (MCI) (n = 369), vascular MCI (n = 80), Alzheimer's disease (n = 147), vascular dementia (n = 41), mixed dementia (n = 33), and healthy controls (n = 305). Logistic regression was used to investigate the relationship between the presence of NPS, age and sex. A generalised additive model was used to investigate the relationship between presence of NPS, age and cognitive impairment. Analysis of variance was used to investigate differences in cognition between younger and older groups with and without NPS. RESULTS: We found an increased likelihood of occurrence of NPS in younger individuals and females across cohorts. Anxiety, depression, agitation, and apathy were associated with higher overall rate of NPS. We also found that individuals under 65 years of age with NPS had worse cognitive scores than their counterpart without NPS. CONCLUSION: The younger group with ADRD and NPS had lower cognitive scores, probably reflecting more aggressive neurodegenerative disease. Further work will be needed to elicit the degree to which imaging or mechanistic abnormalities distinguish this group.

Meningoencephalitis associated with COVID-19: a systematic review.

With the growing number of COVID-19 cases in recent times. significant set of patients with extra pulmonary symptoms has been reported worldwide. Here we venture out to summarize the clinical profile, investigations, and radiological findings among patients with SARS-CoV-2-associated meningoencephalitis in the form of a systemic review. This review was carried out based on the existing PRISMA (Preferred Report for Systematic Review and Meta analyses) consensus statement. The data for this review was collected from four databases: Pubmed/Medline, NIH Litcovid, Embase, and Cochrane library and Preprint servers up till 30 June 2020. Search strategy comprised of a range of keywords from relevant medical subject headings which includes "SARS-COV-2," "COVID-19," and "meningoencephalitis." All peer reviewed, case-control, case report, pre print articles satisfying our inclusion criteria were involved in the study. Quantitative data was expressed in mean ± SD, while the qualitative date in percentages. Paired t test was used for analysing the data based on differences between mean and respective values with a p < 0.05 considered to be statistically significant. A total of 61 cases were included from 25 studies after screening from databases and preprint servers, out of which 54 of them had completed investigation profile and were included in the final analysis. Clinical, laboratory findings, neuroimaging abnormalities, and EEG findings were analyzed in detail. This present review summarizes the available evidences related to the occurrence of meningoencephalitis in COVID-19.

COVID-19: Are we dealing with a multisystem vasculopathy in disguise of a viral infection?

After the emergence of Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV) and Middle East Respiratory Syndrome Coronavirus (MERS-CoV) in the last two decades, the world is facing its new challenge in Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) pandemic with unprecedented global response. With the expanding domain of presentations in COVID-19 patients, the full range of manifestations is yet to unfold. The classical clinical symptoms for SARS-CoV-2 affected patients are dry cough, high fever, dyspnoea, lethal pneumonia whereas many patients have also been found to be associated with a few additional signs and clinical manifestations of isolated vasculopathy. Albeit a deep and profound knowledge has been gained on the clinical features and management of COVID-19, less clear association has been provided on SARS-CoV-2 mediated direct or indirect vasculopathy and its possible correlation with disease prognosis. The accumulative evidences suggest that novel coronavirus, apart from its primary respiratory confinement, may also invade vascular endothelial cells of several systems including cerebral, cardio-pulmonary as well as renal microvasculature, modulating multiple visceral perfusion indices. Here we analyse the phylogenetic perspective of SARS-CoV-2 along with other strains of ß-coronaviridae from a standpoint of vasculopathic derangements. Based on the existing case reports, literature and open data bases, we also analyse the differential pattern of vasculopathy related changes in COVID-19 positive patients. Besides, we debate the need of modulation in clinical approach from a hemodynamical point of view, as a measure towards reducing disease transmission, morbidity and mortality in SARS-CoV-2 affected patients.

Dyskinetopsic Palinopsia: Palinopsia Accompanied by Moving Afterimages.

Palinopsia refers to the abnormal persistence, or recurrence, of visual images after a visual stimulus has subsided. We describe here a case of palinopsia accompanied by a visual motion perception disorder as manifested by moving afterimages. A 71-year-old man presented to us after having experienced acute-onset, vivid, visual hallucinations for 1 week. A detailed history revealed that he was hallucinating multiple living and nonliving objects. He also complained of a persistence of afterimages, particularly in the left visual field. He reported that, on a few occasions, while sitting by the window in his room, he had seen a moving car on the road; immediately after the car had disappeared from his sight, he had then seen the same car moving backward at almost the same speed-as if the driver had applied the reverse gear. A neuropsychological assessment did not reveal any deficits in attention, language, or episodic memory. Visual field testing by confrontational perimetry suggested left hemianopia. An MRI of the brain revealed an arteriovenous malformation in the medial part of the right occipital lobe, affecting both the lingual gyrus and the inferior occipital gyrus. Palinopsia has generally been described in reference to static afterimages. In our case, not only was the afterimage that was perceived by the patient in motion, but the direction of the movement was also opposite to that of the actual object. We propose the term dyskinetopsic palinopsia, or simply motion-related palinopsia, for this particular condition.

Analysis of an Unusual Case of Nonfluent Aphasia With Predominantly Posterior Perisylvian Lesion: An Apparent Paradox.

Lesion site-aphasia type discordance has garnered increasing interest in cognitive neuroscience over the last century. Diaschisis, the network concept of cognitive functions, and interindividual variability are among the plausible explanations cited in the literature for such unusual clinical cases. We describe here the case of a nonfluent type of aphasia following an ischemic stroke predominantly affecting the left posterior perisylvian cortex in a right-handed Bengali-speaking woman. The patient's comprehension was well preserved; however, she presented with a severe motor speech defect. MRI revealed an ischemic lesion in the left parietotemporal area, with slight involvement of the postero-inferior frontal cortex. We suggest two plausible explanations for this lesion-aphasia discordance: Our patient had bilateral representation of language receptive functions in her brain, and additional areas neighboring the classical Broca area may support some critical mechanisms of speech production. Taken together, these explanations may clarify why our patient was able to maintain the ability to decode language even though her language production was significantly affected.

The disease presentation of Moyamoya angiopathy in Eastern India.

INTRODUCTION: Clinical spectrum of Moyamoya angiopathy (MMA) differs across populations with different ethnicity. This study, the largest one done among Indian population was undertaken to assess clinico-radiological profile of MMA patients in eastern India. METHODS: A single centre cross-sectional study was undertaken among 76 MMA cases. Each patient was evaluated for epidemiological, clinical and radiological characteristics. SPSS 25 was used for statistical analysis. P < 0.05 was taken as statistically significant. RESULTS: 36 (47.4%) were children without gender preponderance. There were female predominance among adults (male:female = 1:2.33). Mean age at onset of first neurological symptoms for children was 4.2 ± 2.0years, followed by 34.9 ± 58.2months of latency with final diagnosis at the mean age of 7.4 ± 3.5years. For adults, mean age of onset of first neurological symptoms was 31.5 ± 12.3years, followed by 14.7 ± 41.7months time gap and diagnosed at the mean age of 33.5 ± 12.5years. There was a statistically significant difference between child and adult regarding the diagnostic latency (p = 0.035). Fixed motor weakness (FMW) was the predominant symptom across the whole disease course. Among children predominant first neurological symptom was fixed motor weakness (FMW) (52.8%), followed by seizures (22.2%). FMW was predominant (55%) first neurological complaint, followed by headache (22.5%) among adults. Seizure was more prevalent among children both as first (p = 0.002) and presenting symptom at the time of diagnosis (p = 0.048). Over the course of the disease seizure was more common among children (p = 0.001), while headache was more common among adults (p = 0.017). Recurrence of symptoms was more common among children (p = 0.059). Infarcts were more common among children (91.7%) than adults (72.5%), while hemorrhage was seen only among adults (25%) (p = 0.004). Isolated cerebral cortex was involved more commonly among children (59.4%) than adults (36.1%), while isolated subcortical involvement was seen only among adults (19.4%) (p = 0.016). Majority of the MMA cases were of Suzuki stage 4 (39.5%) and 5 (27.6%). Brain atrophy was associated with diagnostic latency (p = 0.009). CONCLUSION: Indian Moyamoya presents similar to disease presentation in Caucasian and Japanese patients. It is a frequently overlooked cause of stroke in young, often with various non-motor presentations, failure to recognize which leads to delay in diagnosis. Radiological burden disproportionate to number of acute vascular events, with subtle neurological manifestations like headache or seizure, often with cognitive decline, should raise suspicion of MMA.

Incidence and Symptomatology of Vascular Crossed Aphasia in Bengali.

BACKGROUND: Crossed aphasia (CA) refers to aphasia following a right-hemispheric lesion in right-handed individuals. It has been suggested that the prevalence of CA differs with language, although its worldwide incidence, as reported by most studies, is less than 3%. OBJECTIVE: To find the incidence of CA in the Bengali language. METHODS: From 2016 to 2018, in a hospital located in a Bengali-speaking area of eastern India, 515 cases of first-ever stroke were documented, out of which 208 patients presented with aphasia (40.38%) according to their scores on the Bengali version of the Western Aphasia Battery. RESULTS: Among the patients with aphasia, 14 (6.73%; 8 men and 6 women) presented with CA. Of these, 10 were diagnosed with Broca aphasia and four with transcortical motor aphasia. No patient presented with Wernicke aphasia. CONCLUSIONS: The relatively high incidence of CA in our study suggests that bi-hemispheric language representation may be more prevalent in Bengali speakers than in speakers of other languages. The absence of crossed Wernicke aphasia in our study participants may represent a left-hemispheric advantage for receptive language abilities in Bengali speakers. Further studies are required to clarify whether idiosyncrasies in the Bengali language may be responsible for the differential brain representation of language seen in our study participants.

Deciphering seizure semiology in corpus callosum injuries: A comprehensive systematic review with machine learning insights.

INTRODUCTION: Seizure disorders have often been found to be associated with corpus callosum injuries, but in most cases, they remain undiagnosed. Understanding the clinical, electrographic, and neuroradiological alternations can be crucial in delineating this entity. OBJECTIVE: This systematic review aims to analyze the effects of corpus callosum injuries on seizure semiology, providing insights into the neuroscientific and clinical implications of such injuries. METHODS: Adhering to the PRISMA guidelines, a comprehensive search across multiple databases, including PubMed/Medline, NIH, Embase, Cochrane Library, and Cross-ref, was conducted until September 25, 2023. Studies on seizures associated with corpus callosum injuries, excluding other cortical or sub-cortical involvements, were included. Machine learning (Random Forest) and deep learning (1D-CNN) algorithms were employed for data classification. RESULTS: Initially, 1250 articles were identified from the mentioned databases, and additional 350 were found through other relevant sources. Out of all these articles, 41 studies met the inclusion criteria, collectively encompassing 56 patients The most frequent clinical manifestations included generalized tonic-clonic seizures, complex partial seizures, and focal seizures. The most common callosal injuries were related to reversible splenial lesion syndrome and cytotoxic lesions. Machine learning and deep learning analyses revealed significant correlations between seizure types, semiological parameters, and callosal injury locations. Complete recovery was reported in the majority of patients post-treatment. CONCLUSION: Corpus callosum injuries have diverse impacts on seizure semiology. This review highlights the importance of understanding the role of the corpus callosum in seizure propagation and manifestation. The findings emphasize the need for targeted diagnostic and therapeutic strategies in managing seizures associated with callosal injuries. Future research should focus on expanding the data pool and exploring the underlying mechanisms in greater detail.

Bilingualism as a protective factor in aphasia.

BACKGROUND: Bilingualism may affect the profile of cognitive disturbances associated with stroke. Its impact on aphasia severity, however, is in need of substantiation. AIMS: To determine the relationship between bilingualism and vascular aphasia severity. METHODS: This is an observational cross-sectional study conducted on people with post-stroke aphasia. Our sample included 155 monolingual and 53 bilingual vascular aphasia patients. They were selected in a neurological hospital in Kolkata (West Bengal, India). RESULTS: The Bengali version of Western Aphasia Battery (BWAB) was used in this study. Aphasia severity was compared between monolingual and bilingual participants. The overall difference in the mean aphasia quotient (AQ) between bilingual and monolingual participants was statistically significant (p = 0.009). It was also found that in bilingual participants, aphasia was less severe in certain subgroups, namely: higher lesion volume, male gender, and sub-cortical stroke, while in none of the subgroups a monolingual advantage was documented. CONCLUSION: Current results suggest that bilingualism represents a protective factor in vascular aphasia; this effect is observed particularly in some aphasia subgroups.

Behavioral variations among vascular cognitive impairment subtypes - A comparative study.

Dementia of vascular origin is a distinct variety with a heterogeneous neuropsychological profile. Very few studies have compared the behavioral dysfunction in the large vessel and small vessel vascular dementia (VaD) and studied the association between executive dysfunction and behavioral dysfunction documented in these patients, between the white matter load in small vessel disease (SVD) and the behavioral dysfunction. 76 patients having a modified Hachinski Ischemic Scale score of ≥ 4 were recruited and categorized into a small vessel and large vessel VaD. The Neuropsychiatric Inventory (NPI) score ≥ 4 per domain for defining clinically relevant symptoms and the Clinical Dementia Rating Scale (CDR) for evaluating the severity of dementia were used. Behavioral and Psychological Symptoms of Dementia (BPSD) were present in 66.67% of patients with SVD and 53.57% of those having large vessel disease. Apathy, euphoria, and disinhibition were more common in SVD, while appetite alterations were more common in large vessel disease. Behavioral dysfunction was also associated with executive dysfunction in both the VaD subtypes and with white matter loads in SVD. We conclude that different VaD subtypes have different behavioral profiles. This might help in understanding the underlying pathophysiology, diagnosis and thus better management of this disorder.

Subacute Sclerosing Panencephalitis in a 63-Year-Old Woman Presenting as Generalized Choreoathetosis.

The persistence of measles virus infection in childhood and early adolescence can rarely lead to a fatal progressive neurodegenerative disorder known as subacute sclerosing panencephalitis (SSPE), characterized by behavioral disturbances and intellectual disability followed by myoclonic jerks and occasional negative myoclonus. Movement disorders are rarely presenting manifestations in SSPE. We herein report a 63-year-old woman with generalized choreoathetosis as the presenting manifestation of stage-I SSPE. Our case was atypical for the patient's age and clinical presentation with generalized choreoathetosis and bilateral putaminal and caudate nucleus signal hyperintensity. Though highly uncommon, neurologists should keep SSPE as a differential diagnosis among patients with movement disorders. Measles-endemic countries should be more vigilant to the atypical and rare presentations of SSPE, such as generalized choreoathetosis.

MELAS with multiple stroke-like episodes due to the variant m.13513G>A in MT-ND5.

Mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) is characterized by metabolic stroke, seizures, cognitive decline, lactic acidosis, ragged-red fibers, headache, and vomiting, and in 80% of cases due to the mtDNA variant m.3243A>G. We report the case of a MELAS patient carrying a variant in subunit-5 of the respiratory chain (MT-ND5), rarely reported in MELAS. The patient is a 33-year-old male, who experienced a series of stroke-like episodes (StLEs) since age 23 years, which manifested clinically as seizures transient sensory disturbances, weakness, and visual or cognitive impairment. Over 9 years, these StLEs were misinterpreted as ischemic strokes, respectively, as cerebral vasculitis. He presented with mild, recurrent elevations of the creatine kinase. Initially, anti-seizure drugs and steroids appeared to be beneficial. Despite good recovery of each single StLE, the patient experienced a progressive decline of cognitive functions and activities of daily living. Cerebral imaging showed corresponding stroke-like lesions in changing locations. At age 32y, genetic work-up revealed the variant m.13513G>A in MT-ND5. The patient profited significantly from a cocktail with anti-oxidants/cofactors. This case shows that the variant m.13513G>A in MT-ND5 can manifest as MELAS that StLEs recover spontaneously and that the course of MELAS is slowly progressive.

Prognostic indicators and outcomes of hospitalised COVID-19 patients with neurological disease: An individual patient data meta-analysis.

BACKGROUND: Neurological COVID-19 disease has been reported widely, but published studies often lack information on neurological outcomes and prognostic risk factors. We aimed to describe the spectrum of neurological disease in hospitalised COVID-19 patients; characterise clinical outcomes; and investigate factors associated with a poor outcome. METHODS: We conducted an individual patient data (IPD) meta-analysis of hospitalised patients with neurological COVID-19 disease, using standard case definitions. We invited authors of studies from the first pandemic wave, plus clinicians in the Global COVID-Neuro Network with unpublished data, to contribute. We analysed features associated with poor outcome (moderate to severe disability or death, 3 to 6 on the modified Rankin Scale) using multivariable models. RESULTS: We included 83 studies (31 unpublished) providing IPD for 1979 patients with COVID-19 and acute new-onset neurological disease. Encephalopathy (978 [49%] patients) and cerebrovascular events (506 [26%]) were the most common diagnoses. Respiratory and systemic symptoms preceded neurological features in 93% of patients; one third developed neurological disease after hospital admission. A poor outcome was more common in patients with cerebrovascular events (76% [95% CI 67-82]), than encephalopathy (54% [42-65]). Intensive care use was high (38% [35-41]) overall, and also greater in the cerebrovascular patients. In the cerebrovascular, but not encephalopathic patients, risk factors for poor outcome included breathlessness on admission and elevated D-dimer. Overall, 30-day mortality was 30% [27-32]. The hazard of death was comparatively lower for patients in the WHO European region. INTERPRETATION: Neurological COVID-19 disease poses a considerable burden in terms of disease outcomes and use of hospital resources from prolonged intensive care and inpatient admission; preliminary data suggest these may differ according to WHO regions and country income levels. The different risk factors for encephalopathy and stroke suggest different disease mechanisms which may be amenable to intervention, especially in those who develop neurological symptoms after hospital admission.

Left hemispheric stroke in a professional artist: A prospective case study.

Several papers have investigated the effect of stroke on creativity. While initial evidence favored right hemispheric dominance in artwork creation, subsequent well-founded research has established the left hemispheric participation in creativity, supporting the idea of bi-hemispheric role in artistic production. We here describe the case of a renowned artist who suffered a left hemispheric ischemic stroke involving the occipito-temporal region and subsequently manifested several difficulties in producing visual artworks. We documented his recovery phases in a prospective way during the initial months following stroke and observed that, although his constructional abilities recovered to a significant extent over 3 months, spontaneous creation was persistently impaired. The right hemispheric role in visual art is linked mainly to visuo-spatial skills and global attention, while left hemispheric participation is thought to be related to focal attention and visual imagery. Our case study lends support to the idea that art is a bi-hemispheric function with important complementary contributions from both the right and left hemisphere.

Acute dorsal myelopathy resulting from intramedullary cysticercus: a case report.

BACKGROUND: Neurocysticercosis is the most common parasitic infection of the central nervous system, brain being the most frequent site. Intramedullary location of cysticercus is a rarely described entity in literature. Widespread dissemination of cysticercus is also considered a rare occurrence, and only a handful of cases are documented, almost exclusively from tropical nations. Here we present a case of disseminated cysticercosis with rare initial presentation as acute dorsal myelopathy resulting from intramedullary cysticercus. CASE PRESENTATION: A 62-year-old male patient from India (Asian) presented with features of dorsal myelopathy as manifested by acute-onset symmetric paraparesis, sensory loss below umbilicus, and double sphincter dysfunction. General physical examination revealed pea-sized nodules in skin and tongue. On spinal cord imaging, it was found that he had intramedullary cysticercus with diffuse perilesional edema. Brain and muscle imaging showed extensive cysticercosis suggestive of dissemination. Histological examination from skin nodule and antibody assay confirmed the diagnosis of cysticercosis. Following steroid administration, our patient showed improvement with observable increase in power of the lower limbs. He was subsequently discharged with antiepileptics, symptomatic therapy, and regular physiotherapy. Antihelminthic agents were initially avoided in view of extensive cysticercosis in brain including crucial areas such as brainstem. CONCLUSION: Rare manifestation of a rare but treatable disorder makes it an important reportable observation in the context of tropical medicine.

COVID-19 and emerging spinal cord complications: A systematic review.

BACKGROUND: Spinal cord complications associated with coronavirus infectious disease of 2019 (COVID-19) are being widely reported. The purpose of this systematic review was to summarize so far available pieces of evidence documenting de novo novel severe acute respiratory syndrome coronavirus (SARS-CoV-2) mediated spinal cord demyelinating diseases. Indeed, the spinal demyelinating disorders that have been reported in those patients who have suffered from COVID-19 rather than on the people already living with diagnosed or undiagnosed primary demyelinating disorders. METHODS: We used the existing PRISMA consensus statement. Data were collected from PubMed, NIH Litcovid, EMBASE and Cochrane library databases, as well as Pre-print servers (medRxiv, bioRxiv, and pre-preints.org), until September 10, 2020, using pre-specified searching strategies. RESULTS: The 21 selected articles were all case reports and included 11 (52%) men and 10 (48%) women. The mean age was of 46.7 ±â€¯18.0. The neurological manifestations included weakness, sensory deficit, autonomic dysfunction and ataxia. In most cases, elevated cerebrospinal fluid protein as well as lymphocytic pleocytosis were found. SARS-CoV-2 was detected in five (24%) patients, meanwhile in 13 (62%) patients, the testing was negative. Testing was not performed in two cases and, in one, data were unavailable. Nearly half of the cases (N = 9) were associated with isolated long extensive transverse myelitis (LETM), whereas a combination of both LETM and patchy involvement was found in two. Only five patients had isolated short segment involvement and two patchy involvement. Furthermore, concomitant demyelination of both brain and spine was reported in six patients. Concerning the prognosis, most of the patients improved and the mortality rate was low (N = 2, <10%). CONCLUSION: Spinal cord demyelination should be added to the plethora of immune mediated neurologic complications associated with COVID-19.

Clinical and radiological profile of posterior cortical atrophy and comparison with a group of typical Alzheimer disease and amnestic mild cognitive impairment.

Posterior cortical atrophy (PCA) is a rare dementia affecting higher visual processing and other posterior cortical functions with atrophy and hypometabolism in occipito-parieto-temporal areas, more on right side. The objective of the study was to explore the clinical, neuropsychological, and radiological features of PCA patients and to compare them with typical multi-domain amnestic Alzheimer's disease (AD) and amnestic mild cognitive impairment (aMCI) patients. Four out of 9 patients of PCA fulfilling the criteria of Tang-Wai et al. (2004), 10 patients each of AD and aMCI fulfilling NIA-AA criteria were chosen. Patients were assessed clinically by experienced neurologists. Neuropsychological assessment was performed with standardized validated tests. Each patient underwent an MRI. FDG-PET was done for all PCA and six AD patients. PCA patients were younger, cognitively more impaired with rapid progression showing predominant visuospatial deficits consistent with the damage to the upstream of visual processing. AD patients presented predominantly with amnestic symptoms, with visuospatial dysfunction in some and aMCI had mild memory loss. Marked atrophy and hypometabolism in occipital, parietal and temporal areas in PCA, atrophy and hypometabolism in medial temporal areas in AD and minimal non-localized atrophy in MRI in aMCI were seen. Two PCA patients showed hypometabolism extending to the medial temporal and one to the frontal cortex. The clinical and imaging features of PCA are consistent with the damage predominantly to the upstream of visual processing. The difference between PCA and typical AD suggests involvement of AD pathology at different sites within a common disease-relevant network of brain regions.