SARS-CoV-2's brain impact: revealing cortical and cerebellar differences via cluster analysis in COVID-19 recovered patients.

BACKGROUND: COVID-19 is a disease known for its neurological involvement. SARS-CoV-2 infection triggers neuroinflammation, which could significantly contribute to the development of long-term neurological symptoms and structural alterations in the gray matter. However, the existence of a consistent pattern of cerebral atrophy remains uncertain. OBJECTIVE: Our study aimed to identify patterns of brain involvement in recovered COVID-19 patients and explore potential relationships with clinical variables during hospitalization. METHODOLOGY: In this study, we included 39 recovered patients and 39 controls from a pre-pandemic database to ensure their non-exposure to the virus. We obtained clinical data of the patients during hospitalization, and 3 months later; in addition we obtained T1-weighted magnetic resonance images and performed standard screening cognitive tests. RESULTS: We identified two groups of recovered patients based on a cluster analysis of the significant cortical thickness differences between patients and controls. Group 1 displayed significant cortical thickness differences in specific cerebral regions, while Group 2 exhibited significant differences in the cerebellum, though neither group showed cognitive deterioration at the group level. Notably, Group 1 showed a tendency of higher D-dimer values during hospitalization compared to Group 2, prior to p-value correction. CONCLUSION: This data-driven division into two groups based on the brain structural differences, and the possible link to D-dimer values may provide insights into the underlying mechanisms of SARS-COV-2 neurological disruption and its impact on the brain during and after recovery from the disease.

Olfactory performance in spinocerebellar ataxia type 7 patients.

A large body of evidence has shown olfactory deficits in many neurodegenerative diseases. However, the nature of the olfactory impairment remains poorly understood partly because the majority of studies have only explored smell identification capabilities. The purpose of the present study was twofold. First we wanted to test if patients with spinocerebellar ataxia type 7 (SCA7), a progressive neurodegenerative disorder characterized by cerebellar ataxia and visual loss, also have olfactory deficits. Secondly, we wanted to test the nature of the olfactory deficits by testing not only the identification level but also olfactory threshold and discrimination. Based on the olfactory dysfunction found in different neurodegenerative diseases and functional neuroimaging data showing cerebellar activation during olfaction, we hypothesized that SCA7 patients would show an olfactory impairment. To test this hypothesis we studied twenty-eight genetically confirmed SCA7 patients and twenty-seven matched controls using the Sniffing Sticks Test and the University of Pennsylvania Smell Identification Test (UPSIT). The results show that SCA7 patients' ability to discriminate and identify odors is significantly impaired, although their odor detection thresholds were at normal levels. These results suggest that SCA7 neurological damage affects olfactory perception but spares the patients' olfactory sensory capabilities.

Parahippocampal gray matter alterations in Spinocerebellar Ataxia Type 2 identified by voxel based morphometry.

Spinocerebellar Ataxia Type 2 (SCA2) is a genetic disorder causing cerebellar degeneration that result in motor and cognitive alterations. Voxel-based morphometry (VBM) analyses have found neurodegenerative patterns associated to SCA2, but they show some discrepancies. Moreover, behavioral deficits related to non-cerebellar functions are scarcely discussed in those reports. In this work we use behavioral and cognitive tests and VBM to identify and confirm cognitive and gray matter alterations in SCA2 patients compared with control subjects. Also, we discuss the cerebellar and non-cerebellar functions affected by this disease. Our results confirmed gray matter reduction in the cerebellar vermis, pons, and insular, frontal, parietal and temporal cortices. However, our analysis also found unreported loss of gray matter in the parahippocampal gyrus bilaterally. Motor performance test ratings correlated with total gray and white matter reductions, but executive performance and clinical features such as CAG repetitions and disease progression did not show any correlation. This pattern of cerebellar and non-cerebellar morphological alterations associated with SCA2 has to be considered to fully understand the motor and non-motor deficits that include language production and comprehension and some social skill changes that occur in these patients.