UNASSIGNED: RESLES (Reversible splenial lesion syndrome) can be observed secondary to various diseases, and intramyelinic edema may play a crucial role in the pathogenesis of SCC (Splenium of the corpus callosum). Some studies have suggested that hypoxic-ischaemic encephalopathy may constitute a risk factor for SCC lesions. However, the potential impact of high-altitude environments on SCC, especially during chronic exposure, remain obscure.
UNASSIGNED: Our study included 19 patients who satisfied the diagnostic criteria of RESLES at high altitudes. Ten low-altitude patients with RESLES were included as controls. All participants received MRI (Magnetic resonance imaging) scans twice. Routine blood tests, liver, kidney and thyroid function, coagulation function, electrolytes and vitamins were detected during hospitalization and before discharge. In addition, the patients were followed up in May 2023.
UNASSIGNED: Hypoxic environments at high altitudes may increase the risk of RESLES. The two groups showed different clinical symptoms. High-altitude patients had significantly higher CRP levels than low-altitude patients. The lesion size in high-altitude patients showed a positive correlation with SaO2 levels. However, the patients at low altitudes had positive correlation trends between lesion size and several inflammatory markers (WBC, NEU and CRP). All patients had a benign prognosis that may not be affected by the use of prednisone acetate.
UNASSIGNED: Hypoxic environments at high altitudes may play a role in the aetiology of RESLES. Additionally, RESLES is a reversible disease and the administration of glucocorticoids may be dispensable for its treatment.

Multiple sclerosis (MS) is a debilitating demyelinating disease characterized by remyelination failure attributed to inadequate oligodendrocyte precursor cells (OPCs) differentiation and aberrant astrogliosis. A comprehensive cell atlas reanalysis of clinical specimens brings to light heightened clusterin (CLU) expression in a specific astrocyte subtype links to active lesions in MS patients. Our investigation reveals elevated astrocytic CLU levels in both active lesions of patient tissues and female murine MS models. CLU administration stimulates primary astrocyte proliferation while concurrently impeding astrocyte-mediated clearance of myelin debris. Intriguingly, CLU overload directly impedes OPC differentiation and induces OPCs and OLs apoptosis. Mechanistically, CLU suppresses PI3K-AKT signaling in primary OPCs via very low-density lipoprotein receptor. Pharmacological activation of AKT rescues the damage inflicted by excess CLU on OPCs and ameliorates demyelination in the corpus callosum. Furthermore, conditional knockout of CLU emerges as a promising intervention, showcasing improved remyelination processes and reduced severity in murine MS models.

BACKGROUND: Mirror movements (MM) are commonly caused by a defect of interhemispheric pathways also affected in multiple sclerosis (MS), particularly the corpus callosum. We investigated the prevalence of MM in MS in relation to functional and morphological callosal fiber integrity by transcranial magnetic stimulation (TMS), magnetic resonance imaging (MRI), as well as fatigue.
METHODS: In 21 patients with relapsing-remitting MS and 19 healthy controls, MM were assessed and graded (Woods and Teuber scale: MM 1-4) using a bedside test. Fatigue was evaluated using the Fatigue Scale for Motor and Cognitive Functions (FSMC) questionnaire. TMS measured ipsilateral silent period latency and duration. MRI assessed callosal atrophy by measuring the normalized corpus callosum area (nCCA), corpus callosum index (CCI), and lesion volume.
RESULTS: MS patients had significantly more often and pronounced MM compared to healthy controls (p = 0.0002) and nCCA was significantly lower (p = 0.045) in MRI studies. Patients with higher MM scores (MM > 1 vs. MM 0/1) showed significantly more fatigue (higher FSMC sum score, p = 0.04, motor score, p = 0.01). In TMS and MRI studies, no significant differences were found between patients with MM 0/1 and those with MM > 1 (ipsilateral silent period measurements, CCA, CCI and lesion volume).
CONCLUSIONS: MM are common in MS and can easily be detected through bedside testing. As MM are associated with fatigue, they might indicate fatigue in MS. It is possible that other cerebral structures, in addition to the corpus callosum, may contribute to the origin of MM in MS.

It is known that the primate amygdala forms projections to many areas of the ipsilateral cortex, but the extent to which it forms connections with the contralateral visual cortex remains less understood. Based on retrograde tracer injections in marmoset monkeys, we report that the amygdala forms widespread projections to the ipsilateral extrastriate cortex, including V1 and areas in both the dorsal (MT, V4T, V3a, 19M, and PG/PFG) and the ventral (VLP and TEO) streams. In addition, contralateral projections were found to target each of the extrastriate areas, but not V1. In both hemispheres, the tracer-labeled neurons were exclusively located in the basolateral nuclear complex. The number of labeled neurons in the contralateral amygdala was small relative to the ipsilateral connection (1.2% to 5.8%). The percentage of contralateral connections increased progressively with hierarchical level. An injection in the corpus callosum demonstrated that at least some of the amygdalo-cortical connections cross through this fiber tract, in addition to the previously documented path through the anterior commissure. Our results expand knowledge of the amygdalofugal projections to the extrastriate cortex, while also revealing pathways through which visual stimuli conveying affective content can directly influence early stages of neural processing in the contralateral visual field.

Progressive multifocal leukoencephalopathy (PML) is a rare demyelinating disease of the central nervous system (CNS) due to John Cunningham (JC) virus reactivation most often in immunocompromised patients. The brainstem and the anterior corpus callosum are uncommon locations for white matter lesions. We present a case of PML in a 40-year-old female presenting to the emergency department for a tonic seizure with transient postictal confusion. The inpatient workup revealed low cluster of differentiation cell counts (CD3 and CD4), transaminitis, positive drug screen, and abnormal electroencephalogram (EEG). The computed tomogram (CT) of the head and magnetic resonance image (MRI or MR) of the brain showed evidence of subcortical and periventricular white matter lesions in the right hemisphere extending into the brainstem and the left frontal lobe. The hospital course consisted of supportive measures, seizure treatment along with prophylaxis, and human immunodeficiency virus (HIV) management along with prophylactic antibiotics. The patient was discharged with appropriate medications and outpatient referrals. Overall, this case describes some key points. It highlights particular imaging characteristics of PML in the setting of inadequately treated HIV. For example, white matter lesions cross the anterior corpus callosum rather than the splenium, as in the \"barbell\" sign. In addition, the lesions extend inferiorly along the ipsilateral corticospinal tract into the midbrain and pons. This could be one of the first cases to capture both of these features given the rarity of their concomitant occurrence.

Cerebral asymmetry is a defining feature of the human brain, but some controversy exists with respect to the relationship between structural brain asymmetry and the dimensions of the corpus callosum, the brain\'s major inter-hemispheric commissure. On the one hand, more asymmetric brains might house a proportionally smaller corpus callosum (negative link), potentially due to intra-hemispheric connections dominating over inter-hemispheric connections. On the other hand, asymmetric brains may contain a proportionately larger corpus callosum (positive link), to facilitate a possibly enhanced demand of interhemispheric communication, either through excitatory or inhibitory channels. The scientific literature on this topic is relatively sparse, but we have identified 13 studies that directly assess the relationship between structural asymmetries and callosal morphology. The studies suggest a multitude of effects on the global, regional, and local levels, where findings range from negative links, to positive links, to no links whatsoever. These links are systematically summarized, detailed, and discussed in the present review. Discrepancies between study outcomes might arise from the application of different morphometric approaches, the differential treatment of possible confounds, as well as the size and characteristics of the study sample.

Aneurysms of the distal anterior cerebral artery (DACA) are rare but surgically challenging. Despite a known therapeutic implication of the aneurysm location on the DACA territory, the literature is unclear about its clinical and prognostic significance. Our surgical experience over the last 5 years was reviewed to compare the clinical, operative, and outcome characteristics between aneurysms located below the mid portion of the genu of the corpus callosum (called proximal aneurysms) to those distal to this point (called distal aneurysms). A prognostic factor analysis was done using uni and multivariable analysis. A total of 34 patients were treated (M: F = 1:2.3). The distal group had a higher frequency of poor clinical grade at presentation (n = 9, 47.4%) in contrast to (n = 2, 13.3%) proximal aneurysms (p = 0.039). Despite an overall tendency for a delayed functional improvement in these patients, the results were mainly due to favorable outcomes in the proximal group (favourable functional outcomes at discharge and at last follow-up being 80% and 86.7% respectively). On the multivariable analysis, only WFNS grade (> 2) at presentation (OR = 13.75; 95CI = 1.2-157.7) (p = 0.035) and application of temporary clips (AOR = 34.32; 95CI = 2.59-454.1) (p = 0.007), both of which were more in the distal group, independently predicted a poor long term functional outcome. Thus, the aneurysm location impacts the preoperative clinical grade, the intraoperative aneurysm rupture risk rate as well as the temporary clipping requirement. A combination of these factors leads to worse short and long-term functional outcomes in the distal DACA aneurysms.

The cerebral small vessel disease (cSVD) is one of the main causes of vascular and mixed cognitive impairment (CI), and it is associated, in particular, with brain ageing. An understanding of structural tissue changes in an intact cerebral white matter in cSVD might allow one to develop the sensitive biomarkers for early diagnosis and monitoring of disease progression.
OBJECTIVE: to evaluate microstructural changes in the corpus callosum (CC) using diffusion MRI (D-MRI) approaches in cSVD patients with different severity of CI and reveal the most sensitive correlations of diffusion metrics with CI.
METHODS: the study included 166 cSVD patients (51.8% women; 60.4 ± 7.6 years) and 44 healthy volunteers (65.9% women; 59.6 ± 6.8 years). All subjects underwent D-MRI (3T) with signal (diffusion tensor and kurtosis) and biophysical (neurite orientation dispersion and density imaging, NODDI, white matter tract integrity, WMTI, multicompartment spherical mean technique, MC-SMT) modeling in three CC segments as well as a neuropsychological assessment.
RESULTS: in cSVD patients, microstructural changes were found in all CC segments already at the subjective CI stage, which was found to worsen into mild CI and dementia. More pronounced changes were observed in the forceps minor. Among the signal models FA, MD, MK, RD, and RK, as well as among the biophysical models, MC-SMT (EMD, ETR) and WMTI (AWF) metrics exhibited the largest area under the curve (>0.85), characterizing the loss of microstructural integrity, the severity of potential demyelination, and the proportion of intra-axonal water, respectively. Conclusion: the study reveals the relevance of advanced D-MRI approaches for the assessment of brain tissue changes in cSVD. The identified diffusion biomarkers could be used for the clarification and observation of CI progression.

Myelin-forming oligodendrocytes in the vertebrate nervous system co-express the transcription factor Sox10 and its paralog Sox8. While Sox10 plays crucial roles throughout all stages of oligodendrocyte development, including terminal differentiation, the loss of Sox8 results in only mild and transient perturbations. Here, we aimed to elucidate the roles and interrelationships of these transcription factors in fully differentiated oligodendrocytes and myelin maintenance in adults. For that purpose, we conducted targeted deletions of Sox10, Sox8, or both in the brains of two-month-old mice. Three weeks post-deletion, none of the resulting mouse mutants exhibited significant alterations in oligodendrocyte numbers, myelin sheath counts, myelin ultrastructure, or myelin protein levels in the corpus callosum, despite efficient gene inactivation. However, differences were observed in the myelin gene expression in mice with Sox10 or combined Sox8/Sox10 deletion. RNA-sequencing analysis on dissected corpus callosum confirmed substantial alterations in the oligodendrocyte expression profile in mice with combined deletion and more subtle changes in mice with Sox10 deletion alone. Notably, Sox8 deletion did not affect any aspects of the expression profile related to the differentiated state of oligodendrocytes or myelin integrity. These findings extend our understanding of the roles of Sox8 and Sox10 in oligodendrocytes into adulthood and have important implications for the functional relationship between the paralogs and the underlying molecular mechanisms.

Several previous studies reported reduced leftward lateralization in blind participants\' samples compared to the sighted population. The origins of this difference remain unknown. Here, we tested whether functional lateralization is connected with the structural characteristics of white matter tracts [corpus callosum (CC), uncinate fasciculus (UF), and superior longitudinal fasciculus (SLF)], as suggested by previous studies conducted in the typical sighted population. Twenty-three blind and 21 sighted adult participants were tested during fMRI with a semantic decision paradigm presented both auditorily and in the modality appropriate for reading (tactually for the blind and visually for the sighted). Lateralization indices (LI) were calculated based on the activations. The fractional anisotropy (FA) measure was extracted from the white matter tracts of interest. Correlation analyses testing the relationship between FA and LI were conducted. The reduced leftward lateralization of both speech processing and reading-related activations was replicated. Nevertheless, the relationship between the structural integrity of the CC and LI and between the asymmetry of the intrahemispheric tracts and LI was not confirmed, possibly due to the lack of power. The sources of the reduced lateralization of the language network in the sensory-deprived population remain unknown. Further studies should account for environmental variables (e.g., the frequency of contact with written language) and the complexity of the factors that may influence the functional lateralization of the human brain.