To investigate the structural role of glial fibrillary acidic protein (GFAP) in vivo, mice carrying a null mutation in GFAP were generated. In 7/14 mutant animals older than 18 months of age, hydrocephalus associated with white matter loss was detected. Mutant mice displayed abnormal myelination including the presence of actively myelinating oligodendrocytes in adults, nonmyelinated axons in optic nerve, and reduced myelin thickness in spinal cord. White matter was poorly vascularized and the blood-brain barrier was structurally and functionally impaired. Astrocytic structure and function were abnormal, consisting of shortened astrocytic cell processes, decreased septation of white matter, and increased CNS extracellular space. Thus, GFAP expression is essential for normal white matter architecture and blood-brain barrier integrity, and its absence leads to late-onset CNS dysmyelination.

No abstract

Diabetes is said to account for most cases of neuropathy in the elderly. We reviewed records of 223 young-old (65-79 years) and 77 old-old (>or=80 years) patients referred for evaluation of neuropathic symptoms over a 9-year period. We prospectively validated our findings in 102 consecutive elderly (77 young-old) patients receiving intensive evaluation for neuropathy. Diabetes was the most common cause of neuropathy (41%), but was less common in the old-old (25% versus 46%, P < 0.001). Idiopathic neuropathies were more common in the old-old (39% versus 9%, P < 0.001). Alcoholic and nutritional neuropathies were uncommon in the old-old. Electrophysiological studies showed that most patients had an axonal type of neuropathy. Sural and peroneal response amplitudes were poorly correlated with age. We obtained similar results in our prospective study. The distribution of causes of neuropathies in young-old and old-old patients, in a hospital-based sample, is age-related. Future studies need to include the old-old to better understand the nature of neuropathy in the elderly.

Background and Purpose: Ischemic infarction of the corpus callosum is rare and infarction isolated to the corpus callosum alone rarer still, accounting for much <1% of ischemic stroke in most stroke registries. About half of callosal infarctions affect the splenium. Methods: During a 2-week period, at the height of the coronavirus disease 2019 (COVID-19) pandemic in New York City, 4 patients at Montefiore Medical Center in the Bronx were found to have ischemic lesions of the splenium of the corpus callosum, 2 with infarction isolated to the corpus callosum. Results: All patients tested positive for COVID-19 and 3 had prolonged periods of intubation. All had cardiovascular risk factors. Clinically, all presented with encephalopathy and had evidence of coagulopathy and raised inflammatory markers. Conclusions: Infarction of the splenium of the corpus callosum is exceedingly rare and a cluster of such cases suggests COVID-19 as an inciting agent, with the mechanisms to be elucidated.