小出 玲爾

BACKGROUND: This case reports aimed to clarify the characteristic MRI findings in GABAA receptor encephalitis. CASE PRESENTATION: We report the cases of two encephalitis patients who had a history of thymoma surgery and in whom anti-GABAAR antibodies and characteristic MRI findings were observed. These patients were clinically diagnosed as having thymoma-associated paraneoplastic encephalitis (TAPE) before the antibodies were identified. TAPE is often associated with antibodies to various neuronal surface antigens, including GABAAR, AMPAR, CASPR2, LGI1, and GlyR. MRI findings of autoimmune encephalitis are extremely variable, but when multiple homogenous high-signal-intensity lesions are observed on FLAIR images, as in these cases, anti-GABAAR antibodies are likely to be involved. We have named here this MRI finding the "cotton-wool-like appearance". CONCLUSION: In cases of encephalitis with such characteristic radiological findings, neurologists should first investigate the presence or a history of thymoma surgery, and then promptly consider testing for anti-GABAAR antibodies.

Patients with late-onset (LO) multiple system atrophy (MSA), whose initial symptoms appear at age 75 years or older, are more common than previously assumed, but their clinicopathological characteristics remain unclear. We aimed to clarify the clinicopathological features of LO-MSA. Of 102 patients with autopsy-confirmed MSA, 5 were identified as having LO-MSA and 24 as having usual-age-onset MSA (UO-MSA) with a similar disease duration. On the basis of previous reports, we defined UO-MSA as the appearance of initial symptoms between the ages of 55 and 65 years. We compared the clinical pictures of the two groups and assessed their histopathological features using quantitative and semi-quantitative methods. The investigated features included the severity of degeneration in the striatonigral (StrN) and olivopontocerebellar (OPC) systems, the numbers of neurons in the brainstem autonomic and spinal intermediolateral nuclei, and the density of α-synuclein-immunopositive inclusions in the putamen, inferior olivary nucleus, and ventrolateral medulla (VLM). Most patients with both LO-MSA and UO-MSA exhibited the MSA-olivopontocerebellar atrophy (OPCA) subtype (3/5 and 18/24, respectively). The median disease duration for LO-MSA patients was 5.5 years, which was comparable to that for patients in our cohort who had developed symptoms below 75 years of age. Pathologically, degeneration of the StrN and OPC systems in LO-MSA was less severe than that observed in UO-MSA. Quantitative analysis revealed better preservation of neuron numbers in the brainstem autonomic nuclei in LO-MSA than in UO-MSA, with a significantly higher number of serotonergic neurons in the VLM (p = 0.013). The density of α-synuclein-positive inclusions in the putamen was significantly lower in LO-MSA than in UO-MSA (p < 0.001). Neuronal degeneration in LO-MSA may progress more slowly than in UO-MSA. Accordingly, the prognosis of LO-MSA may not necessarily be less favorable than that of MSA generally, especially with appropriate care.