Takashi Ando

Multiple system atrophy is a fatal, sporadic α-synucleinopathy characterized by glial cytoplasmic inclusions in oligodendrocytes. No causative gene for multiple system atrophy has been identified to date. Whole-genome sequencing was performed for a patient with familial multiple system atrophy, in whom an AGG repeat expansion in BIN1 was identified. Based on this finding, we screened for the AGG repeat expansion in BIN1 in a cohort comprising 224 patients with clinically diagnosed multiple system atrophy, 67 patients with pathologically confirmed multiple system atrophy, and control groups including 574 blood samples and 65 brain samples from neurologically healthy individuals. The pathological analysis was performed for four cases with the repeat expansion and five cases without the repeat expansion. The biochemical analysis was performed for nine control subjects, ten cases without the repeat expansion, and eight cases with the repeat expansion. Long-read sequencing identified an AGG repeat expansion in the first intron of BIN1 in the proband. Patients with multiple system atrophy carried a higher frequency of repeat expansions exceeding 80 repeats in the pathological multiple system atrophy group compared to the brain control group (frequency: 13.4% vs. 0%; odds ratio: infinity; 95% confidence interval [CI], 2.1 to infinity; P = 0.003, Fisher’s exact test). In contrast, the difference of frequency did not reach statistical significance in the clinical multiple system atrophy group compared to the blood control group (frequency: 4.5% vs 2.4%; odds ratio: 1.87; 95% CI, 0.8 to 4.5; P = 0.16, Fisher’s exact test). Neuropathological analysis revealed BIN1-positive glial cytoplasmic inclusions more frequently in the brains of patients with repeat expansions. In immunoblot analysis, insoluble BIN1 were increased in the brains of multiple system atrophy irrespective of repeat status. Our findings indicate that the AGG repeat expansion in BIN1 and BIN1 protein aggregation plays an important role in the pathogenesis of multiple system atrophy.

Background The purpose of this study was to clarify the usefulness of the ‘hot cross bun’ sign (HCBS) as a diagnostic imaging marker in a large cohort of patients with multiple system atrophy (MSA) and spinocerebellar ataxia (SCA). Methods This multicentre study included 97 patients with neuropathologically confirmed MSA, and 105 patients with genetically confirmed SCA. Neuroimaging features, including HCBS and middle cerebellar peduncle (MCP) hyperintensities, were assessed. HCBS was graded from 0 to 2: 0, none; 1, only a vertical hyperintense line; and 2, a cruciform hyperintense line. The neuropathological correlates of HCBS were evaluated in 15 patients with MSA with ≤3 months between MRI and autopsy. Results In patients with a disease duration Conclusions Grade 1 or 2 HCBS is a highly sensitive finding in patients with MSA-C, and the observation of grade 2 HCBS within 3 years of motor symptom onset has excellent specificity for discriminating MSA-C from SCA, especially when accompanied by MCP hyperintensities.

Multiple system atrophy (MSA) is an adult‐onset neurodegenerative disorder that presents with variable combinations of autonomic dysfunction, cerebellar ataxia, parkinsonism, and pyramidal signs. The inferior olivary nucleus is targeted in MSA, with a phenotype of olivopontocerebellar atrophy in particular, and involvement of the olivocerebellar tract is well known. However, degeneration of the olivospinal tract has not been studied in MSA. We examined 97 spinal cords from consecutively autopsied patients with MSA. Myelin staining revealed that 22 cords (22.7%) had small, bilateral, triangular‐shaped tract degeneration in the boundary of the anterior and lateral funiculi, which appeared continuously from C1 to C5. The anatomical pathway of the degenerated tract was consistent with the description of the olivospinal tract provided by Helweg in 1888. The MSA patients showing degeneration of this tract were younger at disease onset (average: 56.4 ± 8.7 years, range: 42–74), and had longer disease duration (average: 10.1 ± 4.8 years, range: 2–25) and more severe olivopontocerebellar changes compared to other MSA patients. Quantitative analyses revealed that patients with olivospinal tract degeneration had a lower neuronal density in the inferior olivary nucleus compared to other patients. Microglial density in this tract was negatively correlated with the neuronal density in the inferior olivary nucleus. The densities of glial cytoplasmic inclusions in the inferior olivary nucleus and in the olivospinal tract were strongly correlated with each other. Neurologically healthy controls (n = 22) and disease controls with Lewy body disease (n = 30), amyotrophic lateral sclerosis (n = 30), and progressive supranuclear palsy (n = 30) did not present the olivospinal tract degeneration. Our results indicate an impairment of the neural connection between the inferior olivary nucleus and the spinal cord in MSA patients, which may develop in a descending manner.

The neuropathological background of parkinsonism includes various neurodegenerative disorders, including Lewy body disease (LBD), multiple system atrophy (MSA), progressive supranuclear palsy (PSP), and corticobasal degeneration (CBD). The pathological diagnostic procedure begins by assessing the macroscopic findings to evaluate the degenerative lesions in brains with the naked eye. Usually, degenerative lesions show variable atrophy and brownish discoloration in accordance with disease-specific profiles. These macroscopic appearances support neuropathologists in identifying the relevant regions for microscopic examination. The neuropathological diagnosis of parkinsonism is based on regional distribution and fundamental proteinopathies in neurons and glia cells. LBD and MSA are synucleinopathies, and PSP and CBD are tauopathies. Among them, glial-predominant proteinopathy (MSA, PSP, and CBD) may play a significant role in volume reduction. Therefore, macroscopic inspection provides the appropriate direction for assessment. The disease duration, the severity of lesions, and mixed pathologies make the validation of macroscopic observations more complicated. In this review, we outline the macroscopic diagnostic clues in LBD, MSA, PSP, and CBD that could help with pathological refinement.

Neurolymphomatosis is a neurological manifestation of lymphoma that involves the cranial or spinal peripheral nerves, nerve roots, and plexus with direct invasion of neoplastic cells. Neurolymphomatosis is rare among patients with low‐grade lymphoma. We report an autopsied case of neurolymphomatosis that arose from follicular lymphoma. A 49‐year‐old woman who presented with pain of her neck and shoulder and numbness of her chin. Computed tomography revealed enlarged lymph nodes in her whole body, and biopsy from the axillary lymph node revealed grade 2 follicular lymphoma. Although the patient underwent chemotherapy, she gradually developed muscle weakness in the upper limbs and sensory disturbances of the trunk and limbs. ¹⁸F‐fluorodeoxyglucose positron emission tomography (FDG‐PET) revealed increased tracer uptake of the cervical nerve roots. Repeated FDG‐PET after additional therapy revealed progression of disease within the nerve roots and brachial plexus, whereas gadolinium‐contrast magnetic resonance imaging (MRI) showed weak enhancement of the cervical nerve roots without formation of mass lesions. She died after a total disease duration of 12 months. Postmortem observations revealed invasion of lymphoma cells into the cervical nerve roots, dorsal root ganglia, and subarachnoid spaces of the spinal cord. Neurolymphomatosis was prominent at the segments of C6–Th2. Combined loss of axons and myelin sheaths was observed in the cervical nerve roots and posterior columns. Lymphoma cells also invaded the cranial nerves. The subarachnoid and perivascular spaces of the brain demonstrated focal invasion of the lymphoma. Mass lesions were not observed in the central nervous system. The lymphoma cells did not show histological transformation to higher grades, and the density of the centroblasts remained at grade 2. Our report clarifies that low‐grade follicular lymphoma can manifest as neurolymphomatosis and central nervous system invasion in the absence of transformation toward higher histological grades. FDG‐PET may be more sensitive to non‐mass‐forming lesions, including neurolymphomatosis, than gadolinium‐contrast MRI.

A 57-year-old man presented with difficulty speaking and walking along with increased daytime somnolence. His symptoms fluctuated throughout the day but never completely disappeared. A neurological examination revealed mild dysarthria, limb weakness, and staggering gait. Polysomnography showed rapid eye movement (REM) sleep excess (55.0%). Multiple sleep latency tests revealed a mean sleep latency of zero minutes with sleep-onset REM periods in all naps. The Orexin-A concentration in the cerebrospinal fluid was low (50.8 pg/mL). Human Leukocyte Antigen testing demonstrated DQB1*0602 positivity. His neurological symptoms were relieved by clomipramine. Thus, he was diagnosed with late-onset narcolepsy type 1 with status cataplecticus.

The hot cross bun (HCB) sign encompasses a cross‐shaped hyperintensity area in the pons on axial T2‐weighted magnetic resonance imaging (MRI). The HCB sign is characteristic of multiple system atrophy (MSA) and has occasionally been observed in other neurological disorders. Here, we report an autopsied case of corticobasal degeneration (CBD) that showed the HCB sign. A female patient presented with progressive gait disturbance and cognitive impairment at the age of 60 years. A neurological examination revealed dysarthria, muscle rigidity of the limbs, akinesia, truncal ataxia, urinary incontinence, and dementia. The HCB sign was observed on a brain MRI at the age of 65 years, and a clinical diagnosis of possible MSA was made. She died of pneumonia at the age of 67 years. A postmortem observation, provided neuropathological findings characteristic of CBD, including the presence of astrocytic plaques, pretangles, neuropil threads, and ballooned neurons in association with four‐repeat‐tau aggregation. Interestingly, the pons displayed severe neuronal loss and astrogliosis that were prominent in the pontine and raphe nuclei. Myelin sheath depletion was prominent in the transverse fibers of the pontine base and the myelinated fibers of the pontine tegmentum in contrast to relative sparing of the pontine corticospinal tract and medial lemniscus. The cerebellar dentate nucleus exhibited neuronal loss and grumose degeneration. Western blot analysis of sarkosyl‐insoluble fractions from brain tissue lysates using an anti‐phosphorylated tau antibody identified immunoreactive signal bands in approximately 37–40, 43, 64, and 68 kDa, consistent with CBD. Genetic analysis did not reveal any known pathogenic mutations in the microtubule‐associated protein tau gene (MAPT). Our case was characterized by the HCB sign and concordant neuropathological changes in the pons. CBD should be considered an underlying pathology of the HCB sign, even though the pontocerebellar changes would be unusual in CBD cases.

The striatonigral and olivopontocerebellar systems are known to be vulnerable in multiple system atrophy (MSA), showing neuronal loss, astrogliosis, and alpha‐synuclein‐immunoreactive inclusions. MSA patients who displayed abundant neuronal cytoplasmic inclusions (NCIs) in the regions other than the striatonigral or olivopontocerebellar system have occasionally been diagnosed with variants of MSA. In this study, we report clinical and pathologic findings of MSA patients characterized by prominent pathologic involvement of the hippocampus. We assessed 146 consecutively autopsied MSA patients. Semi‐quantitative analysis of anti‐alpha‐synuclein immunohistochemistry revealed that 12 of 146 patients (8.2%) had severe NCIs in two or more of the following areas: the hippocampal granule cells, cornu ammonis areas, parahippocampal gyrus, and amygdala. In contrast, the remaining 134 patients did not show severe NCIs in any of these regions. Patients with severe hippocampal involvement showed a higher representation of women (nine women/three men; Fisher's exact test, p = 0.0324), longer disease duration (13.1 ± 5.9 years; Mann–Whitney U‐test, p = 0.000157), higher prevalence of cognitive impairment (four patients; Fisher's exact test, p = 0.0222), and lower brain weight (1070.3 ± 168.6 g; Mann–Whitney U‐test, p = 0.00911) than other patients. The hippocampal granule cells and cornu ammonis area 1/subiculum almost always showed severe NCIs. The NCIs appeared to be ring‐shaped or neurofibrillary tangle‐like, fibrous configurations. Three of 12 patients also had dense, round‐shaped NCIs that were morphologically similar to pick bodies. The patients with Pick body‐like inclusions showed more severe atrophy of the medial temporal lobes and broader spreading of NCIs than those without. Immunohistochemistry for hyperphosphorylated tau and phosphorylated TDP‐43 revealed minimal aggregations in the hippocampus of the hippocampal MSA patients. Our observations suggest a pathological variant of MSA that is characterized by severe involvement of hippocampal neurons. This phenotype may reinforce the importance of neuronal alpha‐synucleinopathy in the pathogenesis of MSA.