Terunori Sano

We report the first autopsy‐proven case of colony‐stimulating factor 1 receptor (CSF1R)‐related leukoencephalopathy harboring the CSF1R mutation c.2320T>C (p.Cys774Arg). The patient, a man in his 40s, exhibited progressive neuropsychiatric symptoms with predominant frontal white matter lesions and corpus callosum atrophy. Neuropathological examination revealed frontal‐predominant demyelination with a relatively low number of axonal spheroids compared with typical cases, as well as the absence of intracranial calcifications. In addition, prominent cerebral amyloid angiopathy was observed despite an APOE ε3/ε3 genotype. These findings expand the clinicopathological spectrum of CSF1R ‐related leukoencephalopathy and highlight variability in pathological features associated with different CSF1R mutations.

Some patients with corticobasal degeneration (CBD) present with neuropsychiatric symptoms, including frontal lobe symptoms. However, stupor is rarely reported. Here, we report a case of acute restlessness at onset, which was clinically diagnosed as frontotemporal dementia (FTD) but was found to be CBD at autopsy. A 71‐year‐old woman with COVID‐19 presented to our hospital. At the age of 62, she had suddenly become restless and confused without any preceding motor or psychiatric symptoms. She was treated with psychotropic drugs but subsequently entered stupor and was admitted to a psychiatric hospital. Magnetic resonance imaging showed mild atrophy of the frontal lobe. Single‐photon emission computed tomography showed decreased blood flow in the frontal lobe, and the patient was clinically diagnosed with FTD. At the age of 71, she was transferred to our hospital from a psychiatric hospital for COVID‐19 treatment. Upon transfer to our hospital, the patient presented with akinetic mutism. The patient died of respiratory failure 10 days after the onset of COVID‐19. Immunostaining with AT8 and RD4 antibodies revealed astrocytic plaques, pretangles, coiled bodies, and threads, predominantly in the frontal lobes and basal ganglia. Other pathologies include accumulation of pTDP43 in the basal ganglia, thalamus, and frontal lobes. Argyrophilic grains were observed in the amygdala and the hippocampus, which corresponded to Saito stage 2. Other neurodegenerative proteins, such as amyloid β or α‐synuclein, were not observed. The patient was pathologically diagnosed with CBD. We present a rare autopsy case involving a patient with CBD who presented with acute psychiatric symptoms and stupor. The psychiatric symptoms were characterized by agitation and fear‐related behavior, which differ from the disinhibition and antisocial behavior typically associated with frontal lobe symptoms. Further autopsies are needed to examine the extent of tau pathology spread and accumulation to better understand the psychiatric symptoms of CBD.

Focal cortical dysplasia type II (FCDII) is a malformation of cortical development caused by somatic mutations in the mTOR signaling pathway. Two hallmark pathological cell types in FCDII, dysmorphic neurons (DNs) and balloon cells (BCs), arise as a result of somatic mutations in the mTOR signaling pathway and are implicated in the pathophysiology of drug-resistant epilepsy. However, how these somatic mutations reshape cell states within the human cortex remains poorly understood. Here, we integrate imaging-based spatial transcriptomics (iST), single-nucleus RNA sequencing, and proteomics of surgically resected FCDIIb tissue to define the transcriptional and proteomic profiles of DNs and BCs. Spatial mapping of iST data resolved transcriptional signatures in histologically validated DNs and BCs within FCDIIb sections. Integrative omics analysis further revealed that DNs show upregulation of PI3K-AKT-mTOR and p53-CROT metabolic programs accompanied by suppression of synaptic signaling, whereas BCs exhibit transcriptional signatures of reactive astrocytes with increased phagocytic and immune-like activity. These data delineate cell-type-specific consequences of somatic mTOR pathway mutations at single-cell resolution and reveal previously unrecognized metabolic and immunoregulatory mechanisms contributing to epileptogenesis in drug-resistant epilepsy. Our study establishes a spatial multi-omics framework for dissecting human cortical malformations and highlights potential therapeutic targets for drug-resistant epilepsy.

Background: Sequelae of the acute phase of coronavirus disease 2019 (COVID‐19), termed long COVID, are characterized by a variety of symptoms, including neurological manifestations. Diagnosing long COVID requires excluding alternative conditions that could explain the symptoms. The role of primary care physicians is considered essential in managing long COVID, particularly during the initial screening phase. Methods: This observational, retrospective, single‐center study was conducted at an outpatient clinic from 1 June 2021 to 31 December 2024. We confirmed final diagnoses for patients suspected of having long COVID and included those ultimately diagnosed with other conditions. Clinical data—including symptoms, demographic characteristics, results of clinical examinations, and final diagnoses—were collected. Results: In total, 44 patients were diagnosed with alternative conditions. Of these, 30 were classified as having post‐acute sequelae of SARS‐CoV‐2 mimic, and 14 patients (2.2% of those who believed they had long COVID and visited our clinic) were diagnosed with other diseases. The median age at the time of their clinic visit was 48 years (range, 42.5–61.5). Diagnoses included collagen diseases (5 patients, 35.7%) and central nervous system disorders (5 patients, 35.7%), among others. Weakness was the most common symptom. In contrast to long COVID, fatigue was less frequently reported in this group. Conclusions: We identified a variety of alternative diagnoses among patients suspected of having long COVID. We recommend that primary care physicians exercise caution when diagnosing long COVID, particularly in patients who do not report fatigue.

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.

Background: Little is known about the rare missense variants (RMVs) of APOE in East Asians, including the Japanese, and their association with Alzheimer's disease (AD) and lipid metabolism. Objective: To identify APOE RMVs in the Japanese population and investigate their association with AD and lipid metabolism, including low-density lipoprotein cholesterol levels. Methods: APOE RMVs were explored in the Niigata (NIG; 2589 subjects) and Tohoku (ToMMo; 3307 subjects) cohorts. A case-control study included 6261 AD cases and 16,331 controls, all of whom were aged 65 or older. Sanger sequencing, whole-exome sequencing, or a combination of both was performed on the NIG subjects. We used the genotype data from the ToMMo cohort. APOE RMV frequencies in the Japanese population were compared with various ethnic populations. Associations between APOE RMV genotypes, AD, and lipoproteins were examined. Results: Fourteen RMVs were identified (minor allele frequency 0.02–0.73%), with 10 unique to East Asians. Five previously reported RMVs, such as the Christchurch RMV, were absent in Japanese individuals. Two RMVs (rs140808909 and rs190853081), which exhibit complete linkage disequilibrium, were found to have protective effects against AD: p _Bonferroni = 4.28E-02, OR (95% CI) = 0.70 (0.54–0.92). No significant differences in cholesterol levels were observed between RMV carriers and non-carriers. Conclusions: The two APOE RMVs identified in Japanese individuals may have exhibited potential protective effects against AD. Further large-scale studies are needed to confirm these findings and to explore their roles in AD and lipid metabolism.

ADSS1 myopathy, previously known as adenylosuccinate synthetase‐like 1 (ADSSL1) myopathy, is an autosomal recessive muscle disease caused by variants in ADSS1 (adenylosuccinate synthase 1). ADSS1 myopathy is complicated by respiratory muscle weakness or cardiomyopathy as well as limb muscle weakness. We analyzed two siblings with ADSS1 myopathy, both harboring compound heterozygous pathogenic variants (c.781G>A/c.919delA) in ADSS1 and provided details of their phenotypes together with muscle imaging and autopsy findings. Although it was reported that ADSS1 myopathy usually began with lower limb muscle weakness, our cases showed early involvement of the cervical paraspinal muscle, triceps brachii muscle, flexor digitorum superficialis and profundus muscles, rectus abdominis muscle, gluteus maximus and medius muscles, and cardiomyopathy. While a previous study reported that the trunk and hip muscles were relatively spared, atrophy of paraspinal muscles, gluteus medius and maximus muscles, and adductor muscles were observed. Our two siblings allowed for long‐term follow‐up and will be useful reference cases. We evaluated the frequency of fibers with nemaline bodies in various autopsied muscles and found that the ratio of fibers with nemaline bodies was lower compared to other nemaline myopathies. Postmortem examination revealed, for the first time, nemaline bodies in the diaphragm and myocardium, associated with respiratory failure and cardiomyopathy.

Protein aggregation is a hallmark of neurodegenerative diseases and is also observed in the brains of elderly individuals without such conditions, suggesting that aging drives the accumulation of protein aggregates. However, the comprehensive understanding of age-dependent protein aggregates involved in brain aging remains unclear. Here, we investigated proteins that become sarkosyl-insoluble with age and identified hyaluronan and proteoglycan link protein 2 (HAPLN2), a hyaluronic acid-binding protein of the extracellular matrix at the nodes of Ranvier, as an age-dependent aggregating protein in mouse brains. Elevated hyaluronic acid levels and impaired microglial function reduced the clearance of HAPLN2, leading to its accumulation. HAPLN2 oligomers induced microglial inflammatory responses both in vitro and in vivo . Furthermore, age-associated HAPLN2 aggregation was also observed in the human cerebellum. These findings suggest that HAPLN2 aggregation results from age-related decline in brain homeostasis and may exacerbate the brain environment by activating microglia. This study provides new insights into the mechanisms underlying cerebellar aging and highlights the role of HAPLN2 in age-associated changes in the brain. Author Summary: To identify age-dependent protein aggregates unrelated to disease, we analyzed the sarkosyl-insoluble proteome of young and aged mouse brains. We discovered that hyaluronan and proteoglycan link protein 2 (HAPLN2), a hyaluronic acid-binding protein existing in the nodal extracellular matrix, accumulated with age. Age-dependently accumulated HAPLN2 formed large protein aggregates that cannot be solubilized by the anionic detergent sarkosyl or by hyaluronidase digestion. In addition, HAPLN2 formed irregularly shaped puncta that were mislocalized from the nodes of Ranvier in the cerebellar white matter of not only aged mice but also aged human brains. Oligomers of full-length HAPLN2 specifically induced microglial activation in vitro and in vivo . Our findings suggest that the accumulation of HAPLN2 aggregates is a new hallmark of brain aging and a possible factor contributing to brain inflammation.

Background: Sequelae of the acute phase of coronavirus disease-19, termed long COVID, are characterised by numerous indicators, including neurological symptoms. Functional neurological disorder (FND) can occur with or without various structural diseases. No previous study has examined the relationship between long COVID and FND, with positive signs for FND. This study confirmed positive signs of functional limb weakness (hereafter positive signs) in patients with long COVID.Methods: This was an observational, retrospective, single-centre study at an outpatient clinic conducted from 1 June 2021 to 31 May 2024. We collected patients’ clinical data, including positive signs. The primary outcome was the prevalence of positive signs. Patients with positive signs were followed up over 2 months, and subjective patient perceptions of symptomatic improvements and changes in positive signs were analysed.Results: Overall, 502 were diagnosed with long COVID, and 100 assessed patients had positive signs. Female sex, time of infection after 2022, comorbidity of psychiatric diseases, fatigue, headache and muscle weakness were statistically significant in patients with positive signs compared with those in patients without positive signs. 89 patients (41 with positive signs and 48 without positive signs) were followed up, and 28 (68.3%) with positive signs and 33 (68.8%) without positive signs reported improvements. Positive signs disappeared in patients with symptomatic improvements but not in patients without symptomatic improvements (p=0.0001).Conclusions: Positive signs were found in over one-third of patients (33.9%) who were investigated in this study. Some positive signs disappeared concurrently with their symptomatic improvement.