Genetic Cause of Hybrid Lethality Observed in Reciprocal Interspecific Crosses between Nicotiana simulans and N. tabacum.

Hybrid lethality, a type of postzygotic reproductive isolation, is an obstacle to wide hybridization breeding. Here, we report the hybrid lethality that was observed in crosses between the cultivated tobacco, Nicotiana tabacum (section Nicotiana), and the wild tobacco species, Nicotiana simulans (section Suaveolentes). Reciprocal hybrid seedlings were inviable at 28 °C, and the lethality was characterized by browning of the hypocotyl and roots, suggesting that hybrid lethality is due to the interaction of nuclear genomes derived from each parental species, and not to a cytoplasmic effect. Hybrid lethality was temperature-sensitive and suppressed at 36 °C. However, when hybrid seedlings cultured at 36 °C were transferred to 28 °C, all of them showed hybrid lethality. After crossing between an N. tabacum monosomic line missing one copy of the Q chromosome and N. simulans, hybrid seedlings with or without the Q chromosome were inviable and viable, respectively. These results indicated that gene(s) on the Q chromosome are responsible for hybrid lethality and also suggested that N. simulans has the same allele at the Hybrid Lethality A1 (HLA1) locus responsible for hybrid lethality as other species in the section Suaveolentes. Haplotype analysis around the HLA1 locus suggested that there are at least six and two haplotypes containing Hla1-1 and hla1-2 alleles, respectively, in the section Suaveolentes.

Anti-N-methyl-D-aspartate receptor encephalitis with concurrent human herpes virus-6A deoxyribonucleic acid detection: An autopsy case.

We report an autopsy case of anti-N-methyl-D-aspartate (NMDA) receptor (NMDAR) encephalitis with concurrent human herpes virus-6 (HHV-6) A deoxyribonucleic acid (DNA) detection in cerebrospinal fluid (CSF). A 38-year-old previously healthy Japanese man presented with a generalized seizure. Brain magnetic resonance imaging (MRI) findings were unremarkable, but CSF revealed pleocytosis. On Day 11, HHV-6 DNA was detected in CSF, and IgG antibodies against the NR1 subunit of the NMDAR (GluN1) were subsequently detected. Since HHV-6 encephalitis was initially suspected, the patient was treated with foscarnet and ganciclovir, but the HHV-6A copy number increased from 200 (Day 22) to 2000 copies/mL (Day 47), and the therapy was ineffective. As typical symptoms of anti-NMDAR encephalitis developed, we changed the patient's treatment to combat anti-NMDAR encephalitis. He was repeatedly treated with first-line immunotherapy, and GluN1 antibody titer decreased. He was not treated with second-line immunotherapy because of recurrent infections; he died on Day 310. Postmortem examinations did not show systemic tumors. Microscopic examination of the brain revealed only severe neuronal rarefaction in the hippocampal cornu ammonis (CA) 3-4 areas with gliosis. Early initiation of aggressive immunotherapy may be required in a refractory case of anti-NMDAR encephalitis, even with HHV-6A DNA detection, because the significance of this concurrent detection in autoimmune encephalitis remains unclear.

Status epilepticus suspected autoimmune: Neuronal surface antibodies and main clinical features.

OBJECTIVES: Status epilepticus (SE) can be associated with neuronal surface antibodies (NS-Abs) but NS-Ab detection rate remains unknown in patients with SE of unclear etiology at symptom presentation but suspected of having an autoimmune etiology (SE suspected autoimmune). We aimed to determine the NS-Ab detection rate and the clinical features that predict the presence of NS-Abs in patients with SE suspected autoimmune. METHODS: We retrospectively reviewed the clinical information of 137 patients with SE suspected autoimmune who underwent testing for NS-Abs between January 2007 and September 2020. NS-Abs were examined in both serum and cerebrospinal fluid (CSF) obtained at symptom onset with established assays. We classified brain magnetic resonance imaging (MRI) findings into unremarkable, autoimmune limbic encephalitis (ALE) (bilateral abnormalities highly restricted to the medial temporal lobes), ALE-Plus (ALE pattern and additional extramedial temporal lobe abnormalities), multifocal cortico-subcortical (MCS), or other pattern. We compared the clinical features between patients with and without NS-Abs. RESULTS: Forty-four patients (32.1%) had NS-Abs, including 35 N-methyl-d-aspartate receptor (NMDAR) (one with concurrent γ-aminobutyric acid B receptor [GABAbR] and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor [AMPAR]), 5 γ-aminobutyric acid A receptor (GABAaR), 2 leucine-rich glioma-inactivated 1(LGI1), 1 GABAbR, and 1 unknown antigens. Compared with NS-Ab-negative patients, NS-Ab-positive patients were more likely to have a preceding headache (56.8% vs 26.7%), preceding psychobehavioral or memory alterations (65.9% vs 20.4%), involuntary movements (79.5% vs 16.1%), CSF pleocytosis (81.8% vs 62.0%), elevated immunoglobulin G (IgG) index (45.2% vs 15.6%), oligoclonal bands (51.5% vs 9.5%), tumor (47.7% vs 8.6%), and higher APE2 score (median of 9 vs 7), and they were less likely to have an ALE-Plus pattern (2.3% vs 23.7%). However, preceding fever and ALE or MCS pattern were not different between the two groups of patients. SIGNIFICANCE: When an autoimmune etiology was suspected, there was a relatively high likelihood (one of three patients) of identifying NS-Abs. Some clinical features (preceding symptoms, inflammatory CSF) predict a higher likelihood of finding NS-Ab positivity, but the ALE-Plus MRI pattern is more likely suggestive of NS-Ab negativity.

Neuroimaging pattern and pathophysiology of cerebellar stroke-like lesions in MELAS with m.3243A>G mutation: a case report.

BACKGROUND: Stroke-like episodes (SLEs) in mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) with m.3243A > G mutation usually develop in the cerebral cortex. Few reports have documented SLEs in the cerebellum. The clinical neuroimaging features of cerebellar SLEs have not been fully investigated. We report distinctive features of cerebellar stroke-like lesions (SLLs) in a case of MELAS with m.3243A > G mutation. CASE PRESENTATION: A 47-year-old Japanese man with type-2 diabetes presented to our hospital with acute onset of aphasia. A brain MRI obtained on admission (day 1) showed increased diffusion-weighted imaging (DWI)/fluid-attenuated inversion recovery (FLAIR) signal in the left anterolateral temporal lobe, which subsequently spread along the cortex posteriorly accompanied by a new lesion in the right anterior temporal lobe. The patient was initially treated with acyclovir and subsequently with immunotherapy. However, on day 45, cerebellar ataxia developed. The brain MRI showed extensive increased DWI/FLAIR signals in the cerebellum along the folia without involvement of deep cerebellar nucleus or cerebellar peduncle; SLLs were incongruent with a vascular territory, similarly to classic cerebral SLLs. Apparent diffusion coefficient (ADC) map did not show reduction in ADC values in the affected folia. Genomic analysis revealed m.3243A > G mutation (heteroplasmy in leukocytes, 17%), confirming the diagnosis of MELAS. After the treatment with taurine (12,000 mg/day), L-arginine (12,000 mg/day), vitamin B1 (100 mg/day), and carnitine (3000 mg/day), the patient became able to follow simple commands, and he was transferred to a rehabilitation center on day 146. The follow-up MRI showed diffuse brain atrophy, including the cerebellum. CONCLUSIONS: SLLs develop in the cerebellum in MELAS with m.3243A > G mutation. The neuroimaging similarities to cerebral SLLs suggest the presence of the common pathophysiological mechanisms underlying both SLEs, which include microangiopathy and increased susceptibility of the cortex to metabolic derangements.

Nicotiana suaveolens accessions with different ploidy levels exhibit different reproductive isolation mechanisms in interspecific crosses with Nicotiana tabacum.

Reproductive isolation, including prezygotic and postzygotic barriers, is a mechanism that separates species. Many species in the Nicotiana section Suaveolentes exhibit reproductive isolation in crosses with Nicotiana tabacum. In this study, we investigated whether the chromosome numbers and ploidy levels of eight Nicotiana suaveolens accessions are related to the reproductive isolation after crosses with N. tabacum by flow cytometry and chromosome analyses. Additionally, the internal transcribed spacer (ITS) regions of the eight N. suaveolens accessions were sequenced and compared with the previously reported sequences of 22 Suaveolentes species to elucidate the phylogenetic relationships in the section Suaveolentes. We revealed that four N. suaveolens accessions comprised 64 chromosomes, while the other four accessions carried 32 chromosomes. Depending on the ploidy levels of N. suaveolens, several types of reproductive isolation were observed after crosses with N. tabacum, including decreases in the number of capsules and the germination rates of hybrid seeds, as well as hybrid lethality and abscission of enlarged ovaries at 12-17 days after pollination. A phylogenetic analysis involving ITS sequences divided the eight N. suaveolens accessions into three distinct clades. Based on the results, we confirmed that N. suaveolens accessions vary regarding ploidy levels and reproductive isolation mechanisms in crosses with N. tabacum. These accessions will be very useful for revealing and characterizing the reproductive isolation mechanisms in interspecific crosses and their relationships with ploidy levels.

Overlapping demyelinating syndromes and anti­N-methyl-D-aspartate receptor encephalitis.

OBJECTIVE: To report the clinical, radiological, and immunological association of demyelinating disorders with anti­Nmethyl- D-aspartate receptor (NMDAR) encephalitis. METHODS: Clinical and radiological analysis was done of a cohort of 691 patients with anti-NMDAR encephalitis. Determination of antibodies to NMDAR, aquaporin-4 (AQP4), and myelin oligodendrocyte glycoprotein (MOG) was performed using brain immunohistochemistry and cell-based assays. RESULTS: Twenty-three of 691 patients with anti-NMDAR encephalitis had prominent magnetic resonance imaging (MRI) and/or clinical features of demyelination. Group 1 included 12 patients in whom anti-NMDAR encephalitis was preceded or followed by independent episodes of neuromyelitis optica (NMO) spectrum disorder (5 cases, 4 anti-AQP4 positive) or brainstem or multifocal demyelinating syndromes (7 cases, all anti-MOG positive). Group 2 included 11 patients in whom anti-NMDAR encephalitis occurred simultaneously with MRI and symptoms compatible with demyelination (5 AQ4 positive, 2 MOG positive). Group 3 (136 controls) included 50 randomly selected patients with typical anti-NMDAR encephalitis, 56 with NMO, and 30 with multiple sclerosis; NMDAR antibodies were detected only in the 50 anti-NMDAR patients, MOG antibodies in 3 of 50 anti-NMDAR and 1 of 56 NMO patients, and AQP4 antibodies in 48 of 56 NMO and 1 of 50 anti-NMDAR patients (p<0.0001 for all comparisons with Groups 1 and 2). Most patients improved with immunotherapy, but compared with anti-NMDAR encephalitis the demyelinating episodes required more intensive therapy and resulted in more residual deficits. Only 1 of 23 NMDAR patients with signs of demyelination had ovarian teratoma compared with 18 of 50 anti-NMDAR controls (p50.011). INTERPRETATION: Patients with anti-NMDAR encephalitis may develop concurrent or separate episodes of demyelinating disorders, and conversely patients with NMO or demyelinating disorders with atypical symptoms (eg, dyskinesias, psychosis) may have anti-NMDAR encephalitis.

Biphasic neurovascular changes in prolonged migraine aura in familial hemiplegic migraine type 2.

OBJECTIVE: To report biphasic changes in cerebral blood flow (CBF) in the acute phase of hemiplegic migraine with prolonged aura (HMPA), in which aura symptoms lasted longer than 24 h, in three patients with familial hemiplegic migraine (FHM) carrying a p.H916L mutation in ATP1A2 gene. METHODS: We assessed neurovascular changes with time in the affected cerebral hemisphere corresponding to aura symptoms during the acute phase of HMPA. Arterial spin labelling MRI, SPECT for CBF measurement and EEG in three attacks, in one attack FDG-PET measurement for cerebral metabolism was performed. We evaluated CBF at different phases of aura symptoms in 11 attacks of HMPA. RESULTS: In two attacks, we found biphasic CBF changes beginning with hypoperfusion followed by persistent hyperperfusion. FDG-PET revealed increased cerebral glucose metabolism in the regions corresponding to hyperperfusion on day 4 when aura symptoms still persisted. In four attacks, Z-score-based CBF mapping revealed multifocal hypoperfusion in the early phase. Hypoperfusion in our study was seen within 19 h of the onset of the symptoms in five of seven attacks, while hyperperfusion was seen 18 h or later in eight of nine attacks. EEG showed attenuated alpha activity without paroxysmal discharge. CONCLUSIONS: This is the first report showing biphasic CBF changes during the prolonged aura of FHM2. This study suggested that the results of cross-sectional CBF studies should be interpreted carefully. Initial multifocal hypoperfusion is likely due to functional depression of multifocal origin in the affected hemisphere, but the mechanism of persistent hyperperfusion requires further investigation.

Septal penetration in iodine-123 metaiodobenzylguanidine cardiac sympathetic imaging using a medium-energy collimator.

BACKGROUND: Septal penetration of high-energy photons affects the estimation of the heart-to-mediastinum (H/M) ratio in cardiac (123)I-metaiodobenzylguanidine (MIBG) imaging, and the use of a medium-energy (ME) collimator has been shown to improve quantitative accuracy. We investigated the effect of septal penetration on the estimation of H/M ratios using an ME collimator. METHODS AND RESULTS: Point sources of (99m)Tc and (123)I were imaged using various collimators, which indicated that the effect of high-energy photons with the ME collimator was relatively small but larger than that with the high-energy (HE) collimator. Four hours after (123)I-MIBG injection, 20 patients underwent planar anterior chest imaging by different methods in succession. The ME collimator gave lower H/M ratios (mean 2.52) than the HE collimator (2.57), indicating influence of septal penetration in the ME collimator; however, the difference was limited. Although narrowing the energy window from 20% (2.51) to 15% (2.54) increased the H/M ratios in imaging with the ME collimator, the difference was quite limited. CONCLUSIONS: Septal penetration affects the estimation of the H/M ratios using an ME collimator; however, this influence is small and would not have clinical significance.

An improved method for estimating the heart-to-mediastinum ratio from cardiac sympathetic nerve imaging with low-energy high-resolution collimators.

BACKGROUND: Septal penetration causes underestimation of the heart-to-mediastinum (H/M) ratio in cardiac (123)I-metaiodobenzylguanidine (MIBG) imaging with a low-energy high-resolution (LEHR) collimator. We aimed to improve the method of estimating the H/M ratios using the LEHR collimator. METHODS AND RESULTS: 4 hours after (123)I-MIBG injection, 40 patients were imaged successively with the medium-energy (ME) and LEHR collimators using gamma cameras having 3/8-inch crystals. Severe underestimation of the H/M ratios was observed with the LEHR collimator when compared to the ME collimator. Narrowing the energy window width did not reduce the underestimation. Application of (123)I-dual-window (IDW) correction using a narrow or wide subwindow reduced the underestimation substantially but not entirely. The H/M ratios estimated from the LEHR images with or without IDW correction were corrected based on their correlations with the ratios estimated from the ME images. This empiric correction removed systematic underestimation, and residual errors were reduced when the H/M ratios after IDW correction were converted using the empiric equation. The conversion equation was successfully applied to the correction of the H/M ratios determined in another 40 patients using a 5/8-inch crystal. CONCLUSIONS: In estimating the H/M ratios using an LEHR collimator, empiric correction combined with IDW correction improves concordance with ME-based values in comparison with empiric correction alone.

Elevation in body temperature may increase susceptibility to cortical spreading depression in a rat model.

One characteristic of migraine is recurrent headache attacks, which are known to be induced by changes in climatic variables such as atmospheric pressure, humidity, and outside temperature. However, the relationship between temperature changes and migraine remains unclear. Therefore, we investigated the relationship between body temperature changes and cortical spreading depression (CSD) using KCl-induced rat models of CSD. We initially induced CSD under controlled conditions at a room temperature of 28°C on an operating table maintained at 37°C. Subsequently, we controlled the operating table temperature to induce a second round of CSD under conditions of either a 10 ± 1% increase or decrease in body temperature. We ensured 1 h rest period between the first and second inductions of CSD. The results indicated that the number of CSDs significantly increased after body temperature elevation (before, 8.8 ± 1.2 times vs. after, 13.4 ± 1.3 times; p = 0.0003). The mean percentage change in cerebral blood flow decreased after body temperature increased (before, 33.1 ± 2.4% vs. after, 18.2 ± 1.4%; p = 0.006). There were no significant changes in CSD after body temperature decreased. The susceptibility of the cortex to CSD may increase under conditions of elevated body temperature.

H-intensity scale score to estimate CSF GluN1 antibody titers with one-time immunostaining using a commercial assay.

Introduction: Anti-NMDA receptor encephalitis is an autoimmune disorder caused by autoantibodies (abs) against the conformational epitope on GluN1 subunits. GluN1-abs have been determined with cell-based assay (CBA) co-expressing GluN1/GluN2 subunits. However, commercial fixed CBA expressing only GluN1 subunit has increasingly been used in clinical practice. The ab titers can be determined with serial dilutions, but its clinical significance remains unclear. We aimed to develop an H-intensity scale (HIS) score to estimate GluN1-ab titers in cerebrospinal fluid (CSF) with one-time immunostaining using both commercial CBA and immunohistochemistry and report its usefulness. "H" is the initial of a patient with high CSF GluN1-ab titers (1:2,048). Methods: We first determined the reliability of CBA in 370 patients with suspected autoimmune encephalitis by comparing the results between commercial CBA and established assay in Dalmau's Lab. Then, we made positive control panels using the patient H's CSF diluted in a fourfold serial dilution method (1:2, 1:8, 1:32, 1:128, 1:512, and 1:2,048). Based on the panels, we scored the intensity of ab reactivity of 79 GluN1-ab-positive patients' CSF (diluted at 1:2) on a scale from 0 to 6 (with ≥1 considered positive). To assess inter-assay reliability, we performed immunostaining twice in 21 patients' CSF. We investigated an association between the score of CSF obtained at diagnosis and the clinical/paraclinical features. Results: The sensitivity and specificity of CBA were 93.7% (95% CI: 86.0-97.3) and 98.6% (95% CI: 96.5-99.5), respectively. Linear regression analysis showed a good agreement between the scores of the first and second assays. Patients with a typical spectrum, need for mechanical ventilation support, autonomic symptoms/central hypoventilation, dyskinesias, speech dysfunction, decreased level of consciousness, preceding headache, ovarian teratoma, and CSF leukocyte count >20 cells/µL had a higher median HIS score than those without, but HIS score was not associated with sex, age at onset, or seizure. HIS score at diagnosis had a significant effect on 1-year functional status. Discussion: The severity of disease and four of the six core symptoms were associated with higher GluN1-ab titers in CSF at diagnosis, which may play a role in poor 1-year functional status. An incomplete phenotype can be attributed to low CSF GluN1-ab titers.

Very Long-Term Functional Outcomes and Dependency in Children With Anti-NMDA Receptor Encephalitis.

OBJECTIVES: To assess the daily function of children with anti-N-methyl-d-aspartate receptor encephalitis (NMDARe) after a minimal follow-up of 5 years. METHODS: Patients 18 years and younger by the time of disease onset, whose serum and CSF were studied in our center between 2013 and 2017, were included in the study. Patients' daily life function was assessed by their physicians using a 15-domain question format (Liverpool Outcome Score). RESULTS: Of 76 patients, 8 (11%) died and 68 were followed for a mean of 7.1 years (SD 1.5 years, range: 5.0-10.1). Three outcome patterns were identified: full recovery (50; 73%); behavioral and school/working deficits (12; 18%); and multidomain deficits (6; 9%) involving self-care ability, behavioral-cognitive impairment, and seizures. Younger age of disease onset was significantly associated with multidomain deficits (OR 1.6, 95% CI 1.02-2.4, p = 0.04), particularly in children younger than 6 years, among whom 8 of 23 (35%) remained sociofamiliar dependent. DISCUSSION: After a minimal follow-up of 5 years, most children with NMDARe had substantial or full functional recovery, but approximately one-fifth remained with behavioral and school/working deficits. The younger the patient at disease onset, the more probable it was to remain with multidomain deficits and dependent on sociofamiliar support.

Treatment of cryptogenic new-onset refractory status epilepticus (C-NORSE) with tocilizumab: A case report.

A 35-year-old woman with no prior history of epilepsy developed status epilepticus (SE), which was highly resistant to multiple antiseizure medications and sedatives. The etiology of SE was not identified despite extensive investigation, and the patient was diagnosed with cryptogenic new-onset refractory status epilepticus (C-NORSE). Although first-line immunotherapies such as high-dose corticosteroids and plasma exchange were ineffective, the patient manifested a resolution of SE after the administration of tocilizumab, which inhibits interleukin-6. Non-antibody-mediated inflammation has been hypothesized to be a probable pathophysiology of C-NORSE in recent studies, and tocilizumab may be a plausible second-line treatment.

Investigation of IgG4-positive cell infiltration in biopsy specimens from cases of hypertrophic pachymeningitis.

This study was an immunohistological study of IgG4-positive cell infiltration in 6 cases of hypertrophic pachymeningitis excluding secondary hypertrophic pachymeningitis caused by infectious diseases such as aspergillosis. The cases included 5 males and 1 female, ranging in age from 36 to 82 years (mean, 55 years). A biopsy was performed in all of the cases for diagnostic purposes, revealing fibrous dural hyperplasia with nonspecific inflammatory cell infiltration histologically. Two of the 6 patients had been treated with steroids before the biopsy, which was taken for poor response to steroid treatment. In these two cases, some IgG-positive cell infiltration of the thickened dura was observed; however, most of the cells were IgG4-negative. In the remaining four cases, many IgG- and IgG4-positive cells infiltrated the thickened dura and the IgG4-positive/IgG-positive cell ratio exceeded 40%. One of these patients was finally diagnosed with IgG4-related sclerosing disease, since he was diagnosed subsequently with retroperitoneal fibrosis. There was no evidence of any other lesions associated with IgG4-related sclerosing disease, other than in the dura. It is not rare for IgG4-positive cells to appear in the dura in cases of hypertrophic pachymeningitis; however, no IgG4-related systemic disease is present in these cases. Hypertrophic pachymeningitis with IgG4-positive cells may have some kind of relation to other systemic autoimmune diseases.

Coupling of Cortical Hyperintense Signals and Increased Glucose Metabolism in a Case of Anti-GABAA Receptor Antibody-associated Encephalitis.

We herein report a case of anti-gamma aminobutyric acid type A receptor antibody-associated encephalitis (anti-GABAA-RE) with progressive aphasia and generalized tonic-clonic seizures. Cerebral magnetic resonance imaging (MRI) showed cortical brain lesions coupled with hypermetabolism on fluorodeoxyglucose-positron emission tomography. After two courses of methylprednisolone pulse therapy, improvements in neurological symptoms without sequelae and the total disappearance of MRI lesions were observed. Upon encountering patients with refractory status epilepticus, multifocal cerebral MRI lesions, and suspected autoimmune encephalitis, especially in cases with thymoma, it would be prudent to suspect anti-GABAA-RE and consider the evaluation of anti-GABAA receptor antibody and methylprednisolone pulse therapy.

Reversible Brain Atrophy in Cryptogenic New-onset Refractory Status Epilepticus.

Cryptogenic new-onset refractory status epilepticus (C-NORSE) is a neurologic emergency condition characterized by refractory status epilepticus (RSE) of unknown cause. Brain atrophy in a setting of C-NORSE is usually irreversible. A 33-year-old woman who was highly suspected of C-NORSE once showed mild frontotemporal atrophy on brain magnetic resonance imaging (MRI), but follow-up MRI revealed recovery of the brain atrophy. Her cognitive function also gradually improved, with a reduction in seizure frequency. Early initiation of intensive immunotherapy with anti-seizure medications may have minimized irreversible brain damage associated with RSE, resulting in a relatively good outcome.

Prevalence, Clinical Profiles, and Prognosis of Stiff-Person Syndrome in a Japanese Nationwide Survey.

BACKGROUND AND OBJECTIVES: To elucidate current epidemiologic, clinical, and immunologic profiles and treatments of stiff-person syndrome (SPS) in Japan. METHODS: A nationwide mail survey was conducted using an established method. Data processing sheets were sent to randomly selected departments of internal medicine, neurology, pediatrics, psychiatry, and neurosurgery in hospitals and clinics throughout Japan to identify patients with SPS who were seen between January 2015 and December 2017. RESULTS: Thirty cases were identified as glutamic acid decarboxylase 65 (GAD65)-positive SPS cases on the basis of detailed clinical data of 55 cases. Four patients had α1 subunit of glycine receptor (GlyR) antibodies, and 1 patient had both GAD65 and GlyR antibodies. The total estimated number of patients with GAD65-positive SPS was 140, and the estimated prevalence was 0.11 per 100,000 population. The median age at onset was 51 years (range, 26-83 years), and 23 (76%) were female. Of these, 70% had classic SPS, and 30% had stiff-limb syndrome. The median time from symptom onset to diagnosis was significantly longer in the high-titer GAD65 antibody group than in the low-titer group (13 months vs 2.5 months, p = 0.01). The median modified Rankin Scale (mRS) at baseline was 4, and the median mRS at the last follow-up was 2. Among the 29 GAD65-positive patients with ≥1 year follow-up, 7 received only symptomatic treatment, 9 underwent immunotherapy without long-term immunotherapy, and 13 received long-term immunotherapy such as oral prednisolone. The coexistence of type 1 diabetes mellitus and the lack of long-term immunotherapy were independent risk factors for poor outcome (mRS ≥3) in the GAD65-positive patients (odds ratio, 15.0; 95% CI 2.6-131.6; p = 0.001; odds ratio, 19.8; 95% CI 3.2-191.5; p = 0.001, respectively). DISCUSSION: This study provides the current epidemiologic and clinical status of SPS in Japan. The symptom onset to the diagnosis of SPS was longer in patients with high-titer GAD65 antibodies than in those with low-titer GAD65 antibodies. The outcome of patients with SPS was generally favorable, but more aggressive immunotherapies are necessary for GAD65-positive patients with SPS.