Spinocerebellar degeneration (SCD) is a neurodegenerative disorder characterized by cerebellar ataxia and other multisystem manifestations, such as Parkinsonism and pyramidal tract symptoms. No effective treatment is available for SCD. Approximately one-third of the cases of SCD are inherited, and the remaining two-third are sporadic, including multiple system atrophy. This article provides an overview of hereditary SCD, its clinical features, recent treatment advances, biomarkers, role of genomic medicine, and future treatment prospects.

Autoimmune cerebellar ataxia is a disease entity that affects the cerebellum and is induced by autoimmune mechanisms. The disease is classified into several etiologies, including gluten ataxia, anti-glutamate decarboxylase (GAD) ataxia, paraneoplastic cerebellar degeneration, primary autoimmune cerebellar ataxia and postinfectious cerebellar ataxia. The autoimmune response in the periphery cross-reacts with similar antigens in the cerebellum due to molecular mimicry. Breakdown of the blood‒brain barrier (BBB) could potentially explain the vulnerability of the cerebellum during the development of autoimmune cerebellar ataxia, as it gives rise to the entry of pathogenic autoantibodies or lymphocytes into the cerebellum. In this review, the maintenance of the BBB under normal conditions and the molecular basis of BBB disruption under pathological conditions are highlighted. Next, the pathomechanism of BBB breakdown in each subtype of autoimmune cerebellar ataxia is discussed. We recently identified glucose-regulated protein (GRP) 78 antibodies in paraneoplastic cerebellar degeneration and Lambert–Eaton myasthenic syndrome, and GRP78 antibodies induced by cross-reactivity with tumors can disrupt the BBB and penetrate anti-P/Q type voltage-gated calcium channel (VGCC) antibodies into the cerebellum, thus leading to cerebellar ataxia in this disease.

We investigated the changes in antibody titers after intravenous immunoglobulin (IVIg) administration in patients with neuromuscular diseases. Among patients who received IVIg from April 1, 2020, to August 31, 2022, we retrospectively evaluated 15 patients with antibody measurements before and after IVIg administration for any rise in the following antibody levels and examined the data for subsequent changes of false positive results to negative ones. The levels of anti SS-A, anti-thyroglobulin, anti-thyroid peroxidase, anti-glutamic acid decarboxylase, HBs, and HBc antibodies transiently increased after IVIg administration and showed false-positive results. However, levels of rheumatoid factor and anti-nuclear and antineutrophil cytoplasmic antibodies were not elevated. The false-positive results became negative after 3 months. Here, we report on the changes in antibody levels before and after IVIg administration and note that levels of hepatitis B virus-related antibodies and various autoantibodies transiently rise after IVIg administration.

A 58-year-old, right-handed man noticed difficulty in typing and speech. On day 3 after onset, the day of admission, he had frontal lobe dysfunction including verbal fluency impairment and impairment of recent memory, although he did not have apraxia or visual agnosia. Moreover, he had difficulty typing in romaji, especially words containing contracted or double consonant sounds, although he was able to do this before onset by visually checking the keyboard. He had mild dysgraphia. MRI showed an infarct in the genu and posterior limb of the left internal capsule. SPECT revealed low-uptake lesions in the left frontal lobe. In the present case, we consider that the subcortical infarction disrupted the network between the thalamus and frontal lobe, resulting in dystypia due to difficulty with recalling romaji spelling.

A 51-year-old man developed acute disturbances in consciousness and psychiatric symptoms one month prior to admission. He was referred and admitted to the Department of Psychiatry of our hospital and transferred to the neurology department because diffuse white matter lesions were found on his brain during MRI. ¹²³I-IMP-SPECT showed extensive cerebral hypoperfusion mainly in the frontal lobes. Anti-Tg, anti-TPO, and anti-NAE antibodies were positive. These findings led to a diagnosis of Hashimoto’s encephalopathy. The patient responded to steroid pulse therapy, high-dose steroid therapy, and intravenous immunoglobulin therapy, showing improvement in symptoms and imaging findings. Hashimoto’s encephalopathy often presents with MRI findings similar to those of limbic encephalitis, when the patient presents with acute consciousness disturbance and psychiatric symptoms. However, this case showed diffuse white matter lesions, which may be clinically important for the differential diagnosis.

A 74-year-old woman taking dulvalumab for lung adenocarcinoma developed muscle tonicity in the extremities and trunk. Painful paroxysmal muscle spasms with profuse sweating were frequently observed, and surface electromyography showed simultaneous contraction of the active and antagonist muscles. Blood tests were strongly positive for anti-amphiphysin antibodies, and stiff-person syndrome (SPS) was diagnosed. Intravenous immunoglobulin therapy and clonazepam were initiated, and the paroxysmal painful muscle spasms disappeared. As the primary tumor was under control, and the onset occurred approximately six weeks after the resumption of immune checkpoint inhibitors, we considered SPS to be an immune-related adverse event. Although extremely rare, it should be considered a neuromuscular disease that can occur in association with immune checkpoint inhibitors.

An 88-year-old woman with atrial fibrillation was admitted to our hospital due to the right hemiplegia and aphasia. MRA shows the left middle cerebral artery M2 occlusion. After intravenous rt-PA, her symptoms improved. She was diagnosed with cardioembolic stroke, and was treated with direct oral anticoagulation therapy. However, she had repeated stereotypical transient right hemiparesis a week after index stroke. Her symptoms were considered capsular warning syndrome (CWS). After cilostazol was administered, no further transient neurological deteriorations occurred. CWS can coexist with acute cardioembolic stroke, and cilostazol was effective.

A 71-year-old male who suffered from Hoehn and Yahr stage III Parkinson’s disease with bradykinesia, rigidity and a 5-6-Hz tremor at rest in the right extremities was admitted to our hospital due to the sudden onset of vertigo. Right cerebellar hemorrhage was confirmed by CT. The patient’s resting tremor in the right extremities disappeared immediately following the cerebellar hemorrhage. Six days later, MRI showed Wallerian degeneration in the cerebello-rubro-thalamic tract. Approximately 5 months later, a 2-3-Hz Holmes’ tremor gradually appeared in the right upper extremity. This tremor was improved by increasing L-dopa doses. Case reports of the disappearance of Parkinson’s resting tremor and subsequent emergence of Holmes’ tremor due to cerebellar lesion are rare. Furthermore, the Wallerian degeneration of the cerebello-rubro-thalamic tract identified on MRI between tremors of the different frequencies is very rare. We hypothesize that the cause of the tremor frequency change was simultaneous damage to the nigro-striatal network and the cerebello-thalamo-cerebral network.

A 71-year-old man with hypertension and diabetes mellitus presented to our hospital because he felt lightheaded. Diffusion-weighted images (DWI) on brain MRI showed high signal lesions in the left cerebellar hemisphere and the right pons. The diagnosis of cerebellar infarction was made, but he refused treatment. One month later, he came to our hospital because his body leaned to the left. Neurological examination revealed dysarthria and cerebellar truncal ataxia. An electrocardiogram showed atrial fibrillation. DWI on brain MRI showed high signal lesions in the bilateral cerebellar hemispheres and middle cerebellar peduncles (MCP). Dabigatran 300 ‍mg/day was administered for cardiogenic cerebral embolism. On the 12th day of onset, he was transferred to a rehabilitation hospital. At 72 years old, T₂*-weighted images on brain MRI showed hot cross bun sign (HCBs) in the pons. We considered that HCBs were caused by antegrade or retrograde degeneration (or both) of pontine infarcts and bilateral MCP infarcts in the pontine cerebellar tract. It seemed preferable to use T₂*-weighted images or proton density-weighted images rather than T₂-weighted images to detect HCBs. When HCBs is detected, it should be noted that HCBs can be caused by bilateral MCP infarcts in addition to multiple system atrophy.