Olivary hypertrophy improved by steroid treatment: Two case reports with unique presentations

Olivary hypertrophy (OH) is the secondary degeneration of the inferior olivary nucleus (ION). It is observed one month after the onset of a primary lesion within the dento-rubro-olivary pathway and is usually associated with oculopalatal tremors. Here, we report two unique cases with rare autoimmune diseases leading to OH development with progressive cerebellar ataxia, both of which improved with steroid treatment. The first patient was a 59-year-old man with slowly progressive dysarthria and ataxic gait without palatal tremor. Anti-N-methyl-d-aspartate (NMDA) receptor antibody was positive in the CSF, supporting a diagnosis of anti-NMDA receptor encephalitis. The second patient was a 56-year-old man who developed dysarthria, ataxia, gait disturbance, and palatal tremor. He was diagnosed with chronic lymphocytic inflammation with pontine perivascular enhancement responsive to steroids (CLIPPERS), based on presence of a punctate contrast-enhancing lesion in the middle cerebellar peduncle, pons, and cerebellum on magnetic resonance imaging (MRI). Brain MRI in both patients demonstrated high signal intensity regions in the bilateral IONs. Semi-quantitative volume analysis of MRI revealed significant reduction in ION volume after steroid treatment and accordingly cerebellar ataxia was improved in both cases. Clinical and radiological features of the two cases were unique, indicating potential novel etiologies in the pathophysiology of OH associated with cerebellar ataxia. [Display omitted] •Anti-NMDA receptor encephalitis or CLIPPERS can develop OH.•Some novel etiologies are probably associated with OH.•Primary inflammation within the IONs can lead to OH and cerebellar ataxia.•Palatal tremor secondary to brainstem lesions and cerebellar ataxia mediated by cerebellar lesions can mimic PAPT syndrome in combination.•OH due to immunological processes can be responsive to steroid therapy.•Steroid responsive inflammation, such as anti-NMDA receptor encephalitis or CLIPPERS, within the IONs can lead to OH and PAPT syndrome.