Postmortem cerebellar and brainstem alterations in episodic ataxia type 1 and 2: Expanding the clinicopathological spectrum.

Abstract

Background: Episodic ataxias (EAs) are rare autosomal-dominant channelopathies presenting with recurrent attacks of ataxia and variable neurological features. While MRI studies suggest mild cerebellar atrophy in some patients, detailed neuropathological descriptions are lacking.

Materials and methods: We examined postmortem brains and spinal cords from two genetically confirmed patients: EA1 (KCNA1 Val174Phe mutation) and EA2 (CACNA1A A253Y mutation). Routine histology and immunohistochemistry were performed.

Results: In EA1, the cerebellar vermis and hemispheres showed narrowing of the folia, segmental Purkinje cell loss, Bergmann gliosis, and scattered torpedoes. The dentate nucleus contained focal lipofuscin-laden macrophages and Rosenthal fibers. Concurrently, α-synuclein pathology (Braak stage 3) was also present, along with sparse age-related tau tangles and minimal vascular amyloid. In EA2, only focal Purkinje cell loss was detected, but novel p62-positive axonal and dendritic inclusions were observed in the cerebellar cortex and inferior olive. No additional α-synuclein, tau, or amyloid pathology was found. A concurrent glioblastoma was identified as the immediate cause of death.

Conclusion: These are the first detailed autopsy reports of EA1 and EA2. Both revealed cerebellar pathology, with EA1 showing more pronounced Purkinje cell degeneration, while EA2 demonstrated previously undescribed p62-positive inclusions. These findings expand the clinicopathological spectrum of EAs and highlight the value of postmortem studies in elucidating underlying disease mechanisms.