Chronic Progressive External Ophthalmoplegia (CPEO) and Cerebellar Signs

This is a 60-yo-woman who initially presented with imbalance and ophthalmoparesis. Initially, there was mild horizontal gaze limitation with mild gaze-evoked nystagmus and slow saccades, and over the years, gait ataxia and dysarthria (mainly a scanning quality to her speech) developed, and her ophthalmoparesis and slow saccades worsened (horizontally>vertically). She had undergone bilateral ptosis surgery several years prior. Extensive myasthenia and mitochondrial testing was unrevealing in addition to testing for the most common spinocerebellar ataxias. She was diagnosed with CPEO and cerebellar ataxia of unclear etiology.