Pearls & Oy-sters: Deep Phenotyping of Abnormal Eye Movements Advances the Detection of Gerstmann-Sträussler-Scheinker Syndrome

Abstract

A 58-year-old previously healthy woman presents with three years of rapidly progressive ataxia, parkinsonism, dysautonomia, peripheral neuropathy, leg weakness, spasticity, hyperreflexia, and mild vertical-gaze palsy. She has a matrilineal family history of neurodegenerative diseases. She was initially postulated to have spinocerebellar ataxia or atypical parkinsonism with cerebellar features. But on closer inspection, her abnormal extraocular eye movements suggested rare mimicking disorders such as prion disease as part of the differential diagnosis, requiring further evaluation. This case highlights how deep phenotyping can open new diagnostic considerations, inform additional workup, and yield the precise diagnosis of Gerstmann-Sträussler-Scheinker syndrome (GSS).