Brainstem pathology in spasmodic dysphonia

Abstract

Spasmodic dysphonia (SD) is a primary focal dystonia of unknown pathophysiology, characterized by involuntary spasms in the laryngeal muscles during speech production. We examined two rare cases of postmortem brainstem tissue from SD patients compared to four controls. In the SD patients, small clusters of inflammation were found in the reticular formation surrounding solitary tract, spinal trigeminal, and ambigual nuclei, inferior olive, and pyramids. Mild neuronal degeneration and depigmentation were observed in the substantia nigra and locus coeruleus. No abnormal protein accumulations and no demyelination or axonal degeneration were found. These neuropathological findings may provide insights into the pathophysiology of SD.

Figure 1

Microphotographs of the brainstem regions in the controls and both SD Cases show normal cell morphology in the interstitial part of the solitary tract nucleus (SolI) (AI) and the spinal trigeminal nucleus (Sp5) (BI) (H&E stain); clusters of microglial/macrophage activation (arrows) in the reticular formation surrounding the SolI (AII) and Sp5 (BII) (CD68/KP1 immunostain); and mild neuronal degeneration and depigmentation in the substantial nigra, pars compacta (C) and the locus coeruleus (D) (H&E stain), respectively.