Opalski syndrome caused by vertebral artery compression of the lateral surface of the medulla oblongata.

A 55-year-old man presented with vertigo, nystagmus, and gait ataxia followed by left hemiparesis (Opalski syndrome). T2-weighted magnetic resonance imaging revealed vascular compression of the left lateral side of the medulla oblongata by the left vertebral artery. On diffusion tensor imaging, the level of fractional anisotropy (FA) in the left corticospinal fibers caudal to the pyramidal decussation was lower than that observed in the right corticospinal fibers. Opalski syndrome caused by vascular compression is very rare. This is the first reported case of Opalski syndrome that was imaged on FA.