Periodic Alternating Nystagmus Due to Nodulus Stroke

This is a 70-year-old woman who experienced the acute onset of vertigo and imbalance. MRI demonstrated a diffusion-weighted imaging hyperintensity involving the nodulus (with corresponding ADC hypointensity) consistent with an acute stroke. On examination several weeks after the stroke, periodic alternating nystagmus (PAN) was apparent - e.g., there was spontaneous right-beating nystagmus for ~90 seconds which slowed down and then stopped (null period), and then reversed direction to left-beating nystagmus for ~90 seconds, and so on. Because the nodulus normally mediates the velocity storage mechanism (which prolongs and amplifies peripheral vestibular inputs), disinhibition of velocity storage may result in PAN. Baclofen is usually the most effective therapy for PAN. [[Number of Figures and legend for each: 1, Hyperintensity of the nodulus on MR diffusion-weighted imaging suggestive of acute stroke; Number of Videos and legend for each: 1, Patient with periodic alternating nystagmus following a nodulus stroke.]] See Figure 1, CLICK HERE: https://collections.lib.utah.edu/details?id=1284821