Downbeat Nystagmus and Convergence Spasm

This is a 60-yo-woman with vertical oscillopsia related to her downbeat nystagmus, and diplopia related to an intermittent esotropia. When the esotropia was present, with versions there were bilateral abduction deficits. With ductions and the vestibulo-ocular reflex, it was apparent that the range of abduction OU was normal and convergence spasm was diagnosed. MRI showed few scattered non-specific white matter lesions and an "eye of the tiger" sign of the basal ganglia, although metabolic, mitochondrial, and PANK2 testing was unrevealing. While convergence spasm is often a functional disorder, it can also be organic, and is typically seen with midbrain lesions. In her case, there was no clear midbrain pathology to explain convergence spasm, nor was there clear cerebellar pathology to explain her downbeat nystagmus. Number of Figures and legend for each: 0 Number of Videos and legend for each: 1, Patient with downbeat nystagmus and organic convergence spasm