Idiopathic Downbeat Nystagmus Exacerbated with Positional Maneuvers - Part 2: Patient is Now on 4-Aminopyridine

This is a 45-yo-woman presented in "Idiopathic downbeat nystagmus exacerbated with positional maneuvers". This video was taken after the patient had been on 4-aminopyridine for 3 months. There was marked improvement in subjective oscillopsia and objective downbeat nystagmus. The strong positional component coupled with the pure DBN in right and left gaze and alternating skew deviation, suggests that an otolithic imbalance (as opposed to semicircular canal imbalance) is responsible for her DBN. Saccades, smooth pursuit, VOR suppression, VOR and head impulse testing and tests of appendicular ataxia were all normal, arguing against a flocculus/paraflocculus localization. A lesion involving the nodulus seemed much more likely and SCA 6 testing is pending.