[Intermittent sea-saw nystagmus successfully treated with clonazepam]

See-saw nystagmus is a pendular nystagmus with two distinct components: a conjugate torsional component and a disjonctive vertical component. The acquired form of nystagmus is usually seen with parasellar mass and less frequently in head injury or brainstem infarction. Almost all patients with parasellar mass or head injury have associated bitemporal hemianopia. We report the case of a 27-year-old man who developed intermittent daily oscillopsia five years after a severe head injury. On neurological examination, the patient showed a congenital left eye divergence with left eye convergence paresis, an anosmia, a right optic atrophy and a bitemporal hemianopia. Visual acuity was 7/10 and 3/10 for the right and left eyes. The rest of the neurological examination was unremarkable. Electroencephalogram during oscillopsia was normal. MRI revealed bilateral orbito-frontal low signal intensity on T1 weighted images. The brainstem, the diencephalon and the ventricular system appeared to be intact. Eye movement recordings exhibited intermittent see-saw nystagmus. Clonazepam treatment resolved the see-saw nystagmus. Slowly withdrawal of clonazepam was done without return of the see-saw nystagmus.