Pseudonystagmus--clinical features and quantitative characteristics.

BACKGROUND: A 60 year-old woman with multiple sclerosis (MS) and chronic hearing loss presented with head tremor and vestibular hypofunction, the combination of which can produce oscillopsia--a visual sensation that steady objects in the visual field are oscillating. This case highlights the fact that in patients with pseudonystagmus, oscillopsia is attributable to the association of head tremor and vestibular hypofunction. INVESTIGATIONS: Eye and head movements were measured simultaneously with the search coil technique. DIAGNOSIS: Patients with MS can present with oscillopsia, and spontaneous pendular nystagmus is often observed in these individuals. In our patient, the oscillopsia was not due to pendular nystagmus, but rather to pseudonystagmus (of gaze) resulting from diminished compensatory vestibulo-ocular reflex responses to head tremor. MANAGEMENT: A two-step strategy can be used in patients with pseudonystagmus: pharmacological treatment of head tremor, and vestibular rehabilitation to improve balance and diminish oscillopsia associated with head movement. Various health-care providers at other institutes attempted to address our patient's dystonic head tremor with botulinium toxin injections in the neck muscles; the response was unsatisfactory. We offered treatment with baclofen, which the patient did not tolerate. We also discussed the option of vestibular rehabilitation, which the patient did not pursue.