A 60-year-old hypertensive woman had a pontine
hemorrhage that caused slight right
hemiplegia, deep sensory disturbance on her right side and
dysarthria. Three months after the
stroke, she was transferred to our hospital for rehabilitation. Approximately 6 months later, she gradually began to complain of the visual oscillation. Continual, unceasing conjugate vertical/rotatory eye movements were observed. Fixation was momentary at best because of an inability to dampen the spontaneous eye movements. Electrooculography (EOG) showed bilateral vertical/rotatory sinusoidal eye movements of 2.5 Hz frequency and 10- to 35-degree amplitude. Both vertical and horizontal optokinetic nystagmus were absent. Caloric stimulation did not evoke any responses bilaterally. There were no rhythmical movements at similar frequencies in other parts of the body such as
palatal myoclonus. MRI revealed not only
hematoma mainly at the dorsal pontine tegmentum but also
hypertrophy of the inferior olive nucleus, suggesting disruption of the central tegmental tract. Lesions of this tract may be one cause of
pendular nystagmus. Several
drug therapies were investigated for the nystagmus. There was no response to
baclofen 15 mg.
Trihexyphenidyl 4 mg was discontinued because of
drug-induced
hallucinations.
Tiapride 600 mg and
phenobarbital 90 mg were each slightly effective in reducing both frequency and amplitude of nystagmus. Treatment with
clonazepam 1 mg resulted in the striking disappearance of nystagmus. She was aware of this and no longer experienced oscillopsia. Despite the visual benefit, however, the patient did not wish to continue this
drug because of drowsiness and muscle relaxation. The potential long-term therapeutic application of
clonazepam should be further investigated. To our knowledge, there have been no reports of successful treatment in acquired
pendular nystagmus with
clonazepam. Therefore, based on this favorable experience, it is suggested that
clonazepam should be added to the list of potential
therapies for
pendular nystagmus.