Role of clonazepam in the treatment of idiopathic downbeat nystagmus

Objective/Hypothesis: Downbeat nystagmus is defined as spontaneous nystagmu s present with fixation in the primary position or lateral gaze. Those who have downbeat nystagmus but negative magnetic resonance imaging results are termed as idiopathic. Patients with idiopathic downbeat nystagmus, althoug h unconcerned with their etiology, have visual symptoms such as oscillopsia , diplopia, or blurred vision. The purpose of this study is to evaluate the efficacy of clonazepam in treating idiopathic downbeat nystagmus. Methods. Patients with downbeat nystagmus were rechecked by electronystagmography ( ENG); then 0.5 mg clonazepam was administered orally. One hour later, follo w-up ENG was performed again to evaluate the evolution of the downbeat nyst agmus. If the test was effective, then 1.0 mg clonazepam twice daily was ad ministered to the patients. Results. Seven cases had downbeat nystagmus, in cluding idiopathic in five, cerebellar degeneration in one, and cerebellopo ntine angle tumor in one. The efficacy rate for the clonazepam test was 100 % in five cases of idiopathic downbeat nystagmus, whereas it was ineffectiv e in the case of cerebellar degeneration. After long-term therapy with clon azepam, all patients with idiopathic downbeat nystagmus experienced elimina tion of oscillopsia, relief of diplopia, and improvement of visual acuity. Although temporary relief of downbeat nystagmus was observed 1 hour after t he clonazepam. test, downbeat nystagmus was not eliminated permanently. Con clusion: We recommend long-term therapy by clonazepam with a dosage of 1.0 mg twice daily in cases of idiopathic downbeat nystagmus. Reducing the down beat nystagmus as well as eliminating the oscillopsia can be anticipated.