way from the treatment. The patients in whom the influence of the gravity-depen- dent component is more pronounced also seem to benefit more from a supine head position [41]. In isolated patients with a craniocervical anomaly, a surgical decompression involving the removal of part of the occipital bone in the region of the foramen magnum was beneficial [42, 43].

As a practical rule, treatment should be started by trying clonazepam. If this option does not improve the nystagmus satisfactorily, 4-aminopyridine (10 mg three times daily) should be tried.

Upbeat Nystagmus

Clinical Aspects

Upbeat nystagmus occurs when the eyes are close to the central position and usually increases during upgaze [44]. The nystagmus usually disrupts vertical smooth pursuit. In some patients, the upbeat nystagmus changes to downbeat nystagmus during convergence. An upbeat nystagmus has in general a better prognosis than a downbeat nystagmus and is often only a temporary problem [11].

Etiology

A central vestibular imbalance is involved in upbeat nystagmus as in downbeat nystagmus. The most frequently seen lesions are medullary lesions [44]. Probable causes of upbeat nystagmus are lesions in the ascending pathways from the anterior canals (and/or the otoliths) at the pontomesencephalic or pontomedullary junction, near the perihypoglossal nuclei [44, 45]. The main causes are multiple sclerosis, tumors of the brainstem, Wernicke’s encephalopathy, intoxication (e.g. nicotine), and seldom cerebellar degeneration.

Treatment

Treatment with baclofen (5–10 mg p.o. three times daily) caused an improvement in several patients [37]. Probably 4-aminopyridine will also improve the upbeat nystagmus in some patients [46].

Seesaw Nystagmus

Clinical Aspects

Seesaw nystagmus is a rare pendular or jerk oscillation around the line of gaze. A half-cycle consists of elevation and intorsion of one eye with synchronous