Therapeutic Recommendations

In general, periodic alternating nystagmus does not improve spontaneously. Several case reports describe a positive effect of baclofen, a GABA-B agonist, in a dose of 5–10 mg p.o. three times daily [1, 57, 59, 60].

Other Supranuclear Oculomotor Disorders

Acquired Pendular Nystagmus

Clinical Aspects

Acquired pendular nystagmus is a visually distressing form of nystagmus, in which oscillopsia and impaired vision are common. Acquired pendular nystagmus is a quasi-sinusoidal oscillation that may have a predominantly horizontal, vertical, or mixed trajectory (i.e. circular, elliptical, or diagonal); it can be either predominantly monocular or predominantly binocular [6, 61, 62]. The frequency of this type of nystagmus is 2–7 Hz [63]. It is often associated with head titubation (a kind of head tremor with small amplitude and not synchronized with the nystagmus), trunk and limb ataxia, or visual impairment. The amplitude is small and can often be only seen with an ophthalmoscope.

Etiology

Acquired pendular nystagmus occurs with several myelin disorders (e.g. multiple sclerosis, toluene abuse, Pelizaeus-Merzbacher disease). It is also a component of the syndrome of oculopalatal tremor (myoclonus) and is observed in Whipple’s disease [6, 62]. Common etiologies in adults are multiple sclerosis and brainstem stroke [62, 64]. On the basis of observations that the nystagmus is often dissociated and that eye movements other than optokinetic nystagmus and voluntary saccades are also disturbed, it has been suggested that a lesion in the brainstem near the oculomotor nuclei is the cause [61]. Alternative candidates such as an inhibition of the inferior olive due to lesions of the ‘Mollaret triangle’ or an instability of the gazeholding network (neural integrator) have also been proposed [64].

Treatment

The first reported treatment option was anticholinergic treatment with trihexyphenidyl (20–40 mg p.o. daily) [65, 66]; however, Leigh et al. [67] reported in a double-blind study that only 1 of 6 patients improved during this oral treatment. Starck et al. [68] reported that nystagmus improved with memantine, a glutamate antagonist, in all 9 tested patients (15–60 mg p.o. daily). Gabapentin, an alpha-2-delta calcium channel antagonist, substantially improved the nystagmus (and visual acuity) in 10 of 15 patients (3 300–400 mg daily) [53]. Gabapentin