The localizing value of nystagmus in brainstem disorders

Abstract

As causes for conjugate jerk nystagmus at the midposition of the eye. vestibular imbalance, a neural integrator deficit, smooth pursuit imbalance and a saccade generator deficit have been considered. The authors investigated anatomically brainstem lesions of patients with downbeat, upbeat, torsional and horizontal nystagmus. Although relatively common, downbeat nystagmus is only rarely seen with brainstem lesions. In these instances it is localized in midline medullary structures. Upbeat nystagmus is more often caused by a discrete brainstem lesion in the medulla, which can be as far caudal as the cranio-cervical junction. Lesions have also been found at the pontine level. In the mesencephalon, torsional nystagmus occurs with lesions to the interstitial nucleus of Cajal and the rostral interstitial nucleus of the MLF. In addition torsional nystagmus is seen after vestibular nuclei and lateral medullary lesions. Both lesion sites are also found with horizontal nystagmus.Although in some instances pathophys...