Oculomotor Abnormalities and Nystagmus in Brainstem Disease: A Mini Review

The brainstem plays a pivotal role in the generation and control of eye movements-including saccades, smooth pursuit, the vestibulo-ocular reflex (VOR), vergence, and gaze holding. Beyond its vital physiological functions, it is also essential for the coordination of balance and movement. Consequently, eye movement disorders of brainstem origin are often accompanied by vertigo, imbalance, unsteady gait, and diplopia, particularly during changes in head or body position. A sound understanding of the neural structures involved in oculomotor and vestibular control is therefore crucial for accurately identifying and localizing a wide variety of brainstem syndromes. However, oculomotor abnormalities resulting from brainstem disease represent a major diagnostic challenge for the neurotologist, owing to the wide spectrum of possible etiologies (vascular, traumatic, degenerative, neoplastic), their variable severity and clinical course (acute, fluctuating, or progressive), and the frequent concomitant involvement of other central structures, particularly the cerebellum. This mini review summarizes the pathophysiological mechanisms and clinical features of oculomotor disorders and nystagmus associated with brainstem disease.