Nystagmus and Saccadic Intrusions

PURPOSE OF REVIEW This article provides an overview of nystagmus and saccadic intrusions with the goal of facilitating recognition and differentiation of abnormal eye movements to assist with accurate diagnosis of neurologic disease and evidence-based specific treatment of oscillopsia. Myriad advances have been made in the understanding of several types of nystagmus and saccadic intrusions, even in the past 5 to 10 years, especially regarding underlying pathophysiology, leading to pharmacologic advances rooted in physiologic principles. RECENT FINDINGS Specific recent advances in the study of nystagmus and saccadic intrusions include (1) improved understanding of the underlying etiologies and mechanisms of nystagmus enhanced or unmasked by provocative maneuvers such as supine position or head shaking; (2) recognition of the differences in behavior and treatment responsivity of acquired pendular nystagmus in demyelinating disease versus oculopalatal myoclonus; (3) recognition that oculopalatal myoclonus results from a dual mechanism of abnormal inferior olivary gap junction connection formation and maladaptive cerebellar learning; and (4) well-controlled clinical trials to evaluate the efficacy of pharmacologic interventions, such as memantine for acquired pendular nystagmus and 4-aminopyridine for downbeat nystagmus. SUMMARY Accurate recognition of nystagmus and saccadic intrusions, including familiarity with the subtleties of examination techniques that allow such eye movements to be unmasked, is critical to proper diagnosis and ultimate alleviation of the visual impairment these patients experience.