Saccadic intrusions: review and update.

PURPOSE OF REVIEW: This work reviews saccadic intrusions focusing on recent developments in pathophysiology and treatment. RECENT
FINDINGS: Saccadic intrusions have been recognized as features of oculomotor apraxia type 2 and neuromyelitis optica. Novel fixation instabilities have been identified such as 'staircase' square wave jerks, or the pervasive ocular microtremor seen in Parkinson's disease. Although evidence supports a network underlying the pathophysiology of square wave jerks involving cerebral hemispheres, subcortex, brainstem and cerebellum, the debate regarding the pathogenesis of ocular flutter and opsoclonus centres on a cerebellar and brainstem hypotheses. The cerebellar hypothesis explains functional imaging findings, whereas the brainstem hypothesis provides possible explanations for some therapeutic responses as well as accompanying myoclonus, startle and tremor. A study of immunotherapies in children with opsoclonus-myoclonus syndrome found that treatment combinations were more effective than corticotropin alone.
SUMMARY: Recognition of saccadic intrusions can assist in the diagnosis of neurological disease. We are gaining new insights about pathogenesis through models, functional imaging and genetic approaches.