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.