Opsoclonus, or saccadomania, is an eye movement disorder characterized by involuntary bursts of polydirectional saccades (sometimes with a horizontal preference) without an intersaccadic interval (cf. Square-wave jerks). Like ocular flutter, opsoclonus may be accurately characterized with oculography.
Although some normal individuals can voluntarily induce opsoclonus, generally it reflects mesencephalic or cerebellar disease affecting the omnipause cells which exert tonic inhibition of the burst neurones which generate saccades.
Recognized causes of opsoclonus include:
- Paraneoplasia: in children with neuroblastoma (Kinsbourne’s syndrome); in adults the opsoclonus-myoclonus syndrome is most commonly associated with small-cell lung cancer but it may also occur in association with breast cancer in which case onco neural antibodies (anti-Ri, or type 2 antineuronal nuclear antibodies [ANNA-2]) may be detected in serum and CSF;
- Postinfectious: a monophasic disorder following respiratory or gastrointestinal infection;
- Intraparenchymal (especially mesencephalic) lesions, e.g., tumor, demyelination, sarcoidosis, metabolic/toxic encephalopathy.
Postinfectious opsoclonus generally remits spontaneously. Of the paraneoplastic disorders, opsoclonus associated with lung and breast tumors persists and the patients decline from their underlying illness; neuroblastoma associated opsoclonus may be steroid responsive.