Opsomyoclonus

The combined occurrence of opsoclonus (involuntary, chaotic, multidirectional saccadic eye movements), myoclonus (rapid, shock-like involuntary muscle jerks), and ataxia (impaired coordination and gait instability), representing opsoclonus–myoclonus syndrome (OMS), a rare inflammatory neurological disorder caused by immune-mediated dysfunction of cerebellar and brainstem pathways.

Causes

• Paraneoplastic autoimmune causes

  • Neuroblastoma (especially in children)

  • Small-cell lung carcinoma

  • Breast adenocarcinoma

  • Ovarian cancer

  • Other solid tumors associated with autoimmune neurological syndromes

• Parainfectious and autoimmune causes

  • HIV infection

  • West Nile virus infection

  • COVID-19 infection

  • Other viral infections triggering autoimmune responses

  • Post-infectious autoimmune encephalitis

• Autoimmune neurological causes

  • Antibody-mediated cerebellar inflammation

  • Autoimmune encephalitis

  • Disorders associated with anti-Hu, anti-Ri, anti-Yo, anti-NMDA receptor, or other neuronal antibodies

• Infectious causes

  • Viral encephalitis

  • Post-viral inflammatory syndromes

• Other causes

  • Idiopathic OMS (no identifiable trigger)

  • Toxic or metabolic causes affecting cerebellar and brainstem function

  • Rare medication-related immune activation

  • Neuroinflammatory disorders