✅ Model Answer:
• Diagnosis: Opsoclonus-myoclonus-ataxia syndrome (OMAS) — a paraneoplastic neurological disorder. Characterized by acute ataxia, opsoclonus (dancing eyes), myoclonic jerks, and irritability. Neuroblastoma is the underlying tumor in 50% of young children.
• Any other test: Urine VMA/HVA (catecholamine metabolites — elevated in neuroblastoma), chest/abdomen MRI or CT for paravertebral mass (neuroblastoma), MIBG scan (functional imaging), bone marrow biopsy, biopsy of mass for pathology, CSF (may show oligoclonal bands), serum anti-Hu antibodies.
• What to do next: Oncology referral. Treat neuroblastoma (surgery ± chemotherapy). Immunotherapy for OMAS: corticosteroids (prednisone), IVIG, rituximab, cyclophosphamide. Start early to improve neurologic outcomes.
• Follow-up plan: Monitor neurologic improvement (may be protracted with residual deficits). Long-term cognitive/behavioral follow-up. Cancer surveillance.

✅ Model Answer:
• OMAS (also called Kinsbourne syndrome or dancing eyes-dancing feet syndrome) is a rare neurological disorder characterized by:
- Opsoclonus: Rapid, involuntary, chaotic, multidirectional eye movements ("dancing eyes").
- Myoclonus: Brief, shock-like, involuntary muscle jerks (limbs, trunk).
- Ataxia: Unsteady gait, truncal ataxia.
- Irritability: Behavioral changes, sleep disturbance.
• Age: Most common in children <3 years (peak 18 months).
• Paraneoplastic: Associated with neuroblastoma in 50% of cases (or ganglioneuroblastoma).
• Non-paraneoplastic: Idiopathic or post-infectious (viral, Mycoplasma).
• Pathophysiology: Immune-mediated (autoantibodies against neuronal antigens).

✅ Model Answer:
• Neuroblastoma is the most common underlying tumor in pediatric OMAS (50% of cases).
• Characteristics:
- Usually low-stage (Stage I or II) and favorable histology.
- Often paravertebral (abdomen, chest, or cervical).
- May be occult (not clinically apparent).
- MIBG uptake: Usually positive.
- Urine VMA/HVA: Elevated in 80-90% of neuroblastomas.
• Prognosis: Neuroblastoma in OMAS has a good prognosis (low-stage, favorable histology), but OMAS itself causes significant neurologic morbidity.
• Treatment: Surgical resection of the tumor (if feasible) ± chemotherapy. Tumor removal may not completely resolve OMAS (requires immunotherapy).

✅ Model Answer:
• Urine catecholamines:
- VMA (vanillylmandelic acid): Elevated in 80-90% of neuroblastomas.
- HVA (homovanillic acid): Elevated.
- Dopamine: May also be elevated.
• Imaging:
- Chest/Abdomen MRI or CT: To identify paravertebral mass (neuroblastoma).
- MIBG scan: Functional imaging for neuroblastoma (metaiodobenzylguanidine uptake).
- Bone marrow biopsy: If neuroblastoma is detected (staging).
• CSF:
- May show oligoclonal bands — suggests immune-mediated process.
- Normal cell count and protein (typically).
• Serum:
- Anti-Hu antibodies: May be present (associated with paraneoplastic syndromes).
- Anti-Ri antibodies: Rare.
- Normal inflammatory markers (ESR, CRP) — helps differentiate from infection.

✅ Model Answer:
• Treatment approach:
- Oncology: Identify and treat the underlying tumor (neuroblastoma). Surgery ± chemotherapy.
- Immunotherapy: First-line for neurologic symptoms.
• Immunotherapy agents:
- Corticosteroids: Prednisone 2 mg/kg/day (high-dose pulse or maintenance).
- IVIG: 1-2 g/kg/month (immunomodulatory).
- Rituximab: Anti-CD20 monoclonal antibody — increasingly used as a steroid-sparing agent.
- Cyclophosphamide: For refractory cases.
- Acthar gel: Adrenocorticotropic hormone (ACTH) — may be used.
• Duration: Immunotherapy is often prolonged (months to years).
• Prognosis: Early and aggressive immunotherapy improves neurologic outcomes.
• Multidisciplinary: Neurology, oncology, ophthalmology, physical/occupational therapy.

✅ Model Answer:
• Complications:
- Neurologic: Residual ataxia, cognitive impairment, learning disabilities, behavioral problems, speech delay.
- Ophthalmologic: Persistent opsoclonus, strabismus, visual impairment.
- Motor: Dystonia, chorea, fine motor impairment.
- Growth: Steroid-induced growth failure.
- Psychosocial: Irritability, sleep disturbance, tantrums, social difficulties.
- Relapse: OMAS can relapse even after tumor removal and immunotherapy (requires prolonged treatment).
- Long-term: 50-70% have persistent neurological sequelae (ataxia, cognitive impairment).
- Vision: Opsoclonus may persist, but vision itself is usually intact.

✅ Model Answer:
• MIBG (metaiodobenzylguanidine) scan: A functional imaging study that detects neuroblastoma and other neuroendocrine tumors.
• Mechanism: MIBG is taken up by catecholamine-producing cells (neuroblastoma, pheochromocytoma).
• Sensitivity: 90-95% for neuroblastoma.
• Role in OMAS:
- Detects occult neuroblastoma: Especially if the tumor is small or not visible on CT/MRI.
- Staging: Identifies metastatic disease (bone, bone marrow).
- Post-treatment monitoring: Assesses response to therapy.
- Can be performed on a whole-body scan to identify all sites of disease.
• Limitations: Some neuroblastomas are MIBG-negative (10-15%).
• Alternative: If MIBG is negative, consider PET-CT or meta-iodobenzylguanidine (mIBG) with SPECT.

✅ Model Answer:
• Prognosis:
- Cancer prognosis: Excellent — neuroblastoma in OMAS is usually low-stage and has >90% survival.
- Neurologic prognosis: Variable — 50-70% have residual neurologic deficits (ataxia, cognitive impairment, behavioral issues).
- Early aggressive immunotherapy (steroids, IVIG, rituximab) improves outcomes.
- Relapse: OMAS can relapse; requires prolonged treatment (months to years).
- Quality of life: Can be significantly impacted by neurologic and cognitive deficits.
• Long-term follow-up:
- Neurology: Monitor for ataxia, tremor, dystonia.
- Neuropsychology: Assess cognitive function, behavior, learning difficulties.
- Ophthalmology: Monitor for opsoclonus, strabismus.
- Oncology: Monitor for tumor recurrence (annual urine VMA/HVA).
- Education: Individualized education plans (IEP), special education if needed.
- Family support: Psychological support, social work.
- Immunotherapy: May need to continue for years.