Extrapontine Myelinolysis Presenting as L-DOPA-Unresponsive Parkinsonism (P5.269)

OBJECTIVE: A unique case report on extrapontine myelinolysis (EPM) presenting as parkinsonism. BACKGROUND: EPM is a rare complication (10% of osmotic demyelination cases) of rapid correction of hyponatremia associated with diverse presentations and outcomes. This is a unique case of EPM due to severe parkinsonism, unresponsive to dopaminergic therapy, with spontaneous near-complete resolution of symptoms. DESIGN/METHODS: A 36-year-old man with history of polysubstance abuse, including alcoholism, presented with slurred speech and trouble with ambulation that developed over one week. RESULTS: Initial physical examination revealed limited facial and tongue movement, mask-like facies, hypersalivation, hypokinetic shuffling gait, bradykinesia, resting tremor and severe cogwheel rigidity in both upper extremities. The patient had no detectable weakness in any extremity. Magnetic resonance imaging (MRI) of the brain showed T2 hyperintensities in the pons, midbrain and bilateral putamen. Review of his admission, two weeks prior, revealed that hyponatremia was corrected rapidly, from 107 to 123 mEq/L in 24 hours. The speech and gait abnormalities were not present on discharge, but developed gradually thereafter. The patient was subsequently admitted to an inpatient psychiatric facility and treated with antipsychotics. This confused the picture on presentation due to the association of extrapyramidal symptoms with the recent use of antipsychotics. The patient was initially treated with carbidopa/levodopa with no benefit. Symptoms gradually and spontaneously resolved over several months with no lingering sequelae. CONCLUSIONS: EPM is a rare consequence from rapid correction of hyponatremia. The damage is attributed to rapid osmotic changes causing neuronal cell death and demyelination. EPM has been associated with DOPA-responsive extrapyramidal symptoms in prior reports. Unfortunately, these patients were ultimately left with dystonic sequelae. Our patient had a unique course of having near-complete recovery despite being non-responsive to dopaminergic medications. This case demonstrates the confusion and misdiagnosis that can occur with EPM along with an unusually good outcome. Disclosure: Dr. Anderson has nothing to disclose. Dr. Shah has nothing to disclose.