Extra-pontine Myelinolysis After Rapid Correction of Hyponatremia Responding to Levodopa

Osmotic demyelinating disease of the central nervous system has two variants: central pontine myelinolysis and extra-pontine myelinolysis (EPM). Up to 10% of cases of osmotic demyelination syndrome are associated with EPM, which mostly affects the thalamus and basal ganglia. It is commonly associated with the rapid correction of hyponatremia. An elderly woman in her 60s presented with complaints of acute gastroenteritis and giddiness and visited the emergency ward. On examination, she was conscious and oriented to time but disoriented to place and person and had slurring of speech with signs of dehydration. Her serum sodium levels were 100 meq/L, and her brain MRI was normal. After shifting her to the intensive care unit, she was treated with 200 ml of 3% NaCl bolus to correct her hyponatremia. On day three, she began developing rigidity in both lower limbs, which progressed to the upper limbs with hyperreflexia and mutism. A brain MRI was done, which showed subtle hyperintensities in the caudate lobe with no other new findings. Her serum aldosterone and cortisol were on the lower side of the normal range. Treatment of tablet levodopa-carbidopa (100/25) combination thrice a day (TDS) led to an improvement in her health condition.