Title : Osmotic demyelination syndrome presenting as atypical parkinsonism following correction of hyponatraemia
Osmotic demyelination syndrome (ODS) is a condition which occurs due to rapid osmotic changes which result in myelinolysis of the nervous system. The myelinolysis commonly involves the pontine region resulting in central pontine myelinolysis. Rarely the myelinolysis could involve areas beyond the pons resulting in extrapontine myelinolysis. This demyelination results in a variety of neurological manifestations ranging from neuropathy, behavioural disorders to movement disorders and seizures. ODS has been described following rapid correction of hyponatraemia especially using intravenous hypertonic saline. We report a 70-year-old gentleman who presented with a 2 week history of reduced interaction and altered behavior following oral correction of severe hyponatraemia (serum sodium – 110 mOsm/l). He was administered diuretics for body swelling prior to being hyponatraemic and had few episodes of vomiting. He recovered from the hyponatraemia, following which he had developed bilateral extrapyramidal signs and symptoms. He had bradykinesia with postural instability suggestive of parkinsonism. There was a mild cognitive impairment with short term memory loss. EEG was unremarkable. However magnetic resonance imaging (MRI) of the brain revealed hyperintensities in the T2-weighted FLAIR images involving the pontine region. The characteristic “trident sign” was evident. Interestingly the MRI, which was done 3 weeks following sodium correction, did not reveal changes involving basal ganglia even though the clinical presentation was suggestive of an extrapontine myelinolysis. He was commenced on levodopa/carbidopa combination which resulted in improvement of the parkinsonism. Due to late presentation immunomodulators such as steroids and intravenous immunoglobulin were not commenced. This case illustrates the significance of adhering to recommended protocols when correcting hyponatraemia and the importance of timing brain imaging in ODS.
- This case report reiterates the importance of adhering to proper rate of correction of hyponatraemia to prevent osmotic demyelination as well as the significance of timing of brain imaging not to miss the diagnosis.
- This also discloses that even oral correction of hyponatraemia can lead to osmotic demyelination syndrome.
- Another important finding is the rare presentation of osmotic demyelination syndrome as atypical parkinsonism
- The requirement of a high index of suspicion to diagnose osmotic demyelination is also elaborated.