Introduction: Osmotic demyelination syndrome (ODS) is an uncommon neurological disorder that occurs secondary to rapid plasma osmotic shifts. It is a recognised complication of overcorrection of hyponatraemia.
Methods: We present a case of ODS in a patient with severe hyponatraemia and other predisposing factors.
Results: A 60-year-old man with alcoholic liver disease and malnutrition was hospitalised with delirium. Assessment revealed hypervolaemic hyponatraemia (serum sodium 117mmol/L, range: 135-145), mild hypokalaemia, Wernicke encephalopathy and deranged liver function. Computed tomography of the brain (CTB) was unremarkable. With close monitoring of serum sodium (SNa), fluid restriction was commenced, leading to an increase in SNa to 123mmol/L 24 hours later, 128mmol/L 48 hours later and 132mmol/L 72 hours later. SNa normalised (136mmol/L) on day 7 of admission. He subsequently underwent inpatient rehabilitation for 2 weeks before he self-discharged against medical advice. He represented a week later with functional and cognitive decline. Repeat SNa was normal at 138 mmol/L. Repeat CTB revealed a new 15 mm hypodense focus in the pons. Further evaluation with a magnetic resonance imaging (MRI) demonstrated a region of T2 and fluid-attenuated inversion recovery (FLAIR) hyperintensity and low T1 signal intensity within the central pons with restricted diffusion, in keeping with osmotic demyelination syndrome. At 3-month follow-up, there was minimal improvement in his functional status and cognition. Repeat MRI showed ongoing central pontine abnormality with new surrounding cavitation, indicating coagulative necrosis.
Conclusion: Mechanisms of ODS have classically focused on sudden osmotic shift in the context of overcorrection of hyponatraemia. However, it is important to be vigilant for other conditions that can be associated with ODS, independent of SNa changes, such as those seen in this case: alcoholism, liver disease, hypokalaemia and malnutrition. Judicious correction of hyponatraemia is warranted in those with comorbid factors susceptible to ODS.