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A 55-year-old woman presented to the emergency department with generalised weakness and lightheadedness. She had a history of depression, hypertension, coeliac disease and excessive alcohol use. There were no focal neurological symptoms/signs. Abnormal laboratory results included serum sodium of 99 mmol/L, potassium of 3.0 mmol/L, serum osmolality of 214 mmol/kg, urine sodium of 32 mmol/L and urine osmolality of 630 mmol/kg. We suspected that her hyponatraemia was multifactorial, with contribution from escitalopram, hydrochlorothiazide, diuretic use and excessive alcohol intake. Further investigations found no evidence of primary hyperaldosteronism, adrenal insufficiency, hypothyroidism or occult malignancy. She was treated appropriately over the ensuing days with very slow increase in serum sodium in collaboration with the nephrology and intensive care team (maximum of 8 mmol/L per 24 hours with a typical range between 4 and 6 mmol/L per 24 hours). Fourteen days after admission, she developed dysarthria and left arm/leg weakness despite a normalised serum sodium.
Her examination at the time of clinical decline showed bradykinesia, hypomimia, left pyramidal hemiparesis and hyperreflexia with sustained clonus at the ankles, with ataxic speech and mild dysmetria.
MR scan of brain showed significant FLAIR hyperintensities involving the pons, lower midbrain, thalami medially and symmetric basal ganglia, without diffusion restriction (figure 1).
Her clinical history and radiographic findings were consistent with central pontine and extrapontine myelinolysis (also known as osmotic demyelination syndrome) despite appropriate management of her serum sodium correction. This was probably related to the severity of her initial hyponatraemia, together with concurrent hypokalaemia and a history of excessive alcohol intake.1 There is sometimes a lag in this condition between neurological symptoms and radiographic findings.2 Given that her sodium was normalised at the time of new neurological symptoms, there was no specific validated treatment; we therefore instituted supportive measures. She slowly improved in hospital and was discharged to inpatient rehabilitation.
Central pontine (and extrapontine) myelinolysis can occur despite appropriate sodium correction, likely related to severity, duration of initial hyponatraemia and the underlying cause.
There may be a lag between neurological symptoms and radiographic findings in this condition.
Contributors AM: involved in conception, writing and editing the manuscript. UN: involved in writing and editing the manuscript. WK: involved in conception, writing and editing the manuscript.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient consent for publication Obtained.
Provenance and peer review Not commissioned; externally peer reviewed by Martin Duddy, Newcastle-upon-Tyne, UK.