Endocrine Abstracts

Case History: A 69-year-old lady was admitted to her local district general hospital with a history of confusion, memory disturbance and focal twitching affecting her upper limbs and face. She had a past medical history of type 2 diabetes mellitus, hypertension, hypercholesterolaemia and ischaemic heart disease. Her medications included gliclazide, pioglitazone, atorvastatin, bisoprolol, aspirin and omeprazole. She had never smoked and was teetotal. Neurological examination on admission did not demonstrate any obvious cranial nerve abnormalities or lateralising signs.

Investigations: Admission bloods revealed a severe hyponatraemia of 114 mmol/l (133–146) and low magnesium of 0.54 mmol/l (0.66–0.99). Serum osmolality was low at 270 mOsmol/kg (275–295), urine osmolality was 408 mOsmol/kg (80–1200), and urine sodium was 24 nmol/l. Serum cortisol was appropriate at 884 nmol/l. A vasculitic screen was negative. CSF analysis was completely normal. A CT scan of the chest, abdomen and pelvis showed endometrial thickening but no other significant abnormality. CT head showed multifocal white matter low density lesions at the grey-white matter interface, and MRI brain showed widespread bilateral multifocal areas of increased T2 signal intensity.

Results and treatment: Voltage-gated potassium channel (VGKC) antibody titres were raised with positive LG-I IgG. She was treated with intravenous Methylprednisolone 1 g daily for 3 days followed by a reducing dose of prednisolone (starting dose 60 mg daily). On this regime her MOCA score increased from 7/30 to 13/30 and her sodium rose to 132 mmol/l on discharge from hospital. Subsequently her cognitive function returned to normal relatively quickly and she has remained seizure-free.

Conclusions and points for discussion: Hyponatraemia is the commonest electrolyte disorder affecting hospitalised patients. The clinical triad of poor memory, brachiofacial seizures and severe hyponatraemia is consistent with a VGKC-associated limbic encephalitis. Hence it remains an important differential diagnosis in patients presenting with neurological disturbance and unexplained hyponatraemia. Early recognition of this condition is vital as timely, aggressive immunotherapy may allow reversibility of the disease process and thereby halt neurocognitive decline, as evidenced in our case.