Endocrine Abstracts

A 73-year-old independent female presented with reduced consciousness following a tonic-clonic seizure. Investigations revealed acute hyponatraemia, with a serum sodium of 103 mmol/l. Cortisol reserve and thyroid function was normal and the biochemical diagnosis was consistent with SiADH. A CT brain scan was normal. Hypertonic saline was commenced with empirical anti-viral and antibiotic therapy. Lumbar puncture revealed a slightly elevated CSF protein and her EEG showed non-specific changes. Her conscious level improved, but there was evidence of ongoing confusion.

Clinical concern of central pontine myelinolysis following correction of the hyponatraemia was excluded by MRI brain scan. She was discharged following functional recovery but re-presented 5 days later with acute worsening of confusion, new paranoid delusions and emotional lability.

Repeat investigations showed no metabolic abnormality. Paraneoplastic and autoimmune encephalitis antibody serology was requested. After 2 weeks, these returned from the Oxford Reference Laboratory showing a positive Voltage-gated potassium-channel (VGKC) complex antibody titre. A diagnosis of autoimmune limbic encephalitis was made and 3 days intravenous methylprednisolone treatment was given. The patient made a full cognitive recovery, allowing discharge home independently.

Conclusion: Endocrinologists are increasingly asked to assess hyponatraemic patients both for diagnostic and management purposes. Confusion is common with hyponatraemia, but should reverse if the metabolic situation is corrected appropriately. This case shows the importance of considering a diagnosis of autoimmune encephalitis once other causes of SiADH and cognitive impairment have been excluded.