A case of neuropsychiatric symptoms and recurrent thyrotoxicosis: Thyroid storm or encephalopathy associated with autoimmune thyroid disease?

SN Ali, K Wynne, B Field, T Tan, FF Palazzo, E Hatfield and K Meeran

Imperial Centre for Endocrinology

A 35yr Mongolian gentleman presented with headaches, pyrexia, focal seizures and fluctuating conscious level. Initial treatment was with intravenous antibiotics, aciclovir and dexamethasone. Meningitis was excluded with a normal CT brain and lumbar puncture. Thyroid function tests revealed hyperthyroidism: suppressed TSH, fT4=49pmol/L (NR 9-26pmol/L) and fT3=25.1pmol/L (NR 2.5-5.7pmol/L). Both serum anti-TPO antibodies and anti-TSH receptor antibodies were positive. Neurology review suggested a metabolic encephalopathy. He was switched to Carbimazole, Prednisolone and an anti-epileptic, levetiracetam. Thyroid function tests normalised quickly, yet the encephalopathy took several days to improve. He was referred to the Endocrinologists as an outpatient and discharged.

He was lost to follow-up and re-presented 18 months later off all medications, with identical symptoms: headaches, pyrexia, focal seizures and a fluctuating GCS. CT brain showed evidence of cerebral swelling and nil else. Lumbar puncture showed only a mildly raised CSF protein level. An EEG was suggestive of encephalopathy or encephalitis, with no overt epileptiform features seen. He was biochemically hyperthyroid and serum anti-TPO antibodies were positive. He was discharged home with carbimazole, a tapering dose of prednisolone and levetiracetam.

Several weeks later, due to language barriers and non-compliance with medications, he was again thyrotoxic, with recurrence of symptoms. An urgent total thyroidectomy was recommended and surgery occurred six weeks later. Despite pre-operative close follow-up, potassium iodide and PTU treatment, at the time of surgery fT4 was 30.5pmol/L and fT3 was 11.3pmol/L. Post-operative recovery was complicated by seizures. No abnormalities were detected on CT and MRI brain scans. Lumbar puncture was normal, including negative CSF anti-TPO antibodies. He was treated with antiepileptics and stabilised several days later, when he became biochemically euthyroid.

Encephalopathy associated with autoimmune thyroid disease (EAATD, also known as Hashimoto’s encephalopathy) is characterised by neuropsychiatric symptoms including seizures, cognitive alterations, inflammatory signs of encephalitis and/ or meningitis, and rarely pyrexia has been reported. Thyroid storm may also present with neuropsychiatric symptoms. EAATD is usually associated with raised CSF and/or serum TPO antibodies, raised CSF protein, and normal or slightly abnormal TFTs. Although our patient had features of EAATD including his response to steroid therapy, CSF anti-TPO antibodies have been negative to date and each episode was associated with biochemical thyrotoxicosis. This case demonstrates the challenge of distinguishing between EAATD and thyroid storm.