Encephalitis as an initial presentation of type 2 amiodarone-induced thyrotoxicosis

Area of Science:

• Neurology
• Endocrinology
• Cardiology

Background:

• Amiodarone is a widely used antiarrhythmic medication with known potential for thyroid dysfunction.
• Type 2 amiodarone-induced thyrotoxicosis (AIT) is characterized by iodine-induced hyperthyroidism, distinct from the destructive type 1 AIT.
• Neurological manifestations of AIT are uncommon, with encephalitis being a rare initial presentation.

Observation:

• A woman in her mid-20s with hypertrophic cardiomyopathy presented with acute personality change and myoclonic jerks, initially diagnosed as encephalitis.
• Cerebrospinal fluid analysis was unremarkable for infection or autoimmune/paraneoplastic processes.
• Cranial MRI revealed symmetrical cerebral edema and cerebellar changes, while EEG showed generalized cerebral dysrhythmia.

Findings:

• Thyroid function tests confirmed thyrotoxicosis, but the patient did not meet criteria for thyroid storm.
• Autoimmune and onconeural antibody screens were negative, ruling out other common causes of encephalitis.
• The patient exhibited an excellent clinical, laboratory, and radiological response to glucocorticoid therapy.

Implications:

• This case highlights encephalitis as a potential, albeit rare, initial presentation of type 2 amiodarone-induced thyrotoxicosis.
• The findings suggest that steroid-responsive encephalitis can occur secondary to type 2 AIT, even without overt thyroid storm.
• Early recognition and prompt treatment with glucocorticoids are crucial for managing this specific neurological complication of amiodarone therapy.