SUN-343 - Posterior Reversible Encephalopathy as an Initial Presentation of Thyroid Storm

Case Report:
A 51-year-old female with Grave’s disease presented with a 25-minute seizure and persistent vomiting. She was recently diagnosed with Grave's disease with biochemical hyperthyroidism and positive Thyroid Stimulating Immunoglobulin, and was started on methimazole and propranolol but was unable to tolerate therapy due to vomiting.

On arrival, she was hypertensive (155/71) and in supraventricular tachycardia requiring cardioversion. She was poorly responsive and agitated, necessitating intubation. Laboratory studies demonstrated undetectable thyroid stimulating hormone (TSH) with elevated triiodothyronine (T3) and free thyroxine (T4) levels. CT brain revealed a left sided hypodensity and MRI brain demonstrated symmetric cortical and subcortical flair hyperintensity in the posterior frontal, parietal, and occipital lobes, consistent with PRES. EEG showed generalized cerebral dysfunction without epileptiform activity. She was empirically started on antiepileptics, steroids, propylthiouracil, and esmolol with gradual neurologic recovery. She was weaned off antiepileptic medications and transitioned to oral methimazole and discharged. At two-week endocrine follow up, she reported resolution of neurological symptoms, improvement of thyroid function, and remained seizure free.

Discussion:
Thyroid storm can have multiple different neurologic manifestations. This was an atypical case where the patient presented with seizures and was found to have PRES based on MRI findings, which typically include hyperintense lesions in the parietal-occipital lobes, but can involve the temporal lobe, frontal lobe, and cerebellum. Prior cases have demonstrated MRI hyperintensities in the setting of thyroid storm associated with prolonged neurological dysfunction, which are often reversible with appropriate treatment. Although our patient has similar imaging findings, she had rapid neurological recovery. One study suggested that abnormal MRI findings in the setting of thyroid storm may be due to blood brain barrier disruption from being in a hypermetabolic state, as hyperthyroidism increases oxygen requirement of tissue by increasing mitochondria, resulting in relative hypoxia in the brain.

Conclusion:
PRES has never been reported in association with thyroid storm, but MRI findings of T2 hyperintensities seen in various lobes have been reported in case reports. This case highlights PRES as a reversible presenting manifestation of thyroid storm that responded to antithyroid therapy and steroids.

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