Hashimoto Encephalopathy in Pediatrics: Report of 3 Cases

To describe the rare occurrence of pediatric Hashimoto encephalopathy in 3 patients.

The patients, 9 to 13 years of age, presented with new-onset seizures and other neurologic symptoms, including hemiplegia, aphasia, and memory loss. Thyroid function tests and thyroid antibodies were measured. Magnetic resonance imaging (MRI) of the brain, cerebrospinal fluid analysis, and electroencephalography were also performed.

The first patient had a thyroid-stimulating hormone (TSH) level of 60 μIU/mL (range, 0.4-4.5), free T4 of 0.28 ng/dL (range, 0.7-1.6), and thyroid peroxidase antibody (TPO Ab) of 1243 IU/mL (range < 9). The MRI results indicated a hyperintense signal along the gyri and sulci with diffuse leptomeningeal enhancement bilaterally. The second patient had a TSH level of 25 μIU/mL, free T4 level of 0.7 ng/dL, and TPO Ab level of 3340 IU/mL. The MRI result was normal. The third patient, who was already on levothyroxine, had a TSH level of 17 μIU/mL, free T4 level of 0.81 ng/dL, and TPO Ab level of 1200 IU/mL. The MRI result was normal. All patients had significant elevation of protein in the cerebrospinal fluid and background slowing on electroencephalography. All patients were treated with high doses of intravenous methylprednisolone followed by oral prednisone and thyroid hormone replacement.

These cases underscore the importance of thyroid function tests with antibodies in children presenting with acute neuropsychiatric manifestations, especially new-onset seizures without any identifiable cause. We believe that this condition is underdiagnosed in children, and a high index of suspicion is recommended.