[A case of Hashimoto's encephalopathy with a relapsing course related to menstrual cycle].

A case of 43-year-old woman with Hashimoto's encephalopathy who experienced three relapses closely associated with the menstrual cycle is reported. In April 1992, she began to experience occasional tremors in her arms. Three months later, she experienced a generalized seizure and was transferred to our hospital. Hashimoto's thyroiditis was diagnosed on the basis of high thyroid microsomal titer and mild hypothyroidism. Neurological findings in admission included action tremor in both hands, myoclonus in all extremities, cerebellar ataxia, confusion, and hyperreflexia. Cerebrospinal fluid showed elevated protein level without pleocytosis. Electroencephalogram showed diffuse slowing and magnetic resonance imaging of brain was normal. Hashimoto's encephalopathy was diagnosed from these findings. These episodes of remission and exacerbation were observed during the admission. Her symptoms started at ovulation, worsened during the luteal phase, and improved when menstruation started. After the third relapse, she was treated with oral thyroxine for hypothyroidism and with an estrogen and progesterone combination to regulate the menstrual cycle. Her thyroid function gradually became euthyroid and she did not experience any subsequent relapses. The relation between the relapsing course and menstrual cycle suggests that the periodic alteration of gonadotrophic and/or gonadal hormones or the menstrual regulating center itself in the brain may be an important factor of pathogenetic mechanism of the disorder.