The functions of the hypothalamus have been elucidated by the careful studies of Bard, Fulton, Long, Masserman, Ranson, Sheehan and their co-workers on animals.1 Observations on patients with structural lesions of the hypothalamus have amply confirmed these studies. Most of the clinical examples, however, have been concerned with destructive lesions of some portion of the hypothalamus and, consequently, with more or less static disturbances of function, such as diabetes insipidus, hyperthermia and hypothermia, etc. More unusual have been cases in which periodic massive discharges of hypothalamic activity have taken place, such as the case of a ball valve tumor of the third ventricle reported by Penfield.2 To our knowledge, there is no report of a destructive and fixed lesion outside the hypothalamus leading to disturbance of hypothalamic function with repeated display of exaggerated hypothalamic activity. The present case represents such an example; a cystic, degenerative lesion involving chiefly