The cardinal clinical symptoms of tuberous sclerosis of the brain, also known as Bourneville's disease, are: epilepsy; mental deficiency of varying degree, and the so-called naevus multiplex of Pringle, consisting of multiple wartlike nodules distributed symmetrically in a butterfly fashion over the bridge of the nose and the cheeks and chin. For a detailed account of the symptomatology and pathology of the disease, the reader is referred to earlier publications.1 The condition is often familial and sometimes hereditary, and belongs to the group of ectodermal dysplasias (congenital ectodermoses).1 The disease is more frequent than is generally recognized. When the facial naevus multiplex of Pringle is present in the complete classic form of the disease, the diagnosis is almost self evident. On the other hand, when the nevus is not present and the epilepsy is the only clinical sign, the specific pathologic lesions underlying the disease may easily be