The data upon which this presentation is based consist of continuing and protracted observation of 111 patients with Tay-Sachs' disease and Niemann-Pick's disease (Table 1). Twenty-eight of these patients were hospitalized at this institution for extended terms, and of these, 23 have died and 21 have been autopsied.
The studies herein summarized arose from initial observations four years ago, on a single patient with Tay-Sachs' disease. After 15 months of institutionalization, there suddenly began a progressive cranial enlargement. This seemed contrary to the anticipated evolution of a disease which is generally characterized by arrest of development. On the basis of this observation additional children were admitted, and again a comparable head enlargement was noted. This paradoxical increase in head circumference did not occur early in the disorder but appeared during the later stages of the disease.1
Since the initial observations, a total of 28 children afflicted with Tay-Sachs' disease