Brain weight in autism: normal in the majority of cases, megalencephalic in rare cases.

The brain weights of 21 postmortem autism cases (5 new and 16 previously published) were compared with normal brain weights from six autopsy studies. Of the 21 cases, 17 had normal brain weights and 1 was micrencephalic. Compared with the normal median (1,460 g), three autism cases were megalencephalic: two (1,810 g and 1,820 g) had been previously reported and one (1,880 g) was a new case. Brain weight is thus normal in most postmortem cases of autism. There are, however, rare cases of megalencephaly and possibly micrencephaly.