Abstract
Neuronal migration disorders are a group of malformations of the brain which primarily
affect development of the cerebral cortex. The best known of these is lissencephaly
(smooth brain). Most types result from incomplete neuronal migration to the cortex
during the third and fourth months of gestation. In this review, we describe and illustrate
the different types of neuronal migration disorders. We also review the many different
genetic syndromes associated with neuronal migration disorders.
Over 25 syndromes with lissencephaly or other neuronal migration disorders have been
described. Among them are syndromes with several different patterns of inheritance
including chromosomal or new mutation autosomal dominant, autosomal recessive, X-linked
and unknown. Genetic counseling thus differs greatly between syndromes. The genes
responsible for several of the lissencephaly syndromes have been mapped. X-linked
lissencephaly has tentatively been mapped to chromosome Xq22 based on observation
of a single X-autosomal translocation in a girl. Both Miller-Dieker syndrome and isolated
lissencephaly sequence (in many patients) were mapped to chromosome 17p13.3 by detection
of deletions and other structural chromosome rearrangements. Fukuyama congenital muscular
dystrophy was mapped to chromosome 9q31-33 by homozygosity mapping.
Key words
Agyria - Heterotopia - Lissencephaly - Neuronal migration - Pachygyria - Polymicrogyria
