Cortical Dysplasia

Cortical dysplasia denotes a large scale of malformations due to disorders of neuronal migration and organization. Seizures, often intractable, mental retardation, and motor deficits of variable severity are common clinical manifestations. Known etiologies are chromosomal aberrations, single gene mutations, hypoxic-ischemic insults, maternal infection with cytomegalovirus, maternal methylmercury poisoning, anticoagulant therapy, and inherited metabolic diseases caused by peroxisomal disorders, such as Zellweger syndrome and neonatal adrenoleukodystrophy. MRI readily demonstrates the convolutional anomalies.

Lissencephaly Type 1 or Agyria

Grossly, the cortical surface is smooth, with no signs of fissures and sulci (Fig. 13.15). Histologically, a thick cortex is densely packed with immature neurons that display a large vesicular nucleus and scanty or no cyto-

figure 13.13

Hydranencephaly in a 3-year-old, quadriplegic, epileptic girl. A. Ventral aspect of the brain shows rudimentary orbital, hippocampal, and occipital convolutions. The rest of the cerebral wall is absent. A paper-thin membrane attached to the dura roofed the interior of the brain.

figure 13.13

Hydranencephaly in a 3-year-old, quadriplegic, epileptic girl. A. Ventral aspect of the brain shows rudimentary orbital, hippocampal, and occipital convolutions. The rest of the cerebral wall is absent. A paper-thin membrane attached to the dura roofed the interior of the brain.

figure 13.14

Schematic drawing of sequences of development of fissures, sulci, and convolutions.

figure 13.14

Schematic drawing of sequences of development of fissures, sulci, and convolutions.

plasm. Various patterns of cortical dysplasias may occur in the same brain.

Lissencephaly type 1 occurs sporadically or is inherited as an autosomal dominant, autosomal recessive, or X-linked trait. Mutations in four different genes have been identified: LIS1 on chromosome 17; XLIS on chro

figure 13.15

Lissencephaly. The lateral aspect of the hemisphere is smooth. A shallow Sylvian fissure is present. The temporal sulci are shallow, and the convolutions broad. The cortex is abnormally thick, the white matter is reduced, and the ventricle is enlarged (LFB-CV).

figure 13.15

Lissencephaly. The lateral aspect of the hemisphere is smooth. A shallow Sylvian fissure is present. The temporal sulci are shallow, and the convolutions broad. The cortex is abnormally thick, the white matter is reduced, and the ventricle is enlarged (LFB-CV).

mosome X 22.3-23, associated with male occurrence; RELN, associated with recessive inheritance and cere-bellar hypoplasia; and ARX on chromosome X.

Lissencephaly Type 2

An autosomal recessive disorder, often coexists with cerebellar dysplasia, ocular anomalies, and congenital muscular dystrophy.

Grossly, the cortical surface is uneven (cobblestone) and histologically, the cortical lamination is greatly disorganized. Myelin tracts are intermixed with neurons, which can also be found in the leptomeninges.

Lissencephaly type 2 is a feature of Fukuyama congenital muscular dystrophy (FCMD), Finnish muscle-eye-brain (MEB) disease, and the Walker-Warburg syndrome (WWS) of oculocerebral dysplasia. The FCMD gene, fukutin, maps to chromosome 9; the MEB disease gene maps to chromosome 1p32; and the WWS gene maps to chromosome 9q34.

Macrogyria

The brain has a greatly simplified convolutional pattern with broad, abnormally oriented convolutions (Fig. 13.16).

figure 13.16

Macrogyria. Lateral aspect of the hemisphere displays broad convolutions separated by shallow sulci.

figure 13.16

Macrogyria. Lateral aspect of the hemisphere displays broad convolutions separated by shallow sulci.

Polymicrogyria

Refers to numerous small convolutions, abnormally oriented and separated by shallow sulci (Fig. 13.17). The extent varies from circumscribed areas to total involvement of one or both hemispheres. On cut sections, miniature convolutions are partially fused. The white matter is significantly reduced, and the ventricles are enlarged (colpocephaly). The histologic picture varies from lack of lamination to a four-layered cortex displaying wavy, glandular, or multifoliated patterns (see Fig. 13.17). Familial cases of polymicrogyria have an autosomal dominant, autosomal recessive, or X-linked inheritance. The malformation can be associated with maternal cyto-megalovirus infection, Zellweger cerebrohepatic disease, blood loss, and loss of a twin. Polymicrogyria and mac-rogyria may occur in the same brain (Fig. 13.18).

figure 13.17

Polymicrogyria in a 9-year-old mentally defective, quadriplegic girl. A. Lateral aspect of the cerebral hemisphere reveals a simplified con-volutional pattern with abnormally oriented irregular, embossed convolutions. B. Transverse section shows partially fused miniature convolutions, markedly reduced white matter, and large ventricles (colpocephaly). C. A four-layered cerebral cortex has a glandular and multifoliated pattern.

figure 13.18

Polymicrogyria and macrogyria in the same brain.

figure 13.18

Polymicrogyria and macrogyria in the same brain.

0 0

Post a comment