Malformations of the Convolutions and Cortical Cytoarchitecture

Fissures, sulci, and convolutions appear on the cortical surface in an orderly sequence according to a strict timetable. Up to 12 to 13 weeks' gestation, the cortical surface is smooth. By the 14th week, a shallow indentation appears at the site of the future Sylvian fissure. Secondary and tertiary sulci appear at 7 to 9 months' gestation (Fig. 13.14).

figure 13.11

Schizencephaly or porencephaly. A and B. A large oval-shaped defect along the Sylvian fissure extends through the entire width of the cerebral wall. The lateral ventricle communicates with the subarachnoid space. C. A 5-year-old epileptic, quadriplegic, mentally retarded boy. Symmetrically situated large defects involve the medial and lateral walls of both hemispheres (doughnut brain). D. The cortical lamination is abnormal in the lips of the defect.

figure 13.11

Schizencephaly or porencephaly. A and B. A large oval-shaped defect along the Sylvian fissure extends through the entire width of the cerebral wall. The lateral ventricle communicates with the subarachnoid space. C. A 5-year-old epileptic, quadriplegic, mentally retarded boy. Symmetrically situated large defects involve the medial and lateral walls of both hemispheres (doughnut brain). D. The cortical lamination is abnormal in the lips of the defect.

figure 13.12

Hydranencephaly in a 3-year-old, blind, quadriplegic, profoundly retarded epileptic boy. Basal (A) and dorsal (B) views of the brain; the cerebral hemispheres are transformed into smooth-walled cysts, only the temporo-basal lobes have some rudimentary convolution.

figure 13.12

Hydranencephaly in a 3-year-old, blind, quadriplegic, profoundly retarded epileptic boy. Basal (A) and dorsal (B) views of the brain; the cerebral hemispheres are transformed into smooth-walled cysts, only the temporo-basal lobes have some rudimentary convolution.

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