lissencephaly
Pronunciation: lis-en-SEF-ah-lee
Rare brain malformation characterized by absent or reduced cerebral gyri resulting in a smooth brain surface.
Full Definition
Lissencephaly, literally meaning 'smooth brain,' is a rare neuronal migration disorder that results in the absence of normal brain folds (gyri and sulci). This condition occurs when neurons fail to migrate properly during fetal brain development, typically between 12-24 weeks of gestation. The brain surface appears abnormally smooth, and affected children typically present with severe developmental delays, seizures, and intellectual disability. Two main types exist: classical lissencephaly (type I) and cobblestone lissencephaly (type II). In pediatric pathology, gross examination reveals the characteristic smooth brain surface, while microscopic examination shows a disorganized four-layered cortex instead of the normal six layers.
Usage
Usage note: May be graded I-IV based on severity. Related terms pachygyria (thick gyri) and agyria (absent gyri) describe the spectrum.
In Context
- "Gross examination of the brain revealed grade I lissencephaly with nearly absent sulcation." — Neuropathology report
- "Genetic testing confirmed LIS1 deletion in this case of classical lissencephaly." — Clinical genetics report