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Adam MP, Feldman J, Mirzaa GM, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2024.

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Table 2.

Clinical Severity of Lissencephaly and Subcortical Brain Heterotopia in General

GradeSubtypesImaging PatternTypical Clinical Outcome
1 (mild) 1-1Partial SBH a>p or p>aBorderline-to-moderate ID, seizures of variable severity; survival into adulthood expected
1-2Diffuse thin SBH (<10 mm)
1-3Partial pachygyria a>p or p>a
1-4Isolated "thin" or undulating LIS
2 (moderate) 2-1Diffuse thick SBH (>10 mm)Moderate-to-severe ID, severe language impairment, seizures often poorly controlled; life expectancy may be ↓, although many survive to adulthood.
2-2Mixed pachygyria-SBH
2-3Diffuse pachygyria a>p or p>a
3 (severe) 3-1Mixed pachygyria-agyriaProfound ID, poorly controlled seizures, short survival typical: mortality rate ~50% by age 10 yrs w/normal cerebellum; much higher w/cerebellar hypoplasia
3-2Diffuse agyria
3-3Agyria w/cerebellar hypoplasia

a = anterior; ID = intellectual disability; LIS = lissencephaly; p = posterior; SBH = subcortical band heterotopia

From: PAFAH1B1-Related Lissencephaly / Subcortical Band Heterotopia

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