= AGYRIA-PACHYGYRIA COMPLEX

= “smooth brain” = most severe of neuronal migration anomalies; autosomal recessive disease with abnormal cortical stratification

agyria = absence of gyri on brain surface

pachygyria = focal / diffuse area of few broad flat gyri

1. COMPLETE LISSENCEPHALY = AGYRIA
   most frequently parietooccipital in location
2. INCOMPLETE LISSENCEPHALY
   = areas of both agyria + pachygyria, pachygyric areas most frequently in frontal + temporal regions

Histo: thick gray + thin white matter with only four cortical layers I, III, V, VI (instead of six layers)

Often associated with:

1. CNS anomalies: microcephaly, hydrocephalus, agenesis of corpus callosum, hypoplastic thalami
2. micromelia, clubfoot, polydactyly, camptodactyly, syndactyly, duodenal atresia, micrognathia, omphalocele, hepatosplenomegaly, cardiac + renal anomalies

• microencephaly, severe mental retardation
• hypotonia + occasional myoclonic spasm
• early seizures refractory to medication
• smooth thickened cortex with diminished white matter
• figure-eight appearance of cerebrum on axial images ← shallow widened vertically oriented sylvian fissures
• absent / shallow sulci and gyri (brain looks similar to that in fetuses of <23 weeks GA)
• middle cerebral arteries close to inner table of calvarium ← absence of sulci
• small splenium + absent rostrum of corpus callosum
• hypoplastic brainstem ← lack of formation of corticospinal + corticobulbar tracts
• ventriculomegaly (affecting atrium + occipital horns)
• midline round calcification in area of septum pellucidum (CHARACTERISTIC)
• polyhydramnios (50%)

Prognosis: death by age 2

DDx: polymicrogyria (= formation of multiple small gyri mimicking pachygyria on CT + MR, most common around sylvian fissures, broad thickened gyri with frequent gliosis subjacent to polymicrogyric cortex as the most important differentiating feature)