Polymicrogyria

KEY FACTS

TERMINOLOGY

• Malformation due to abnormality in late neuronal

migration and cortical organization

○ Neurons reach cortex but distribute abnormally, forming

multiple small, undulating gyri

○ Result is cortex containing multiple small sulci that often

appear fused on gross pathology and imaging

IMAGING

• Excessively small and prominent convolutions

• Predilection for perisylvian regions; when bilateral, often

syndromic

• Small irregular gyri, but cortex appears normal or thick on

MR

• May appear as deep infolding of thick cortex

• MR comprehensively assesses malformation; NECT for

suspected Ca++ (TORCH)

TOP DIFFERENTIAL DIAGNOSES

• Microcephaly with simplified gyral pattern

• Hemimegalencephaly

• Congenital cytomegalovirus

• Pachygyria

• "Cobblestone" malformations

CLINICAL ISSUES

• Polymicrogyria most commonly → developmental delay,

seizure

• Onset and severity of seizures, neurological deficits relate

to extent of malformation, presence of associated

anomalies

DIAGNOSTIC CHECKLIST

• Remember that polymicrogyria can result from injury,

infection, or metabolic or destructive causes

• If visual or auditory symptoms, rule out congenital infection

(Left) Coronal oblique graphic

shows the thickened pebbly

gyri of polymicrogyria

involving the frontal ﬈ and

temporal ﬊ opercula. Note

the abnormal sulcation and

the irregular cortical-white

matter junction ﬉ in the

affected regions. (Right) Axial

T2WI MR of a patient with

bilateral perisylvian

polymicrogyria shows a

thickened, irregular cortex in

the insulae ﬈, as well as

frontal and parietal opercula

﬉. Incidental cavum septi

pellucidi is also seen.

(Left) Coronal T1WI MR of the

same patient shows thickened,

deeply undulating insulae ﬈

and opercula around the

abnormal sylvian fissures.

Polymicrogyria is often more

poorly characterized in the

coronal plane. The microgyri

are not as well seen. (Right)

Sagittal T1WI MR shows the

characteristic continuation of

the perisylvian polymicrogyria

posteriorly into the superior

parietal lobule ﬈, which

establishes the diagnosis.

Other abnormal horizontal

sulci with thick, irregular

cortex ﬉ are present.

Brain: Pathology-Based Diagnoses: Malformations,

Trauma, and Stroke

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