February 16, 2017
A 5-month-old infant with history of abnormal head ultrasound showing nonspecific echogenic foci in bilateral perisylvian regions; normal development at this stage, without focal neurologic symptoms
Polymicrogyria/Congenital CMV
- Background:
- Developmental abnormality resulting from disruption of late neuronal migration and postmigrational cortical organization, occurring after 20 weeks of gestation
- Associated with various genetic abnormalities and in utero insults, such as congenital infection and cerebral ischemia
- Congenital CMV is the most common infectious etiology for PMG.
- Vascular insufficiency in twin gestations is associated with PMG.
- PMG is seen with sporadic mutations/deletions and in syndromes such as Zellweger (peroxisomal disorder), Sturge Weber, Di-George, and Aicardi.
- Clinical Presentation:
- Varies depending on location of polymicrogyria, severity/involvement, and etiology
- May be asymptomatic; however, clinical presentations include intractable epilepsy, developmental delay, and severe cognitive dysfunction.
- Key Diagnostic Features:
- Thick-appearing cortex with small, irregular gyri and shallow sulci
- Bumpy appearance of superficial cortex with corrugated inner surface at the gray-white interface
- PMG has a predilection for the bilateral perisylvian region of the brain. The association of PMG and parenchymal calcifications is highly suggestive of CMV. Other findings also include mineralizing angiopathy and bilateral temporal cysts.
- Other patterns: generalized, associated periventricular nodular heterotopia (PNH), focal (frontal, parietal, temporal, occipital) and other rarer patterns associated with specific syndromes.; developmental venous anomalies are often seen in association with PMG.
- Differential Diagnoses:
- Many etiologies are associated with polymicrogyria, including:
- Congenital Zika virus: periventricular calcifications, ventriculomegaly, subarachnoid space enlargement, microcephaly, periventricular leukomalacia, and cerebellar hypoplasia have been described recently, with a similar pattern of congenital CMV, but more severe involvement.
- Hereditary bilateral perisylvian polymicrogyria: heterogeneously inherited, perisylvian predominant PMG; schizencephaly is often present.
- Peroxisomal diseases (including Zellweger Syndrome): can see both perisylvian PMG and frontotemporal pachygyria.; white matter abnormalities, cerebellar malformations, and caudothalamic cysts are also seen.
- Cobblestone malformations (including Walker-Warburg and Fukuyama type): results from overmigration of neurons; PMG-like (cobblestone) malformations of the cortex; presence of white matter/myelination abnormalities differentiates from PMG
- Pachygyria: cortex is thicker, deep white matter more often normal, gyri are more broad and thickened than with PMG, and there is a temporooccipital predilection; the primary sulci are present.
- Many etiologies are associated with polymicrogyria, including:
- Treatment:
- Prognosis ranges widely based on the severity of disease. Early timing of infection may result in a greater degree of insult.
- Treatment is aimed at controlling seizures when present.
- Infants with confirmed CNS cytomegalovirus infection may benefit from treatment with ganciclovir.
