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Schizencephaly


KEY FACTS

Imaging

  • Transmantle gray matter (GM) lining clefts

    • Look for dimple in wall of ventricle if cleft is narrow/closed

  • Up to 1/2 of schizencephalies are bilateral

    • When bilateral, 60% are open-lipped on both sides

  • GM lining clefts may appear hyperdense

  • Ca++ when associated with CMV or COL4A1 mutations

  • Prior to myelination, T2WI more clearly defines lesion

Top Differential Diagnoses

  • Encephaloclastic porencephaly

    • Lined by gliotic white matter, not dysplastic GM

  • Hydranencephaly

    • Residual tissue is supplied by posterior circulation

  • Semilobar holoprosencephaly

    • Can mimic bilateral open-lip schizencephaly

Pathology

  • Can be result of acquired in utero insult affecting neuronal migration

  • 1/3 of children with schizencephaly have non-CNS abnormalities

  • Infection (CMV), vascular insult, maternal trauma, toxin

Clinical Issues

  • Unilateral: Seizures or mild motor deficit

  • Bilateral: Developmental delay, paresis, microcephaly, spasticity

  • Seizure more common with unilateral clefts

  • Size of clefts and presence of associated malformative lesions govern severity of impairment

Coronal graphic shows right closed-lip
and left open-lip
schizencephaly, both lined by gray matter. Note absence of septum pellucidum
.

Coronal T2FS MR shows bilateral schizencephaly. A closed-lip defect is seen on the right
, extending from the pial surface to the ventricular outpouching
, while a mildly open-lip defect lined with dysplastic gray matter is present on the left
. Note the abnormal vessels in the left-sided schizencephalic cleft
.

Axial NECT in a 19-year-old man in the ER for trauma shows a “nipple” or outpouching of the left lateral ventricle
that extends into a full-thickness cerebrospinal fluid cleft
. The cleft is lined with heterotopic gray matter
. This is a classic unilateral schizencephaly.

Coronal T2WI shows large bilateral open-lip schizencephalic clefts
.

TERMINOLOGY

Synonyms

  • Agenetic porencephaly

Definitions

  • Clefts in brain parenchyma that extend from cortical surface to ventricle (pia to ependyma), lined by dysplastic gray matter (GM)

IMAGING

General Features

  • Best diagnostic clue

    • Transmantle gray matter lining clefts

      • –

        Look for dimple in wall of ventricle if cleft is narrow/closed

  • Location

    • Frontal and parietal lobes near central sulcus

  • Size

    • Closed-lip (small defect) or open-lip (large defect)

  • Morphology

    • Up to 1/2 of schizencephalies are bilateral

      • –

        When bilateral, 60% are open-lipped on both sides

CT Findings

  • NECT

    • Cleft of CSF density (in open-lip schizencephaly)

    • GM lining clefts may appear hyperdense

    • Dimple on lateral wall of lateral ventricle indicating ependymal margin of cleft

    • Ca++ when associated with cytomegalovirus (CMV)

    • Thinning and expansion of calvaria can be seen with large open-lipped clefts

  • CECT

    • Large, primitive-appearing veins near cleft

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