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Schizencephaly

What is schizencephaly?

Schizencephaly

Axial T2-weighted MRI demonstrates a small open-lip schizencephaly. The septum pellucidum is absent.

Schizencephaly is a rare, congenital cortical malformation characterized by abnormal slits, or clefts, in the cerebral hemispheres of the brain.

Classification and known presentations

Schizencephaly is a disorder with heterogeneous causes, many of which are vascular disruptive in origin. It is unquestionably associated with polymicrogyria (PMG) of disruptive aetiology. Accordingly, it is classified with PMG.  There are 5 known presentations of schizencephaly:

PMG (classic) with transmantle clefts (schizencephaly) or calcification

Clinically defined with clefts suggesting vascular pathogenesis or unknown cause

Schizencephaly

Axial T2-weighted MRI in unilateral closed-lip schizencephaly. The cleft is lined by grey matter and extends from the pial surface to the lateral ventricle.

Clinically defined with prenatal viral exposure (especially CMV)

Clinically defined with AR inheritance

  • Familial schizencephaly with single unilateral or bilateral clefts (Haverkamp et al., 1995)
  • Familial schizencephaly with multiple bilateral clefts

Characteristics

It appears as a cleft filled with CSF and extending medially from the subarachnoid space into the lateral ventricle.  The wall of the cleft is lined with dysmorphic grey matter.  The grey matter sometimes extends into the lateral ventricle in the form of subependymal heterotopias.  The cleft may be small or large, unilateral or bilateral.  The anomaly may be of the open-lip or closed-lip type.  Closed-lip schizencephaly is characterized by grey matter-lined lips, which are in contact with each other.  Open-lip schizencephaly has separated lips and a cleft of CSF extending to underlying ventricles. It might be associated with septo-optic dysplasia, optic nerve hypoplasia or the absence of septumpellucidum, pachygyriapolymicrogyriaheterotopia, hydrocephalus, an abnormally small head, and arachnoid cysts.

Schizencephaly

Unilateral open-lip schizencephaly. T1-weighted coronal MRI. A large cleft in the right hemisphere spans from the subarachnoid space to the lateral ventricle.

Symptoms

Clinical manifestations of schizencephaly most often include varying degrees of developmental delay, intellectual impairment, motor impairment, poor muscle tone, and seizures.  Children with clefts in both hemispheres (called bilateral clefts) commonly have developmental delays, delays in speech and language skills, and problems with brain-spinal cord communication.  Individuals with clefts in only one hemisphere (called unilateral clefts) are often paralyzed on one side of the body, but may have average to near-average intelligence.

Diagnosis

Magnetic resonance imaging (MRI) is the preferred imaging modality because of its superior differentiation of gray matter and white matter, and its ability to image in more than one plane.  Identification of gray matter lining the cleft is the pathognomonic finding in differentiating schizencephaly from porencephaly, and this is best demonstrated on MRIs.

Causes

The causes of schizencephaly are heterogeneous and can include teratogens, prenatal infection, or maternal trauma. Reported genetic causes include chromosomal aneuploidy, EMX2 mutations, and possible autosomal recessive familial cases based on recurrence in siblings.

Treatment

Treatment generally consists of physical therapy, occupational therapy (with emphasis on neuro-developmental therapy techniques), seizure control, and, in cases that are complicated by hydrocephalus, as shunt.

Prognosis

The prognosis varies depending on the size of the clefts and the degree of neurological deficit.

Prevalence

The exact prevalence is unknown.  A study published in 2011 found a prevalence of 1.48 cases per 100,000 births in the UK.

Sources

  1. Barkovich AJ, Kjos BO. Schizencephaly: correlation of clinical findings with MR characteristics. AJNR Am J Neuroradiol 1992;13:85–94.
  2. Howe DT, Rankin J, Draper ES. Shizenzephaly prevalence, prenatal diagnosis and clues to etiology: a register-based study. Ultrasound Obstet Gynecol. 2012 Jan;39(1):75-82. doi: 10.1002/uog.9069. Epub 2011 Dec 5.
  3. Oh K, Kennedy A, Frias A, et al. Fetal schizencephaly: pre-and postnatal imaging with review of the clinical manifestations. Radiographics 2005;25:647–57.
  4. Hung P, Wang H, Yeh Y, et al. Coexistence of schizencephaly and intracranial arteriovenous malformation in an infant. AJNRAm J Neuroradiol 1996;17:1921–22.
  5. Barkovich AJ, Guerrini R, Kuzniecky RI, Jackson GD, Dobyns WB. “A developmental and genetic classification for malformations of cortical development:  update 2012. Brain 2012. 10.1093/brain/aws019.