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Schizencephaly -neuronal migration disorder

Schizencephaly

Poornachand Veerapaneni; Karthika Durga Veerapaneni; Sisira Yadala.

Last Update: August 10, 2020.

Introduction

Schizencephaly is a rare congenital neuronal migration disorder characterized by the presence of a full-thickness cleft, lined with heterotopic gray matter, and filled with cerebrospinal fluid (CSF), which connects the pial surface of the cerebral hemisphere with the ependymal surface of the lateral ventricle.

Schizencephaly was first described by Wilmarth in 1887. The term was coined from the Greek word “schizen” ‘to divide’ and introduced by Yakovlev and Wadsworth in 1946, based on their work on cadavers, that classified schizencephaly into two types:

  • Type I (closed-lip): Cleft is fused, which prevents the cerebrospinal fluid passage.
  • Type II (open-lip): A cleft is present, which permits CSF to pass between the ventricular cavity and subarachnoid space.

Schizencephaly can be either unilateral or bilateral.

Recent literature classifies schizencephaly into three types, as the full thickness cleft containing CSF is not mandatory for the definition.

  • Type 1 (trans-mantle): No CSF-containing cleft on magnetic resonance imaging (MRI), but contains a trans-mantle column of abnormal gray matter.
  • Type 2 (closed-lip): Presence of cleft containing CSF, but the lining lips of abnormal gray matter are abutting and opposed to each other.
  • Type 3 (open-lip): Presence of cleft containing CSF. The lining lips of abnormal gray matter are not abutting each other.

Etiology

The exact etiopathogenesis of schizencephaly is not yet clearly understood in the scientific world. Possible etiological factors include exposure to teratogenic agents, viral infections prenatally, genetic, stroke in utero, and young maternal age.

Some environmental exposures have been implicated: Teratogens such as alcohol, warfarin, or cocaine; viral infection, especially cytomegalovirus; as well as attempted abortion, hypoxia, amniocentesis, or chorionic villus biopsy, or maternal trauma, etc.

Fetal intracranial hemorrhage caused by abnormal type IV collagen has also been implicated.

Some genetic mutations have been reported as possible etiological factors for schizencephaly. The main genes identified in this regard are the following:

  1. COL4A1 mutations
  2. EMX2-germline mutations
  3. SHH gene
  4. SIX3 gene

MORE INFO

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