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Neuroradiology Case of the Week

Case 58

Ravinder Sidhu MD, Jeevak Almast MD, Henry Wang MD, PhD,
and P-L Westesson MD, PhD, DDS

Clinical Presentation: An 11-month-old male presented with perinatal stroke and right-sided weakness.

Radiological Findings: Axial T1-weighted MR image showed a cleft at the posterior aspect of right frontal lobe connecting the extra-axial fluid space with the right lateral ventricle (Fig. 1A). The cleft was lined by gray matter, which had a small gap in between opposing surfaces indicating an open lip schizencephaly (Fig. 1B). Right cerebral hemisphere was smaller than left hemisphere. Septum pellucidum was absent giving a boxlike configuration of ventricles. The right lateral ventricle was mildly dilated (Fig. 2A). Posterior part of the body of corpus callosum was thin (Fig. 2B). There was thickened gray matter along with effacement of sulci in the region of right frontal lobe suggestive of pachygyria (Fig. 3).Optic nerve and optic chiasm were normal.

Diagnosis: Schizencephaly

Discussion:  Schizencephaly is an uncommon congenital disorder of cerebral cortical development, defined as a gray matter-lined cleft extending from the pial surface to the ventricle. The spectrum of cleavage ranges from a thread of cerebrospinal fluid connecting the subarachnoid space to the ventricle, which is encircled by abnormal gray matter (closed-lip schizencephaly), to a wide communication between the subarachnoid space and the ventricle with edges of abnormal cortex (open-lip schizencephaly). The clefts can be unilateral or bilateral, symmetric or asymmetric. The schizencephalic clefts occur more often in the anterior than in the posterior neocortex. Schizencephaly may be associated with other central system anomalies such as absent septum pellucidum and corpus callosum, septo-optic dysplasia [1].
   These patients may exhibit a broad range of neurological disabilities, which are presumably related to the amount of brain tissue involved. They may present with seizures, developmental delay, and hydrocephalus.
   The etiology of schizencephaly remains unclear. The damage to the germinal matrix, radial glia, or the neuroblasts could occur due to multiple etiologies, such as genetic, toxic, vascular, infectious, or metabolic. Schizencephaly is most likely the end result of a variety of insults occurring at a critical time in brain development.
   Radiologically, CT scan can demonstrate the cleft as a linear hypodense lesion extending from the cerebral cortex to the lateral ventricle. The presence of a ventricular dimple is a characteristic feature of schizencephaly. In open type schizencephaly there may be changes on inner table of skull vault due to pressure effects caused by cerebrospinal fluid pulsations from lateral ventricles. However, MR imaging is more sensitive than CT scan in detecting the clefts as well as the associated abnormalities such as heterotopias, polymicrogyria, pachygyria, and septo-optic dysplasia. MR imaging provides excellent demonstration of the anatomic changes in schizencephaly [2,3].
   The imaging differential diagnosis of schizencephaly is porencephalic cyst. Since porencephalic cyst results from insults to otherwise normally developed brain, the cerebrospinal fluid space is lined by gliotic white matter rather than dysplastic heterotopic cortex [4].

References:

1. Packard AM, Miller VS, Delgado MR. Schizencephaly: correlations of clinical and radiological features. Neurology 1997; 48:1427-1434.
2. Srikanth SG, Jayakumar PN, Vasudev MK. Open and minimally open lips schizencephaly. Neurol India 2000; 48:155-157.
3. Barkovich JA, Norman D. MR imaging of schizencephaly. AJR Am J Roentgenol 1988; 150:1391-1396.
4. Osborn A. Disorders of diverticulation and cleavage, sulcation and cellular migration. Diagnostic Radiology. St. Louis; Mosby, 1994, pp52.