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Neuroradiology Case of the Week

Case 180

A. R. Klekers, MD, and Per-Lennart Westesson, MD, PhD, DDS

Clinical Presentation: Patient is a 28-year-old male with a 20-year history of partial and generalized seizures refractory to medical therapy.

Radiological Findings: T1 post- contrast and T2-weighted MR images demonstrate a large cystic cavity occupying a majority of the left parietal and occipital lobes. The anterior aspect communicates with the left lateral ventricle. There is little brain parenchyma adjacent to the cyst in the parieto-occipital region. On post-contrast T1-weighted image there is no enhancement of the cyst. T2-weighted image demonstrates no gray matter lining the cyst.

Diagnosis: Porencephalic cyst

Discussion: Porencephalic cysts develop secondary to focal injury during the fetal period [1]. These cysts may be bilateral or unilateral [2]. Often they follow vascular territories supplied by cerebral arteries and may develop secondary to infarction, hemorrhage, or infectious injury secondary to agents such as CMV [1,3]. There are rare cases of familial porencephaly which is not well understood [3]. Clinical presentation may include mental retardation, intractable epilepsy, or ophthalmological signs [3].
     Porencephalic cysts are best imaged by MRI which can demonstrate a smooth walled cystic structure isointense to CSF in the brain parenchyma with volume loss and often communicating with the subarachnoid space or ventricular system [3]. There is no enhancement after contrast administration [3]. Porencephalic cysts can be differentiated from schizencephaly in that the CSF space is lined by gliotic white matter and not gray matter [2]. These lesions may be difficult to differentiate from enlargement of a lateral ventricle [1].

References:

1. Barkovich AJ. Pediatric Neuroimaging. Lippincott, Williams & Wilkins, 4th ed. 2005:191-192.
2. Donnelly L. Fundamentals of Pediatric Radiology. Saunders, 2001: 235-236.
3. Osborn A. Diagnostic Imaging Brain. Amirsys, 1st ed. 2004: 36-39.