Cerebrospinal fluid cleft with cortical dimple: MR imaging marker for focal cortical dysgenesis

PURPOSE: To determine whether the magnetic resonance (MR) imaging feature o f a cerebrospinal fluid (CSF) cleft and cortical dimple can be used as a ma rker for cortical dysgenesis. MATERIALS AND METHODS: MR images in 875 patients with epilepsy were evaluat ed for the following features of focal cortical dysgenesis: cortical thicke ning, indistinct junction between gray and white matter, macrogyria, and ab normal sulcal pattern. Images with these features were reevaluated to deter mine the relationship between the CSF cleft-cortical dimple complex and foc al cortical dysgenesis and its contribution to diagnosis. The cleft-dimple complex was defined as a prominent CSF space associated with a region of co rtical volume loss adjacent to the dysgenesis. RESULTS: Seventy-one patients had cortical dysgenesis, including 27 with ce llular proliferation abnormalities, 18 with migration abnormalities, 25 wit h cortical organization abnormalities, and one with miscellaneous anomalies . Histologic correlation was available in 20 patients. There was an associa ted cortical dimple in 29 (41%) patients. This association was strongest in patients with cortical organization abnormalities: It was present in 22 of the 25 (88%) patients. In 12 (48%) patients with abnormalities of cortical organization, the CSF cleft was easier to detect than other features of co rtical dysgenesis or contributed directly to the MR imaging diagnosis. CONCLUSION: The cleft-dimple complex is a marker for subtle cases of focal cortical dysgenesis and may be due to maldevelopment. In patients with seiz ures, the presence of a cleft-dimple complex should alert the physician to scrutinize adjacent regions for developmental anomalies.