Ultrasonographic Features of Focal Cortical Dysplasia and Their Relevance for the Surgical Treatment of Epilepsy

Aim: Surgery has shown to be the best therapeutic option for medically refractory cases of focal cortical dysplasia (FCD)-associated epilepsy. Seizure outcome primarily depends on the extent and completeness of resection, making intraoperative visualization and delineation of FCDs essential. Our study assesses the diagnostic yield of intraoperative ultrasound (IOUS) for such lesions.

Methods: Fifteen consecutive patients with therapy–refractory epilepsy undergoing IOUS-assisted microsurgical resection of a radiologically suspected FCD were prospectively followed between January 2013 and July 2016. Morphological appearance on IOUS was compared with preoperative postprocessed magnetic resonance imaging (MRI) and the sonographic characteristics were analyzed in relation to histological subtype. IOUS was studied in regard to its value to improve completeness of resection and improve postoperative seizure outcome.

Results: In all cases of FCD, the surgeon was able to identify the dysplastic area. Visualization of FCD I proved to be more difficult than FCD II and demarcation of its borders was less clear, resulting in residual dysplasia on postoperative coregistered MRI in two out of three patients. In every case of FCD II, IOUS allowed clear intraoperative visualization and demarcation with high topographical–morphological correlation to preoperative postprocessed MRI. Postoperative MRI showed complete resection in every case of FCD II. Sonographic features and their severity correlate to the underlying histological degree of dysplasia (FCD IA/FCD IB < FCD IC < FCD IIA < FCD IIB). In one patient, IOUS showed features atypical for FCD, which proved to be nonspecific gliosis on later histological analysis.

Conclusion: The distinct sonographic features on IOUS allow for intraoperative differentiation between FCD and non-FCD lesions as well as discrimination between the different histological subtypes of FCD. Sonographic demarcation depends on the underlying degree of dysplasia. IOUS allows for more tailored and improved extent of resection by clearly delineating the dysplastic area, which in turn correlates with favorable seizure outcome.

No conflict of interest has been declared by the author(s).