The use of intraoperative ultrasound in patients with focal cortical dysplasia: preliminary observations

Abstract

Introduction . The cessation of epileptic seizures after surgical treatment of focal epilepsy is the main objective of the surgeon. When a neurosurgeon operates focal cortical dysplasia (FCD), he/she faces difficulties with the radical removal of pathological tissue, which looks similar to healthy one. Using the neuronavigation system may not be helpful because of errors caused by displacement of brain tissues after opening the dura mater and resection of pathological foci. Intraoperative MRI examination requires significant financial expenses. One alternative is the intraoperative ultrasound (US) test, which allows one to visualize areas of pathological tissue in real time. The aim of this study is to assess the feasibility of using intraoperative US test. Materials and methods . We conducted a retrospective analysis of 20 cases of pharmacoresistant epilepsy that involved US examination during surgical operation for epilepsy caused by focal cortical dysplasia. In the preoperative period, all patients underwent EEG video monitoring in which at least three seizures were detected. In addition, three patients underwent invasive EEG video monitoring as well as preoperative and postoperative brain MRI. Based on histological verification, the distribution of patients was as follows: Ia type – 1 case (5%); Ib type – 4 cases (20%); Ic type –3 cases (15%); IIa type –3 cases (15%); IIb type – 8 cases (40%); IIIa type – 1 case (5%). Postoperative follow-up continued for 14±10 months (min – 2 months, max – 31 months). Results . Twenty (100%) patients underwent intraoperative US examination where signs of an altered cortex were found in locations similar to those revealed with preoperative MRI scans. Based on the US images, radical resection of pathological tissues was performed in these patients. In 15 (75%) patients, the seizures stopped (Engel class I). According to the US data, FCD had the following characteristics: hyperechogenicity as compared to the brain parenchyma; uneven, fuzzy, irregularly shaped contours; lack of a clear border between the white and gray matter. Conclusion . Intraoperative ultrasound is a safe, inexpensive and effective method for intraoperative imaging of FCD. The authors declare the absence of conflict of interest with respect to this publication. All authors contributed equally to this article.