Evaluating intraoperative ultrasound (IOUS) in focal cortical dysplasia (FCD) resection surgery: A systematic review

Surgery is the best approach to treating focal cortical dysplasia (FCD)-related epilepsy; yet, it has suboptimal outcomes because distinguishing the boundaries between the FCD region and normal brain tissue intraoperatively poses a challenge. The use of intraoperative ultrasound (IOUS) helps demarcate FCD lesion borders leading to more accurate intraoperative resection. In this review, the use of IOUS for the resection of FCD was evaluated. This systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The Medline, Embase, Cochrane Library, Scopus Library, and Dynamed Library databases were searched, and two independent reviewers examined the articles. The search terms related to “drug-resistant epilepsy” and “intraoperative ultrasound.” The results between January 2008 and April 2022 were abridged for FCD type, ultrasound resolution, extent of lesion resection, correction of brain shift, postoperative neurological deficits, and postoperative seizure freedom (Engel classification). Ten articles were included in the study. The parameters used to assess the efficacy of IOUS in FCD surgery were ultrasound resolution, demarcation of lesion boundaries, correction of brain shift, postoperative neurological deficits, and seizure freedom. Most studies have shown that IOUS produces high-resolution images. Surgery for Type 2 FCD patients had better outcomes than surgery for Type 1 FCD patients due to better visualization by IOUS. Patients were classified as Engel class 1 or class 2 postoperatively. Eight studies found that IOUS was superior to magnetic resonance imaging in brain shift correction. The preliminary results look promising, especially for the international league against epilepsy class 2 FCD. However, there is a need for more high-quality research evaluating the use of IOUS in FCD and comparing it to other intraoperative imaging modalities.