Original ArticleIntraoperative Magnetic-Resonance Tomography and Neuronavigation During Resection of Focal Cortical Dysplasia Type II in Adult Epilepsy Surgery Offers Better Seizure Outcomes
Introduction
Focal cortical dysplasia (FCD) was first recognized by Taylor et al. as a cause of drug-resistant epilepsy, resembling a relatively localized lesion amenable for surgical resection showing the histologic features of dysmorphic neurons (International League Against Epilepsy [ILAE] Type IIA) or both dysmorphic neurons and balloon cells (ILAE IIB).1, 2 Many factors are important for a favorable seizure outcome postoperatively, such as the site of resection, FCD subtype, patient age at surgery and duration of epilepsy, lesion localization, but the most important for the surgical approach is the extent of resection, because incompletely resected FCDs show a worse seizure outcome.3 Thus, surgical techniques are necessary that allow for localization according to preoperative multimodal imaging4 and intraoperative magnetic-resonance tomographical imaging (MRI), which allows the investigation of residual FCD tissue and further resection (“intraoperative second-look surgery”). As recent reports give reference that neuronavigation and intraoperative magnetic-resonance tomographical imaging (iopMRI) might be of value in FCD surgery in children,5, 6 we retrospectively investigated our adult patients with FCD II (n = 24) in whom we applied iopMRI during surgery to clarify a possible benefit concerning long-term seizure outcome.
Section snippets
Patients
In total, 24 patients (16 female, 8 male; mean age 34 ± 10 years) suffering from drug-resistant electroclinical and focal epilepsy for a mean of 20.7 ± 5 years (12 frontal lobes, 10 parietal lobes, 1 occipital lobe, and 1 temporo-parietal lobes; 13 were left sided and 11 right sided) were included. In 18 patients (75%), the FCDs were in a highly eloquent region, where motor, sensory, or speech cortical areas were involved (Table 1).
The preoperative epileptological workup consisted of an
Results
In 75% of patients (18/24) with FCD II, complete resection was performed (Table 1). In 89% (16/18) of those patients who had a complete resection, we documented an Engel I seizure outcome after a mean follow-up of 42 months. All incompletely resected patients had a worse outcome (Engel II-IIII, P < 0.0002). Altogether, 67% (16/24) of all patients had an excellent postoperative Engel Grade I seizure outcome. Patients with FCD IIB had also a significantly better seizure outcome compared with
Discussion
Complete surgical resection auf FCD II lesions in medically refractory focal epilepsy resulted in significant more seizure-free patients than incomplete surgery (89% of complete resected vs. none of incomplete resected patients, P < 0.0002). In addition, histologically diagnosed patients with FCD IIB had also significant better seizure outcome compared with patients with FCD IIA (82% vs. 28% Engel I, P < 0.02). In addition, the use of iopMRI led to significantly more seizure-free patients,
Conclusions
In our retrospective study of an institutional consecutive series of resected patients with FCD II in which we used neuronavigation and iopMRI intraoperatively, excellent seizure outcome positively correlated with the amount of resection, the histologic subtype of FCD IIB, and the use of iopMRI, especially when intraoperative second-look surgeries were undertaken.
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Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
K.R. and B.S.K. are co–first authors.