Focal Cortical Dysplasia and Refractory Epilepsy: Role of Multimodality Imaging and Outcome of Surgery

Abstract

BACKGROUND AND PURPOSE: Focal cortical dysplasia (FCD) is one of the most common causes of drug resistant epilepsy. Our aim was to evaluate the role of presurgical noninvasive multimodality imaging techniques in selecting patients with refractory epilepsy and focal cortical dysplasia for epilepsy surgery and the influence of the imaging modalities on long-term seizure freedom. MATERIALS AND METHODS: We performed a retrospective analysis of data of 188 consecutive patients with FCD and refractory epilepsy with at least 2 years of postsurgery follow-up. Predictors of seizure freedom and the sensitivity of neuroimaging modalities were analyzed. RESULTS: MR imaging showed clear-cut FCD in 136 (72.3%) patients. Interictal FDG-PET showed focal hypo-/hypermetabolism in 144 (76.6%); in 110 patients in whom ictal SPECT was performed, focal hyperperfusion was noted in 77 (70.3%). Focal resection was the most common surgery performed in 112 (59.6%). Histopathology revealed FCD type I in 102 (54.3%) patients. At last follow-up, 124 (66.0%) were seizure-free. Complete resection of FCD and type II FCD were predictors of seizure freedom. Localization of FCD on either MR imaging or PET or ictal SPECT had the highest sensitivity for seizure freedom at 97.5%. Among individual modalities, FDG-PET had the highest sensitivity (78.2%), followed by MR imaging (75.8%) and ictal SPECT (71.8%). The sensitivity of MR imaging to localize type I FCD (60.8%) was significantly lower than that for type II FCD (84.8%, P Ͻ .001). Among 37 patients with subtle MR imaging findings and a focal FDG-PET pattern, 30 patients had type I FCD. CONCLUSIONS: During presurgical multimodality evaluation, localization of the extent of the epileptogenic zone in at least 2 imaging modalities helps achieve seizure freedom in about two-thirds of patients with refractory epilepsy due to FCD. FDG-PET is the most sensitive imaging modality for seizure freedom, especially in patients with type I FCD.

Definitions and classification of malformations of cortical development: practical guidelines

“…In case of a suspicion of MCD causing epilepsy, radiologists should also consider using nuclear medicine techniques, such as FDG PET, especially in MRI negative scans. Indeed, interictal FDG PET coregistered to structural MRIs may aid in localizing epileptogenic MCD in surgical workup because of its hypometabolic appearance ( Jayalakshmi et al , 2019 ). If this still give equivocal results, an ictal SPECT can be performed to help to identify the epileptic zone by showing hyperperfusion.…”

In vivo MRI Successfully Reveals the Malformation of Cortical Development in Infant Rats

“…In addition, many patients with FCD type I are diagnosed only after the surgical excision of epileptic foci, and some of them experience surgical failures due to incomplete resection (Choi et al, 2018;Chen et al, 2019). Thus, non-invasive imaging diagnosis of FCD is important to offer the right therapeutic option to patients with intractable focal epilepsies (Jayalakshmi et al, 2019).…”

7T MRI with post-processing for the presurgical evaluation of pharmacoresistant focal epilepsy

“…Co-registered PET has been reported to correctly localize 72.6–89.3% of FCD type II cases. 28 , 29 , 43 Occasionally, there are remote hypometabolic regions on PET, 43 which often occurs in the temporal lobe and may mislead the detection of extratemporal FCD, as with cases P2 and P10 in our cohort.…”

“… 27 However, subtle epileptogenic lesions always require multimodal imaging data to be identified in presurgical evaluation. 28 – 30 As of yet, it remains unclear whether 7T MRI with post-processing can enhance the detection of epileptogenic lesions in MRI-negative patients who have been comprehensively evaluated through multimodal imaging data. Herein, we investigated the diagnostic value of 7T MRI with post-processing in a cohort of epilepsy surgical candidates whose 3T MRI results were negative or inconclusive after comprehensive evaluation.…”