Occult focal cortical dysplasia may predict poor outcome of surgery for drug-resistant mesial temporal lobe epilepsy

Abstract

Purpose The results of surgery in patients with mesial temporal lobe epilepsy (MTLE) associated with hippocampal sclerosis (HS) are favorable, with a success rate over 70% following resection. An association of HS with focal cortical dysplasia (FCD) in the temporal lobe is one of the potential causes for poor surgical outcome in MTLE. We aimed to analyzed seizure outcome in a population of MTLE patients and recognize the role of occult FCD in achieving postoperative seizure control. Methods We retrospectively analyzed postoperative outcomes for 82 consecutive adult patients with the syndrome of MTLE due to HS, who had no concomitant lesions within temporal lobe in MRI and who underwent surgical treatment in the years 2005–2016, and correlated factors associated with seizure relapse. Results At the latest follow-up evaluation after surgery, 59 (72%) were free of disabling seizures (Engel Class I) and 48 (58,5%) had an Engel Class Ia. HS associated with FCD in neocortical structures were noted in 33 patients (40%). Analyzes have shown that dual pathology was the most significant negative predictive factor for Engel class I and Engel class Ia outcome. Conclusions The incidence of dual pathology in patients with temporal lobe epilepsy seems to be underestimated. An incomplete epileptogenic zone resection of occult focal temporal dysplasia within temporal lobe is supposed to be the most important negative prognostic factor for seizure freedom after epilepsy surgery in MTLE-HS patients. The study indicates the need to improve diagnostics for other temporal lobe pathologies, despite the typical clinical and radiological picture of MTLE-HS.

Postoperative seizure and memory outcome of temporal lobe epilepsy with hippocampal sclerosis: A systematic review

“…Of 3019 potentially relevant reports identified, with 915 duplicates removed, 56 reports proved potentially eligible after title and abstract screening. After full text screening, 15 cohort studies with 2485 patients were included in the meta‐analysis of seizure outcomes 14–16,18,20,41–50 . Seven articles including six cohorts with detailed information of postoperative memory outcome were included 14,17–20,50,51 .…”

“…In 12 eligible studies, 14,15,18,[42][43][44][45][46][47][48][49][50] HS type 3 achieved the highest pooled rate of seizure freedom (64.8%, 95% CI = 46.1-83.4; five studies, 43 patients), 14,[44][45][46]49 followed by type 1 (63.4%, 95% CI = 58.6-68.2; 11 studies, 923 patients), 14,15,[42][43][44][45][46][47][48][49][50] type 2 (56.7%, 95% CI = 44.3-69.1; 11 studies, 194 patients), 14,15,[42][43][44][45][46][47][48][49][50] and no-HS (47.6%, 95% CI = 37.2-58.0; 6 studies, 202 patients), 14,18,44,45,49,50 with moderate to substantial heterogeneity. Nevertheless, pooling of data showed no significant difference in postoperative seizure freedom between HS type 2 and type 1 (crude RR = .98, 95% CI = .84-1.15, p = .81, I 2 = 32%), HS type 3 and type 1 (crude RR = 1.11, 95% CI = .82-1.52, p = .50, I 2 = 37%), or no-HS and HS patients (crude RR = .80, 95% CI = .62-1.03, p = .08, I 2 = 52%), with no significant heterogeneity across studies (Table 2, Figure…”

“…The 12 trials involved 1494 patients, consisting of 1084 HS type 1, 210 type 2, 62 type3, and 138 no-HS cases. [14][15][16]20,[41][42][43][44][45][46][47][48] The overall pooled incidence of patients who achieved an improved outcome after surgery was 73.5% (95% CI = 63.4-83.7, I 2 = 94%) in HS type 1, 67.5% (95% CI = 56.5-78.6, I 2 = 68%) in type 2, 65.4% (95% CI = 49.4-81.5, I 2 = 40%) in type 3, and 61.5% (95% CI = 40.6-82.5, I 2 = 85%) in the no-HS group. Pooled RR indicated no significant difference of improved outcome among different HS subtypes (p > .05; Table 2, Figure 3).…”

“…The improved outcome of patients with isolated HS and coexistent FCD were compared in four (28.6%) studies, 15,16,43,48 and no significant difference was found between the HS type 1 and type 2 groups (Table 2, Figure 4).…”

“…This is in accord with trials by Blümcke et al 10 and de Lanerolle et al, 58 which reported no significant difference of Engel 1 at 1 year after hippocampal resection in mesial temporal sclerosis (MTS) No-HS vs. HS 14,18,44,45,49,50 Crude RR = .80 (. HS type 2 vs. HS type 1 isolated HS 15,16,43,48 Crude RR = .93 (.81-1.07)…”