Temporal pole blurring in temporal lobe epilepsy revealed by 3D Edge-Enhancing Gradient Echo MRI

While abnormalities of the hippocampus have been well characterized in temporal lobe epilepsy, various additional temporal lobe abnormalities have also been described. One poorly understood entity, the so-called temporal pole blurring (TPB), is one of the more frequently described neocortical abnormalities in TLE and is thought to represent dysmyelination and axonal loss due to chronic electrical perturbations in early age-onset temporal lobe epilepsy. In this study, we describe the first reported cases of TPB diagnosed by a recently described MRI sequence known as 3D Edge-Enhancing Gradient Echo (3D-EDGE), which has an effective "myelin weighting" making it exquisitely sensitive to this temporal pole dysmyelination. The value of detection of TPB lies in lateralizing seizure onset, as well as predicting a lower baseline neuropsychological performance compared to temporal lobe epilepsy without TPB. Additionally, it is critical to not mistake TPB for alternative diagnoses, such as focal cortical dysplasia or neoplasm.

Diagnostic Accuracy of Epilepsy-dedicated MRI with Post-processing

PURPOSE

To evaluate the diagnostic accuracy of epilepsy-dedicated 3 Tesla MRI including post-processing by correlating MRI, histopathology, and postsurgical seizure outcomes.

METHODS

3 Tesla-MRI including a magnetization-prepared two rapid acquisition gradient echo (MP2RAGE) sequence for post-processing using the morphometric analysis program MAP was acquired in 116 consecutive patients with drug-resistant focal epilepsy undergoing resection surgery. The MRI, histopathology reports and postsurgical seizure outcomes were recorded from the patient's charts.

RESULTS

The MRI and histopathology were concordant in 101 and discordant in 15 patients, 3 no hippocampal sclerosis/gliosis only lesions were missed on MRI and 1 of 28 focal cortical dysplasia (FCD) type II associated with a glial scar was considered a glial scar only on MRI. In another five patients, MRI was suggestive of FCD, the histopathology was uneventful but patients were seizure-free following surgery. The MRI and histopathology were concordant in 20 of 21 glioneuronal tumors, 6 cavernomas, and 7 glial scars. Histopathology was negative in 10 patients with temporal lobe epilepsy, 4 of them had anteroinferior meningoencephaloceles. Engel class IA outcome was reached in 71% of patients.

CONCLUSION

The proposed MRI protocol is highly accurate. No hippocampal sclerosis/gliosis only lesions are typically MRI negative. Small MRI positive FCD can be histopathologically missed, most likely due to sampling errors resulting from insufficient harvesting of tissue.

Gray-White Matter Blurring of the Temporal Pole Associated With Hippocampal Sclerosis: A Microstructural Study Involving 3 T MRI and Ultrastructural Histopathology

Hippocampal sclerosis (HS) is often associated with gray-white matter blurring (GMB) of the anterior temporal lobe. In this study, twenty patients with unilateral temporal lobe epilepsy and HS were studied with 3 T MRI including T1 MP2RAGE and DTI/DMI sequences. Anterior temporal lobe white matter T1 relaxation times and diffusion measures were analyzed on the HS side, on the contralateral side, and in 10 normal controls. Resected brain tissue of three patients without GMB and four patients with GMB was evaluated ultrastructurally regarding axon density and diameter, the relation of the axon diameter to the total fiber diameter (G-ratio), and the thickness of the myelin sheath. Hippocampal sclerosis GMB of the anterior temporal lobe was related to prolonged T1 relaxation and axonal loss. A less pronounced reduction in axonal fraction was also found on imaging in GMB-negative temporal poles compared with normal controls. Contralateral values did not differ significantly between patients and normal controls. Reduced axonal density and axonal diameter were histopathologically confirmed in the temporopolar white matter with GMB compared to temporal poles without. These results confirm that GMB can be considered an imaging correlate for disturbed axonal maturation that can be quantified with advanced diffusion imaging.

Focal Cortical Dysplasia IIIa in Hippocampal Sclerosis-Associated Epilepsy: Anatomo-Electro-Clinical Profile and Surgical Results From a Multicentric Retrospective Study

BACKGROUND

Hippocampal sclerosis (HS) may be associated with focal cortical dysplasia IIIa (FCD IIIa) in patients undergoing surgery for temporal lobe epilepsy (TLE).

OBJECTIVE

To investigate whether the anatomo-electro-clinical profile and surgical outcome in patients with HS-related TLE are affected by coexisting FCD IIIa.

METHODS

A total of 220 patients, operated in 5 centers, with at least 24 mo follow-up (FU), were retrospectively studied. Preliminary univariate and subsequent multivariate analyses were performed to investigate possible associations between several potential presurgical, surgical, and postsurgical predictors and different variables (Engel's class I and Engel's class Ia, co-occurrence of FCD IIIa).

RESULTS

At last available postoperative control (FU: range 24-95 mo, median 47 mo), 182 (82.7%) patients were classified as Engel's class I and 142 (64.5%) as Engel's class Ia. At multivariate analysis, extension of neocortical resection and postoperative electroencephalogram were significantly associated with Engel's class I, whereas length of FU had a significant impact on class Ia in the whole cohort and in isolated HS (iHS) patients, but not in the FCD IIIa group. No differences emerged in the anatomo-electro-clinical profile and surgical results between patients with FCD IIIa and with iHS.

CONCLUSION

Coexistence of FCD IIIa did not confer a distinct anatomo-electro-clinical profile to patients with HS-related epilepsy. Postoperative seizure outcome was similar in FCD IIIa and iHS cases. These findings indicate limited clinical relevance of FCD IIIa in HS-related epilepsy and might be useful for refining future FCD classifications. Further studies are needed to clarify the correlation of class Ia outcome with the duration of FU.

Comparison of minimally invasive and traditional surgical approaches for refractory mesial temporal lobe epilepsy: A systematic review and meta-analysis of outcomes

Magnetic resonance-guided laser interstitial laser therapy (MRgLITT) and radiofrequency ablation (RFA) represent two minimally invasive methods for the treatment of drug-refractory mesial temporal lobe epilepsy (mTLE). We performed a systematic review and a meta-analysis to compare outcomes and complications between MRgLITT, RFA, and conventional surgical approaches to the temporal lobe (i.e., anterior temporal lobe resection [ATL] or selective amygdalohippocampectomy [sAHE]). Forty-three studies (13 MRgLITT, 6 RFA, and 24 surgery studies) involved 554, 123, 1504, and 1326 patients treated by MRgLITT, RFA, ATL, or sAHE, respectively. Engel Class I (Engel-I) outcomes were achieved after MRgLITT in 57% (315/554, range = 33.3%-67.4%), RFA in 44% (54/123, range = 0%-67.2%), ATL in 69% (1032/1504, range = 40%-92.9%), and sAHE in 66% (887/1326, range = 21.4%-93.3%). Meta-analysis revealed no significant difference in seizure outcome between MRgLITT and RFA (Q = 2.74, p = .098), whereas ATL and sAHE were both superior to MRgLITT (ATL: Q = 8.92, p = .002; sAHE: Q = 4.33, p = .037) and RFA (ATL: Q = 6.42, p = .0113; sAHE: Q = 5.04, p = .0247), with better outcome in patients at follow-up of 60 months or more. Mesial hippocampal sclerosis (mTLE + hippocampal sclerosis) was associated with significantly better outcome after MRgLITT (Engel-I outcome in 64%; Q = 8.55, p = .0035). The rate of major complications was 3.8% for MRgLITT, 3.7% for RFA, 10.9% for ATL, and 7.4% for sAHE; the differences did not show statistical significance. Neuropsychological deficits occurred after all procedures, with left-sided surgeries having a higher rate of verbal memory impairment. Lateral functions such as naming or object recognition may be more preserved in MRgLITT. Thermal therapies are effective techniques but show a significantly lower rate of Engel-I outcome in comparison to ATL and sAHE. Between MRgLITT and RFA there were no significant differences in Engel-I outcome, whereby the success of treatment seems to depend on the approach used (e.g., occipital approach). MRgLITT shows a similar rate of complications compared to RFA, whereas patients undergoing MRgLITT may experience fewer major complications compared to ATL or sAHE and might have a more beneficial neuropsychological outcome.

Quantitative analysis of double inversion recovery and FLAIR signals in temporal lobe epilepsy

This study aimed to quantitatively compare the signals from double inversion recovery (DIR) and fluid-attenuated inversion recovery (FLAIR) in temporal lobe epilepsy (TLE) with a focus on anterior temporal lobe white matter abnormal signal (ATLAS) lesions. We recruited 59 patients with TLE (32 left, 27 right) and 24 healthy controls (HCs). All patients underwent 3T-MRI scans including 3D DIR and FLAIR images, and the images were normalized and compared among the three groups by the software program SPM 12. We also explored the association of the ATLAS with disease duration, seizure types, and the existence of hippocampal sclerosis (HS). As a result, compared to the HCs, there were significantly increased DIR signals in the ipsilateral anterior temporal white matter of both the left and right TLE patients. There was no significant signal difference in FLAIR images between the HCs and patients except for a trend-level increase in left TLE. There was also no significant association between the ATLAS and disease duration, seizure type, or HS. These results quantitatively confirmed the significant signal increases of DIR in the ipsilateral anterior temporal lobe in both left and right TLE, whereas FLAIR revealed no significant between-group differences. These findings may indicate greater usefulness of DIR compared to FLAIR for detecting ATLAS lesions.

Systematic review and network meta-analysis of resective surgery for mesial temporal lobe epilepsy

OBJECTIVE

To evaluate the effectiveness of anterior temporal lobectomy (ATL) versus selective amygdalohippocampectomy (SAH) on seizure-free outcome in patients with temporal lobe epilepsy, using both direct and indirect evidence from the literature.

METHODS

MEDLINE, Embase and Cochrane databases were searched for original research articles and systematic reviews comparing ATL versus SAH, and ATL or SAH versus medical management (MM). The outcome was seizure freedom at 12 months of follow-up or longer. Direct pairwise meta-analyses were conducted, followed by a random-effect Bayesian network meta-analysis (NMA) combining direct and indirect evidence.

RESULTS

Twenty-eight articles were included (18 compared ATL vs SAH, 1 compared ATL vs SAH vs MM, 8 compared ATL vs MM, and 1 compared SAH vs MM). Direct pairwise meta-analyses showed no significant differences in seizure-free outcome of ATL versus SAH (OR 1.14, 95% CI 0.93 to 1.39; p=0.201), but the odds of seizure-free outcome were higher for ATL versus MM (OR 29.16, 95% CI 10.44 to 81.50; p<0.00001), and SAH versus MM (OR 28.42, 95% CI 10.17 to 79.39; p<0.00001). NMA also showed that the odds of seizure-free outcome were no different in ATL versus SAH (OR 1.15, 95% credible interval (CrI) 0.84-1.15), but higher for ATL versus MM (OR 27.22, 95% CrI 15.38-27.22), and SAH versus MM (OR 23.57, 95% CrI 12.67-23.57). There were no significant differences between direct and indirect comparisons (all p>0.05).

CONCLUSION

Direct evidence, indirect evidence and NMA did not identify a difference in seizure-free outcome of ATL versus SAH.

Prognostic factors determining poor postsurgical outcomes of mesial temporal lobe epilepsy

Objectives

To investigate the long-term postoperative outcomes and predictive factors associated with poor surgical outcomes in mesial temporal lobe epilepsy (MTLE).

Materials and methods

We enrolled patients with MTLE who underwent resective surgery at single university-affiliated hospital. Surgical outcomes were determined using a modified Engel classification at the 2^nd and 5^th years after surgery and the last time of follow-up.

Results

The mean duration of follow-up after surgery was 7.6 ± 3.7 years (range, 5.0–21.0 years). 334 of 400 patients (83.5%) were seizure-free at the 5^th postoperative year. Significant predictive factors of a poor outcome at the 5^th year were a history of generalized tonic clonic (GTC) seizures (odds ratio, OR; 2.318), bi-temporal interictal epileptiform discharge (IED) (OR; 3.107), bilateral hippocampal sclerosis (HS) (OR; 5.471), unilateral HS and combined extra-hippocampal lesion (OR; 5.029), and bi-temporal hypometabolism (BTH) (OR; 4.438). Bi-temporal IED (hazard ratio, HR; 2.186), BTH (HR; 2.043), bilateral HS (HR; 2.541) and unilateral HS and combined extra-hippocampal lesion (HR; 2.75) were independently associated with seizure recurrence. We performed a subgroup analysis of 208 patients with unilateral HS, and their independent predictors of a poor outcome at the 5^th year were BTH (OR; 5.838) and tailored hippocampal resection (OR; 11.053).

Conclusion

This study demonstrates that 16.5% of MTLE patients had poor long-term outcomes after surgery. Bilateral involvement in electrophysiological and imaging studies predicts poor surgical outcomes in MTLE patients.

Temporal pole abnormalities in temporal lobe epilepsy with hippocampal sclerosis: Clinical significance and seizure outcome after surgery

PURPOSE

To assess the clinical significance of temporal pole abnormalities (temporopolar blurring, TB, and temporopolar atrophy, TA) in patients with temporal lobe epilepsy (TLE) and hippocampal sclerosis (HS) with a long post-surgical follow-up.

METHODS

We studied 60 consecutive patients with TLE-HS and 1.5 preoperative MRI scans who underwent surgery and were followed up for at least 5 years (mean follow-up 7.3 years). Based on findings of pre-surgical MRI, patients were classified according to the presence of TB or TA. Groups were compared on demographic, clinical, neuropsychological data, and seizure outcome.

RESULTS

TB was found in 37 (62%) patients, while TA was found in 35 (58%) patients, always ipsilateral to HS, with a high degree of overlap (83%) between TB and TA (p<0.001). Patients with TB did not differ from those without TB with regard to history of febrile convulsions, GTCSs, age of epilepsy onset, side of surgery, seizure frequency, seizure outcome, and neuropsychological outcome. On the other hand, they were significantly older, had a longer duration of epilepsy, and displayed lower preoperative scores on several neuropsychological tests. Similar findings were observed for TA. Multivariate analysis corroborated the association between temporopolar abnormalities and age at onset, age at surgery (for TB only), and lower preoperative scores on some neuropsychological tests.

CONCLUSIONS

Temporopolar abnormalities are frequent in patients with TLE-HS. Our data support the hypothesis that TB and TA are caused by seizure-related damages. These abnormalities did not influence seizure outcome, even after a long-term post-surgical follow-up.

White matter in temporal lobe epilepsy: clinico-pathological correlates of water diffusion abnormalities

Using magnetic resonance imaging, it is possible to measure the behavior of diffusing water molecules, and the metrics derived can be used as indirect markers of tissue micro-architectural properties. Numerous reports have demonstrated that patients with temporal lobe epilepsy (TLE) have water diffusion abnormalities in several white matter structures located within and beyond the epileptogenic temporal lobe, showing that TLE is not a focal disorder, but rather a brain network disease. Differences in severity and spatial extent between patients with or without mesial temporal sclerosis (MTS), as well as differences related to hemispheric seizure onset, are suggestive of different pathophysiological mechanisms behind different forms of TLE, which in turn result in specific cognitive disabilities. The biological interpretation of diffusion abnormalities is based on a wealth of information from animal models of white matter damage, and is supported by recent reports that directly correlate diffusion metrics with histological characteristics of surgical specimens of TLE patients. Thus, there is now more evidence showing that the increased mean diffusivity (MD) and concomitant reductions of diffusion anisotropy that are frequently observed in several white matter bundles in TLE patients reflect reduced axonal density (increased extra-axonal space) due to smaller-caliber axons, and abnormalities in the myelin sheaths of the remaining axons. Whether these histological and diffusion features are a predisposing factor for epilepsy or secondary to seizures is still uncertain; some reports suggest the latter. This article summarizes recent findings in this field and provides a synopsis of the histological features seen most frequently in post-surgical specimens of TLE patients in an effort to aid the interpretation of white matter diffusion abnormalities.

Neurocognitive and Seizure Outcomes of Selective Amygdalohippocampectomy versus Anterior Temporal Lobectomy for Mesial Temporal Lobe Epilepsy

Objective. To report our institutional seizure and neuropsychological outcomes for a series of patients with mesial temporal lobe epilepsy (mTLE) undergoing anterior temporal lobectomy (ATL) or selective amygdalohippocampectomy (SelAH) between 2004 and 2011. Methods. A retrospective study of patients with mTLE was conducted. Seizure outcome was reported using time-to-event analysis. Cognitive outcome was reported using the change principal in component factor scores, one each, for intellectual abilities, visuospatial memory, and verbal memory. The Boston Naming Test was used for naming assessment. Language dominant and nondominant resections were compared separately. Student's t-test was used to assess statistical significance. Results. Ninety-six patients (75 ATL, 21 SelAH) were included; fifty-four had complete neuropsychological follow-up. Median follow-up was 40.5 months. There was no statistically significant difference in seizure freedom or any of the neuropsychological outcomes, although there was a trend toward greater postoperative decline in naming in the dominant hemisphere group following ATL. Conclusion. Seizure and neuropsychological outcomes did not differ for the two surgical approaches which is similar to most prior studies. Given the theoretical possibility of SelAH sparing language function in patients with epilepsy secondary to mesial temporal sclerosis and the limited high-quality evidence creating equipoise, a multicenter randomized clinical trial is warranted.

An 18-year follow-up of seizure outcome after surgery for temporal lobe epilepsy and hippocampal sclerosis

OBJECTIVES

To evaluate the very long-term clinical outcome of surgery for mesial temporal lobe epilepsy and unilateral hippocampal sclerosis (MTLE/HS) without atypical features. The impact of surgical technique and postoperative reduction of medication on this outcome was investigated.

DESIGN

Prospective longitudinal cohort follow-up study for up to18 years.

SETTING

Epilepsy surgery centre in a university hospital.

PATIENTS

108 patients who underwent unilateral MTLE/HS.

INTERVENTION

Surgery for MTLE/HS.

MAIN OUTCOME MEASURE

Engel classification (I). Clinical evaluations were based on systematic interviews in person or by phone. Kaplan-Maier survival curves estimated the probability of remaining seizure free. The impact of medication management in the postoperative outcome was analysed using Cox regression.

RESULTS

The probability of remaining completely seizure-free at 12 and 18 years after MTLE/HS surgery was 65% and 62%, respectively. The risk of having any recurrence was 22% during the first 24 months and increased 1.4% per year afterwards. Type of surgical technique (selective amygdalohippocampectomy vs anterior temporal lobectomy) did not impact on outcome. Remaining on antiepileptic drugs and history of generalised clonic seizure diminished the probability of remaining seizure free.

CONCLUSIONS

MTLE/HS surgery is able to keep patients seizure free for almost up to two decades. Removal of the neocortex besides the mesial portion of the temporal lobe does not lead to better chances of seizure control. These findings are applicable to the typical unilateral MTLE/HS syndrome and cannot be generalised for all types of TLE. Future longitudinal randomised controlled studies are needed to replicate these findings.

Is there evidence for clinical differences related to the new classification of temporal lobe cortical dysplasia?

PURPOSE

The new International League Against Epilepsy (ILAE) classification for focal cortical dysplasia (FCD) differentiates between patients with isolated FCD (type 1) and FCD with an associated hippocampal sclerosis (HS) (type 3a). In contrast to the former FCD classification by Palmini, which considered only histologic features, the novel ILAE classification also relies on magnetic resonance imaging (MRI) findings and presumed pathogenesis. We investigated in a cohort of 100 patients with exclusively temporal FCD if the new subdivision of FCD is reflected in clinical characteristics.

METHODS

Thirty-one patients with FCD type 1 and 50 patients with FCD type 3a in the temporal lobe were included. In all patients MRI and histology of the FCD were available. Both patient groups were compared to 19 patients with temporal FCD type 2 with clearly different histologic appearance.

KEY FINDINGS

Patients with FCD type 1 and type 3a presented with similar clinical features in many respects. In univariate analyses, no statistically significant differences were found as to age at epilepsy onset (p = 0.07) and epilepsy surgery (p = 0.14), a normal appearing neocortical temporal lobe (p = 0.08) or diagnosis of FCD by visual inspection of MRI (p = 0.08), preoperative seizure frequency (p = 0.06), and the predominance of an epigastric aura (p = 0.08). The postoperative outcome was nearly identical 1 year (p = 0.8) and 2 (p = 0.8), 3 (p = 0.8), 5 (p = 0.7), and 8 (p = 1.0) years postoperatively. Only febrile seizures (p = 0.025) and an aura (p = 0.03) were significantly more frequently reported in patients with FCD type 3a. Similar results were obtained from a multivariate logistic regression analysis. Patients with FCD type 2 were more different: Compared to FCD type 3a, age at epilepsy surgery was significantly lower (p = 0.004) and auras (p = 0.005) were significantly less frequently reported. Epigastric auras (p = 0.04) and febrile seizures (p = 0.025) occurred significantly less frequently in patients with FCD type 2 without HS compared to FCD type 3a. The diagnosis of an FCD was significantly more frequently made (p = 0.03) by visual inspection of the MRI compared to FCD type 1.

SIGNIFICANCE

Clinical features did not allow to clear separation of temporal FCD types 1 and 3a. Statistically significant differences were seen in a history of febrile seizures and the occurrence of auras more common in FCD type 3a. However, FCD type 2 in the same localization but with different histology presented with further differences such as more frequent FCD diagnosis by visual inspection of MRI, earlier operation, and less frequent epigastric auras.

Anterior temporal lobe white matter abnormal signal (ATLAS) as an indicator of seizure focus laterality in temporal lobe epilepsy: comparison of double inversion recovery, FLAIR and T2W MR imaging

OBJECTIVES

To investigate the diagnostic capability of anterior temporal lobe white matter abnormal signal (ATLAS) for determining seizure focus laterality in temporal lobe epilepsy (TLE) by comparing different MR sequences.

METHODS

This prospective study was approved by the institutional review board and written informed consent was obtained. Three 3D sequences (double inversion recovery (DIR), fluid-attenuated inversion recovery (FLAIR) and T2-weighted imaging (T2WI)) and two 2D sequences (FLAIR and T2WI) were acquired at 3 T. Signal changes in the anterior temporal white matter of 21 normal volunteers were evaluated. ATLAS laterality was evaluated in 21 TLE patients. Agreement of independent evaluations by two neuroradiologists was assessed using κ statistics. Differences in concordance between ATLAS laterality and clinically defined seizure focus laterality were analysed using McNemar's test with multiple comparisons.

RESULTS

Pre-amygdala high signals (PAHS) were detected in all volunteers only on 3D-DIR. Inter-evaluator agreement was moderate to almost perfect for each sequence. Correct diagnosis of seizure laterality was significantly more frequent on 3D-DIR than on any other sequences (P ≤ 0.031 for each evaluator).

CONCLUSIONS

The most sensitive sequence for detecting ATLAS laterality was 3D-DIR. ATLAS laterality on 3D-DIR can be a good indicator for determining seizure focus localization in TLE.

Neuropathologic measurements in focal cortical dysplasias: validation of the ILAE 2011 classification system and diagnostic implications for MRI

Focal cortical dysplasias (FCD) which represent a composite group of cortical malformations are increasingly recognized as morphological substrate for severe therapy-refractory epilepsy in children and young adults. However, presurgical evaluation remains challenging as not all FCD variants can be reliably detected by high-resolution magnetic resonance imaging (MRI). Here, we studied a cohort of 52 epilepsy patients with neuropathological evidence for FCD using the 2011 classification of the International League against Epilepsy (ILAE) and systematically analysed those histopathologic features applicable also for MRI diagnostics. Histopathologic parameters included quantitative measurements of cellular profiles, cortical thickness, heterotopic neurons in white matter, and myelination that were compared between FCD subtypes and age-/localization-matched controls (n = 36) using multivariate analysis. Dysmorphic neurons in both FCD Type II variants showed significantly increased diameter of their cell bodies and nuclei. Cortical thickness was also increased with a distinct loss of myelin content specifying FCD Type IIb from IIa. The data further suggested that myelination deficits in FCD Type IIb result from compromised oligodendroglial lineage differentiation and we concluded that the "transmantle sign" is a unique finding in FCD Type IIb. In contrast, FCD Type Ia was characterized by a smaller cortical ribbon and higher neuronal densities, but these parameters failed to reach statistical significance (considering age- and location-dependent variability in controls). All FCD variants showed abnormal grey-white matter boundaries with increased numbers of heterotopic neurons. Similar results were obtained also at deep white matter location. Thus, many FCD variants may indeed escape visual MRI inspection, but suspicious areas with increased or decreased cortical thickness as well as grey-white matter blurring may be uncovered using post-processing protocols of neuroimaging data. The systematic analysis of well-specified histopathological features could be helpful to improve sensitivity and specificity in MRI detection during pre-surgical work-up of patients with drug-resistant focal epilepsies.