Lateralization of epileptic foci by magnetic resonance imaging in temporal lobe epilepsy

1H-MR spectroscopy indicates severity markers in temporal lobe epilepsy: correlations between metabolic alterations, seizures, and epileptic discharges in EEG

PURPOSE

In this study, hippocampal metabolite alterations in (1)H-MR spectroscopy ((1)H-MRS) were correlated to the findings of intensive video-EEG monitoring and duration of seizure symptoms in patients with temporal lobe epilepsy (TLE).

METHODS

The 14 patients with mesial TLE and no pathological findings in imaging were investigated by (1)H-MRS. Seizures were analyzed by: number of clinical seizures in 24 h, exact duration of clinical symptoms in 24 h, frequency of interictal epileptiform discharges (IEDs) and ictal activity, duration of ictal activity, and IEDs occurring within 24 h in intensive EEG monitoring. Pearson Correlation Coefficient (PCC) was calculated between spectral metabolite alterations and the parameters mentioned above.

RESULTS

In the analysis, a negative correlation was found between total (t) NAA values and degree of IEDs in EEG (p = 0.04); a positive correlation was found between Cr levels and duration of seizure symptoms registered by video monitoring (p = 0.01).

CONCLUSIONS

Our study shows that, in some patients, (1)H-MRS is able to refer the severity of TLE. The degree of tNAA reduction in (1)H-MRS, probably indicating neuronal dysfunction, is associated with interictal spiking in intensive EEG monitoring. Duration of seizure symptoms associated with increased Cr peaks probably reflects increased gliosis.

False lateralization of mesial temporal lobe epilepsy by noninvasive neurophysiological examinations

Mesial temporal lobe epilepsy (mTLE) is the most common form of symptomatic localization-related epilepsy and is surgically remediable. Lateralization of the seizure onset is particularly important to determine from a surgical perspective. A 39-year-old woman with intractable mTLE first exhibited seizure at the age of 3 years. She experienced epigastric sensation and placed her right hand on her abdomen before falling backward. Although interictal scalp electroencephalography (EEG), sphenoidal scalp ictal EEG, and magnetoencephalography showed right temporal side focus, computed tomography and magnetic resonance imaging showed atrophy of the left cerebral hemisphere. Single photon emission computed tomography with technetium-99m ethyl cysteinate dimmer and I-123 iomazenil showed obscure focus on the left side. As a discrepancy existed between the results of neurophysiological examinations and imaging, we performed subdural electrode implantation on the bilateral temporal lobe. Although a bemegride-induced seizure arose from the right side during the subdural recording, the onset of 5 habitual seizures was observed in the left hippocampus. On the basis of these results, the seizure was diagnosed as left mTLE, and left anterior temporal lobectomy and amygdalohippocampectomy were performed. The patient has been free from the seizures for more than 1.5 years of follow up. Bilateral subdural electrode measurement of habitual seizures is indispensable for clarifying the actual focus when a discrepancy exists between neuroimaging and noninvasive neurophysiological examinations.

Sex differences in face recognition memory in patients with temporal lobe epilepsy, patients with generalized epilepsy, and healthy controls

The influence of sex on face recognition memory was studied in 49 patients with temporal lobe epilepsy, 20 patients with generalized epilepsy, and 32 healthy controls. After learning 20 faces, serially presented for 5 seconds each, subjects had to recognize the 20 among 40 faces (including 20 new faces) immediately and 24 hours later. Women had better face recognition than men, with no significant differences between groups. Women's advantage was due mainly to superior delayed recognition. Taken together, the results suggest that sex has a similar impact on face recognition in patients with epilepsy and healthy controls, and that testing delayed face recognition raises sensitivity for sex differences. The influence of sex on face recognition in patients with epilepsy should be acknowledged when evaluating individuals or comparing groups.

MR-based neurological disease classification methodology: Application to lateralization of seizure focus in temporal lobe epilepsy

Classification approaches for neurological diseases tend to concentrate on specific structures such as the hippocampus (HC). The hypothesis for the novel methodology presented in this work is that pathologies will impact large tissue areas with detectable variations of T1-weighted MR signal intensity and registration metrics. The technique is applied to lateralization of seizure focus in 127 patients with intractable temporal lobe epilepsy (TLE), in which the site of seizure onset was determined by comprehensive evaluation (69 with left MTL seizure focus (SF) (group "L") and 58 with right SF (group "R")). The method analyses large, non-specific Volumes of Interest (VOI) centered on the left and right medial temporal lobes (MTL) (55 x 82 x 80 voxels) in pre-processed scans aligned in stereotaxic space. Extracted VOIs are linearly and nonlinearly registered to a reference target image. Principal Components Analyses of (i) the normalized intensity and (ii) the trace, a measure of local volume change, are used to generate a multidimensional reference space from a set of 152 neurologically healthy subjects. VOIs from TLE patients, processed in a similar fashion, are projected in this space, and leave-one-out, forward stepwise linear discriminant analysis of the eigencoordinate distributions is used for classification. Following manual MRI volumetric analysis, 80 patients had HC atrophy (group "HA") ipsilateral to the SF (42 with left SF or "LHA", and 38 with right or "RHA"), and the remaining 47 had normal HC volumes (group "HNV") (27 with left SF or "LNV", and 20 with right SF or "RNV"). The automated method was 100% accurate at separating "HA" vs. "HNV", "LHA" vs. "RHA", and "LNV" vs "RNV". It was also 96% accurate at separating "L" vs. "R". Our results indicate that MR data projected in multidimensional feature domains can lateralize SF in epilepsy patients with a high accuracy, irrespective of HC volumes. This single-scan, practical and objective method holds promise for the pre-surgical evaluation of TLE patients.

PET in pediatric diseases

FDG-PET is being increasingly applied to pediatric conditions, particularly in oncology. PET and PET/CT scanning in children are not currently supported by Centers for Medicare and Medicaid Services unless the disease condition coincides with a reimbursed adult condition. The recent merger of the Children's Cancer Group and the Pediatric Oncology Group to form the Children's Oncology Group creates an opportunity to examine the use of FDG-PET in the management of childhood tumors in multi-institutional, cooperative efforts. The interest in incorporating PET imaging technology in pediatric medicine has been evidenced by several recent review articles summarizing the ongoing progress in this area. Future data will show that FDG-PET provides useful diagnostic information and can play a pivotal role in the clinical management and care of children with disease.

Lateralising value of neuropsychological protocols for presurgical assessment of temporal lobe epilepsy

PURPOSE

To estimate the value of neuropsychological measurements in determining the side of seizure onset for presurgical assessment in patients with temporal lobe epilepsy. The lateralising value of neuropsychological protocols was evaluated for all patients and in subpopulations depending on surgical outcome with regard to seizure control, speech dominance, neuropathology, and need for intracranial EEG recordings.

METHODS

A battery of neuropsychological procedures was carried out preoperatively in 125 patients who underwent left (n = 66) or right (n = 59) temporal lobectomies. Binary logistic regression analysis was performed to find sets of variables that allowed the best prediction of the side of seizure onset (assumed to be the operated-on side).

RESULTS

Combinations of noninvasive neuropsychological tests and Wada subscores showed the highest lateralising values: 80.8% for all patients, 79.4% in seizure-free patients, 86.0% in patients not rendered seizure free, 85.7% in left speech patients, 77.8% in non-left speech patients, 89.3% in patients with mesial temporal sclerosis (MTS), 78.1% in non-MTS patients, 80.3% in patients who underwent intracranial EEG recordings, and 77.3% in those who did not.

CONCLUSIONS

The lateralising value (80-90%) of neuropsychological protocols appears similar to that of other tests widely accepted for lateralisation (ictal and interictal scalp EEG and neuroimaging). Attention should be paid to neuropsychological results, particularly from the Wada test, during presurgical assessment of temporal lobe epilepsy, as they can provide strong support for findings from other lateralising tests, particularly in patients with presumed MTS or in left-speech patients.

The localizing yield of sphenoidal and anterior temporal electrodes in ictal recordings: a comparison study

PURPOSE

To compare the localizing yield of sphenoidal electrodes placed under fluoroscopic guidance (SEs) and anterior temporal electrodes (ATEs) in ictal recordings from a group of patients with seizure disorders of anterior temporal origin.

METHODS

We compared ictal recordings of 156 seizures obtained with SEs and ATEs from 40 consecutive patients with seizures of anterior temporal origin. Four electroencephalographers reviewed ictal recordings independently and blind to the patients' identity, presurgical data, and inclusion of ATEs or SEs. Outcome variables included (a) number of correctly localized seizures with SE and ATE recordings by at least three raters; (b) number of ictal foci in which all seizures were localized only with SEs; and (c) number of seizures in which SEs identified the ictal onset > or =5 s earlier than ATEs.

RESULTS

Interrater agreement among the four raters was significantly greater with SE than with ATE recordings (p < 0.0001). The number of seizures correctly localized was significantly greater with SEs (n = 144) than with ATEs (n = 99; p < 0.0001). All the seizures [n = 36 (23%)] originating from 14 ictal foci (29%) in 11 patients (27.5%) were localized only with SEs. Finally, the ictal onset was detected at SEs > or =5 s earlier than at ATEs in 67 (43%) seizures originating from 33 (69%) foci in 30 (75%) patients.

CONCLUSIONS

SEs improve interrater agreement in the localization of seizures of anterior temporal origin, and in about one fourth of patients, SEs add ictal data not identified by ATEs.

Comparative utility of technetium-99m hexamethylpropylenamine oxime single photon emission computed tomography (SPECT) with anatomic neuroimaging and electroencephalography (EEG) in childhood intractable epilepsy

Intractable epilepsies pose a therapeutic challenge. Precise localization of the epileptic focus is imperative before planning surgical intervention. Functional imaging is an important component of presurgical work-up. Positron emission tomography is unavailable in developing countries; hence, the need to evaluate the available imaging modality, single photon emission computed tomography (SPECT), was felt. We investigated 61 children with intractable epilepsy, identified by predefined criteria, by performing electroencephalography (EEG), magnetic resonance imaging (MRI), computed tomography (CT), and ictal and interictal SPECT. The localizing value of ictal and interictal SPECT imaging for epileptic foci was correlated with clinical, electrophysiologic, and anatomic neuroimaging data. An ictal SPECT was obtained in 9, and interictal SPECT was performed in all (61). Ictal SPECT was localizing in 8 of 9 (88.8%). Interictal SPECT was localizing in a significantly higher proportion of patients (47.54%) than either the scalp EEG (16.39%) (P = .0003) or CT scan (21.56%) (P = .0046). Our data demonstrated that interictal and ictal SPECT identified more focal changes in children with intractable epilepsy than interictal EEG, CT, and probably MRI. The definitive proof of the SPECT-based findings being epileptogenic foci awaits correlation with intraoperative monitoring and postoperative follow-up.

Qualitative MRI segmentation in mesial temporal sclerosis: clinical correlations

Magnetic resonance imaging (MRI) is reliable and sensitive in the detection of mesial temporal atrophy in patients with temporal lobe epilepsy. We investigated the MRI patterns of atrophy in 47 patients with histologically confirmed hippocampal sclerosis and correlated the imaging findings to the clinical features and surgical outcome. One hundred percent of patients had hippocampal body atrophy, 70% had hippocampal tail atrophy, 23% had amygdala atrophy, and 10% had focal hippocampal body atrophy without other segmental involvement. Correlative analysis of the segmented MRI findings with other clinical variables, including a previous history of childhood febrile convulsions, showed no significant associations except for younger age of seizure onset associated with hippocampal tail atrophy (p <0.03). No associations between surgical outcome and the patterns of mesial temporal atrophy were detected. Our results demonstrate that variable patterns of atrophy exist in mesial temporal atrophy, but invariably atrophy involves the hippocampal body segment. Segmental MRI analysis in mesial temporal atrophy provides added useful diagnostic information.