Relationship between anatomic lesions of the temporal lobe and temporal lobe epilepsy

A structural lesion of the brain is a frequent finding in intractable partial epileptic patients. We analyse anatomo-electro-clinical characteristics of 58 patients in which MR showed a lesion inside the temporal lobe. They are 29 males and 29 females with a mean age at surgery of 23.5 +/- 10.7 years (2.6-45.9). The mean epilepsy duration is of 13.4 +/- 8 years (1.3-35.5), with a mean seizure frequency of 28.7 +/- 43.6 per month, with a great inter-individual variability (from 3 per month to 15 a day). The minimum follow-up is 3.5 years. A video-EEG monitoring was performed in 21 cases, while a stereo-EEG investigation was judged mandatory in 26. On the basis of anatomo-electro-clinical correlations and of the results of presurgical investigations, the epileptogenic area was proved to be temporal in 49 cases, temporal but controlateral to the lesion in 1, and at least bilobar in 8 patients.     

Outcome after temporal lobectomy in bilateral temporal lobe epilepsy

We determined how noninvasive presurgical data relate to prognosis after temporal lobectomy in patients with independent bilateral temporal lobe (IBTL) complex partial seizures on the intracranial electroencephalogram (EEG). Between 1986 and 1994, 28 patients had IBTL seizures on intracranial EEG. Fifteen of these 28 patients underwent temporal lobectomy and 13 were not offered surgery. Of the 15 patients who had surgery, 10 patients became seizure-free. Magnetic resonance imaging (MRI) and the Wada test were the only variables associated with a seizure-free outcome. Seven of 10 seizure-free patients had a lateralized Wada result or the presence of unilateral hippocampal sclerosis, whereas none of the patients with persistent seizures had either of these findings. Variables not found to be predictive of a seizure-free outcome included location of scalp interictal spikes, degree of seizure-onset laterality, presence of early epilepsy risk factor, duration of epilepsy, and full-scale intelligence quotient. We conclude that MRI and the Wada test provide information of prognostic value in patients with bilateral temporal seizures independent of intracranial EEG data.     

Periventricular nodular heterotopia and intractable temporal lobe epilepsy: poor outcome after temporal lobe resection

We describe 5 women and 5 men with periventricular nodular heterotopia and electroclinical features suggestive of temporal lobe epilepsy, who were surgically treated for control of medically refractory seizures. Magnetic resonance imaging revealed bilateral periventricular nodular heterotopia in 7 of the 10 patients. Because of the lack of clear localization, 6 patients were studied with intracranial depth electrode recordings. Seizures were of hippocampal onset (3 patients), regional temporal lobe onset (2 patients), or occipital-temporal onset (1 patient). Anterior temporal lobectomy was performed in 6 patients; selective amygdalohippocampectomy, in 1; and anterior temporal lobectomy plus resection of the heterotopic tissue, in 3. None of the 9 patients followed for more than 12 months postoperatively were seizure free. Two patients were initially seizure free for approximately 18 months, but then seizures recurred. One patient had a major reduction in seizure frequency at a 39-month follow-up after most of the unilateral heterotopic tissue was included in the temporal resection. Temporal resection did not lead to a long-term favorable outcome in this group of patients with periventricular nodular heterotopia and epileptogenic discharges involving the temporal lobe. This suggests a more widespread disorder with epileptogenic activity possibly originating in or near the heterotopic tissue. The clinical and electrographic features of periventricular nodular heterotopia pointing to temporal lobe origin are misleading and temporal resection does not result in long-term cessation of seizures.     

Stereotaxic surgery of temporal lobe epilepsy

Forty patients with temporal epilepsy were operated on with a stereotaxic technique. Eleven patients had a unilateral localization of the epileptic focus, and in 29 bitemporal foci were diagnosed. In evaluating the results of the treatment the dynamics of the epileptic fits, the peculiarities of changes in the mental status, and the degree of social adaptation were taken into consideration. A postoperative improvement was achieved in 73% of the patients with monotemporal lesions, while in those with bitemporal epilepsy and distinct persistent mental disorders the state was improved in 44% of the cases. Indications for the choice of the zone of destruction depending on the clinical peculiarities of the lesion are presented.     

Surgical anatomy of the temporal lobe

The complex functional and anatomic relationships between the structures in and around the temporal lobe are central to the problem of intractable partial complex seizures. Resecting those areas that are responsible for seizures and protecting those that are essential for the normal functioning of the patient are the fundamental tasks of the epilepsy surgeon. A thorough understanding of the structural and functional anatomy of this region is essential to achieve these goals.     

Memory and imagery in the temporal lobe

Experimental and clinical studies in primates indicate that visual information is stored and retrieved by interactions between the temporal association area and the medial temporal lobe structures. Recent findings from single-neuron recordings have provided new evidence that perceptual aspects of the temporal neocortex are closely related to its memory function based on association. They further suggest that imagery is also implemented by the same neural mechanism that subserves memory retrieval.     

Temporal lobe epilepsy and neuro-ophthalmology. Ophthalmological findings in 74 temporal lobe resected patients

A survey is presented of the ophthalmological findings in 74 patients with drug-resistant temporal lobe epilepsy, who underwent unilateral anterior temporal lobectomy 1960-1969 at Rigshospitalet, Copenhagen. At follow-up, 1970-1971, one to ten years following the operation, 81% of the patients had no or only few seizures. Preoperatively 11% of the patients suffered from strabismus as compared to an expected frequency of 5%, but this trend just falls short of statistical significance. The visual acuity remained unchanged in all patients following the operation. Preoperatively a visual field defect was observed in 2 patients. At follow-up 51 patients had homonymous hemianopias, in 38 of them this was limited to the upper quadrants, and in 13 patients also included the lower quandrants, but was characterized as a total homonymous hemianopia in only 6 patients. The presence and extent of the visual field defects were correlated to surgical results, age at onset of epilepsy, age at operation, preoperative duration of epilepsy, presence of grand mal, preoperative complications, and neuropathological findings, but without observing any statistically significant conclusions. On the other hand, the extent of the postoperative visual field defect was significantly influenced by the side of the operation, with more and larger defects following right-sided lobectomies. In the 51 patients with postoperative hemianopias, this defect was either unobserved by the patient or regarded as a considerably less important handicap than the frequent and socially invalidating preoperative seizures...     

Dynamics of the paroxysmal syndrome in temporal lobe epilepsy

Results of studying the time course of the paroxysmal syndrome based on long-term follow-up of 151 patients with temporal epilepsy are presented. Some regularities of the syndrome course are determined, a rather high degree of the variability of its manifestations over the period of the disease is established, a relative constancy of the aura, transformations of which were noted only in half of the observations, is shown. It is noted that the paroxysmal syndrome is the most developed within a period of 5 to 15 years after the disease onset. Results of conservative therapy are evaluated.     

Amygdala damage in experimental and human temporal lobe epilepsy

The amygdala complex is one component of the temporal lobe that may be damaged unilaterally or bilaterally in children and adults with temporal lobe epilepsy (TLE) or following status epilepticus. Most MR (magnetic resonance) imaging studies of epileptic patients have shown that volume reduction of the amygdala ranges from 10-30%. In the human amygdala, neuronal loss and gliosis have been reported in the lateral and basal nuclei. Studies in rats have more specifically identified the amygdaloid regions that are sensitive to status epilepticus-induced neuronal damage. These areas include the medial division of the lateral nucleus, the parvicellular division of the basal nucleus, the accessory basal nucleus, the posterior cortical nucleus, and portions of the anterior cortical and medial nuclei. Otherwise, other amygdala nuclei, such as the magnocellular and intermediate divisions of the basal nucleus and the central nucleus, remain relatively well preserved. Amygdala kindling studies in rats have shown that the density of a subpopulation of GABAergic inhibitory neurons that also contain somatostatin may be reduced even after a low number of generalized seizures. While analyses of histological sections and MR images indicate that in approximately 10% of TLE patients, seizure-induced damage is isolated to the amygdala, more often amygdala damage is combined with damage to the hippocampus and/or other brain areas. Moreover, recent data from rodents and nonhuman primates suggest that structural and functional alterations caused by seizure activity originating in the amygdala are not limited to the amygdala itself, but may also affect other temporal lobe structures. The information gathered so far on damage to the amygdala in epilepsy or after status epilepticus suggests that local alterations in inhibitory circuitries may contribute to a lowered seizure threshold and greater excitability within the amygdala. Furthermore, damage to select nuclei in the amygdala may predict impairment of performance in behavioral tasks that depend on the integrity of the amygdaloid circuits.     

Functional MRI lateralization of memory in temporal lobe epilepsy

OBJECTIVE: To determine the feasibility of using functional magnetic resonance imaging (fMRI) to detect asymmetries in the lateralization of memory activation in patients with temporal lobe epilepsy (TLE). BACKGROUND: Assessment of mesial temporal lobe function is a critical aspect of the preoperative evaluation for epilepsy surgery, both for predicting postoperative memory deficits and for seizure lateralization. fMRI offers several potential advantages over the current gold standard, intracarotid amobarbital testing (IAT). fMRI has already been successfully applied to language lateralization in TLE. METHODS: fMRI was carried out in eight normal subjects and 10 consecutively recruited patients with TLE undergoing preoperative evaluation for epilepsy surgery. A complex visual scene encoding task known to activate mesial temporal structures was used during fMRI. Asymmetry ratios for mesial temporal activation were calculated, using regions of interest defined in normals. Patient findings were compared with the results of IAT performed as part of routine clinical evaluation. RESULTS: Task activation was nearly symmetric in normal subjects, whereas in patients with TLE, significant asymmetries were observed. In all nine patients in whom the IAT result was interpretable, memory asymmetry by fMRI concurred with the findings of IAT including two patients with paradoxical IAT memory lateralization ipsilateral to seizure focus. CONCLUSIONS: fMRI can be used to detect asymmetries in memory activation in patients with TLE. Because fMRI studies are noninvasive and provide excellent spatial resolution for functional activation, these preliminary results suggest a promising role for fMRI in improving the preoperative evaluation for epilepsy surgery.     

Familial temporal lobe epilepsy: a clinically heterogeneous syndrome

We describe the clinical characteristics of a group of patients with familial temporal lobe epilepsy (TLE) in 11 kindreds with 36 affected individuals identified and investigated at the Montreal Neurological Hospital. Seizure types were simple partial (n = 20), complex partial (n = 29), and rare generalized tonic-clonic. Simple and complex partial seizures were infrequent or well controlled by anticonvulsant medication in 17 of 29 patients (59%) and without optimal response to medical therapy in 12 of 29 patients (41%). Pedigree analysis suggested autosomal dominant inheritance with incomplete penetrance. The syndrome of familial TLE has heterogeneous clinical manifestations and is not always benign.     

Anterior temporal abnormality in temporal lobe epilepsy: a quantitative MRI and histopathologic study

OBJECTIVE: To examine the nature and frequency of anterior temporal lobe (AT) abnormalities that occur in intractable temporal lobe epilepsy (TLE). METHODS: We reviewed the MR scans and clinical histories of 50 consecutive patients with intractable TLE. Histopathology was available in 42 surgically treated cases. RESULTS: MRI demonstrated loss of the gray-white matter differentiation and decreased T1- and increased T2-weighted signal in the ipsilateral AT in 58% of the 50 patients. This appearance was observed in 64% of the 36 patients with hippocampal sclerosis (HS) but was also seen in patients without HS. These changes were associated with temporal lobe atrophy, a higher hippocampal T2 relaxation time, and a history of febrile convulsions. Pathologic examination showed that the MRI appearances were not caused by dysplasia, degenerative abnormalities, or inflammatory change. Histologic quantitation showed increased glial cell nuclei counts in the intractable TLE cases compared with controls. There was no difference in glial cell numbers between cases with AT abnormality and those without this appearance. Presence or absence of changes was not predictive of preoperative neuropsychology, postoperative change in neuropsychology, or seizure outcome after surgery. CONCLUSIONS: These frequently seen ipsilateral changes are not caused by gliosis and may reflect a nonspecific increase in water content in the temporal lobe. This may be due to myelin abnormalities or some other as yet unidentified pathologic factor.     

Cortical and hippocampal volume deficits in temporal lobe epilepsy

PURPOSE: To use quantitative magnetic resonance imaging (MRI) methods to examine the extent of volume abnormalities in the hippocampus and in extrahippocampal brain regions in localization-related epilepsy of temporal lobe origin (TLE). METHODS: Hippocampal, temporal lobe, and extratemporal lobe volumes were examined with 3-mm spin-echo coronal MRI scans in patients with unilateral TLE who were candidates for temporal lobe resection. Measures were adjusted for normal variation due to intracranial volume and age based on 72 healthy male controls. Group differences between 14 male TLE [7 left TLE (LTLE), 7 right TLE (RTLE)] patients and a subset of 49 age range-matched controls were examined with analysis of variance (ANOVA). RESULTS: As compared with controls, patients with TLE had smaller temporal lobe and frontoparietal region gray matter volumes, bilaterally, smaller temporal lobe white matter volumes bilaterally, and larger ventricular volumes. In contrast to these bilateral tissue volume deficits, hippocampal volume deficits in TLE were ipsilateral to the epileptogenic temporal lobe. CONCLUSIONS: Extrahippocampal volume abnormalities were bilateral and occurred in both temporal and extra-temporal cortical regions in TLE, whereas hippocampal deficits were related to the side of the epileptogenic focus. These data suggest that brain abnormalities in TLE are not limited to the epileptogenic region.     

Sex differences in patients with mesial temporal lobe epilepsy

Possible sex differences in the pattern of interictal hypometabolism were investigated, and also seizure spread in patients with mesial temporal lobe epilepsy (n=48) and hippocampal sclerosis (MTLE). Male patients (n=21) more often had a frontal lobe hypometabolism ipsilateral to the seizure onset (p<0.0001) and a spread of epileptiform activity to this region (p=0.001). By contrast, female patients more often exhibited hypometabolism (p=0.0052) and an ictal spread to the contralateral temporal lobe (p=0.0097). These findings suggest sex differences in spatial distribution of brain dysfunction in MTLE, perhaps reflecting sexual dimorphism in regional cerebral connectivity.     

Quantitative analysis of interictal behavior in temporal lobe epilepsy

Patients with unilateral temporal epileptic foci were contrasted with normal subjects and patients with neuromuscular disorders in the evaluation of specific psychosocial aspects of behavior. Eighteen traits were assessed in equivalent questionnaires completed by both subjects and observers. The epileptic patients self-reported a distinctive profile of humorless sobriety, dependence, and obsessionalism; raters discriminated temporal lobe epileptics on the basis of circumstantiality, philosophical interests, and anger. The right temporal epileptic displayed emotional tendencies in contrast to ideational traits of left temporal epileptic. Right temporal epileptics exhibited "denial," while left temporal epileptics demonstrated a "catastrophic" overemphasis of dissocial behavior. The results support the hypotheses that sensory-affective associations are established within the temporal lobes, and that, in man, there exists a hemispheric asymmetry in the expression of affect.     

Pure amnesia caused by bilateral temporal lobe astrocytoma--case report

A 32-year-old male presented with progressive pure amnesia caused by astrocytoma invading the bilateral medial temporal lobes. Methionine positron emission tomography demonstrated the extent of tumor invasion well. His memory impairment was partially improved by treatment for the astrocytoma. Lesion of the bilateral hippocampus causes memory impairment, but pure memory loss without other associated neurological sign or deterioration of consciousness is rare in a case of cerebral neoplasm.