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.

Normalization of neuronal metabolic dysfunction after surgery for temporal lobe epilepsy. Evidence from proton MR spectroscopic imaging

Surgery is a safe and effective treatment for patients with temporal lobe epilepsy (TLE) who do not respond adequately to anticonvulsant medication and in whom the seizure generator can be identified and safely removed. Proton MR spectroscopic imaging (MRSI) can image and quantify neuronal damage in patients with TLE based on reduced signals from N-acetylaspartate (NAA), a compound localized exclusively in neurons. We performed proton MRSI in patients with TLE before and after surgical treatment to determine whether NAA or other resonance intensities changed in the temporal lobes of patients with TLE after surgery, and whether these changes correlated with surgical outcome. N-acetylaspartate resonance intensity relative to creatine (NAA/Cr) was abnormally low preoperatively in at least one temporal lobe in all 14 patients examined. It was low ipsilaterally in the patients who became seizure free and bilaterally in those who did not. Postoperatively, it increased to the normal range on the side of surgery in all patients who became seizure free. In the one patient who became seizure free and who had low NAA/Cr in both temporal lobes before surgery, NAA/Cr values in the contralateral, unoperated temporal lobe also increased to the normal range. In contrast, NAA relative intensity ratios did not change in those patients who continued to have seizures after surgery. The creatine resonance intensity (Cr) in the temporal lobes was high, relative to the brainstem, in seven patients preoperatively. After surgery, the Cr remained high in two patients, both of whom continued to have seizures. We conclude that NAA (and Cr) abnormalities in TLE do not result solely from neuronal loss and gliosis but can be reversible after postsurgical control of seizures. This implies that the NAA and Cr abnormalities in patients with TLE, at least in part, are dynamic markers of both local and remote physiologic dysfunction associated with ongoing seizures.

Relations between EEG seizure morphology, interhemispheric spread, and mesial temporal atrophy in bitemporal epilepsy

PURPOSE

A strong relation exists between lateralization of seizure onset in temporal-lobe epilepsy and atrophic mesial structures measured by volumetric magnetic resonance imaging (MRI). We examined whether this relation extended to subregions of the mesial temporal lobe and whether the trend for seizures to spread contralaterally could be related to the localization of atrophy.

METHODS

We analyzed 362 seizures (with and without clinical signs) from 23 patients having bitemporal epilepsy in whom intracerebral electrodes were implanted for presurgical evaluation. Patients had measurements of hippocampal and amygdala volumes, including comparison with normal controls. We assessed on EEG the lateralization and localization of seizure onset and the trend to spread to the contralateral side (proportion of seizures that spread for each patient). We included all seizures, independent of the presence of clinical manifestations. These features were related to presence and localization of atrophy.

RESULTS

Among the 19 patients with mesial atrophy, agreement between side of prevalent seizure onset and predominant atrophy was found in 10 (53%). From 99 seizures starting in a temporal lobe with atrophy limited to the hippocampus, 67% started simultaneously in amygdala and hippocampus, 20% in hippocampus, and 13% in amygdala. From 137 seizures starting in a temporal lobe with amygdala and hippocampal atrophy, 47% started in amygdala and hippocampus, 48% in hippocampus, and 5% in amygdala. The trend to spread was 45% to the most atrophic side and 62% to the normal or less atrophic side.

CONCLUSIONS

When examining amygdala and hippocampus in this group of patients with bitemporal epilepsy, regions of seizure onset did not correspond to regions of predominant atrophy. The likelihood that seizures spread contralaterally was not influenced by atrophy in the region targeted by the spread. Precise relation between mesial temporal atrophy and seizures remain to be elucidated.

Volumetric magnetic resonance imaging. Clinical applications and contributions to the understanding of temporal lobe epilepsy

In recent years, magnetic resonance imaging-based volumetric measurements of the amygdala and hippocampus have proved useful in the diagnosis and treatment of patients with temporal lobe epilepsy. This imaging modality allows amygdaloid and hippocampal volumes to be correlated with neurophysiological, neuropathological, and neuropsychological findings, surgical outcome, and clinical findings. We evaluated the technical and anatomical aspects underlying the successful use of the modality that were reported in previous studies. We also evaluated issues such as the sensitivity and specificity of volumetric magnetic resonance imaging, its use in bilateral temporal lobe epilepsy, and the debate concerning the sensitivity of qualitative visual analysis vs quantitative volumetric analysis of magnetic resonance images. Volumetric magnetic resonance imaging, when used in conjunction with video electroencephalographic monitoring, neuropsychological studies, and other neuroimaging studies, will enable patients with temporal lobe epilepsy to be treated in an appropriate, efficient, and cost-effective manner.

Proton magnetic resonance spectroscopic imaging and magnetic resonance imaging volumetry in the lateralization of temporal lobe epilepsy: a series of 100 patients

Surgery is a safe and effective treatment for drug-resistant temporal lobe epilepsy (TLE). However, bilateral electroencephalographic (EEG) abnormalities are frequently present, making presurgical lateralization difficult. New magnetic resonance (MR) techniques can help; proton magnetic resonance spectroscopic imaging (MRSI) can detect and quantify focal neuronal damage or dysfunction based on reduced signals from the neuronal marker N-acetylaspartate, and magnetic resonance imaging (MRI)-based measurements of amygdala-hippocampal volumes (MRIVol) can improve the detection of atrophy of these structures. We performed proton MRSI and MRIVol in 100 consecutive patients with medically intractable TLE to determine how well these techniques agreed with the lateralization by extensive EEG investigation. We found that the EEG, MRSI, and MRIVol findings were highly concordant. The MRSI was abnormal in 99 of 100 patients (bilateral in 54%). The MRIVol was abnormal in 86 of 98 patients (bilateral in 28%). We obtained lateralization in 83% of patients using MRIVol alone, in 86% using MRSI alone, and in 90% by combining MRSI and MRIVol (vs 93% lateralization by EEG). MRSI was abnormal in 12 patients with normal MRIVol. The combination of proton MRSI and MRIVol can lateralize TLE accurately and noninvasively in the great majority of patients. By reducing reliance on EEG, these imaging techniques could reduce prolonged presurgical evaluation and make seizure surgery available to more patients.

Contribution of medial versus lateral temporal-lobe structures to human odour identification

To investigate possible distinct contributions of different temporal-lobe structures to odour identification, the University of Pennsylvania Smell Identification Test was administered monorhinally to seizure-free patients who had undergone one of three types of temporal-lobe resection practised in three different institutions for surgical treatment of epilepsy. The resections were neocorticectomy (Dublin), selective amygdalohippocampectomy (Zurich), or anterior temporal-lobe resection with encroachment on amygdala and hippocampus (Montreal). Resections, analysed from MRI scans, showed unexpected encroachment on medial structures in most patients of the neocorticectomy groups, and largest amygdala and hippocampal resections in the amygdalohippocampectomy groups. Impaired odour identification was observed in all patient groups, irrespective of surgical approach, with greatest impairment in the nostril ipsilateral to the resection. The finding of deficits in all three surgical groups suggests that damage in the anterior temporal area, perhaps in piriform cortex, is sufficient to disrupt performance on this task; it may be that function is disrupted in the medial temporal-lobe region by disconnection when the periamygdaloid area is damaged, even when amygdala and hippocampus are left intact. An alternative explanation for our results is that damage in any one of these areas disrupts a complex network involving several distinct temporal-lobe structures.

Function and organization in dysgenic cortex. Case report

Cerebral dysgenesis is a subject of interest because of its relationship to cerebral development and dysfunction and to epilepsy. The authors present a detailed study of a 16-year-old boy who underwent surgery for a severe seizure disorder. This patient had dysgenesis of the right hemisphere, which was composed of a giant central frontoparietal nodular gray matter heterotopia with overlying large islands of cortical dysplasia around a displaced central fissure. Exceptional insight into the function, biochemistry, electrophysiology, and histological structure of this lesion was obtained from neurological studies that revealed complementary information: magnetic resonance (MR) imaging, [18]fluoro-2-deoxy-D-glucose positron emission tomography (PET), functional PET scanning, proton MR spectroscopic (1H-MRS) imaging, intraoperative cortical mapping and electrocorticography, in vitro electrophysiology, and immunocytochemistry. These studies demonstrated compensatory cortical reorganization and showed that large areas of heterotopia and cortical dysplasia in the central area may retain normal motor and sensory function despite strikingly altered cytoarchitectonic organization and neuronal metabolism. Such lesions necessitate appropriate functional imaging studies prior to surgery and cortical mapping to avoid creating neurological deficits. Integrated studies, such as PET, 1H-MRS imaging, cortical mapping, immunocytochemistry, and electrophysiology may provide information on the function of developmental disorders of cerebral organization.

Learning and retention of words and designs following excision from medial or lateral temporal-lobe structures

We sought to elucidate the contributions of the amygdala, hippocampus and temporal neocortex to learning and memory for verbal and visuospatial material. Two matched learning tasks, using abstract words versus abstract designs, were administered to patients with unilateral neocorticectomy (NCE; Dublin), selective amygdalohippocampectomy (AHE; Zurich) or anterior temporal-lobe resection invading the amygdala and hippocampus (ATL; Montreal). Data were analysed according to side and type of resection. Learning and recall for words was impaired in groups with resection from the left temporal lobe, irrespective of whether mediobasal structures were spared or temporal neocortex was spared. All right-resection groups were unimpaired. Learning for abstract designs was impaired across all trials in the right AHE and NCE groups, and on the last two trials in the right ATL group. Restricted deficits of lower magnitude were observed on some trials in left-resection groups. These results show a partial dissociation between side of excision and type of material, but the finding of similar deficits in all resection types was unexpected. We propose that excision from either the hippocampal region or temporal neocortex may result in a disconnection, giving a similar functional outcome, as both types of resection interrupt a circuit likely to be essential for normal storage and retrieval of information.

Surgical treatment of patients with single and dual pathology: relevance of lesion and of hippocampal atrophy to seizure outcome

Modern neuroimaging can disclose epileptogenic lesions in many patients with partial epilepsy and, at times, display the coexistence of hippocampal atrophy in addition to an extrahippocampal lesion (dual pathology). We studied the postoperative seizure outcome of 64 patients with lesional epilepsy (median follow-up, 30 months) and considered separately the surgical results in the 51 patients with a single lesion and in the 13 who had dual pathology. In patients with a single lesion, 85% were seizure free or significantly improved (Engel's class I-II) when the lesion was totally removed compared with only 40% when there was incomplete resection (p < 0.007). All three patients with dual pathology who had both the lesion and the atrophic hippocampus removed became seizure free. In contrast, only 2 of the 10 patients with dual pathology undergoing surgery aimed at the lesion or at the hippocampus alone became seizure free (p < 0.05), although 4 of them showed significant improvement (Engel's class II). We conclude that the outcome in patients with single epileptogenic lesions is usually dependent upon the completeness of lesion resection. In patients with dual pathology, surgery should, if possible, include resection of both the lesion and the atrophic hippocampus.

Specificity of volumetric magnetic resonance imaging in detecting hippocampal sclerosis

BACKGROUND

Magnetic resonance imaging (MRI)-based volumetric measurements of the hippocampal formation are useful in detecting unilateral hippocampal sclerosis (HS) in patients with temporal lobe epilepsy. In this pathologic entity, volumetric MRI analysis shows the epileptogenic structure to be atrophic when compared with the normal, nonepileptogenic side. Some authors have suggested that the radiological features of atrophy of medial temporal lobe structures are common in patients with complex partial seizures, but also are seen frequently in other seizure types and can occur even in patients without epilepsy.

OBJECTIVE

To determine if seizures originating in extrahippocampal sites cause gliosis, cell loss, and atrophy of medial temporal lobe structures (i.e., HS).

METHODS

We studied 110 patients with chronic epilepsy using volumetric MRI measurements of the hippocampal formation. Seventeen patients had pathologically proven HS, 27 patients had seizures due to extratemporal structural lesions, 15 patients had seizures caused by extrahippocampal temporal lobe lesions, 29 patients had primary generalized epilepsy, and 22 patients had secondary generalized epilepsy.

RESULTS

All 17 patients with HS showed significantly reduced absolute hippocampal formation volumes of greater than 2 SDs below the mean of the control groups. The preoperative hippocampal formation volume measurements correlated well with the severity of HS on pathological examination. Hippocampal volumes were within the normal range in all patients with primary generalized epilepsy, secondary generalized epilepsy, extratemporal structural lesions, and extrahippocampal temporal lobe lesions.

CONCLUSIONS

Seizures originating at extrahippocampal sites do not cause gliosis, cell loss, or atrophy of medial temporal structures. Significant reduction in hippocampal volumes is a specific marker for HS.

Proton magnetic resonance spectroscopic imaging for discrimination of absence and complex partial seizures

We performed proton magnetic resonance spectroscopic imaging of the temporal lobes between, during, and soon after nonconvulsive seizures in 20 patients with documented temporal lobe epilepsy, 5 patients with primary generalized epilepsy, and 2 patients with secondary generalized epilepsy. Our objective was to determine whether there were metabolic changes observable by magnetic resonance spectroscopic imaging during seizures and whether these changes were specific for focal or generalized nonconvulsive seizures. We found a significant increase in lactate to creatine plus phosphocreatine (lactate/creatine) values, reflecting an imbalance in energy supply and demand or an adaptation in response to ictal neuronal discharges, during and soon after complex partial seizures, but not during or soon after absence seizures associated with generalized epilepsy. In patients with temporal lobe epilepsy, the N-acetylaspartate resonance relative to creatine plus phosphocreatine was low in one or both temporal lobes, indicating neuronal loss or damage. This was not observed in patients with primary generalized epilepsy. The regions with abnormal lactate/creatine and N-acetylaspartate/creatine values corresponded to the epileptogenic focus as defined by clinical-electroencephalographic investigation. There was no change in the N-acetylaspartate/creatine values in the temporal lobes between the interictal, ictal, or postictal states. We conclude that (1) partial seizures are associated with abnormally high lactate levels, but absence seizures are not, and (2) no short-term changes of N-acetylaspartate occur during or soon after complex partial seizures or absence seizures. These findings may be related to the lack of postictal confusion in patients with absence seizures, as well as with the more benign course of primary generalized epilepsy with nonconvulsive attacks.

Mesial atrophy and outcome after amygdalohippocampectomy or temporal lobe removal

We studied 74 consecutive patients with temporal lobe epilepsy who were treated surgically and in whom the volumes of mesial temporal structures were determined preoperatively by magnetic resonance imaging. We divided the patients into three groups according to the volumetric findings: unilateral (63.5% of the patients), bilateral (23%), or no atrophy (13.5%) of the amygdala-hippocampal formation. Two distinct surgical approaches were used: selective amygdalohippocampectomy (n = 37) or anterior temporal lobe resection (n = 37). Outcome was assessed at least 1 year after surgery, according to Engel's modified classification. Patients with unilateral mesial temporal atrophy had significantly better results compared with the other two groups (p < 0.001): We found excellent results (class I or II outcome) in 93.6% of the patients with unilateral atrophy, in 61.7% of those with bilateral atrophy, and in 50% of the group with no significant atrophy of mesial temporal structures. The two different surgical techniques were equally effective, regardless of the pattern of atrophy. In conclusion, magnetic resonance volumetric studies in temporal lobe epilepsy proved to be an important preoperative prognostic tool for surgical treatment, but they did not provide guidance for selecting one surgical approach compared to the other.

Significance of mesial temporal atrophy in relation to intracranial ictal and interictal stereo EEG abnormalities

We studied 31 consecutive patients with temporal and extratemporal epilepsy who underwent presurgical evaluation with stereotaxic depth EEG (SEEG) to assess the relationships between amygdalo-hippocampal (AM-HF) atrophy and the location of SEEG seizure onset and SEEG interictal abnormalities. Scalp EEG recordings with sphenoidal electrodes had shown bitemporal ictal or interictal epileptic abnormalities in all. Patients underwent high quality MRI scans, including MRI volumetric measurements of mesial temporal structures. None had foreign tissue lesions. The final conclusions of the SEEG investigation coincided with the lateralization obtained by MRI volumetric measurements in the eight patients who had significant unilateral atrophy of the amygdala, hippocampus or both (> 2 SD below the mean of controls). In these patients with unilateral atrophy, all or > 75% of clinical seizures originated from the atrophic side. The seven patients with bilateral, but significantly asymmetrical, mesial atrophy had bilateral seizure onsets with > 70% originating from the more atrophic side in four, from the less atrophic side in two, and without predominance in one. The one patient with severe bilateral symmetrical atrophy had seizures originating equally from both sides. Five patients had no atrophy on MRI, but depth electrodes revealed predominant unilateral ictal temporal onsets in four of them. There was no significant correlation between the frequency of SEEG interictal spikes and the amount of AM-HF atrophy. However, we found a significant correlation between the severity of SEEG background disturbance in AM and HF and the degree of atrophy of these structures. Patients with unilateral atrophy were more frequently free of seizures after surgery than those with bilateral or no atrophy (P < 0.05). We conclude that unilateral mesial atrophy predicts ipsilateral mesial SEEG seizure onset despite bitemporal extracranial EEG foci. However, in patients with significant bilateral mesial atrophy, SEEG seizures may originate from either side, even in the presence of significant asymmetry. Finally, the identification of unilateral mesial atrophy has prognostic importance.

Genetic linkage studies in familial frontal epilepsy: exclusion of the human chromosome regions homologous to the El-1 mouse locus

Familial frontal epilepsy has been recently described in six pedigrees. All families reported show autosomal dominant inheritance with incomplete penetrance. Affected individuals develop predominantly nocturnal seizures with frontal lobe semiology. In 1959, a genetic mouse model for partial epilepsy, the El mouse, was reported. In the El mouse, a major seizure susceptibility gene, El-1, segregates in an autosomal dominant fashion and has been localized to a region distal to the centromere of mouse ch 9. Comparative genetic maps between man and mouse have been used to predict the location of several human disease genes. The El-1 locus in the mouse is homologous to human chromosomes 3p23-p21.2, 3p11.2-q11.2, 3q21-q25.3, 6p12-q12 and 15q24. Polymorphic microsatellite markers covering these candidate regions were used for genotyping individuals in the three larger families ascertained, one of which is French-Canadian and two are Australian. Significant negative two-point and multipoint lod scores were obtained separately for each family, thus excluding linkage with the candidate regions on chromosomes 3, 6 and 15.

Frequency and characteristics of dual pathology in patients with lesional epilepsy

We studied 167 patients who had identifiable lesions and temporal or extratemporal partial epilepsy. Pathology included neuronal migration disorders (NMDs) (48), low-grade tumors (52), vascular malformations (34), porencephalic cysts (16), and gliotic lesions as a result of cerebral insults early in life (17). MRI volumetric studies using thin (1.5- or 3-mm) coronal images were performed in all patients and in 44 age-matched normal controls. An atrophic hippocampal formation (HF), indicating dual pathology, was present in 25 patients (15%). Abnormal HF volumes were present in those with lesions involving temporal (17%) but also extratemporal (14%) areas. Age at onset and duration of epilepsy did not influence the presence of HF atrophy. However, febrile seizures in early childhood were more frequently, although not exclusively, found in patients with hippocampal atrophy. The frequency of hippocampal atrophy in our patients with low-grade tumors (2%) and vascular lesions (9%) was low. Dual pathology was far more common in patients with NMDs (25%), porencephalic cysts (31%), and reactive gliosis (23.5%). Some structural lesions, such as NMDs, are more likely to be associated with hippocampal atrophy, independent of the distance of the lesion from the HF. In other types of lesions, such as vascular malformations, dual pathology was found when the lesion was close to the HF. A common pathogenic mechanism during pre- or perinatal development may explain the occurrence of concomitant mesial temporal sclerosis and other structural lesions because of either (1) associated developmental abnormalities or (2) predisposition to prolonged febrile convulsions.(ABSTRACT TRUNCATED AT 250 WORDS)

Imaging of axonal damage in vivo in Rasmussen's syndrome

We obtained magnetic resonance spectroscopic images (MRSIs) in three patients with Rasmussen's syndrome. The relative resonance intensity of N-acetylaspartate (NAA) to creatine (NAA:Cr), an index of neuronal loss or damage, was determined for various regions within the brain, and the affected:unaffected hemisphere asymmetry ratio was determined. All three patients had decreased relative NAA signal intensity over the entire affected hemisphere. The decrease in NAA:Cr involved cortex and white matter, was most prominent in the anterior periventricular region, and showed a tendency to be worse in patients with longer duration of disease. 1 year follow-up MRSI showed further reduction of the relative NAA signal in all patients, indicating progression of the disease. All patients were free of seizures for at least 48 h before the first MRSI, but two of them had epilepsia partialis continua (EPC) during the follow-up examination. There was no significant increase of the lactate resonance intensity, except in the two MRSIs performed during EPC. This indicates that lactate accumulation results from repetitive seizures rather than from the disease process itself. The spatial distribution of the metabolic abnormality on MRSI was more widespread than that of the structural abnormality on MRI. The relative NAA resonance intensity was not reduced in the contralateral hemisphere. Our findings indicate that MRSI can identify and quantify neuronal damage and loss throughout the affected hemisphere of patients with Rasmussen's syndrome, including areas that appear normal on conventional MRI.

The relation of spike foci and of clinical seizure characteristics to different patterns of mesial temporal atrophy

We reviewed clinical data and scalp electroencephalograms in 61 consecutive patients with temporal lobe epilepsy and mesial temporal atrophy assessed with volumetric magnetic resonance imaging: 39 patients had unilateral and 22 patients had bilateral atrophy. We attempted to determine whether any aspects of seizure symptoms and any electrographic features could be correlated to degree and anatomic pattern of mesial temporal atrophy. Spikes were always confined to temporal regions and were frequently bilateral without a statistically significant difference between patients with unilateral atrophy (33%) and those with bilateral atrophy (50%). Twenty-five of 40 foci associated with amygdala atrophy had maximum field over the anterior temporal regions. In contrast, 19 of 19 foci with isolated hippocampal formation atrophy were never maximum anteriorly. Secondarily generalized seizures and temporal lobe syncopes were correlated with anatomically extensive, particularly amygdala, atrophy. Prolonged postictal confusion was always associated with bitemporal abnormalities in the form of atrophy or spiking. These results explain some of the variability in the clinical and electrographic manifestations of temporal epilepsy and outline the specific role of amygdala involvement in addition to the commonly reported hippocampal atrophy.

Autosomal dominant nocturnal frontal lobe epilepsy. A distinctive clinical disorder

The disorder of autosomal dominant nocturnal frontal lobe epilepsy has recently been identified, and is now delineated in detail. A phenotypically homogeneous group of five families from Australia, Britain and Canada, containing 47 affected individuals, was studied. The largest family contained 25 affected individuals spanning six generations. This disorder is characterized by clusters of brief nocturnal motor seizures, with hyperkinetic or tonic manifestations. Subjects often experienced an aura, and remained aware throughout the attacks. Seizures occurred in clusters (mean eight attacks/night) typically as the individual dozed, or shortly before awakening. The epilepsy usually began in childhood, and persisted through adult life, with considerable intra-family variation in severity. Seizures were often misdiagnosed as benign nocturnal parasomnias, psychiatric and medical disorders. Interictal EEG studies were unhelpful. Ictal video-EEG studies showed that the attacks were partial seizures with frontal lobe seizure semiology. Neuro-imaging was normal. Carbamazepine monotherapy was frequently effective. This disorder showed autosomal dominant inheritance. Recognition of this entity is clinically important for diagnosis, appropriate therapy and genetic counselling. Moreover, this disorder now offers an opportunity to identify a gene for partial epilepsy.

Focal intermittent delta activity in patients with mesiotemporal atrophy: a reliable marker of the epileptogenic focus

We attempted to determine the significance of background abnormalities and their relation with spikes and location of atrophy in 56 patients with temporal lobe epilepsy (TLE) and mesiotemporal atrophy (MTA) assessed by volumetric magnetic resonance imaging (MRI): 35 patients had unilateral (group I) and 21 had bilateral atrophy with lateralized predominance (group II). Trains of delta waves over temporal regions were observed in > or = 90% of patients. They lateralized with accuracy equal to that of the spikes to the site of atrophy (delta 92% or 29 of 32 patients in group I and 63% or 12 of 19 of group II; spikes 85% or 28 of 33 of group I and 65% or 13 of 20 of group II). Delta waves and spikes occurred together in > 85% of cases. With respect to their location, a striking concordance was observed: delta activity almost always occurred ipsilateral with unilateral spiking (90% or 19 of 21 of patients with unilateral and 88% or 7 of 8 of patients with bilateral atrophy) and bilaterally independently with bilateral spiking (67% or 6 of 9 of patients in group I and 100% or 10 of 10 in group II). Furthermore, spiking and delta activity were never in disagreement with respect to lateralization. In TLE related to MTA, delta transients are a reliable indicator of the epileptogenic focus and presumably reflect the epileptogenic process rather than the underlying structural pathology.

Proton magnetic resonance spectroscopic images and MRI volumetric studies for lateralization of temporal lobe epilepsy

We obtained 2D magnetic resonance (MR) spectroscopic images (MRSI) and MRI volumetric measurements (MRIV) of amygdala and hippocampus in 30 consecutive patients with temporal lobe epilepsy (TLE) being evaluated for surgical treatment. Both MRSI and MRIV lateralization showed good agreement with the current gold standard of clinical-EEG lateralization. Each exam separately correctly lateralized 25 out of 30 patients with no false lateralization. Combining both exams, lateralization could be achieved in 28 out of 30 patients. The two patients with no significant asymmetry had bitemporal EEG abnormalities, and bilateral damage on both MRIV and MRSI. There was a good correlation between the magnitude of the MRSI and MRIV asymmetry (Pearson coefficient = 0.83; p < .0001). Both MRSI and MRIV were normal in our patients with seizures originating outside the temporal lobes. Both MRIV and MRSI can lateralize TLE in 83% of patients. Combination of the two modalities allows lateralization in 93% of patients. Patients who cannot be lateralized generally have symmetrical bitemporal abnormalities; they are not incorrectly lateralized. The structural and chemical pathologic abnormalities seen in TLE seem to be associated with the seizure focus, and may be as, or even more, reliable than a few recorded seizures in predicting the side from which most seizures originate.

Curvilinear reconstruction of 3D magnetic resonance imaging in patients with partial epilepsy: a pilot study

In an attempt to better delineate the abnormalities associated with focal cortical dysgenesis, we performed curvilinear reformatting of the cortex from 3D magnetic resonance (MR) images. Illustrative patients with partial seizures and conventional orthogonal MRI evaluation show that small regions of cortical thickening suggestive of focal dysplastic lesions may not be recognized. In three such patients the curvilinear reformatting demonstrated two additional focal abnormalities of the cortical gyri and better defined the two focal lesions found on conventional orthogonal MR images. This method promises to be a useful tool in the evaluation of epileptic patients with proven or suspected subtle structure cortical abnormalities, particularly focal neuronal migration disorders where cortical thickening, abnormal gyral pattern, and poor delineation of the gray-white matter transition are the main findings.

Temporal lobe epilepsy caused by domoic acid intoxication: evidence for glutamate receptor-mediated excitotoxicity in humans

We describe the development of temporal lobe epilepsy in an 84-year-old man who had suffered domoic acid intoxication. Following intoxication he had nausea, vomiting, confusion, and coma. Generalized convulsions and complex partial status epilepticus progressively developed. After 3 weeks he improved and was seizure free with severe residual memory deficit. Electroencephalograms initially showed periodic epileptiform discharges, later evolving to epileptic abnormalities over frontotemporal regions with diffuse slow waves. Eight months after the intoxication the electroencephalogram was normal. One year after the acute episode, complex partial seizures developed. Electroencephalograms showed epileptic discharges independently over both temporal lobes, with left-sided predominance. Magnetic resonance imaging revealed a hyperintense T2-weighted signal and atrophy of both hippocampi; a positron emission tomographic scan showed bitemporal decreased glucose metabolism. Pneumonia developed and the patient died 3 1/4 years after the intoxication. Autopsy disclosed severe bilateral hippocampal sclerosis. The seizures following acute domoic acid intoxication, the postmortem pathology, and the fact that temporal lobe epilepsy developed 1 year after intoxication indicate that the human hippocampus is also vulnerable to kainate receptor excitotoxicity, and provide strong evidence supporting the role of excitotoxic injury in epileptogenesis. This report provides a unique human parallel to, and validates the animal model of, kainate-induced epilepsy as an important tool for studying temporal lobe epilepsy.

Relationship between atrophy of the amygdala and ictal fear in temporal lobe epilepsy

Viscerosensory and affective manifestations are often elicited by temporal lobe seizure discharges. They have been reproduced by amygdaloid stimulation in awake patients during stereotaxic exploration or neurosurgical procedures. They are not exclusively reproduced by stimulation of the amygdala, though most commonly they are evoked from it. Ictal fear is frequently, but not invariably, associated with a rising epigastric sensation, palpitations, mydriasis and pallor. We studied 50 patients (mean age 33 years) with intractable temporal lobe epilepsy (TLE): MRI volumetric measurements of amygdala and hippocampus were performed using a protocol previously described by our group (Watson et al., Neurology 1992; 42: 1743-50). All patients had extensive EEG investigation and at least two seizures recorded by video-EEG monitoring. Seventeen patients (34%) had a clear history of fear accompanied by a rising epigastric sensation as the initial manifestation of their habitual attacks. The amygdala volumes in this group were significantly (P = 0.001) smaller (mean 2131.6 mm3) compared with the volumes of the 33 patients without these symptoms (mean 2561.5 mm3). Both patient groups had smaller mean amygdala volumes compared with normal controls (mean 2828.2 mm3). Postoperative pathology correlated well with volumetric atrophy. In addition, we found that patients with more pronounced amygdaloid atrophy more commonly had prolonged febrile convulsions in early childhood and also more frequently secondarily generalized seizures. Results support the finding that ictal fear is related to pathology of the amygdala and that it, like the hippocampus, is an important substrate of TLE.

Late-onset drop attacks in temporal lobe epilepsy: a reevaluation of the concept of temporal lobe syncope

We report the clinical, radiologic, and EEG features of six patients with temporal lobe drop attacks (TLDA), all of whom underwent temporal resection. Postoperative follow-up of at least 1 year was available in all. TLDA were never the first manifestation but followed the onset of epilepsy after a long delay ranging from 7 to 43 years (mean, 24.4 years). Seizures were of unilateral temporal origin. In one patient, stereo EEG recording of TLDA showed rapid spread of the ictal discharge away from the temporal lobe in less than 1 second. Postoperatively, three patients were seizure free; one has had no TLDA but experiences sporadic auras; another, despite a reduction of more than 50%, continues to have complex partial seizures and TLDA; and the sixth has had sporadic secondarily generalized seizures upon reduction of antiepileptic medication. In conclusion, drop attacks may occur in temporal lobe epilepsy, usually long after the onset of epilepsy. They lead to increased disability and suggest a rapid spread of the ictal discharge and possible involvement of the pontine reticular formation rather than the presence of bitemporal foci or an extratemporal origin.