Lateralization of temporal lobe epilepsy (TLE) and discrimination of TLE from extra-TLE using pattern analysis of magnetic resonance spectroscopic and volumetric data

PURPOSE

To examine whether or not pattern analysis of magnetic resonance volumetric (MRVol) and proton magnetic resonance spectroscopic imaging (1H-MRSI) data would enable (a) the accurate lateralization of temporal lobe epilepsy (TLE) and (b) the discrimination of TLE from extratemporal epilepsy (E-TLE).

METHODS

For lateralization analysis, we used data from 150 nonforeign tissue lesional TLE patients [88 left-sided (L-TLE), 46 right-sided (R-TLE), and 16 bilateral (Bi-TLE)]. For the discrimination of TLE from E-TLE, we used data from 174 patients (145 with unilateral TLE, 14 with unilateral E-TLE, and 15 with widespread epileptogenic zones involving both the TL and extra-TL regions-multilobar epilepsy). A series of "leave-one-out" cross-validated linear discriminant analyses were performed using the MRVol and 1H-MRSI data sets to lateralize TLE and discriminate it from E-TLE.

RESULTS

Lateralization: The leave-one-out linear discriminant analyses were able to correctly lateralize (with a posterior probability >0.50) 120 (90%) of the 134 L-TLE and R-TLE patients. Imposing higher posterior probability (>0.95) increased accuracy of lateralization to 98%, with only two discordant cases who underwent surgery on the side of electroencephalogram, and both had bad outcome. Discrimination: the leave-one-out linear discriminant analyses were able to correctly classify (with a posterior probability >0.50) 142 (89%) of the 159 TLE and E-TLE patients. Accuracy increased slightly as higher posterior probability cutoffs were imposed, with fewer patients being classified.

CONCLUSIONS

Pattern analysis of 1H-MRSI and MRVol data can accurately lateralize TLE. Discriminating TLE from E-TLE was less accurate, probably due to the presence of temporal lobe damage in some patients with E-TLE reflecting dual pathology.

Familial perisylvian polymicrogyria: a new familial syndrome of cortical maldevelopment

Two familial X-linked dominant syndromes of cortical maldevelopment have recently been described: double cortex/lissencephaly syndrome and bilateral periventricular nodular heterotopia. We report on 12 kindreds with familial perisylvian polymicrogyria (FPP) presenting at 10 centers, examine the clinical presentation in these familial cases, and propose a possible mode of inheritance. The clinical and radiological pattern was variable among the 42 patients, with clinical differences among the families and even within members of the same family. Pseudobulbar signs, cognitive deficits, epilepsy, and perisylvian abnormalities on imaging studies were not found in all patients. When present, they displayed a spectrum of severity. The only clear correlation in this study was between bilateral imaging findings and abnormal tongue movements and/or pronounced dysarthria. Most of the families provided evidence suggestive of, or compatible with, X-linked transmission. On the other hand, the pedigrees of 2 families ruled out X-linked inheritance. The most likely mode of inheritance for these 2 families was autosomal dominant with decreased penetrance; however, autosomal recessive inheritance with pseudodominance could not be ruled out in 1 family. We conclude that FPP appears to be genetically heterogeneous. However, most of the families probably represent a third previously undescribed X-linked syndrome of cortical maldevelopment.

[Dose-dependent relationship of chronic use of phenytoin and cerebellar atrophy in patients with epilepsy]

The chronic treatment with phenytoin or the acute intoxication by this drug may cause permanent cerebellar injury with atrophy of cerebellum vermis and hemispheres, which can be detected by neuroimaging studies. The aim of the present study was to investigate the correlation between the dosage and duration of treatment with phenytoin and the occurrence of cerebellar atrophy. Sixty-six patients were studied and had their tomographies analyzed for cerebellar atrophy. Of the 66 patients studied, 18 had moderate/severe atrophy, 15 had mild atrophy and 33 were considered to be normal. The patients with moderate/severe atrophy were those with higher exposure to phenytoin (longer duration of treatment and higher total dosage) showing statistically significant difference when compared to patients with mild atrophy or without atrophy (p=0. 02). Further, the patients with moderate/severe atrophy had serum levels of phenytoin statistically higher than those of patients with mild atrophy or without atrophy (p = 0.008). There was no association between other antiepileptic drugs dosage or duration of treatment and degree of cerebellar atrophy. We also found that older patients had cerebellar atrophy more frequently, indicating that age or duration of the seizure disorder may also be important in the determination of cerebellar degeneration in these patients. We conclude that although there is a possibility that repeated seizures contribute to cerebellar damage, long term exposure to phenytoin, particularly in high doses and toxic serum levels, cause cerebellar atrophy.

Spatial extent of neuronal metabolic dysfunction measured by proton MR spectroscopic imaging in patients with localization-related epilepsy

PURPOSE

To assess the spatial extent of the decrease in the neuronal marker N-acetyl-aspartate (NAA) relative to creatine (Cr) in patients with localization-related epilepsy, and to assess clinical differences between patients with and without widespread NAA/Cr reduction.

METHODS

We studied 51 patients with localization-related epilepsy. Patients were divided into three groups according to the EEG investigation: (a) temporal lobe epilepsy (TLE, n = 21), (b) extratemporal lobe epilepsy (extra-TLE, n = 20), and (c) multilobar epilepsy (patients with a wider epileptogenic zone, n = 10). We acquired proton magnetic resonance (MR) spectrocopic imaging (1H-MRSI) of temporal and frontocentroparietal regions in separate examinations for both patients and controls. NAA/Cr values 2 standard deviations below the mean of normal controls were considered abnormal.

RESULTS

Twenty-three (45%) patients including 12 with TLE had normal MR imaging including volumetric studies of the hippocampus. Forty-nine (96%) patients had low NAA/Cr, indicating neuronal dysfunction in either temporal and/or extratemporal 1H-MRSIs; 38% of patients with TLE and 50% of patients with extra-TLE also had NAA/Cr reduction outside the clinical and EEG-defined primary epileptogenic area. The NAA/Cr reduction was more often widespread in the multilobar group [six (60%) of 10] than in temporal or extratemporal groups [five (31%) of 16]. Nonparametric tests of (a) seizure duration, (b) seizure frequency, and (c) lifetime estimated seizures showed no statistically significant difference (p > 0.05) for TLE and extra-TLE patients with or without NAA/Cr reduction outside the seizure focus.

CONCLUSIONS

Of patients with localization-related epilepsy, 40-50% have neuronal metabolic dysfunction that extends beyond the epileptogenic zone defined by clinical-EEG and/or the structural abnormality defined by MRI.

De novo psychogenic seizures after epilepsy surgery: case report

The occurrence of de novo psychogenic seizures after epilepsy surgery is rare, and is estimated in 1.8% to 3.6%. Seizures after epilepsy surgery should be carefully evaluated, and de novo psychogenic seizures should be considered especially when there is a change in the ictal semiology. We report a patient with de novo psychogenic seizures after anterior temporal lobe removal for refractory temporal lobe epilepsy. Once psychogenic seizures were diagnosed and psychiatric treatment was started, seizures stopped.

Medial temporal lobe neuronal damage in temporal and extratemporal lesional epilepsy

OBJECTIVE

To assess the extent of medial temporal lobe (TL) abnormalities of the neuronal marker N-acetylaspartate (NAA) in TL and extra-TL lesional partial epilepsy, and to determine whether decreases in NAA are related to lesion location, to lesion pathology, or to the seizures themselves.

METHODS

The authors studied 19 patients with intractable partial epilepsy and an isolated structural cerebral lesion (10 TL, 9 extra-TL; 10 cortical dysplasia [CD], 9 non-CD lesions). Proton MRS imaging was used to determine the average relative resonance intensity of NAA for the TL regions of the left and right hemispheres. Values less than two SDs below the mean of normal control subjects were considered abnormal.

RESULTS

Fourteen patients (74%) had abnormally low NAA relative to creatine (NAA/Cr) in at least one TL. Three-way analysis of variance (ANOVA; lesion pathology, lesion location, side of NAA/Cr decrease) showed that ipsilateral NAA/Cr was lower than contralateral (p = 0. 04). Three-way ANOVA (lesion location, generalized tonic-clonic seizures, side of NAA/Cr decrease) showed that generalized tonic-clonic seizures were associated with lower TL NAA/Cr (p = 0. 02). Lesion location and pathology showed no main effect on the NAA-to-Cr ratio in either analysis (p > 0.05). Linear regression analyses between seizure duration and NAA/Cr decrease was not significant.

CONCLUSION

The authors demonstrated abnormally low TL NAA/Cr in the majority of patients with structural cerebral lesions. This abnormality did not differ with lesion location or pathology. They propose that the altered function of neuronal networks by an isolated structural cerebral lesion results in remote "functional dual pathology."

Is ictal recording mandatory in temporal lobe epilepsy? Not when the interictal electroencephalogram and hippocampal atrophy coincide

OBJECTIVE

To investigate the concordance between scalp electroencephalogram (EEG) lateralization and side of hippocampal atrophy in patients with temporal lobe epilepsy (TLE).

METHODS

We studied 184 consecutive patients with TLE without lesions other than those compatible with mesial temporal sclerosis. In this study, we studied specifically hippocampal atrophy and the results of scalp EEG investigation. Patients were classified according to the localization of interictal epileptiform discharges as unilateral, bilateral asymmetric, and bilateral symmetric. The EEG seizure onsets were also classified separately as unilateral, bilateral asymmetric, and bilateral symmetric. The hippocampal atrophy was determined by volumetric measurements using high-resolution magnetic resonance imaging (MRIVol).

RESULTS

Only 3% of patients had discordance between the ictal and interictal EEG lateralizations; however, none of these had unilateral interictal EEG abnormalities. Interictal EEGs were considered unilateral in 62.0% of patients, bilateral asymmetric in 31.5%, and bilateral symmetric in 6.5%. Ictal EEGs were considered unilateral in 63.5% of patients, bilateral asymmetric in 30.0%, and bilateral symmetric in 6.5%. The MRIVol showed unilateral hippocampal atrophy in 60.9% of patients, bilateral asymmetric hippocampal atrophy in 19.0%, symmetric hippocampal atrophy in 3.8%, and normal volumes in 16.3%. There was a significant concordance between MRIVol lateralization and both interictal and ictal EEG lateralization (P<.001). All patients with unilateral hippocampal atrophy had concordant interictal and ictal EEG lateralization. Six (18.2%) of the 33 patients with bilateral asymmetric hippocampal atrophy had MRI lateralization discordant with EEG lateralization.

CONCLUSIONS

We found a strong concordance between EEG and MRIVol lateralization in patients with TLE. Unilateral hippocampal atrophy predicted ipsilateral interictal epileptiform abnormalities and ipsilateral seizure onsets with no false lateralization. Previous studies in addition to the present series support that a concordant outpatient EEG evaluation in patients with TLE and unilateral hippocampal atrophy would obviate the need for inpatient EEG monitoring.

Neuronal dysfunction in children with newly diagnosed temporal lobe epilepsy

We sought to determine whether neuronal dysfunction throughout the temporal lobes of children with temporal lobe epilepsy (TLE) is already as severe at the time of diagnosis as it is in patients with long-standing intractable TLE (INT-TLE). Proton magnetic resonance spectroscopic imaging was used to measure N-acetylaspartate/creatine (NAA/Cr) ratios in the temporal lobes of five consecutive children with newly diagnosed TLE (ND-TLE), five with INT-TLE, and 30 normal control subjects. The median age of those with ND-TLE and those with INT-TLE did not significantly differ (P = 0.92). All five patients with ND-TLE had bilateral reductions in the NAA/Cr ratio. Two of the five patients with INT-TLE had bilateral reductions in the NAA/Cr ratio; three had unilateral reductions in the NAA/Cr ratio. In the three patients with lesions the NAA/Cr ratio decrease extended outside these lesions. No significant differences were detected in any temporal lobe region between the ND-TLE and INT-TLE groups. The severity of the neuronal dysfunction in the children with ND-TLE was at least as severe as in those with INT-TLE and was not restricted to one temporal lobe, implying that the neuronal abnormalities observed in patients with TLE occur before the clinical manifestations.

Magnetic resonance imaging in the evaluation of patients with aseptic meningoencephalitis and connective tissue disorders

OBJECTIVE

To describe the role of magnetic resonance imaging (MRI) in the evaluation of patients with chronic and recurrent aseptic meningitis.

METHOD

A retrospective study of five patients with aseptic meningoencefalitis diagnosed by clinical and CSF findings. CT scans showed without no relevant findings.

RESULTS

MRI showed small multifocal lesions hyperintense on T2 weighted images and FLAIR, with mild or no gadolinium enhancement, mainly in periventricular and subcortical regions. Meningoencephalitis preceded the diagnosis of the underlying disease in four patients (Behçet's disease or systemic lupus erythematosus). After the introduction of adequate treatment for the rheumatic disease, they did not present further symptoms of aseptic meningoencephalitis.

CONCLUSION

Aseptic meningoencephalitis can be an early presentation of an autoimmune disease. It is important to emphasize the role of MRI in the diagnosis and follow-up of these patients.

Prognostic value of proton magnetic resonance spectroscopic imaging for surgical outcome in patients with intractable temporal lobe epilepsy and bilateral hippocampal atrophy

The objective of this study was to assess which features of temporal lobe proton magnetic resonance spectroscopic imaging (1H-MRSI) are associated with satisfactory surgical outcome in patients with intractable temporal lobe epilepsy and bilateral hippocampal atrophy. We studied 21 patients with intractable temporal lobe epilepsy and bilateral hippocampal atrophy defined by magnetic resonance imaging volumetric measurements who underwent surgical treatment. 1H-MRSI was used to determine the relative resonance intensity ratio of the neuronal marker N-acetylaspartate to creatine + phosphocreatine (NAA/Cr) for mid and posterior temporal lobe regions of the left and right hemisphere, as well as an asymmetry index. Values lower than 2 SDs below the normal mean were considered abnormal. We used Engel's classification to assess surgical outcome with respect to seizure control. Eleven patients (52%) were in class I-II and 10 (48%) were in class III-IV. All 21 were operated on the side of maximal electroencephalographic (EEG) lateralization. Concordant lateralization of decreases in NAA/Cr to the side of surgery and normal NAA/Cr values in the contralateral posterior-temporal region were significantly associated with good surgical outcome: 11 (69%) of 16 patients with 1H-MRSI abnormalities concordant with EEG lateralization and none of the 5 patients with nonconcordant 1H-MRSI had a good outcome (class I-II); 10 (77%) of 13 patients with normal NAA/Cr contralateral to the EEG lateralization versus 1 (12.5%) of 8 of those with NAA/Cr reduction contralateral to EEG lateralization were in class I-II. Regression correlation analysis showed significant linear correlation between the midtemporal NAA/Cr relative asymmetry ratio and surgical outcome; the greater the asymmetry, the better the outcome. We conclude that discriminant 1H-MRSI features associated with favorable surgical outcome in patients with temporal lobe epilepsy and bilateral hippocampal atrophy were (1) concordant 1H-MRSI lateralization, (2) a greater side-to-side asymmetry of NAA/Cr, and (3) an absence of contralateral posterior NAA/Cr reduction.

EEG background delta activity in temporal lobe epilepsy: correlation with volumetric and spectroscopic imaging

PURPOSE

With quantitative electroencephalogram (EEG) and neuroimaging methods, we examined delta activity, atrophy, and neuronal-axonal dysfunction of the cerebral gray and white matter in patients with intractable temporal lobe epilepsy (TLE). Based on evidence that lesions of the white matter result in EEG delta activity, we postulated that background abnormalities in patients with TLE are related to changes of the temporal lobe white matter.

METHODS

We measured interictal delta activity in 34 TLE patients and 10 controls. Spike-free and artifact-free EEG samples were selected by visual inspection. A spectral analysis was used to compute the energy in the delta frequency band. We compared the results of the spectral analysis to magnetic resonance imaging- (MRI) based volumes of the temporal lobe white and gray matter, the hippocampus and the amygdala; and N-acetyl aspartate (NAA) in the lateral and posterior temporal lobe by using proton magnetic resonance spectroscopic imaging (1H-MRSI). The degree of correlation between delta activity and the neuroimaging measurements was assessed by using the Pearson correlation coefficient (r). An analysis of variance (ANOVA) was used to examine the influence of the seizure-focus lateralization on the delta activity and the neuroimaging parameters.

RESULTS

There was no significant difference in the amount of delta activity in the temporal lobe between the controls and patients. We found no correlation between delta activity and the neuroimaging measures (p>0.05). The ANOVA showed significant differences between the patients and controls for the volume of the gray and white matter of the temporal lobe and for the NAA in the lateral and posterior temporal lobe (p<0.002).

CONCLUSIONS

The interictal background delta activity was not explained by reduced volume of the temporal lobe white matter, gray matter, or by abnormalities seen in 1H-MRSI.

[Magnetic resonance imaging and clinical features in adults with monophasic demyelinating disease. Acute disseminated encephalomyelitis or a variant of multiple sclerosis?]

Acute disseminated encephalomyelitis (ADEM) is a widespread monophasic inflammatory disease affecting the central nervous system, that usually follows an infection or vaccination. In this study, we present an analysis of magnetic resonance imaging (MRI), cerebrospinal fluid (CSF) and clinical aspects in four patients with clinical diagnosis of ADEM. The presence of MRI demyelinating lesions was crucial, but not in itself sufficient for definitive diagnosis. Clinical and MRI follow up, in order to exclude new lesions and to reevaluate the former ones, as well as CSF, were important for the differential diagnosis with other demyelinating diseases, particularly multiple sclerosis. In addition, we have shown that early treatment with methylprednisolone after the initial symptoms was effective for improving clinical manifestations as well as for reducing MRI lesions.

Diagnosis of subtle focal dysplastic lesions: curvilinear reformatting from three-dimensional magnetic resonance imaging

Focal cortical dysplasia is a frequent cause of medically intractable partial epilepsy. These lesions are being increasingly identified by high quality images provided by magnetic resonance imaging (MRI), resulting in improved seizure control of surgically treated patients. Small dysplastic lesions are often missed by conventional MRI methods. The identification of subtle structural abnormalities by rectilinear slices is often limited by the complex convolutional pattern of the brain. We developed a method of curvilinear reformatting of three-dimensional MRI data that improves the anatomical display of the gyral structure of the hemispheric convexities. It also reduces the asymmetric sampling of gray-white matter that may lead to false-positive results. We present 5 patients in whom conventional two-dimensional and three-dimensional MRI with multiplanar reformatting was initially considered normal. Subsequent studies using curvilinear reformatting identified lesions in all. Four patients underwent surgery with histological diagnosis of focal cortical dysplasia. Three patients are seizure-free and 1 had significant improvement in seizure control. These results indicate that an increase in the detection of subtle focal dysplastic lesions may be accomplished when one improves the anatomical display of the brain gyral structure by performing curvilinear reformatting.

Dyskinesia induced by phenytoin

Phenytoin is an effective antiepileptic drug, although, it can be associated with many side effects, including dyskinesia.

OBJECTIVE

To describe the clinical characteristics of phenytoin induced dyskinesia.

METHODS

We investigated the occurrence of involuntary movements in patients followed at our adult and pediatric epilepsy clinics during the period of one year.

RESULTS

Three patients presented with phenytoin-induced dyskinesia: one adult with axial and orofacial dyskinesia, and two children with choreoathetosis. They did not have other signs of phenytoin intoxication and had complete recovery after phenytoin withdrawal.

CONCLUSION

Phenytoin induced dyskinesia may occur during either chronic or initial treatment and with normal serum phenytoin levels. However, it occurs most often in patients on polytherapy, usually after increasing dosage and with toxic serum levels. Other signs of phenytoin intoxication may be present in these patients, but often the dyskinesia is the only side effect, which may delay the diagnosis and treatment. The clinical characteristics of the involuntary movements vary and may be focal or generalized, most often characterized by choreoathetosis and dyskinesias. These may last for hours, days or even years, but frequently disappear completely after phenytoin withdrawal.

Neuroimaging evidence of progressive neuronal loss and dysfunction in temporal lobe epilepsy

Whether temporal lobe epilepsy is the result of an isolated, early injury or whether there is ongoing neuronal dysfunction or loss due to seizures is often debated. We attempt to address this issue by using magnetic resonance techniques. Proton magnetic resonance spectroscopic imaging can detect and quantify focal neuronal dysfunction or loss based on reduced signals from the neuronal marker N-acetylaspartate (NAA), and magnetic resonance imaging (MRI)-based measurements of hippocampal volumes (MRIvol) can quantify the amount of atrophy in this structure. We performed magnetic resonance spectroscopic imaging and MRIvol in 82 consecutive patients with medically intractable temporal lobe epilepsy to determine whether there was a correlation between seizure frequency, or type or duration of epilepsy, with NAA to creatine (Cr) values or hippocampal volumes. Volumes and spectroscopic resonance intensities were categorized as to whether they were measured from the temporal lobe ipsilateral or contralateral to the predominant electroencephalographic focus. Ipsilateral and contralateral NAA/Cr was negatively correlated with duration of epilepsy. Hippocampal volumes were negatively correlated with duration ipsilaterally but not contralaterally. Frequency of complex partial seizures was not correlated with any of the magnetic resonance measures. However, patients with frequent generalized tonic-clonic seizures had lower NAA/Cr bilaterally and smaller hippocampal volumes ipsilaterally than patients with none or rare generalized tonic-clonic seizures. The results suggest that although an early, fixed injury may cause asymmetric temporal lobe damage, generalized seizures may also cause progressive neuronal dysfunction or loss.

Surgical outcome in patients with epilepsy and dual pathology

High-resolution MRI can detect dual pathology (an extrahippocampal lesion plus hippocampal atrophy) in about 5-20% of patients with refractory partial epilepsy referred for surgical evaluation. We report the results of 41 surgical interventions in 38 adults (mean age 31 years, range 14-63 years) with dual pathology. Three patients had two operations. The mean postoperative follow-up was 37 months (range 12-180 months). The extrahippocampal lesions were cortical dysgenesis in 15, tumour in 10, contusion/infarct in eight and vascular malformation in five patients. The surgical approach aimed to remove what was considered to be the most epileptogenic lesion, and the 41 operations were classified into lesionectomy (removal of an extrahippocampal lesion); mesial temporal resection (removal of an atrophic hippocampus); and lesionectomy plus mesial temporal resection (removal of both the lesion and the atrophic hippocampus). Lesionectomy plus mesial temporal resection resulted in complete freedom from seizures in 11/15 (73%) patients, while only 2/10 (20%) patients who had mesial temporal resection alone and 2/16 (12.5%) who had a lesionectomy alone were seizure-free (P < 0.001). When classes I and II were considered together results improved to 86, 30 and 31%, respectively. Our findings indicate that in patients with dual pathology removal of both the lesion and the atrophic hippocampus is the best surgical approach and should be considered whenever possible.

Clinical patterns of patients with temporal lobe epilepsy and pure amygdalar atrophy

PURPOSE

MRI volumetric measurements (MRIvol) have been proven reliable in determining mesial temporal atrophy in patients with TLE. We attempted to correlate the clinical features with different patterns of hippocampal formation (HF) and amygdala (AM) atrophy in patients with TLE without foreign tissue lesion.

METHODS

We studied 65 patients with refractory TLE. They were divided into five groups according to MRIvol results: pure AM atrophy (n = 11, 10 unilateral and one bilateral), unilateral HF atrophy (n = 16), bilateral HF atrophy (n = 12), unilateral AM + HF atrophy (n = 13), and patients with normal volumes of AM and HF (n = 13). MRIvol of AM and HF were performed by using a protocol previously described by Watson et al. (Neurology 1992;42:1743-50).

RESULTS

Patients with AM atrophy had later onset of seizures compared with those with unilateral HF atrophy (p < 0.01). History of febrile convulsions (p < 0.0001) and frequent secondarily generalized tonic-clonic seizures (GTCSs) were more often found in patients with HF atrophy compared with those with pure AM atrophy and those with normal volumes (p = 0.04). Prolonged postictal confusion was more often found with AM atrophy (p = 0.05). Memory impairment was more severe in patients with HF atrophy than in those with AM atrophy only or in those with normal volumes (p = 0.03). There were no significant differences among the five groups in the following parameters: age, duration of epilepsy, seizure frequency, and presence and type of aura.

CONCLUSIONS

Prolonged postictal confusion appeared to be related to AM atrophy, in keeping with previous clinical observations. These patients also had a lower incidence of early febrile convulsions, older age at epilepsy onset, lower frequency of secondary GTCS, and lesser memory dysfunction compared with patients with hippocampal atrophy.

Hypothalamic hamartomas and gelastic epilepsy: a spectroscopic study

BACKGROUND

Patients with hypothalamic hamartomas present with epileptic attacks of laughter and later experience multiple seizure types and cognitive decline, suggestive of secondary generalized epilepsy. It has been suggested in the past that gelastic seizures originate in the temporal lobes rather than in the hamartoma, but temporal resections have been ineffective. Recent electrophysiologic evidence suggests that the epileptogenic discharges may originate in the hamartoma itself.

METHODS

We used proton magnetic resonance spectroscopic imaging to quantify the amount of neuronal damage in the temporal lobes and hamartomas of patients with hypothalamic hamartomas and gelastic seizures. Five patients were studied and the relative intensity of N-acetylaspartate to creatine (NAA/Cr) was determined for both temporal lobes as well as for the hamartoma. These values were compared with signals from the temporal lobes and hypothalami of normal control subjects.

RESULTS

NAA/Cr was not significantly different from normal control subjects for either temporal lobe, nor was there a significant asymmetry between the two temporal lobes for any of the patients. NAA resonance signals were present in the hamartomas, and the ratio of NAA to Cr was decreased in the hamartomas compared with the hypothalami of normal control subjects (t = 4.5, p = 0.005).

CONCLUSIONS

We found no detectable neuronal damage in the temporal lobes of patients with hypothalamic hamartomas and gelastic epilepsy. This is further evidence that gelastic seizures do not originate in the temporal lobes of these patients.

Spectroscopic imaging of frontal neuronal dysfunction in hyperekplexia

We used proton magnetic resonance spectroscopic imaging (MRSI) to assess in vivo cortical neuronal involvement in hyperekplexia. Cerebral neuronal function was measured using proton MRSI in four unrelated patients with hyperekplexia and 20 healthy controls. All patients had the major form of hyperekplexia, with additional atypical clinical features in two of them. Family history was positive in three patients and absent in one. The neuronal marker N-acetylaspartate (NAA), choline-containing compounds (Cho) and creatine (Cr) were measured in frontal, central and parietal areas. The MRSI showed a reduction of the relative resonance intensity of NAA/(Cr + Cho) in frontal and central regions in three patients, and in the right frontal region of the fourth. In one patient a second MRSI showed normal relative NAA resonance intensities over both temporal lobes as well as in the brainstem. In two subjects the topography of EEG abnormalities in the frontal lobes coincided with the MRSI findings. This proton MRSI study indicates the presence of frontal neuronal dysfunction in hyperekplexia. Whether this represents cortical dysfunction or an epiphenomenon of diencephalic or brainstem abnormalities remains open. However, the observation of normal proton MRSI in the temporal regions and brainstem in one of the patients seems to concur with the hypothesis of a facilitatory role of cortical dysfunction within areas of sensorimotor representation in the generation of the pathological startle reaction in hyperekplexia.

Nocturnal temporal lobe epilepsy

OBJECTIVE

To analyze clinical, electrophysiologic, and neuroradiologic characteristics and prognostic factors in a group of patients with temporal lobe epilepsy (TLE) and complex partial seizures (CPS) occurring exclusively or predominantly after they fall asleep or before they awaken.

BACKGROUND

CPS arising during sleep are classically identified with frontal lobe epilepsy. TLE associated with seizures occurring only or predominantly during sleep (nocturnal TLE) is less common.

METHODS

From a series of patients with refractory TLE studied between 1980 and 1996, the authors identified 26 patients (15 men) with nonlesional nocturnal TLE (mean age, 40 years). Clinical and laboratory characteristics of these individuals were studied and compared with a group of 72 age-matched, randomly selected patients with nonlesional TLE and predominantly diurnal seizures (diurnal TLE).

RESULTS

Mean age at seizure onset was similar for both groups (16.3 versus 18.7 years). In the nocturnal TLE group, 2 of 26 patients had a positive family history of epilepsy, 18 reported an aura, 4 presented with CPS in clusters, 11 had unilateral and 15 bilateral temporal EEG abnormalities, and 14 of 21 studied had unilateral mesial temporal atrophy. None of these factors differed significantly in the two groups except for higher frequency of the following in the diurnal TLE group compared with the nocturnal TLE group: positive family history for epilepsy (33% versus 8%, p=0.01), estimated frequency of seizures (median, 14 versus 2 per month; p < 0.01), and presence of antecedent febrile convulsions (33% versus 11%, p=0.04). In the nocturnal TLE group, eight patients underwent surgical therapy and became seizure free (follow-up, > 12 months). Only two were seizure free on medication.

CONCLUSIONS

Infrequent and nonclustered seizures, rare family history of epilepsy, and low prevalence of childhood febrile convulsions characterize nocturnal TLE. Within the TLEs, the nocturnal TLE form seems to have a better surgical prognosis.

Intracranial aneurysms and sickle cell anemia: multiplicity and propensity for the vertebrobasilar territory

OBJECTIVE

We describe a case of sickle cell anemia and multiple intracranial aneurysms and review the English-language-reported cases of sickle cell disease associated with intracranial aneurysms proven angiographically or by autopsy, to assess whether there are associations with aneurysm multiplicity and sites of aneurysm occurrence.

CLINICAL PRESENTATION

A 28-year-old woman with sickle cell disease and a subarachnoid hemorrhage underwent successful clipping of three intracranial aneurysms.

RESULTS

Among 44 reviewed cases, 57% of patients demonstrated multiple aneurysms, and aneurysms from patients with multiple aneurysms comprised nearly 80% of the total number of aneurysms. There were, on average, three aneurysms per patient for patients with multiple aneurysms. There was a predominance of female patients (female/male ratio, 1.6:1), although there existed no significant differences in age or gender for patients with single or multiple aneurysms. None of the patients with multiple aneurysms was older than 40 years of age at the time of presentation. Patients with multiple aneurysms and sickle cell disease showed a significant difference in the distribution of the aneurysm sites, with a significantly large number occurring in the vertebrobasilar axis. Multiple aneurysms associated with sickle cell disease showed a higher rate of simultaneous occurrence in the posterior and anterior circulation, compared with multiple aneurysms in the general population.

CONCLUSION

There are strong statistical associations for aneurysm multiplicity and sites of aneurysm occurrence among reported patients with sickle cell disease. Patients with sickle cell anemia and neurological symptoms should undergo magnetic resonance angiography or four-vessel angiography to detect potentially harmful, but neurosurgically treatable, pathological conditions.

Late-onset temporal lobe epilepsy and dilatation of the hippocampal sulcus by an enlarged Virchow-Robin space

MRI signal changes within the hippocampal sulcus have been attributed to a dilated Virchow-Robin space within that sulcus, but no clinical correlates have previously been described. We present a 64-year-old man who developed right temporal seizures. MRI revealed an unusually enlarged Virchow-Robin space within the hippocampus, suggesting space-occupying effect. Such an abnormality should be considered a possible etiology in patients with late-onset temporal lobe epilepsy.

Neuronal metabolic dysfunction in patients with cortical developmental malformations: a proton magnetic resonance spectroscopic imaging study

Cortical developmental malformations are best diagnosed by MRI and are often the cause of refractory epilepsy. Little is known about the metabolic cell function on MR spectroscopy of these types of brain anomaly. We studied 23 patients with cortical developmental malformations and refractory epilepsy using proton MR spectroscopic imaging. Mean age was 28 years (range, 9 to 47 years). The lesions examined were focal cortical dysplasia (n = 5), heterotopia (four band, six periventricular, two subcortical), polymicrogyria (n = 3), tuberous sclerosis (n = 2), and polymicrogyria and periventricular nodular heterotopia (n = 1). We measured the relative signal intensity of N-acetylaspartate/creatine (NAA/Cr) in the lesion, in the perilesional region, and in the region remote from the visible lesion. The values were compared with those from similar brain regions of 25 normal control subjects. The mean NAA/Cr z score values for the 23 patients were as follows: lesion, -2.20 +/- 0.32 (mean +/- SE), n = 21; perilesional region, -1.01 +/- 0.38, n = 15; and distant region, -0.03 +/- 0.34, n = 18 (p < 0.0002). Despite the presence of a large number of neurons, heterotopia showed a relative decrease of NAA in some patients, suggesting that the neurons present were dysfunctional. The maximal NAA/Cr decrease, indicating metabolic dysfunction, colocalized to the structural malformation as defined by MRI and extended to normal-appearing regions adjacent to the visible lesion.

Proton magnetic resonance spectroscopic imaging in patients with extratemporal epilepsy

PURPOSE

Reduced levels of N-acetylaspartate (NAA) in temporal lobes responsible for temporal lobe epilepsy have been observed consistently in proton magnetic resonance spectroscopy (MRS) studies.

METHODS

We investigated the potential of proton MRS to detect low NAA outside of the temporal lobes in patients with non-lesional partial extratemporal epilepsy. Proton MR spectroscopic imaging (MRSI) data of both frontal lobes and central/postcentral regions were obtained in 20 such patients and 16 normal control subjects. The epileptogenic region was determined by an extensive clinical-EEG investigation, including the recording of habitual seizures in each patient, and intracranial EEG recordings in 10 patients.

RESULTS

The relative NAA resonance intensities (i.e., NAA/phosphocreatine plus creatine (CR(t)), NAA/choline-containing metabolites (Cho(t)) and NAA/Cr(t) + Cho(t)), were all significantly reduced throughout the spectroscopic image as compared with that of the controls. Furthermore, reduction of the NAA ratios was greater in the epileptogenic region as compared with the nonepileptogenic regions, on EEG investigation.

CONCLUSIONS

In vivo proton MRSI of patients with nonlesional partial extratemporal epilepsy detected evidence of widespread neuronal damage or dysfunction that was greatest in the region of seizure focus.