Computed tomography in chronic seizure disorder caused by glioma

The spectrum of long-term epilepsy-associated tumors: long-term seizure and tumor outcome and neurosurgical aspects

PURPOSE

To describe the histologic spectrum and clinical characteristics of patients with neuroepithelial tumors and drug-resistant epilepsy and to analyze clinical data and treatment related to seizure outcome and survival.

METHODS

Data were analyzed from 207 consecutive patients with intractable epilepsy (aged 2-54 years), who between 1988 and 1999 had >or=50% resection of supratentorial, neuroepithelial tumors. Extent of resection was assessed on postoperative magnetic resonance imaging (MRI); seizure outcome was classified according to Engel's outcome scale; and follow-up data were prospectively updated.

RESULTS

Median follow-up was eight years (range, 2-14 years). Histologic examination revealed 154 classic epilepsy-associated tumors (ganglioglioma, dysembryoplastic neuroepithelial tumor, pleomorphic xanthoastrocytoma, and pilocytic astrocytomas) and 53 others (astrocytomas and oligodendrogliomas). Four World Health Organization (WHO) grade III tumors were found (astrocytoma, n = 3; ganglioglioma, n = 1). After surgery, 82% of the patients were seizure free (class I). The following factors were associated with improved seizure outcome: Short duration of epilepsy before surgery, single EEG focus, absence of additional hippocampal sclerosis or cortical dysplasia, transsylvian approach, other than astrocytomas, and complete tumor resection. After 5 years, only nine (4%) patients had tumor recurrence, four (2%) with malignant transformation and death. None of the four patients with anaplastic tumors died. Even patients with astrocytomas of WHO grade II or III showed 10-year recurrence of only 25% and 10-year survival of 90%.

CONCLUSIONS

Tumors associated with long-term epilepsy should be removed early for two different reasons: high rate of seizure freedom and rare but potential risk of malignant tumor progression. The unexpected long survival of these astrocytomas should be investigated by using immunohistochemistry and molecular biology.

Magnetic resonance imaging in temporal lobe epilepsy: usefulness for the etiological diagnosis of temporal lobe epilepsy

With improvement in magnetic resonance (MR) imaging techniques, the ability to identify lesions responsible for temporal lobe epilepsy has increased. MR imaging has also enabled the in vivo diagnosis of hippocampal sclerosis. Brain tumors are responsible for 2-4% of epilepsies in adult population and 10-20% of medically intractable epilepsy. The sensitivity of MR imaging in the diagnosis of tumors and other lesions of the temporal lobe (vascular malformations, etc.) is around 90%. Both hippocampal sclerosis and other temporal lobe lesions are amenable to surgical therapy with excellent postsurgical seizure outcome. In this article, we characterize and underline distinguishing features of the different pathological entities. We also suggest an approach to reviewing the MR images of an epileptic patient.

Surgical management of pediatric tumor-associated epilepsy

Brain tumors are a common cause of seizures in children. Early surgical treatment can improve seizure outcome, but controversy exists regarding the most appropriate type of surgical intervention. Some studies suggest tumor resection alone is sufficient, while others recommend mapping and resection of the surrounding epileptogenic foci to optimize seizure outcome. To address this issue, we reviewed the charts of 34 pediatric patients aged 18 months to 20 years with medically intractable epilepsy and primary brain tumors. The average age at operation was 12.6 years, and patients had seizures for an average of 6.4 years. The majority of tumors were located in the temporal lobe. Seventeen patients, because of tumor location near an eloquent area, underwent extraoperative mapping using subdural electrode grids prior to definitive tumor resection. Fourteen of these patients had a gross total tumor resection, yet only two had a distinct zone of ictal onset identified and resected. The remaining 17 patients had tumors either in the nondominant hemisphere or far removed from speech-sensitive areas, and therefore did not undergo extraoperative subdural electroencephalograph mapping. Fourteen of these patients also had a gross total tumor resection, while none had intraoperative electrocorticography to guide the resection of additional nontumoral tissue. Overall, of the 28 patients treated with a gross total tumor resection, 24 (86%) are seizure free, while the other four are significantly improved. Of the six patients who had a subtotal tumor removal, five have persistent seizures. The mean follow-up was 3.6 years. We conclude that in children and adolescents, completeness of tumor resection is the most important factor in determining seizure outcome. The routine mapping and resection of epileptogenic foci might not be necessary in the majority of patients. As a corollary, the use of subdural electrode grids in pediatric patients with tumor-associated epilepsy should be limited to cases requiring extraoperative cortical stimulation for localization of nearby eloquent cortex.

Epilepsia do lobo temporal: tratamento cirúrgico

Os autores apresentam 32 pacientes com crises epilépticas não controladas ou intratáveis mesmo fazendo uso de medicamentos em doses adequadas. O eletrencefalograma mostrou descargas paroxísticas focais na região temporal em todos os casos. O material foi dividido em dois grupos. O primeiro é composto de 18 pacientes em que os exames por neuroimagem (ressonância magnética e tomografia computadorizada craniana) mostraram imagens compatíveis com lesões expansivas cerebrais (como gliomas, malformações artério-venosas, tumor epidermóide); foi realizada exérese da lesão em todos os casos, associada à área irritativa adjacente que foi identificada pela eletrocorticografia intraoperatória, em seis casos; só foi possível a exérese dessas áreas irritativas nos casos em que elas se localizavam em zonas não eloquentes. O segundo é composto de 14 pacientes nos quais a ressonância magnética não mostrou imagem compatível com processo expansivo cerebral; o exame histopatológico mostrou esclerose mesial temporal em nove casos e cérebro normal em cinco; todos os casos deste grupo foram submetidos a lobectomia temporal. Observamos que os casos com lesões expansivas cerebrais apresentaram melhor evolução em relação ao controle das crises epilépticas do que os casos sem estas lesões, pois 15 (83,4%) dos 18 casos do primeiro grupo evoluíram sem crises e 10 (71,4%) dos 14 casos do segundo grupo também evoluíram sem crises após a cirurgia.

Surgical treatment of epilepsy: the problem of lesion/focus incongruence

BACKGROUND

This study suggests an alternative surgical strategy for treating patients with intractable epilepsy in whom a lesion, visualized by imaging, is found to be at a distance from the maximal electroencephalographic abnormality (focus).

METHODS

Sixty patients (divided into three groups of 20), all of whom have had surgical resection for intractable epilepsy, are reviewed. Group A patients, representing the most common situation of a congruent electroencephalographic focus and structural lesion, underwent resection of the lesion/focus. Group B patients, in whom the focus and the lesion are incongruent, underwent resection of the focus only. Group C patients are those where the focus and lesion are incongruent; in this group, the lesion only was resected.

RESULTS

Group A patients underwent resection of the lesion/focus (sites: 13 temporal, six frontal, and one parietal) with excellent results. Group B patients, in whom the focus only was resected (lesion sites: 14 temporal, four parietal, and two occipital) obtained poor results. Group C patients had excellent results following resection of the lesion only (lesion sites: 12 temporal, seven frontal, and one parietal). The superior surgical outcome in seizure control of group C is comparable to that seen in group A (Chi2 contingency test; Chi2 = 3.27 p > .05, 3 degrees of freedom) and is in contrast to the poor results seen in group B (Chi2 = 20.59 p < .001, 3 degrees of freedom).

CONCLUSION

In those patients where a choice between a focus and a lesion is imperative, the lesion detected by imaging should be given priority in surgical resection.

Glial tumourettes (glial microtumours): their clinical and histopathological manifestations

This study represents our experience with eight cases (males: 4; females: 4; 13-47 years old, average age 28.5 years) of a "glial tumourette" (minute glioma), which measured less than 15 mm in diameter on an MRI. Four tumours were located in the frontal lobe, one in the rostrum of the corpus callosum, two in the midbrain, and one in the thalamus. The symptoms and signs lasted from two days to 15 months prior to diagnosis, and they consisted of epileptic seizures in five patients and increased intracranial pressure due to hydrocephalus resulting from aqueductal stenosis in three. All patients had a CT scan and an MRI as a part of their initial neuroimaging evaluations. While the CT findings failed to show the lesion in four patients, MRI demonstrated it in all cases. Five tumours were either totally or subtotally removed while the remaining three were biopsied. Histological examinations revealed six tumours to be low-grade gliomas (fibrillary astrocytoma: 4; oligoastrocytoma: 2) and two to be high-grade gliomas (anaplastic astrocytoma: 1; anaplastic oligodendroglioma: 1). Regarding adjuvant therapy, three patients received radiation and/or chemotherapy. One of the patients with midbrain fibrillary astrocytoma died of the disease 38 months after the operation, however, no evidence of progression in the remaining seven has been observed in the follow-up period ranging from five to 65 months after the operation (average: 25.4 months). The histogenesis of benign and malignant gliomas and the importance of surgical exploration in the management of such patients with minute intracerebral tumours are also discussed.

Surgical treatment of temporal lobe epilepsy: clinical, radiological, and histopathological findings in 178 patients

The surgical treatment of pharmacoresistant temporal lobe epilepsy is increasing rapidly. The correlation of preoperative MRI, histopathological findings, and postoperative seizure control is reported for 178 patients with chronic medically intractable temporal lobe epilepsy who were operated on between November 1987 and January 1993. Histopathologically there were distinct structural abnormalities in 97.2% of the surgical specimens. Signal abnormalities on MRI were present in 98.7% of patients with neoplastic lesions (n = 79), 76.6% of patients with non-neoplastic focal lesions (n = 55), and 69.2% of patients with Ammon's horn sclerosis (n = 39). Overall, structural abnormalities were detected by MRI in 82.7% of all patients. The mean postoperative follow up period was three years. Some 92% of the patients benefited from surgery: 103 patients (61.7%) were seizure free, 26 (15.5%) had no more than two seizures a year, and 24 (14.4%) showed a reduction of seizure frequency of at least 75%. Fourteen patients (8.4%) had a < 75% reduction of seizure frequency. The percentage of patients who were completely free of seizures after operation was 68.5% for patients with neoplastic lesions, 66.7% for Ammon's horn sclerosis, and 54.0% for patients with non-neoplastic focal lesions. By contrast, none of the patients in whom histopathological findings were normal became seizure free postoperatively. The data show that the presence of focal lesions or Ammon's horn sclerosis as determined by histopathological examination is associated with improved postoperative seizure control compared with patients without specific pathological findings. Brain MRI was very sensitive in detecting neoplasms; however, its sensitivity and specificity were limited with respect to non-neoplastic focal lesions and Ammon's horn sclerosis. Improvement of imaging techniques may provide a more precise definition of structural lesions in these cases and facilitate limited surgical resections of the epileptogenic area rather than standardised anatomical resections.

The relative contributions of MRI, SPECT, and PET imaging in epilepsy

Functional and structural neuroimaging techniques are increasingly indispensable in the evaluation of epileptic patients for localization of the epileptic area as well as for understanding pathophysiology, propagation, and neurochemical correlates of chronic epilepsy. Although interictal single photon emission computed tomography (SPECT) imaging of cerebral blood flow is only moderately sensitive, ictal SPECT markedly improves yield. Positron emission tomography (PET) imaging of interictal cerebral metabolism is more sensitive than measurement of blood flow in temporal lobe epilepsy. Furthermore, PET has greater spatial resolution and versatility in that multiple tracers can image various aspects of cerebral function. Interpretation of all types of functional imaging studies is difficult and requires knowledge of time of most recent seizure activity and structural correlates. Only magnetic resonance imaging (MRI) can image the structural changes associated with the underlying epileptic process, and quantitative evidence of hippocampal volume loss has been highly correlated with seizure onset in medial temporal structures. Improved resolution and interpretation have made quantitative MRI more sensitive in temporal lobe epilepsy, as judged by pathology. When judged by electroencephalography (EEG), ictal SPECT and interictal PET have the highest sensitivity and specificity for temporal lobe epilepsy; these neuroimaging techniques have lower sensitivity and higher specificity for extratemporal EEG abnormalities. Regardless of the presence of structural abnormalities, functional imaging by PET or SPECT provides complementary information. Ideally these techniques should be used and interpreted together to improve the localization and understanding of epileptic brain.

Surgical pathology of chronic epileptic seizure disorders

The surgical treatment of chronic epilepsies is increasing rapidly and involves neuropathologists in the care of patients with chronic and medically intractable seizure disorders. Herein we review the histopathologic findings in 279 consecutive surgical specimens of patients with chronic pharmacoresistant epileptic disorders. Aspects that are relevant to the diagnostic surgical pathologist such as the terminology of developmental lesions and Ammon's horn sclerosis are discussed. In 87 cases (31.2%), there were tumors in which all but two were of low histopathological grade (WHO grade I or grade II). The most common tumors were gangliogliomas, pilocytic astrocytomas, oligodendrogliomas, fibrillary astrocytomas and dysembryoplastic neuroepithelial tumors. Among the most frequent non-neoplastic focal lesions, microscopic glioneuronal hamartias, circumscribed vascular malformations, glioneuronal hamartomas and porencephalic defects were most frequent. The hippocampal formation was structurally well preserved in 71 specimens of patients with temporal lobe epilepsy. In 51 of these (71.8%) cases, Ammon's horn sclerosis was present. The findings suggest that the structural lesions observed in the great majority of the specimens are closely related to the pathogenesis of intractable seizures.

Temporal lobectomy for complex partial seizures that began in childhood

Forty-six consecutive patients who underwent surgery for intractable temporal lobe seizures originating in childhood are reported; invasive preoperative monitoring (e.g., depth electrodes and subdural arrays) was not used in the selection process. Our results, with respect to the control of seizures and improvement in behavior, are comparable to those of series in which invasive monitoring was used in the selection process. Eighty-five percent of the 46 patients (96% of the 28 operated after the introduction of long-term electroencephalographic monitoring) became either seizure free or experienced near total control of their seizures. Our results indicate that many patients can be selected successfully for temporal resection without exposure to the risk and expense of invasive presurgical procedures. A long duration of epilepsy prior to surgery in patients with neoplasia portended a less satisfactory outcome. Our results strengthen the argument for early operation in children with intractable epilepsy.

Outcome in subjects with alcohol-provoked seizures

The outcome in 165 subjects with either an unknown (n = 93) or an alcohol-related (n = 72) seizure etiology, admitted to the emergency room of a general hospital in 1977-1978, was assessed after 10 years on the basis of subsequent hospital records and death-certificate-based mortality data. Alcohol and/or drug poisoning was the most frequent cause of death in the group with alcohol-related seizures. Sixty-four percent of the deaths in this group were directly related to alcohol abuse. The crude mortality was 45.8 (expected 8.6)/100 persons/10 years in the group with alcohol-related seizures and 15.1 (expected 6.0)/100 persons/10 years in the other group, the odds ratio between the groups being 4.8. Twenty percent of those with an unknown seizure etiology were found to show alcohol-related seizures, while the seizure etiology remained unknown in 59%, and a specific etiology other than alcohol abuse was revealed in 21% during the follow-up period. We conclude that alcohol abuse is an important, though often undetected, seizure etiology carrying a poor prognosis. The difference in mortality between the groups was due more to alcoholism than to seizures. There was no difference in mortality between those with a first alcohol-related seizure and those with previous alcohol-related seizures.

Ganglioglioma: 13 years of experience

A 13-year retrospective review of 17 patients with gangliogliomas treated at the University of Iowa was conducted to investigate the association between tumor location, extent of resection, pathological findings, and patient prognosis. Thirteen were in the cerebral hemispheres and 4 in the midline. The mean ages at diagnosis and symptom onset were 16 and 8.8 years, respectively. The most common presenting symptom was seizures (11 patients); focal neurological deficit was seen in 5 patients and headache in 1. Patients with hemispheric tumors had an older age at time of diagnosis and a longer duration of symptoms. Pathologically, they had more microcalcifications, lymphocytic infiltration, microcystic degeneration, and eosinophilic bodies. Cerebral hemispheric tumors were more amenable to total resection than midline neoplasms, 77% versus 25%, respectively. In the patients with hemispheric tumors, 10 patients were tumor-free after total resection. Two of the 3 patients with partial resection had stable residual tumors. The third died of tumor progression. In the 4 patients with midline neoplasms, one was tumor-free after total resection. The other 3 had subtotal resection and radiation therapy. Two died within 2 years; the third is still alive with progressive tumor. Five of 9 patients who had seizure disorders and who underwent total tumor removal were seizure-free postoperatively. The other 4 patients and the 2 with partial surgical resection continued to have seizures.

Epileptogenic anaplastic astrocytoma imaged only by T2-weighted magnetic resonance studies: clinical and surgical implications

The case of a 28-year-old woman who presented with focal sensory seizures and later developed mild sensory loss in the face and hand is described. An EEG, two contrast-enhanced CT and non-enhanced T1-weighted magnetic resonance (MR) scans were normal, but T2-weighted MR scans revealed a lesion measuring 3 x 2 cm in the mid-rolandic region. This lesion did not enlarge over a 6-month period. Resection of the abnormal gyrus was guided by electrocorticography and histology revealed an anaplastic astrocytoma. Although there was resolution of the facio-digital sensory loss postoperatively the frequency and pattern of the partial sensory seizures was unchanged. The neuroradiological and histological findings in this case highlight the difficulties concerning the indications for surgical intervention in adult patients who present with epilepsy and have lesions visualized only on magnetic resonance imagery.

Intracranial, intraaxial, space-occupying lesions in patients with intractable partial seizures: an anatomoclinical, neuropsychological, and surgical correlation

Fifty of approximately 250 patients evaluated for intractable partial seizures were shown to have a space-occupying lesion detected with radiographs and/or neuroimaging. Twenty-eight males and 22 females had a mean age at seizure onset of 13 years and a mean duration of seizures of 11 years. All patients had closed-circuit television with EEG monitoring and complete neurologic and neuropsychological assessment. Findings were correlated with lesion location and surgical data. Twenty-seven lesions (54%) were located in the temporal lobe. Thirty-five lesions (70%) were neoplastic. All patients with temporal lobe lesions had complex partial seizures, as did 74% of patients with extratemporal lesions. A good correlation between clinical seizure characteristics and lesion localization was found with the temporal, occipital, and frontal lesions but not with the parietal lesions. Sixty-six percent of patients had focal interictal EEG findings. Lateralization corresponded to the side of the lesion in 64% and was localized to the region of the lesion in 30%. Lateralized ictal EEGs occurred in 58% of patients, corresponding with the side of the lesion in all but one patient. Abnormal findings on neuropsychological testing were congruent with lesion lateralization in 56% of patients and were localized to the region in 26%. Thirty-nine of 47 patients who underwent a subtotal lobectomy to include the lesion are seizure-free after greater than or equal to 1 year of follow-up, and five others are markedly improved.

Hippocampal neuronal density in temporal lobe epilepsy with and without gliomas

The majority of patients with temporal lobe epilepsy show hippocampal sclerosis, which pathologically represents neuronal loss and gliosis. We studied volumetric neuronal density on a representative mid to mid-posterior level slice of hippocampi surgically removed from intractable temporal lobe epilepsy cases, and compared the results between 25 non-tumor epilepsy (NTE) cases and 5 tumor-associated epilepsy (TAE) cases. Eleven age-matched non-epileptic autopsy cases were studied as controls. Cells were counted in the CA1 through CA4 fields and the stratum granulosum of the dentate fascia. In NTE every hippocampal field showed statistically significant loss of neurons, the neuronal density in each field ranging from 35% to 50% of that of control. The mean neuronal density between the TAE and NTE groups also showed statistically significant differences in all hippocampal fields. The neuronal density of hippocampal fields of NTE ranged from 43% to 58% of that of TAE. Tumor-associated epilepsy cases, however, failed to show any statistically significant deviation from the control in their neuronal density. The etiology of the difference in neuronal density between the TAE and NTE groups is discussed.

Pediatric epilepsy surgery

The use of implantable arrays of epidural electrodes has made it possible to carry out extraoperative electrocorticography (ECoG) and functional localization in the awake child. This has permitted cortical excisions that are determined by criteria similar to those obtained during surgical procedures performed under local anesthesia in adults. In addition, the method also permits simultaneous ECoG and video monitoring during the child's symptomatic seizures, providing additional important localizing information that is impractical to obtain in operations under local anesthesia. We report our experience with 75 children, ages 5 months to 15 years, whom we have managed with epidural electrode arrays. The method of extraoperative ECoG is described and illustrative cases are presented to demonstrate its feasibility and utility in children. In addition, we call attention to gliomas as a common cause of chronic focal seizures in children. Of 49 children undergoing resection and followed for from 1 to 14 years (mean of 5.8 years), 32 (65%) are either seizure free or have had a significant reduction in seizure frequency that has unambiguously improved their quality of life. The results are analyzed further by relating the surgical outcome to each of the pathologic entities that caused the seizures. This analysis reveals the variety of neurological conditions that commonly cause intractable focal seizure disorder in children and distinguishes those pathologic entities in which the seizure disorder is apt to respond to surgical intervention from those that will not.