Anterior Temporal Resection Research Articles

Simple partial seizures (isolated auras) in medial temporal lobe epilepsy

We analysed whether the medial temporal lobe epilepsy (MTLE) with isolated auras makes any difference in the clinical picture in comparison with MTLE in which only complex partial seizures (CPS) occur. We included 100 patients (aged 16–59 years) with unilateral medial temporal lobe lesions who consecutively underwent presurgical evaluation due to intractable MTLE and who became completely aura- and seizure-free after the anterior temporal resection. Preoperatively, isolated auras were present in 70 patients. These patients were categorised into the IA group. The remaining 30 patients in whom the auras preceded seizures were categorised into the NIA group. We found no difference between the two groups for the age at onset, epilepsy duration or aura types. Conversely, a right-sided epileptogenic region (61%) occurred more frequently in the IA group than in the NIA group (27%, P=0.001). Conclusively, isolated auras show affinity to the right hemisphere. One explanation may be that seizures stop more quickly in the right hemisphere. Another hypothesis is that consciousness can be disturbed much easier by the ictal activity in left temporal seizures: auras evolve more frequently to CPS due to the disturbance of consciousness.

Potentially misleading extratemporal lobe lesions in patients with temporal lobe epilepsy

From a series of 217 consecutive temporal resections for intractable epilepsy between 1993 and 2000, we identified all patients with large non-neoplastic extratemporal lesions. Only patients with known postsurgical outcomes...

Distractibility after unilateral resections from the frontal and anterior cingulate cortex in humans

The prefrontal and anterior cingulate cortex figure prominently in current models of directed attention. The efficacy of selective attention was studied in a distractibility study carried out with patients who had unilateral surgical excisions from the frontal cortex with or without involvement of the cingulate gyrus, patients with unilateral anterior temporal resections, and normal control subjects. In Task A, participants responded to target stimuli presented at the foveal location in the presence or absence of distracting peripheral stimuli that appeared 200 ms before the target’s onset. The presence of a distractor caused a comparable increase in reaction times to targets across all groups. In Task B, a distractor appeared during every trial but it appeared at a new location on 12% of the trials. A comparable transient increase in reaction times was observed in patients with frontal cortical resections that spared the anterior cingulate gyrus, patients with anterior temporal lobe resections, and the normal control group. Thus, lesions restricted to the prefrontal cortex need not impair the ability to attend and respond to a target event in the presence of distraction. Interestingly, no distracting effect was observed during Task B in patients with lesions that invaded the anterior cingulate gyrus, suggesting that this cortical region is involved in responding to or habituating to environmental stimuli.

Abstracts of Literature

Abstracts of Literature

Matrix Metalloproteinase-9 in Cerebral Aneurysms

OBJECTIVE: Generalized disruption of arterial wall morphological changes in patients harboring cerebral aneurysms has been documented; however, little is known regarding the pathogenesis of these changes. To explore the role of the elastolytic gelatinase, matrix metalloproteinase-9 (MMP-9), levels of this enzyme in the wall of intracranial aneurysms were compared with those in both intracranial and extracranial arteries. The tissue levels of its major inhibitor, tissue inhibitor of metalloproteinase (TIMP), were measured in these tissues as well. The activity of MMP-9 in plasma was also evaluated. METHODS: The aneurysm wall was excised from three of six patients undergoing craniotomies for aneurysm clipping. A 1-cm segment of superficial temporal artery (STA) was obtained from each of six patients. Additional STAs were obtained from six patients in the control group who were undergoing craniotomies for nonvascular disease. An intracranial artery was also obtained from the anterior temporal neocortical resection of a patient undergoing a craniotomy for mesial temporal sclerosis. MMP-9 and TIMP levels were determined via Western blot analysis. Using substrate gel zymography, MMP-9 plasma activity was determined for a separate cohort of patients with aneurysms (n = 6) and patients in the control group (n = 6). RESULTS: MMP-9 and TIMP levels in the aneurysm wall were markedly increased beyond levels in both extracranial arteries (STAs from patients with aneurysms and patients in the control group) and the intracranial artery. There were no differences in the levels of MMP-9 in the STAs of patients harboring aneurysms when compared with patients in the control group. Also, no differences were noted in plasma MMP-9 activity. CONCLUSION: Local rather than systemic perturbations in MMP-9 levels may contribute to the matrix disruption associated with cerebral aneurysms. This local up-regulation is not the result of TIMP down-regulation. The lack of increased systemic metalloproteinase activity precludes the use of plasma MMP-9 activity as a screening tool for presymptomatic aneurysms. However, local therapeutic modulation of MMP-9 activity may help arrest aneurysm progression.

Matrix metalloproteinase-9 in cerebral aneurysms.

Generalized disruption of arterial wall morphological changes in patients harboring cerebral aneurysms has been documented; however, little is known regarding the pathogenesis of these changes. To explore the role of the elastolytic gelatinase, matrix metalloproteinase-9 (MMP-9), levels of this enzyme in the wall of intracranial aneurysms were compared with those in both intracranial and extracranial arteries. The tissue levels of its major inhibitor, tissue inhibitor of metalloproteinase (TIMP), were measured in these tissues as well. The activity of MMP-9 in plasma was also evaluated. The aneurysm wall was excised from three of six patients undergoing craniotomies for aneurysm clipping. A 1-cm segment of superficial temporal artery (STA) was obtained from each of six patients. Additional STAs were obtained from six patients in the control group who were undergoing craniotomies for nonvascular disease. An intracranial artery was also obtained from the anterior temporal neocortical resection of a patient undergoing a craniotomy for mesial temporal sclerosis. MMP-9 and TIMP levels were determined via Western blot analysis. Using substrate gel Zymography, MMP-9 plasma activity was determined for a separate cohort of patients with aneurysms (n = 6) and patients in the control group (n = 6). MMP-9 and TIMP levels in the aneurysm wall were markedly increased beyond levels in both extracranial arteries (STAs from patients with aneurysms and patients in the control group) and the intracranial artery. There were no differences in the levels of MMP-9 in the STAs of patients harboring aneurysms when compared with patients in the control group. Also, no differences were noted in plasma MMP-9 activity. Local rather than systemic perturbations in MMP-9 levels may contribute to the matrix disruption associated with cerebral aneurysms. This local up-regulation is not the result of TIMP down-regulation. The lack of increased systemic metalloproteinase activity precludes the use of plasma MMP-9 activity as a screening tool for presymptomatic aneurysms. However, local therapeutic modulation of MMP-9 activity may help arrest aneurysm progression.

Temporal lobe epilepsy surgery in childhood: rationale for greater use.

Anterior temporal resection may effectively relieve therapy-resistant seizures in children and give social, psychological and economic benefits. Epidemiological and prognostic data demonstrate that this is an under-utilised procedure: although an estimated 677 Ontario children per year would be candidates for anterior temporal resection, only 18 were performed in a 12 month period.

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

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

Focal suppression-burst on electrocorticography after temporal lobectomy.

Of 40 patients with cortical resections for epilepsy, three had focal suppression-burst (S-B) on postresection intraoperative electrocorticography (ECoG). Eighteen to 24 months later, two patients were seizure-free and one had rare seizures. Follow-up neuropsychological testing and MRI did not reveal unexpected postoperative abnormalities. Follow-up scalp surface EEGs did not show S-B. Although S-B on postresection ECoG suggests severe localized cortical damage, this pattern near anterior temporal lobectomy resection margins was not associated with postoperative deficits.

Periventricular and subcortical nodular heterotopia. A study of 33 patients.

Grey matter heterotopias, demonstrated by MRI, may present with a broad spectrum of clinical severity. We have studied 33 patients with periventricular nodular heterotopias (PNH); 19 (58%) had unilateral and 14 (42%) bilateral lesions. Thirteen of the 19 patients (68%) with unilateral subependymal nodules of grey matter had, in addition, unilateral focal subcortical heterotopias (SNH), comprising 39% of the entire group. Most had normal intellectual and motor function but some presented with mild mental retardation and neurological deficits. Recurrent seizures were described in 82%, mainly partial attacks with temporo-parieto-occipital auras. Nodular heterotopias led to unilateral or bilateral independent temporal epileptic discharges in 47% of epileptic patients with PNH alone and in 61% of those who had SNH in addition. Extratemporal or multilobar, unilateral or bilateral interictal spiking was present in 10 other patients (36%). Two first degree relatives of patients with seizures were affected but had no seizures, three were investigated for other apparently unrelated neurological symptoms: memory impairment, vertigo or transient ischaemic attacks in one person each. Contiguous ovoid nodules of grey matter, symmetrically lining both lateral ventricles, were described in nine patients. Seven of them were female, including four with familial incidence of PNH. Such lesions may explain the familial occurrence of epilepsy in some families. Seven patients underwent anterior temporal resection: two patients with unilateral subependymal and focal subcortical heterotopias were seizure free or significantly improved. Four patients, three with PNH alone and one with additional subcortical nodules, did not improve significantly after surgery. The remaining patient was followed for less than 6 months.

An Approach to Radical Excision of Craniopharyngioma by the Temporal Route

Attempts at radical excision of craniopharyngioma has been made increasingly possible by the advent of neuroradiological imaging and the use of microscopic technique. Between 1977 and 1993, 62 patients of The National Hospital for Neurology and Neurosurgery, London, have undergone surgical excision of craniopharyngioma by the temporal route, with a small anterior temporal resection. Surgical mortality was 4%. Forty-eight patients (76%) remain well on average follow-up of 34 months. Twelve percent had major complications (hypothalamic damage, subdural haematoma, scalp collections requiring shunt drainage). There were four recurrences in patients where the initial operations were considered as complete microscopic excision. Maximal control of tumour recurrence by removal of all tumour accessible and visible to the surgical microscope is best achieved by radical excision at the first operation.

Increased neocortical spiking and surgical outcome after selective amygdalo-hippocampectomy

We studied the electrocorticogram (ECoG) before and immediately after transcortical selective amygdalo-hippocampectomy, prospectively in 13 consecutive patients and retrospectively in three others. ECoG was performed with surface and two depth electrodes inserted through T2 aimed at the amygdala and anterior hippocampus. Before resection the ECoG showed a variable amount of interictal spiking, recorded either independently from the depth and surface, or synchronously. A small cortical incision (2–3 cm) was made in T2. The hippocampus, amygdala and parahippocampal gyrus were removed subpially. After the resection, increased epileptiform abnormality was observed in all 16 patients and a different ECoG pattern emerged. It consisted of repetitive, high amplitude spikes and polyspikes, separated by attenuated background, recorded from the most anterior temporal area. Similar observations were reported by Niemeyer in 1958. The outcome was comparable to that of standard anterior temporal resection: 62.5% class I and 25% class II (Engel's scale). ECoG is often used to tailor the amount of resection, and the persistence of epileptic abnormalities correlates with worse outcome. This is not the case in selective amygdalo-hippocampectomy, suggesting that a different underlying mechanism is responsible for the increased interictal spiking following this procedure.

High-resolution (2.6-mm) PET in partial complex epilepsy associated with mesial temporal sclerosis.

Eleven patients with medically refractory partial seizures underwent positron emission tomography (PET) with a 600-crystal tomograph and fluorine-18 fluorodeoxyglucose. All patients had been selected for temporal lobe resection, and the side of the epileptogenic focus had been demonstrated with electroencephalography (EEG). Only patients in whom structural lesions had been excluded with magnetic resonance (MR) imaging were studied. Ten of 11 patients were found to have temporal cortical hypometabolism on the same side as the focal abnormality that was demonstrated with EEG. In two patients, PET showed hypometabolism in the mesial temporal cortex only. There were no incorrectly lateralizing PET results. MR imaging showed an abnormality in the corresponding temporal lobe in seven patients. In one patient, both PET and MR images were normal. All patients underwent anterior temporal resection, and histologic examination of resected tissue showed mesial temporal sclerosis in all cases.

Developmental anterobasal temporal encephalocele and temporal lobe epilepsy

The authors describe the association between an antero-basal temporal lobe encephalocele and medically intractable temporal lobe epilepsy in three patients treated successfully by surgery. Two men and one woman, aged 26 to 37 years (mean 31 years), had onset of complex automatism and generalized seizures in their second and fourth decades (mean age 22.7 years). They had been epileptic for 6 to 14 years (mean 8.3 years) before surgery. Preoperative electroencephalograms localized ictal epileptic activity to the left mesial temporal lobe in all cases, and neuropsychological testing revealed dominant temporal lobe dysfunction. Magnetic resonance (MR) imaging demonstrated an anteromedial basal temporal encephalocele extending into the pterygopalatine fossa through a bone defect at the base of the greater sphenoid wing in the region of the foramen rotundum and pterygoid process, a discrete center of embryonal chondrification. At surgery, the encephaloceles were found in front of the uncus, and an area of gliosis extended from the encephalocele to the amygdalohippocampal region. All patients have been seizure-free following anterior temporal resection and amygdalohippocampectomy including the encephalocele. These three cases delineate a condition of disordered embryogenesis wherein a developmental anterobasal temporal encephalocele acts as the substrate for temporal lobe epilepsy. This lesion may be diagnosed preoperatively with MR imaging and should be considered in the differential diagnosis of late-onset temporal lobe epilepsy.

Radical excision of craniopharyngioma by the temporal route: A review of 50 patients

Attempts at radical excision of craniopharyngioma have been made increasingly possible by progress in neuroradiological imaging and the use of microscopic technique. Between 1977 and 1990, 50 patients of The National Hospital for Neurology and Neurosurgery, London, have undergone radical surgical excision of craniopharyngioma by the temporal route, with a small anterior temporal resection. Surgical mortality was 4%. Thirty-eight (76%) patients remain well at average follow-up of 30 months; 15% had major complications (hypothalamic damage, subdural haematoma, scalp collections requiring shunt drainage). There were three recurrences in those patients where the initial operations were considered as complete microscopic excision. It is concluded that maximal control of tumour recurrence by removal of all tumour accessible and visible to the surgical microscope is best achieved by a radical excision at the first operation.

Risk and benefit in the surgery of epilepsy: complications and positive results on seizures tendency and intellectual function.

A review of complications in a series of 560 consecutive craniotomies for surgery of epilepsy shows the mortality to be nil and the morbidity very low. Results on the seizure tendency for temporal resections are presented with emphasis on extent and modalities of removal. In this series the success/failure ratio was in the order of 80/20%. Patients with-right sided removal tend to do better than those with left-sided operations. Removal of the hippocampal formation appears to significantly improve the results. Patients studied with intracerebral electrodes tend as a group to do better than those operated without depth electrodes. Anterior temporal resection is usually followed by a significant increase in intellectual function when measured one year after surgery.

Right-left asymmetries in sound field localization in normal and anterior temporal lobectomized subjects

Normal right-handed subjects (15 male and 15 female) localized 5-s complex sounds without head movements from one of seven small loud speakers (separated by 30° on the azimuth) under two conditions. In the first, the “target” sound was presented in isolation (the speakers in the unused positions being silent). In the second condition the same target was used but six discriminably different sounds were also present—each emanating from a different loudspeaker. Under the first condition there was no significant right-left asymmetry in localization accuracy in normal or temporal lobectomized subjects (33). In the second condition, a right auditory field superiority in localization accuracy was observed for the 30 normal subjects (p < 0.0003). The right anterior temporal lobectomized subjects also exhibited the (normal) right field superiority (p <0.001), while left anterior temporal resections appeared to obliterate this normal asymmetry. These effects may derive from the larger auditory association cortex (planum temporale) on the left side which may be involved in localizing sounds in a complex auditory field. [Work supported by Research Service, Veteran Administration.]

Mechanism and localization of speech in the parietotemporal cortex.

Cortical stimulation of the supramarginal and angular gyri elicited dysphasia. Delays in verbal response, misnaming, and difficulties in speech production were also elicited from this region. In two patients speech arrest occurred when stimulation was extended into the occipital cortex and the cortex medial to the supramarginal gyrus, respectively. In a left-handed patient, with speech representation presumed to be in the right hemisphere, neither stimulation nor ablation of the angular gyrus resulted in dysphasia. After anterior temporal resections two patients exhibited dysphasia in association with cortical edema. In one of these an additional resection in the inferior temporo-occipital region produced a marked but transient dyslexia. Observations of the disintegration of speech function during stimulation suggest that such stimulation interferes with a search mechanism by which the nonverbal concept of a visual stimulus is linked to a specific word in memory that is then withdrawn for use. A review of autopsy specimens demonstrates how close the cortex bearing indispensable speech representation lies to the occipital pole and the parietal midline. Because the gyral pattern is obscured by the meninges and is subject to anomalies, elective resection in these areas should be preceded by cortical stimulation and functional mapping.

Mechanism and localization of speech in the parietotemporal cortex

Cortical stimulation of the supramarginal and angular gyri elicited dysphasia. Delays in verbal response, misnaming, and difficulties in speech production were also elicited from this region. In two patients speech arrest occurred when stimulation was extended into the occipital cortex and the cortex medial to the supramarginal gyrus, respectively. In a left-handed patient, with speech representation presumed to be in the right hemisphere, neither stimulation nor ablation of the angular gyrus resulted in dysphasia. After anterior temporal resections two patients exhibited dysphasia in association with cortical edema. In one of these an additional resection in the inferior temporo-occipital region produced a marked but transient dyslexia. Observations of the disintegration of speech function during stimulation suggest that such stimulation interferes with a search mechanism by which the nonverbal concept of a visual stimulus is linked to a specific word in memory that is then withdrawn for use. A review of autopsy specimens demonstrates how close the cortex bearing indispensable speech representation lies to the occipital pole and the parietal midline. Because the gyral pattern is obscured by the meninges and is subject to anomalies, elective resection in these areas should be preceded by cortical stimulation and functional mapping.