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PubMed1988

The impaired learning of semantic knowledge following bilateral medial temporal-lobe resection.

The integrity of several aspects of semantic memory (including knowledge of the meaning, lexical status, perception, and pronunciation of words and famous names) was examined in H.M., a patient with anterograde amnesia following bilateral medial temporal-lobe excision. Despite normal memory for such semantic knowledge acquired prior to the onset of his amnesia in 1953, H.M. showed a severe deficit in memory for semantic information encountered subsequently. In combination with the previously reported impairments in new learning shown by H.M., the deficits observed here point to an association between semantic and episodic memory, and do not lend support to a distinction between them. The acquisition of semantic and episodic information, therefore, appears to depend upon a common memory system that requires the intact functioning of medial temporal-lobe structures.

Aged↗
PubMed2004

Non-parametric evaluation of memory changes at group and individual level following temporal lobe resection for pharmaco-resistant partial epilepsy.

Group versus individual verbal and visuospatial memory outcome following epilepsy surgery was evaluated by a non-parametric method in 25 left and 29 right temporal lobectomy patients. Twenty-five controls were assessed twice. Analyses of change at an individual level evaluated by this statistical approach based on paired-ranks were compared to results with a method based on distances (Reliable Change). The left temporal lobectomy group deteriorated in the two verbal memory variables (p < 0.01 and 0.05). High levels of individual changes unexplained by group patterns were disclosed in the three memory variables analyzed in the patients. Significant individual change, although less pronounced, also occurred in the controls. Group versus individual outcome was adequately distinguished by the non-parametric method. To properly analyze memory change after epilepsy surgery, evaluation at group and individual level ought to combined.

Adult↗
PubMed2000

Effects of inter-item lag on recognition memory in seizure patients preceding temporal lobe resection: evidence from event-related potentials.

The electrophysiological correlates of word recognition are well characterized. Repeated 'old' words evoke a more positive-going waveform starting at approximately 300 ms compared with first-presented, 'new' words. The old/new effect is thought to be generated, in part, by structures within the medial temporal lobe. In the present study, event-related potentials were recorded during a continuous verbal recognition memory task in unoperated patients with either left (L) or right (R) unilateral temporal lobe epilepsy (Epil) and neurologically intact controls. To manipulate the difficulty of the memory task, the lag between the initial and subsequent presentation of the repeated words was varied from one, four to 16 items. In the controls, ERPs to old words were more positive going than new words from approximately 350-650 ms. The old/new effect diminished as the inter-item lag increased. Patient old/new effects showed a later onset (450 ms) and resolution (750 ms) compared with the controls. Furthermore, the late component of the old/new effect was significantly reduced in the L Epil. Although patient behavioral performance did not differ significantly from that of the controls, neuropsychological testing revealed impaired verbal memory function in the L Epil patients. It is concluded that the reduced old/new effect in the L Epil patients provides evidence that medial temporal lobe structures contribute to the scalp-recorded old/new effect.

Adolescent↗
PubMed2004

Hippocampal function and spatial memory: evidence from functional neuroimaging in healthy participants and performance of patients with medial temporal lobe resections.

Several strategies can be used to find a destination in the environment. Using a virtual environment, the authors identified 2 strategies dependent on 2 different memory systems. A spatial strategy involved the use of multiple landmarks available in the environment, and a response strategy involved right and left turns from a given start position. Although a probe trial provided an objective measure of the strategy used, classification that was based on verbal reports was used in small groups to avoid risks of misclassification. The authors first demonstrated that the spatial strategy led to a significant activity of the hippocampus, whereas the response strategy led to a sustained activity in the caudate nucleus. Then, the authors administered the task to 15 patients with lesions to the medial temporal lobe, showing an impaired ability using the spatial strategy. Imaging and neuropsychological results are discussed to shed light on the human navigation system.

Adult↗
PubMed2000

Impaired preference conditioning after anterior temporal lobe resection in humans.

Research with animals suggests that structures within the amygdaloid nuclear complex (ANC) are critical for acquiring associations between rewarding events and neutral stimuli, a form of conditioning often manifested in a subsequent preference for those (conditioned) stimuli. In this study, we investigated the relationship between the ANC and preference learning in humans. Three abstract monochrome patterns were presented to each subject over 180 trials in the context of a counting task requiring working memory. One pattern was paired with food reward on 90% of the trials in which it was presented and with no food reward on the other 10% of trials. The other patterns were similarly reinforced, but at ratios of 50:50% and 10:90% with reward and nonreward, respectively. Subsequently, a group of 21 normal participants preferred the pattern paired most often with reward to that paired least often with reward, and they did not explicitly relate their preferences to the conditioning procedure, but instead attributed them to the characteristics of the patterns themselves. Unlike the normal controls, a group of patients with unilateral surgical lesions that included the ANC (15 left, 18 right) did not show conditioned preferences, but performed normally on a measure of working memory. In contrast, 13 patients with unilateral damage confined to frontal cortex exhibited normal conditioned preferences but were impaired on the working memory task. This double dissociation provides clear evidence that, in humans as in other animals, reward-related learning (conditioned reward) critically depends on a circuit involving inferotemporal cortex and the ANC.

Adolescent↗
PubMed1975

Kinetic properties of hexokinase in resected temporal lobes of patients with drug-resistant epilepsy.

Properties of the cerebral glycolytic enzyme, hexokinase, were studied in biopsy samples of human temporal lobe, obtained during lobectomy for drug-resistant epilepsy and compared "blind" with contol biopsy samples of human cerebral cortex. No significant changes in the total activity or subcellular distribution of the enzyme were observed but the Km value for glucose was altered. The 17 control samples gave a normal mean value for Km (glucose) of 0.05 mM and the 14 epileptic samples gave a significantly higher mean value of 0.09 mM. The drugs used in previous treatment of the epilepsies were "scored" with respect to type and dose; analysis of these in relation to the kinetic results eliminated the possibility that the increase in Km value was an artifact due to the drugs. The observed change in enzyme kinetic properties is discussed in terms of potential interactions of small molecules with the isoenzymes of cerebral hexokinase.

Age Factors↗
PubMed1996

Implications of seizure termination location in temporal lobe epilepsy.

Where propagating symptomatic seizures terminate has not been studied, but might provide insight into mechanisms of seizure termination as well as localization of epileptogenic tissue. We investigated location of seizure termination in 50 refractory temporal lobe epilepsy (TLE) patients who had intracranial EEG recording of spontaneous seizures and subsequent temporal lobe resection with > 1-year follow-up. Only seizures that had onset in the resected temporal lobe were included. Location of the electrical termination for each seizure in each patient was categorized as diffuse, localized to the onset location, or localized elsewhere. The proportion of all seizures in each patient in each category was analyzed with respect to the outcome of surgery. Outcome was classified as seizure-free or persistent seizures. Diffuse seizure termination was noted equally frequently in both outcome groups. However, the 27 patients without seizures postoperatively had a significantly greater proportion of seizures with termination in the onset location (67%) than did the 23 patients with persistent seizures (36%, p < 0.01). The seizure-free patients also had a significantly lower proportion of seizures with localized termination elsewhere than the onset site (13%) than did patients with persistent seizures (45%, p < 0.005). Localization of the site of termination of seizures of focal origin to cortical regions other than the onset is associated with a poorer surgical prognosis. This observation raises the possibility of additional abnormal epileptogenic cortical regions with impaired seizure-terminating capabilities.

Adolescent↗
PubMed1997

Spatial memory deficits in patients with unilateral damage to the right hippocampal formation.

Patients with unilateral temporal lobe damage resulting from intractable temporal lobe epilepsy (TLE, n = 30) or from temporal lobe resection (temporal lobectomy, TLR, n = 47) were investigated on the Nine-box Maze. The task, analogous to the radial arm maze, was designed to compare spatial mapping and working memory theories of the functions of the hippocampus. The task provides measures of spatial, object, working and reference memory, incorporated into a within subjects design. The spatial component was designed to encourage the formation of allocentric rather than egocentric spatial representations. Spatial memory deficits were found (across working and reference memory components) in both TLE and TLR patients with right temporal lobe damage, with intact spatial memory in patients with corresponding left temporal lobe damage. Performance on the matched non-spatial (object) working memory component was equal to healthy controls for all groups. However all patient groups showed a deficit on object reference memory. These findings are discussed in relation to the underlying temporal lobe pathology and particularly atrophy of the hippocampal formation. Overall, the results support the cognitive mapping theory of hippocampal function, with the demonstration of a selective (and probably allocentric) spatial memory deficit in patients with right hippocampal damage.

Adolescent↗
PubMed1999

Cortical dysplasia with angiodysgenesis and chronic inflammation in multifocal partial epilepsy.

A 25-year-old man with a long history of temporal lobe epilepsy developed right occipital lobe seizures and a progressive right homonymous hemianopia. MRI showed diffuse enhancement of the left temporoparieto-occipital white matter and cortical thickening of the left medial temporal lobe. The resected temporal lobe revealed cortical dysplasia and angiodysplasia with foci of more recent ischemic necrosis and chronic inflammation as an explanation for the clinical deterioration.

Adolescent↗
PubMedDate not supplied

[Defects in the visual field in resective surgery for temporal lobe epilepsy].

INTRODUCTION: Temporal lobe resection is the most used procedure in epilepsy surgery. Visual field defects after resection are frequent. AIM. We try to detect the frequency and severity of visual field defect after anterior temporal lobectomy (ATL) and to study the functional consequences. PATIENTS AND METHODS: We studied 30 patients with refractory temporal lobe epilepsy (15 men, 12 51 years, m= 32.9), in which ATL was performed (11 right, 19 left). The neocortical and hippocampal resection was variable. Visual field was studied with computerized campimetry type Humphrey. Our survey was filled to study the campimetric consequence, seizures incidence, quality of life and surgery satisfaction. RESULTS: Some campimetric disturb was found in 27 patients (90 %), superior or minor homonimus quadantapnosia in 18 (60 %), major one 8 and homonimus hemianopsia in one. Incongruent defects appeared in 19. The bigger neocortical and hippocampal resection was, the bigger defect, with exceptions. Only patient with a hemianopsia was conscious the deficit. 20 patients (66.6 %) were seizures free in the last year. 28 had better quality of life and 29 (96.6 %) would have chosen surgery again. CONCLUSION: Visual field defects after ATL, although frequent, have little functional consequences and in quality of life. The quality of life is better when seizures stopped. After ATL patients are very glad with their decision.

Adolescent↗
PubMed1998

Failure of standard magnetic resonance imaging in patients with refractory temporal lobe epilepsy.

OBJECTIVE: To compare the sensitivity of standard magnetic resonance imaging (MRI) scans done outside an epilepsy center with that of special protocol MRI scans done at an epilepsy center in delineating relevant lesions of the temporal lobe. SUBJECTS: Eighty-four consecutive patients who had temporal lobe resections for refractory temporal lobe epilepsy between January 1, 1993, and February 1, 1996. DESIGN: The reports of findings on standard MRI scans done outside an epilepsy center were compared with the findings of special protocol MRI scans done with 1.5-mm T1-weighted coronal and 3-mm T2-weighted coronal images (no gaps) on a 1.5-T system. Both sets of MRI findings were compared with findings on histologic examination of the resected tissue. RESULTS: Of the 84 patients, 51 had standard MRI scans done outside an epilepsy center; of these, there were 34 patients with normal results, 10 with tumors, 2 with vascular malformations, 2 with hippocampal atrophy, 2 with unclassified abnormalities, and 1 with cortical malformation. In 32 of the 34 patients with normal results of an MRI scan done outside an epilepsy center, abnormalities were found on our special protocol MRI scans. These included hippocampal atrophy in 27 patients, tumors in 2, and cortical malformations in 1. Additionally, all 17 of the abnormalities detected on the standard MRI scans done outside the epilepsy center were identified on our special protocol MRI scans. Important pathologic abnormalities of the temporal lobe were identified in 16 (35%) of the 46 patients with standard MRI scans done outside an epilepsy center and in 44 (96%) with our special protocol MRI scans. In the 29 patients for whom adequate surgical specimens were available and results of standard MRI scans were normal, our special protocol MRI scans showed the abnormality in 27 (93%). CONCLUSIONS: Conventional neuroimaging studies are inadequate for diagnosing hippocampal sclerosis although they fairly readily detect low-grade tumors and vascular malformations. Magnetic resonance imaging scans for the evaluation of patients with refractory temporal lobe epilepsy should be done with a special temporal lobe protocol and read by physicians experienced with the findings in hippocampal sclerosis. Health care dollars are wasted on neuroimaging done for refractory temporal lobe epilepsy outside epilepsy centers.

Atrophy↗
PubMed2002

Prognostic factors and outcome after different types of resection for temporal lobe epilepsy.

OBJECT: It is unknown whether different resection strategies for temporal lobe epilepsy (TLE) produce alterations in seizure control or neuropsychological performance. METHODS: A series of 321 patients who underwent surgery for TLE between 1989 and 1997 was submitted to a uni- and multifactorial analysis of clinical, electrophysiological, neuroimaging, neuropsychological, and surgical factors to determine independent predictors of outcome. Until 1993, most patients with TLE underwent standard anterior temporal lobectomy (ATL); beginning in 1993, surgical procedures were increasingly restricted to lesions detected on magnetic resonance (MR) imaging and the presumed epileptogenic foci: for example, amygdalohippocampectomy (AH) or lesionectomy/corticectomy began to be used more often. The mean follow-up duration in this study was 38 months. Two hundred twenty-seven patients were classified as seizure free (70.7%), and 36 patients had rare and nondisabling seizures (11.2%); these groups were summarized as having good seizure control (81.9%). Twenty-four patients attained more than 75% improvement (7.5%), and no worthwhile improvement was seen in 34 cases (10.6%); these groups were summarized as having unsatisfactory seizure control (18.1%). On unifactorial analysis the following preoperative factors were associated with good seizure control (p < 0.05): single and concordant lateralizing focus on electroencephalography studies, low seizure frequency, absence of status epilepticus, concordant lateralizing memory deficit, clear abnormality on MR images, suspected ganglioglioma or dysembryoplastic neuroepithelial tumor (DNT), and absence of dysplasia on MR images. Stepwise logistic regression revealed a model containing five factors that were predictive for good seizure control (p < 0.1): 1) clear abnormality on MR images; 2) absence of status epilepticus; 3) MR imaging-confirmed ganglioglioma or DNT; 4) concordant lateralizing memory deficit; and 5) absence of dysplasia on MR images. Seizure outcome was mainly correlated with diagnosis and clinical factors. No significant differences were found regarding different resection types performed for comparable tumors. Neuropsychological testing revealed better postoperative results after limited resections compared with standard ATL, especially with regard to attention level, verbal memory, and calculated total neuropsychological performance. CONCLUSIONS: Different strategies for surgical approaches in TLE result in equally good outcomes. Seizure outcome is mainly dependent on the diagnosis and clinical factors, whereas the neuropsychological results are more beneficial after resections limited to an epileptogenic lesion and focus.

Adolescent↗