Bilateral hippocampal atrophy: consequences to verbal memory following temporal lobectomy

Hippocampus and Insula Are Targets in Epileptic Patients With Glutamic Acid Decarboxylase Antibodies

Background: Antibodies to glutamic acid decarboxylase (GAD ab) have been found in patients with limbic encephalitis (LE) and chronic pharmacoresistant focal epilepsy (FE). The objectives of the study were to: (1) analyze the clinical and neuroimaging course of patients with FE+GAD ab, (2) compare these characteristics with a control group, and (3) describe the most affected cerebral areas with structural and functional imaging. Methods: Patients with FE + high titers of GAD ab and a follow-up of at least 5 years were selected. Titers of serum GAD ab exceeding 2,000 UI/ml were considered high. Evolutive clinical and radiological characteristics were studied in comparison to two different control groups: patients with bilateral or with unilateral mesial temporal sclerosis (BMTS or UMTS) of a non-autoimmune origin. Results: A group of 13 patients and 17 controls were included (8 BMTS, 9 UMTS). The most frequent focal aware seizures (FAS) reported by patients were psychic (5/13: 33%). Somatosensorial, motor, and visual FAS (4/13:32%) (p: 0.045), musicogenic reflex seizures (MRS), and a previous history of cardiac syncope were reported only patients (2/13:16% each) (p: NS). Comparing EEG characteristics between patients and controls, a more widespread distribution of interictal epileptiform discharges (IED) was observed in FE+ GAD ab patients than in controls (p:0.01). Rhythmic delta activity was observed in all controls in anterior temporal lobes while in patients this was less frequent (p: 0.001). No IED, even in 24 h cVEEG, was seen in 6 patients (46%).First MRI was normal in 4/5 (75%) patients. During the follow-up mesial temporal lobe (MTsL) sclerosis was observed in 5/8 (62%) of patients. All patients had abnormal FDG-PET study. MTL hypometabolism was observed in 10/11 (91%) patients, being bilateral in 7/11 (63%). In controls, this was observed in 16/17 (94%), and it was bilateral in 8/17 (47%) (p: NS). Insular hypometabolism was observed in 5/11 (45%) patients (P:0.002). Conclusions: Clinical, EEG, and FDG-PET findings in FE+GAD ab suggest a widespread disease not restricted to the temporal lobe. Progressive MTL sclerosis may be observed during follow-up. In comparison to what is found in patients with non-autoimmune MTL epilepsy, insular hypometabolism is observed only in patients with GAD ab, so it may be an important diagnostic clue.

How Different Are the Patients With Bilateral Hippocampal Sclerosis From the Unilateral Ones Clinically?

PURPOSE

There is a lack of knowledge on consecutive patients with epilepsy associated with bilateral hippocampal sclerosis (BHS). We aimed to investigate the differentiating features of BHS in comparison with unilateral HS (UHS).

METHOD

We investigated our database for patients with epilepsy fulfilling the major magnetic resonance imaging criteria for BHS; namely, presence of bilateral atrophy and high signal changes on T2 and FLAIR series in the hippocampi. UHS patients seen in past 2 years were included as the control group. Clinical, EEG, and other laboratory findings, data on treatment response and epilepsy surgery were investigated from their files.

RESULTS

A total of 124 patients (31 with BHS and 93 with UHS; 49 right-sided and 44 left-sided) were included. We found that 16.1% of the BHS and 18.3% of the UHS groups were not drug-refractory. A binary logistic regression analysis performed with significant clinical features disclosed that history of febrile status epilepticus, mental retardation, and status epilepticus were statistically more common in BHS group. Moreover, diagnosis of psychosis established by an experienced psychiatrist and slowing of the EEG background activity were both found significantly more frequent in BHS. 66.67% of the operated BHS patients showed benefit from epilepsy surgery.

CONCLUSIONS

BHS is a heterogeneous group, showing significant differences such as increased frequencies of mental retardation, status epilepticus, febrile status epilepticus and psychosis, in comparison to UHS. In all, 16.1% of the BHS cases showed a benign course similar to the UHS group and some patients with drug-resistant epilepsy may show benefit from epilepsy surgery.

Neuropsychological outcome after epilepsy surgery in patients with bilateral Ammon's horn sclerosis

Object

The purpose of this study was to retrospectively assess the objective and subjective neuropsychological outcome after epilepsy surgery in patients with bilateral Ammon's horn sclerosis (AHS).

Methods

Memory and executive functions were evaluated at baseline and at follow-up in 11 surgically treated patients and compared with 8 pharmacologically treated patients with temporal lobe epilepsy and bilateral AHS. The median follow-up duration was 16 months in the surgically treated patients and 80.5 months in the pharmacologically treated group. Subjective outcome was evaluated by questionnaires and included mood, quality of life, subjective memory, and activities of daily living.

Results

At the follow-up assessment, 82% of the surgically treated patients as opposed to 0% of the nonsurgery patients were seizure free. In the surgical group, nonverbal memory performance did not change significantly in any patient after surgery, but there was a floor effect in 55% of the surgical patients. Regarding verbal memory, 9% of the surgical patients improved while 73% declined, despite severe impairments already evident at baseline. In the nonsurgery control group, 13% of the patients declined in nonverbal memory (floor effect in 63%) and 25% declined in verbal memory (floor effect in 25%) at follow-up. None of the controls improved at follow-up. Executive functions remained unchanged on an impaired level in both groups. At follow-up, the patient groups did not differ significantly with respect to mood, quality of life, subjective memory, or activities of daily living. However, in most aspects, surgically treated patients reported a slightly better subjective outcome than pharmacologically treated patients and a significantly improved quality of life.

Conclusions

These results suggest that beyond benefits concerning seizure control, surgically treated patients with bilateral AHS, despite already poor baseline performance, are still at risk for severe postoperative decline in memory. In the light of predominantly minor benefits on a subjective level, the findings put the overall outcome of epilepsy surgery in bilateral AHS patients into perspective.

Memory and health-related quality of life in severe pediatric epilepsy

OBJECTIVES

The purpose of this paper was to investigate the contributions of sociodemographic, neurologic, and neuropsychological variables to health-related quality of life (HRQoL) in children with epilepsy and high seizure burden. Focus was placed on the relationship between memory and HRQoL, which has not been previously investigated.

METHODS

Ninety children with epilepsy receiving clinical care at a tertiary-level children's hospital were retrospectively identified. Primary assessment measures were verbal memory (California Verbal Learning Test-Children's Version) and HRQoL. Other neuropsychological variables included intellectual function, executive function, emotional and behavioral function, and adaptive function. Sociodemographic and neurologic variables were extracted from chart review.

RESULTS

No significant correlations were found between HRQoL and sociodemographic or neurologic variables. Moderate correlations were found between neuropsychological variables and HRQoL. Emotional function (Child Behavior Checklist) and verbal memory (California Verbal Learning Test-Children's Version) emerged as significant predictor variables of HRQoL. Low verbal memory was associated with a twofold risk of low HRQoL, emotional and behavioral difficulty with a 10-fold risk, and the combination of emotional and behavioral difficulty and low verbal memory with a 17-fold risk.

CONCLUSIONS

Verbal memory and emotional and behavioral difficulty are associated with increased risk of low HRQoL, even when other important variables are considered in children with high seizure burden. The results reinforce the importance of neuropsychological assessment in clinical care in pediatric epilepsy and suggest important areas of focus for psychological intervention.

Hyperactivation of parahippocampal region and fusiform gyrus associated with successful encoding in medial temporal lobe epilepsy

PURPOSE

Performance in recognition memory differs among patients with medial temporal lobe epilepsy (MTLE). We aimed to determine if distinct recognition performances (normal vs. impaired) could be related to distinct patterns of brain activation during encoding.

METHODS

Event-related functional magnetic resonance imaging (fMRI) activation profiles were obtained during successful encoding of non-material-specific items, in 14 MTLE patients tested for recognition of stimuli afterward. Findings were compared to those of 25 healthy subjects, and voxel-based correlations were assessed between brain activation and performance.

KEY FINDINGS

Patients with left and right MTLE showed similar activations and similar performances. As a whole, the group of patients demonstrated altered recognition scores, but three of the seven patients with left MTLE and three of the seven patients with right MTLE exhibited normal performance relative to controls. In comparison to healthy subjects and patients with impaired recognition, patients with normal recognition showed weaker activations in left opercular cortex, but stronger activations in bilateral parahippocampal region/fusiform gyrus (PH/FG). By contrast, patients with impaired performance showed weaker activations in bilateral PH/FG, but stronger activations in a frontal/cingulate and parietal network. Recognition performance was correlated positively to bilateral PH/FG activations, and negatively correlated to bilateral frontal/cingulate activations, in the whole group of patients, as well as in subgroups of patients with either left or right MTLE.

SIGNIFICANCE

These results suggest occurrence of effective functional compensation within bilateral PH/FG in MTLE, allowing patients to maintain recognition capability. In contrast, impairment of this perceptive-memory system may lead to alternative activation of an inefficient nonspecific attentional network in patients with altered performance.

Neuropsychological outcomes after epilepsy surgery: Systematic review and pooled estimates

PURPOSE

Epilepsy surgery is a safe surgical procedure, but it may be associated with cognitive changes. Estimates of the risk of decline in specific neuropsychological domains after epilepsy surgery would assist surgical decision making in clinical practice. The goal of this study was to conduct a systematic review to derive pooled estimates of the rate of losses and gains in neuropsychological functions after epilepsy surgery, using empirically based methods for quantifying cognitive change.

METHODS

An extensive literature search using PubMed, EmBase, and the Cochrane database was conducted, yielding 5,061 articles on epilepsy surgery, with 193 on neuropsychological outcomes (IQ, memory, language, executive functioning, attention, and subjective cognitive changes).

KEY FINDINGS

Of these, 23 met final eligibility criteria, with 22 studies involving temporal surgery only. Key aspects of inclusion criteria were N ≥ 20 and use of reliable change index or standardized regression-based change estimates. In addition to the proportion of patients experiencing losses and gains in each individual test, a single pooled estimate of gains and losses for each cognitive domain was derived using a random effects model. Weighted estimates indicated a risk to verbal memory with left-sided temporal surgery of 44%, twice as high as the rate for right-sided surgery (20%). Naming was reduced in 34% of left-sided temporal patients, with almost no patients with gains (4%). Pooled data on IQ, executive functioning, and attention indicated few patients show declines post surgery, but a substantial rate of improvement in verbal fluency with left-sided temporal surgery (27%) was found. Self-reported cognitive declines after epilepsy surgery were uncommon, and gains were reported in some domains where losses were found on objective tests (i.e., verbal memory and language). Variations in surgical techniques did not appear to have a large effect on cognitive outcomes, except for naming outcomes, which appeared better with more conservative resections. Sensitivity to postoperative changes differed across visual memory tests, but not verbal memory tests. Few conclusions could be made regarding cognitive risks and benefits of extratemporal epilepsy surgery, or of epilepsy surgery in children.

SIGNIFICANCE

In sum, epilepsy surgery is associated with specific cognitive changes, but may also improve cognition in some patients. The results provide base rate estimates of expected cognitive gains and losses associated with epilepsy surgery that may prove useful in clinical settings.

Presurgical epilepsy localization with interictal cerebral dysfunction

Localization of interictal cerebral dysfunction with 2-[(18)F]fluoro-2-D-deoxyglucose (FDG) positron emission tomography (PET) and neuropsychological examination usefully supplements electroencephalography (EEG) and brain magnetic resonance imaging (MRI) in planning epilepsy surgery. In MRI-negative mesial temporal lobe epilepsy, correlation of temporal lobe hypometabolism with extracranial ictal EEG can support resection without prior intracranial EEG monitoring. In refractory localization-related epilepsies, hypometabolic sites may supplement other data in hypothesizing likely ictal onset zones in order to intracranial electrodes for ictal recording. Prognostication of postoperative seizure freedom with FDG PET appears to have greater positive than negative predictive value. Neuropsychological evaluation is critical to evaluating the potential benefit of epilepsy surgery. Cortical deficits measured with neuropsychometry are limited in lateralizing and localizing value for determination of ictal onset sites, however. Left temporal resection risks iatrogenic verbal memory deficits and dysnomia, and neuropsychological findings are useful in predicting those at greatest risk. Prognostication of cognitive risks with resection at other sites is less satisfactory.

New evidence supports cognitive decline in temporal lobe epilepsy

Cognitive Prognosis in Chronic Temporal Lobe Epilepsy. Hermann BP, Seidenberg M, Dow C, Jones J, Rutecki P, Bhattacharya A, Bell B. Ann Neurol 2006;60:80–87.

Objective

First, to determine whether patients with chronic temporal lobe epilepsy have a different cognitive trajectory compared to control subjects over a prospective 4-year interval; second, to determine the proportion of patients who exhibit abnormal cognitive change and their profile of demographic, clinical epilepsy, and baseline quantitative magnetic resonance imaging characteristics; and third, to determine the most vulnerable cognitive domains.

Methods

Participants with chronic temporal lobe epilepsy ( N = 46) attending a tertiary referral clinic and healthy control subjects ( N = 65) underwent neuropsychological assessment and reevaluation 4 years later. Analysis of test–retest patterns identified individual patients with adverse cognition outcomes.

Results

The prospective cognitive trajectory of patients with chronic temporal lobe epilepsy differs from age- and sex-matched healthy control subjects. Lack of practice effects is common, but frank adverse cognitive outcomes are observed in a subset of patients (20%–25%), particularly in vulnerable cognitive domains that include memory. Cognitive declines are associated with a profile of abnormalities in baseline quantitative magnetic resonance volumetrics, lower baseline intellectual capacity, as well as longer duration of epilepsy and older chronological age.

Interpretation

Cognitive prognosis is poor for a subset of patients characterized by chronicity of epilepsy, older age, lower intellectual ability, and more baseline abnormalities in quantitative magnetic resonance volumetrics.

Hippocampal volumetry and functional MRI of memory in temporal lobe epilepsy

This study examined the utility of structural and functional MRI at 1.5 and 3T in the presurgical evaluation and prediction of postsurgical cognitive outcome in temporal lobe epilepsy (TLE). Forty-nine patients undergoing presurgical evaluation for temporal lobe (TL) resection and 25 control subjects were studied. Patients completed standard presurgical evaluations, including the intracarotid amobarbital test (IAT) and neuropsychological testing. During functional imaging, subjects performed a complex visual scene-encoding task. High-resolution structural MRI scans were used to quantify hippocampal volumes. Both structural and functional imaging successfully lateralized the seizure focus and correlated with IAT memory lateralization, with improvement for functional imaging at 3T as compared with 1.5 T. Ipsilateral structural and functional MRI data were related to cognitive outcome, and greater functional asymmetry was related to earlier age at onset. These findings support continued investigation of the utility of MRI and fMRI in the presurgical evaluation of TLE.

Predicting memory performance in normal ageing using different measures of hippocampal size

A number of different methods have been employed to correct hippocampal volumes for individual variation in head size. Researchers have previously used qualitative visual inspection to gauge hippocampal atrophy. The purpose of this study was to determine the best measure(s) of hippocampal size for predicting memory functioning in 102 community-dwelling individuals over 80 years of age. Hippocampal size was estimated using magnetic resonance imaging (MRI) volumetry and qualitative visual assessment. Right and left hippocampal volumes were adjusted by three different estimates of head size: total intracranial volume (TICV), whole-brain volume including ventricles (WB+V) and a more refined measure of whole-brain volume with ventricles extracted (WB). We compared the relative efficacy of these three volumetric adjustment methods and visual ratings of hippocampal size in predicting memory performance using linear regression. All four measures of hippocampal size were significant predictors of memory performance. TICV-adjusted volumes performed most poorly in accounting for variance in memory scores. Hippocampal volumes adjusted by either measure of whole-brain volume performed equally well, although qualitative visual ratings of the hippocampus were at least as effective as the volumetric measures in predicting memory performance in community-dwelling individuals in the ninth or tenth decade of life.

Verbal memory outcome in patients with normal preoperative verbal memory and left mesial temporal sclerosis

PURPOSE

Previous studies have shown that structural integrity (i.e., presence/absence of mesial temporal sclerosis (MTS)) of the left mesial temporal lobe is associated with verbal memory outcome following left anterior temporal lobectomy (ATL). However, the functional integrity of the left temporal lobe, as exemplified by preoperative verbal memory performance, has also been associated with verbal memory outcome following surgery. We investigated the risk of verbal memory loss in patients with known structural abnormality (i.e., left mesial temporal sclerosis by MRI) and normal preoperative verbal memory performance who undergo left ATL.

METHODS

Seventeen patients with left temporal lobe epilepsy, MRI-based exclusive left MTS, and normal preoperative verbal memory were identified. Normal verbal memory was defined as performance on both Acquisition (learning across trials 1-5) and Retrieval (long delayed free recall) portions of the California Verbal Learning Test (CVLT) above a T score of 40 (>16%ile). Postoperative verbal memory outcome was established by incorporating standardized regression-based (SRB) change scores.

RESULTS

Postoperative declines across both CVLT Retrieval T scores and Acquisition T scores (average 20% and average 15% declines from baseline scores, respectively) were measured for the group. The average CVLT Retrieval SRB change score was -2.5, and the average CVLT Acquisition SRB change score was -1.0. A larger proportion of patients demonstrated postoperative declines on Retrieval scores than Acquisition scores (64.7% vs 17.6%, respectively).

CONCLUSIONS

Even in the presence of left MTS, patients exhibiting normal presurgical verbal memory are at risk for verbal memory declines following ATL. These results suggest that the functional integrity of the left mesial temporal lobe may play an important role in the verbal memory outcome in this patient group.

MR-based in vivo hippocampal volumetrics: 2. Findings in neuropsychiatric disorders

Magnetic resonance imaging (MRI) has opened a new window to the brain. Measuring hippocampal volume with MRI has provided important information about several neuropsychiatric disorders. We reviewed the literature and selected all English-language, human subject, data-driven papers on hippocampal volumetry, yielding a database of 423 records. Smaller hippocampal volumes have been reported in epilepsy, Alzheimer's disease, dementia, mild cognitive impairment, the aged, traumatic brain injury, cardiac arrest, Parkinson's disease, Huntington's disease, Cushing's disease, herpes simplex encephalitis, Turner's syndrome, Down's syndrome, survivors of low birth weight, schizophrenia, major depression, posttraumatic stress disorder, chronic alcoholism, borderline personality disorder, obsessive-compulsive disorder, and antisocial personality disorder. Significantly larger hippocampal volumes have been correlated with autism and children with fragile X syndrome. Preservation of hippocampal volume has been reported in congenital hyperplasia, children with fetal alcohol syndrome, anorexia nervosa, attention-deficit and hyperactivity disorder, bipolar disorder, and panic disorder. Possible mechanisms of hippocampal volume loss in neuropsychiatric disorders are discussed.

Patients' Perceptions of Memory Functioning Before and After Surgical Intervention to Treat Medically Refractory Epilepsy

PURPOSE

One risk associated with epilepsy surgery is memory loss, but perhaps more important is how patients perceive changes in their memories. This longitudinal study evaluated changes in memory self-reports and investigated how self-reports relate to changes on objective memory measures in temporal or extratemporal epilepsy patients who underwent surgery.

METHODS

Objective memory (Wechsler Memory Scale-Revised) and subjective memory self-reports (Memory Assessment Clinics Self-Rating Scale) were individually assessed for 136 patients approximately 6 months before and 6 months after surgery. A measure of depressive affect (Beck Depression Inventory-2nd Edition) was used to control variance attributable to emotional distress.

RESULTS

Despite a lack of significant correlational relationships between objective and subjective memory for the entire sample, significant correlations between objective memory scores and self-reports did emerge for a subset of patients who evidenced memory decline. Differences also were found in the subjective memory ratings of temporal lobe versus extratemporal patients. Temporal lobe patients rated their memories more negatively than did extratemporal patients and were more likely to report significant improvements in their memory after surgery.

CONCLUSIONS

In general, patients were not accurate when rating their memories compared to other adults. However, patients with significant declines in their memories were sensitive to actual changes in their memories over time relative to their own personal baselines.

Structural versus functional prediction of memory change following anterior temporal lobectomy

Decline in recent memory function is a significant risk for patients undergoing anterior temporal lobectomy. We report a patient with a febrile seizure history, complex partial seizures arising from the left anterior temporal lobe, and MRI evidence suggesting left hippocampal sclerosis, all of which indicate a low likelihood of significant postoperative memory decline. However, high normal verbal memory on neuropsychological testing and bilaterally normal Wada memory scores indicated increased risk for postoperative memory decline. Following left anterior temporal lobectomy, the patient displayed a significant decline in verbal recent memory that affected school performance. Despite the worsening in memory, the patient reported a significant improvement in his self-reported quality-of-life perception, demonstrating that factors other than change in cognitive performance are related to whether a patient considers epilepsy surgery worthwhile. In the present case, behavioral measures were superior to structural measures in predicting cognitive change following surgery.

Confirmatory Factor Analysis of the California Verbal Learning Test in Patients With Epilepsy: Relationship to Clinical and Neuropathological Markers of Temporal Lobe Epilepsy

Latent constructs involved in California Verbal Learning Test (D. C. Delis, J. H. Kramer, E. Kaplan, & B. A. Ober, 1987) performance were examined using confirmatory factor analysis in 388 epilepsy surgery candidates. Eight factor models were compared. A single-factor model was examined, along with 7 models accommodating constructs of auditory attention, inaccurate recall, and delayed recall in different combinations. The retained model consisted of 3 correlated factors: Auditory Attention. Verbal Learning, and Inaccurate Recall. Validity of this factor structure was examined in a subsample of patients with left and right temporal lobe epilepsy. All 3 factors were related to seizure focus and magnetic resonance imaging hippocampal volume. Only Verbal Learning was related to hippocampal neuropathology, supporting the distinction between learning and attention in the factor structure.

Presurgical assessment of memory-related brain structures: the Wada test and functional neuroimaging

Medial temporal lobe structures are known to play a major role in memory processing. Recent work has revealed that extratemporal structures (e.g. the frontal lobe and thalamus) may also be important in memory function. In candidates for epilepsy surgery, particularly in those with temporal lobe seizures, presurgical evaluation of memory function is essential, since seizures may originate in the neural substrate that is critical for memory. In this article, we review the tools used for presurgical evaluation and their contribution to the understanding of memory function, focusing on the Wada test, [18F]fluorodeoxy-glucose positron emission tomography ([18F]FDG-PET) and functional magnetic resonance imaging (fMRI). We also explore perspectives on future studies that may elucidate the role of the temporal and extratemporal structures in memory function and the mechanisms of cerebral plasticity.

Advanced brain imaging procedures and human memory disorder

The impact of advanced brain imaging procedures in the field of human memory disorder is reviewed, with particular emphasis on current and potential applications that may impact upon the diagnosis and management of memory-disordered patients. While both advanced structural, resting physiological and functional physiological brain imaging procedures have been applied to conditions where memory disorder is a major feature, the specific implications of research findings for diagnosis and treatment in routine clinical practice remain tentative and promising, but not yet substantive enough to inform clinical decisions to a significant degree. In terms of diagnostic applications, several promising areas include dementia, epilepsy, and transient amnesic states. In the case of applications in treatment settings, advanced brain imaging procedures may help to monitor neural correlates of spontaneous recovery or progression of memory function, and may also help in the planning and monitoring of therapeutic intervention.

Seizure-related outcome after corticoamygdalohippocampectomy in patients with refractory temporal lobe epilepsy and mesial temporal sclerosis evaluated by magnetic resonance imaging alone

OBJECT

The authors conducted a study to assess the efficacy of surgery in patients who underwent magnetic resonance (MR) imaging alone for localization of foci in temporal lobe epilepsy (TLE).

METHODS

One hundred patients (43 men, 57 women) with a clinical diagnosis of TLE were prospectively studied (mean age 28 +/- 9 years [+/- standard deviation {SD}]). All patients underwent high-resolution MR imaging, and in all unilateral mesial temporal sclerosis (MTS) was diagnosed by visual inspection. All patients underwent interictal preoperative electroencephalography (EEG) and in 87 patients pre- and 1-year postoperative neuropsychological testing was performed. Both EEG and neuropsychological examinations were conducted in a blinded fashion, and these data were not taken into account during the surgery-related decision-making process. All patients underwent a corticoamygdalohippocampectomy at the side of the MTS. Surgery-related outcome was rated as Class I (seizure free or simple partial seizures only) or Class II (> or = 90% improvement). The follow-up period ranged from 18 to 48 months (mean 24 +/- 5 months [+/-SD]). No patient underwent prolonged video-EEG monitoring, Wada testing, positron emission tomography, or single-photon emission computerized tomography. In eighty-nine patients Class I results were achieved, and 11 Class II results were achieved postoperatively. There was no mortality in this series. Except for in two patients who underwent surgery in the dominant temporal lobe, there was no postoperatively cognitive decline. In these two patients verbal memory decline occurred, which was associated with posterior temporal cortical damage, demonstrated postoperatively on MR imaging. Twenty-five percent of the patients experienced improved memory function related to the nonoperated side, and 54% experienced a 10% gain in general intelligence quotient status.

CONCLUSIONS

In patients with clinically suspected TLE, MR imaging alone is able to localize temporal lobe foci correctly. Ruling out pseudoseizures remains the only indication for prolonged video-EEG recordings in this group of patients.

Epilepsy surgery within the temporal lobe and its short-term and long-term effects on memory

In patients with pharmacologically intractable, complex-partial seizures, surgical excision of the involved temporal lobe may have significant therapeutic benefit. Resection of mesial structures of the temporal lobes, however, entails a significant risk of decreased memory function. Recent advances in the assessment of memory changes following temporal lobectomy surgery emphasize the complexity of subjective ratings of memory functioning in this population. Neuroimaging tools useful in the diagnostic evaluation of epilepsy surgical candidates have now been shown to be useful in predicting memory change in the post-surgical period. Functional magnetic resonance imaging appears to provide significant information regarding hemispheric representation of language in the temporal lobe epilepsy patient, and the use of this technique to predict memory status following surgery appears promising. Clinical studies involving patients who had temporal lobectomy surgeries have also revealed changes in emotional learning related to the degree of amygdala involvement. Moreover, there is increasing evidence to suggest that differential changes in emotional learning occur among patients with right versus left temporal lobe resections.

Inferring Function from Structure: Relationship of Magnetic Resonance Imaging-Detected Hippocampal Abnormality and Memory Function in Epilepsy

Although temporal lobectomy is an effective alternative treatment for many patients with medication-resistant epilepsy, the risk of cognitive morbidity is not inconsequential. The ability to predict cognitive outcome is increasingly dependent on convergent information from multiple sources, including direct (e.g., Wada test) and indirect (e.g., psychometric testing) functional assessments along with magnetic resonance imaging studies that detect structural abnormalities. This brief review summarizes the relationship between imaging and function at baseline and predicting cognitive outcome following temporal lobectomy.

Inferring Function from Structure: Relationship of Magnetic Resonance Imaging-Detected Hippocampal Abnormality and Memory Function in Epilepsy

Although temporal lobectomy is an effective alternative treatment for many patients with medication-resistant epilepsy, the risk of cognitive morbidity is not inconsequential. The ability to predict cognitive outcome is increasingly dependent on convergent information from multiple sources, including direct (e.g., Wada test) and indirect (e.g., psychometric testing) functional assessments along with magnetic resonance imaging studies that detect structural abnormalities. This brief review summarizes the relationship between imaging and function at baseline and predicting cognitive outcome following temporal lobectomy.