Chronic epilepsy and cognition: A longitudinal study in temporal lobe epilepsy

Adult-onset hippocampal-specific neuropeptide Y overexpression confers mild anxiolytic effect in mice

The anticonvulsive properties of neuropeptide Y (NPY) are opening up opportunity for the development of NPY gene transfer as a therapy for epilepsy. In order to pursue the potential clinical translation of this approach, the effects of somatic NPY gene transfer on other hippocampal functions need to be assessed. The present study characterized the behavioral effects of recombinant adeno-associated viral vector (rAAV)-mediated hippocampal NPY overexpression in adult male mice and also Y1 receptor knockout mice. In wild-type mice, there were no obvious adverse effects on the general health, motor function and cognition following rAAV-NPY treatment. Moreover, hippocampal NPY overexpression induced a moderate anxiolytic effect in the open field test and elevated plus maze. Intriguingly, the treatment also increased depressive-like behavior in the tail suspension test. Elevated hippocampal NPY levels in the absence of Y1 signalling had no effects on anxiety or cognition and actually improved the depressive-like phenotype observed in the wild-type mice treated with rAAV-NPY.

A longitudinal study of cognition in nursing home residents with multiple sclerosis

PURPOSE

Examine cognitive change in nursing home residents with multiple sclerosis (MS) over the first 4 years of their nursing home stay.

METHOD

Nine hundred and twenty-four individuals with MS in nursing homes were longitudinally studied. Of these, 121 had MS but no psychiatric or neurological co-morbidities, 169 had MS plus another neurological disorder (MS-Neuro), 269 had MS plus a psychiatric disorder (MS-Psych) and 365 had MS plus both psychiatric and neurological disorders (MS-Comb). Data were obtained from a large government data-set, the minimum data set (MDS), and cognition was rated on the MDS-Cognition Scale.

RESULTS

Data were analysed using a mixed-model ANOVA with a repeated factor of time and a fixed factor Group. We found a significant time effect with declines in cognition between each assessment, except 2000 and 2001, and a significant group effect so that the MS-Neuro and the MS-Comb groups had worse cognition than the MS-Psyc and the MS groups. A significant time x group interaction indicated differences in how the groups declined over time.

CONCLUSIONS

Over the first 4 years of a nursing home stay, cognition deteriorates in individuals with MS. Though there are not different rates of decline, residents with MS-Neuro and MS-Comb perform worse than residents with MS or MS-Psyc.

Treatment strategies for focal epilepsy

BACKGROUND

Treatment strategies for focal epilepsy need to take account of the phase and severity of the seizure disorder, comorbidity, gender and age.

METHODS

Expert review and evaluation of major studies on the treatment of focal epilepsy.

RESULTS

Complete seizure control is most often achieved with antiepileptic drug (AED) monotherapy. In the choice of AED, possible unfavourable endocrine, cognitive or psychiatric adverse effects and their interaction with the non-seizure manifestations of focal epilepsy have to be considered. In women teratogenic risks associated with AED may be relevant. If complete seizure control cannot be achieved with the first three steps of AED treatment, epilepsy surgery becomes the most likely treatment modality to provide complete seizure control. It is proposed that AED combination treatment should be limited to two or three agents to minimize the risk of side effects, especially negative effects on cognition.

CONCLUSIONS

Recent developments in the treatment of focal epilepsy have made it easier to tailor AED therapy to patients' demographic and clinical profile.

Unique and shared validity of the "Wechsler logical memory test", the "California verbal learning test", and the "verbal learning and memory test" in patients with epilepsy

RATIONALE

This study was set-up to evaluate the construct validity of three verbal memory tests in epilepsy patients.

METHODS

Sixty-one consecutively evaluated patients with temporal lobe epilepsy (TLE) or extra-temporal epilepsy (E-TLE) underwent testing with the verbal learning and memory test (VLMT, the German equivalent of the Rey auditory verbal learning test, RAVLT); the California verbal learning test (CVLT); the logical memory and digit span subtests of the Wechsler memory scale, revised (WMS-R); and testing of intelligence, attention, speech and executive functions.

RESULTS

Factor analysis of the memory tests resulted in test-specific rather than test over-spanning factors. Parameters of the CVLT and WMS-R, and to a much lesser degree of the VLMT, were highly correlated with attention, language function and vocabulary. Delayed recall measures of logical memory and the VLMT differentiated TLE from E-TLE. Learning and memory scores off all three tests differentiated mesial temporal sclerosis from other pathologies. A lateralization of the epilepsy was possible only for a subsample of 15 patients with mesial TLE.

CONCLUSION

Although the three tests provide overlapping indicators for a temporal lobe epilepsy or a mesial pathology, they can hardly be taken in exchange. The tests have different demands on semantic processing and memory organization, and they appear differentially sensitive to performance in non-memory domains. The tests capability to lateralize appears to be poor. The findings encourage the further discussion of the dependency of memory outcomes on test selection.

Epilepsy treatment as a predeterminant of psychosocial ill health

Epilepsy is a chronic disorder with complex effects on social, vocational, physical, and psychological well-being. Patient-oriented research has demonstrated that recurrent seizures have a strong adverse effect on health-related quality of life, but also that seizure rate in persons with pharmacoresistant epilepsy has only a modest correlation with quality of life. Although treatment side effects have received limited attention in epilepsy research, available evidence indicates that adverse medication effects may explain more variance in quality of life than any other clinical variable in persons with pharmacoresistant epilepsy. Furthermore, systematic screening for adverse effects has been shown to be associated with significant reduction in subjective toxicity and improvement in quality of life. There has been only limited research on the relative contribution of specific adverse effects to impaired health-related quality of life. The relative importance of reduction of medication burden after resective epilepsy surgery or vagal nerve stimulation has similarly received sparse attention. Existing deficiencies in the available published research present challenges and opportunities to perform further investigations to define and improve best clinical practices in epilepsy care.

Deep brain stimulation for medically refractory epilepsy

Epilepsy is a chronic neurological disorder that affects 0.5-1% of the population. Up to one-third of patients will have incompletely controlled seizures or debilitating side effects of anticonvulsant medications. Although some of these patients may be candidates for resection, many are not. The desire to find alternative treatments for epilepsy has led to a resurgence of interest in the use of deep brain stimulation (DBS), which has been used quite successfully in movement disorders. Small pilot studies and open-label trials have yielded results that may support the use of DBS in selected patients with refractory seizures. Because of the diversity of regions involved with seizure initiation and propagation, a variety of targets for stimulation have been examined. Moreover, stimulation parameters such as amplitude, frequency, pulse duration, and continuous versus intermittent on vary from one study to the next. More studies are necessary to determine if there is an appropriate population of seizure patients for DBS, the optimal target, and the most efficacious stimulation parameters.

[Influence of cognitive reserve on neuropsychological performance in epileptic patients]

BACKGROUND AND OBJECTIVE

Our goal was to determine the influence of the cognitive reserve (CR) on the neuropsychological performance of patients with temporal lobe epilepsy (TLE).

PATIENTS AND METHOD

Twenty-eight patients with TLE from a program of epilepsy surgery were assessed with a neuropsychological battery that included standard clinical measures of memory, attention, visual-construction skills and language. Raw scores adjusted according normative data were transformed to z scores. CR scores were based on a combination of educational level, occupational attainment and estimated premorbid intelligence.

RESULTS

There were no significance differences in socio-demographic and clinical features between the 2 groups. Epileptic patients with low CR showed significantly lower scores than patients with high CR, with regard to measures of verbal memory (p<0.039), attention (p<0.001), visual-construction skills (p<0.019), and phonetic (p<0.003) and semantic (p<0.005) fluency.

CONCLUSIONS

Epileptic patients with low CR showed greater neuropsychological morbidity than patients with high CR. These findings suggest that higher CR may decrease vulnerability or delay the clinical manifestation related to cognitive deficits following TLE.

Changes in neuropsychological functioning following temporal lobectomy in patients with temporal lobe epilepsy

PURPOSE

This study was conducted to evaluate the changes in neuropsychological functioning in patients with temporal lobe epilepsy (TLE) after temporal lobe resection.

METHODS

Fifty-four TLE patients were evaluated before and after surgery using comprehensive neuropsychological tests to assess general intelligence, executive functioning, language, verbal and visual memory, working memory, visuo-spatial ability, attention and motor function.

RESULTS

The patients with left TLE showed no impairment of neuropsychological functioning after surgery, with the exception of auditory immediate memory. Furthermore, they showed significant improvement in performance IQ, executive function, working memory, visual memory, attention and psychomotor speed. The patients with right TLE did not show any significant impairment in post-operative neuropsychological functioning. They showed improvements in intellectual and executive functions, language, visual memory, visuo-spatial ability, attention and motor function post-operatively. The patients with hippocampal sclerosis showed greater post-operative improvements than the patients without hippocampal sclerosis regardless of the side. Patients with better pre-operative neuropsychological function had a higher chance of successfully discontinuing all seizure medications after surgery.

DISCUSSION

The results of this study suggest that temporal lobectomy does not harm the neuropsychological functioning of patients with intractable TLE and that it improves cognitive functions of the contralateral hemisphere.

Curing epilepsy: progress and future directions

During the past decade, substantial progress has been made in delineating clinical features of the epilepsies and the basic mechanisms responsible for these disorders. Eleven human epilepsy genes have been identified and many more are now known from animal models. Candidate targets for cures are now based upon newly identified cellular and molecular mechanisms that underlie epileptogenesis. However, epilepsy is increasingly recognized as a group of heterogeneous syndromes characterized by other conditions that co-exist with seizures. Cognitive, emotional and behavioral co-morbidities are common and offer fruitful areas for study. These advances in understanding mechanisms are being matched by the rapid development of new diagnostic methods and therapeutic approaches. This article reviews these areas of progress and suggests specific goals that once accomplished promise to lead to cures for epilepsy.

Seizures in the elderly: impact on mental status, mood, and sleep

Comorbidities of epilepsy have not been well explored in the elderly. Herein, we examined mental status, mood, and sleep in elderly patients with epilepsy, compared with age- and gender-matched community controls without epilepsy from the Einstein Aging Study. Testing included a mental status test, the Blessed Information Memory and Concentration (BIMC) test; Prime-MD Patient Health Questionnaire (PHQ) Depression and Anxiety Modules; and Medical Outcomes Study Sleep Scale. Persons with epilepsy (n=31) had higher mean BIMC scores than controls (n=31, BIMC 6.3 vs.1.2, P<0.0001). Mean PHQ Depression scores were higher for cases than controls, indicating more depressive symptoms (4.2 vs 0.8, P=0.006); six cases (18%) and no controls met screening criteria for depression. Mean PHQ Anxiety scores were also higher for cases than controls (3.7 vs 0.0, P=0.001). Cases had poorer sleep scores in the categories of somnolence (P=0.009) and shortness of breath/headache (P=0.021). Thus, comorbidities of epilepsy in this elderly population included decreased mental status, a higher prevalence of depression and anxiety, and poorer sleep health when compared with agemates without epilepsy. Mental status impairment was not related to antiepileptic medication or mood disturbance. Further investigation will explore these associations prospectively.

Verbal memory in mesial temporal lobe epilepsy: beyond material specificity

The idea that verbal and non-verbal forms of memory are segregated in their entirety, and localized to the left and right hippocampi, is arguably the most influential concept in the neuropsychology of temporal lobe epilepsy, forming a cornerstone of pre-surgical decision making, and a frame for interpreting postoperative outcome. This critical review begins by examining some of the unexpressed but inescapable assumptions of the material-specificity model: (i) verbal and non-verbal memory are unitary and internally homogenous constructs; and (ii) left and right memory systems are assumed to be independent, self-contained modules. The next section traces the origins of an alternative view, emanating largely from three challenges to these assumptions: (i) verbal memory is systematically fractionated by left mesial temporal foci; (ii) the resulting components are differentially localized within the left temporal lobe; and (iii) verbal and non-verbal memory functions are not entirely lateralized. It is argued here that the perirhinal cortex is a key node in a more extensive network mediating protosemantic associative memory. Impairment of this fundamental memory system is a proximal neurocognitive marker of mesial temporal epileptogenesis.

Longitudinal and cross-sectional analysis of atrophy in pharmacoresistant temporal lobe epilepsy

BACKGROUND

Whether recurrent epileptic seizures induce brain damage is debated. Disease progression in epilepsy has been evaluated only in a few community-based studies involving patients with seizures well controlled by medication. These studies concluded that epilepsy does not inevitably lead to global cerebral damage.

OBJECTIVE

To track the progression of neocortical atrophy in pharmacoresistant temporal lobe epilepsy (TLE) using longitudinal and cross-sectional designs.

METHODS

Using a fully automated measure of cortical thickness on MRI, we studied a homogeneous sample of patients with pharmacoresistant TLE. In the longitudinal analysis (n = 18), fixed-effect models were used to quantify cortical atrophy over a mean interscan interval of 2.5 years (range = 7 to 90 months). In the cross-sectional analysis (n = 121), we correlated epilepsy duration and thickness. To dissociate normal aging from pathologic progression, we compared aging effects in TLE to healthy controls.

RESULTS

The longitudinal analysis mapped progression in ipsilateral temporopolar and central and contralateral orbitofrontal, insular, and angular regions. In patients with more than 14 years of disease, atrophy progressed more rapidly in frontocentral and parietal regions that in those with shorter duration. The cross-sectional study showed progressive atrophy in the mesial and superolateral frontal, and parietal cortices.

CONCLUSIONS

Our combined cross-sectional and longitudinal analysis in patients with pharmacoresistant temporal lobe epilepsy demonstrated progressive neocortical atrophy over a mean interval of 2.5 years that is distinct from normal aging, likely representing seizure-induced damage. The cumulative character of atrophy underlies the importance of early surgical treatment in this group of patients.

Shrinkage of the hippocampal remnant after surgery for temporal lobe epilepsy: impact on seizure and neuropsychological outcomes

The aim of this study was to investigate the influence of the postoperative hippocampal remnant on postoperative seizure and neuropsychological outcome in temporal lobe epilepsy (TLE). Postoperative volumetric MRI measurements of 53 patients surgically treated for TLE revealed a postoperative volume loss of the hippocampal remnant compared with the respective preoperative segment in all patients. Extent of preoperative hippocampal pathology, remnant shrinkage, resection volume, and postoperative volume of the hippocampal remnant did not correlate with seizure outcome 1 year after surgery. With respect to neuropsychological outcome, performance on tasks assessing verbal memory and language-related functions was impaired in patients with left-sided pathology after surgery. Performance of patients with right-sided pathology (n=26) demonstrated no significant correlation with hippocampal measures or with neuropsychological data. Degree of hippocampal remnant shrinkage seems to be associated with decreased verbal memory performance in patients with left-sided TLE.

Debate: Should antiepileptic drugs be stopped after successful epilepsy surgery?

There is no consensus on whether or when to stop anticonvulsant drug treatment in patients after apparently successful epilepsy surgery. Although there are compelling reasons to consider antiepileptic drug (AED) discontinuation, there are relatively few data, and no class 1 data, to guide patient and physician decision-making on this topic. This debate lays out a conceptual framework for considering the issue of AED discontinuation, and reviews and critiques the available data. The goal is to provide physicians with the best available data, a context in which to consider it, and a full understanding of its limitations. This article also highlights an area that is ripe for further prospective study.

Facial emotion recognition impairment in chronic temporal lobe epilepsy

PURPOSE

To evaluate facial emotion recognition (FER) in a cohort of 176 patients with chronic temporal lobe epilepsy (TLE).

METHODS

FER was tested by matching facial expressions with the verbal labels for the following basic emotions: happiness, sadness, fear, disgust, and anger. Emotion recognition performances were analyzed in medial (n = 140) and lateral (n = 36) TLE groups. Fifty healthy subjects served as controls. The clinical and neuroradiologic variables potentially affecting the ability to recognize facial expressions were taken into account.

RESULTS

The medial TLE (MTLE) group showed impaired FER (86% correct recognition) compared to both the lateral TLE patients (FER = 93.5%) and the controls (FER = 96.4%), with 42% of MTLE patients recording rates of FER that were lower [by at least 2 standard deviations (SDs)] than the control mean. The MTLE group was impaired compared to the healthy controls in the recognition of all basic facial expressions except happiness. The patients with bilateral MTLE were the most severely impaired, followed by the right and then the left MTLE patients. FER was not affected by type of lesion, number of antiepileptic drugs (AEDs), aura semiology, or gender. Conversely, the early onset of seizures/epilepsy was related to FER deficits. These deficits were already established in young adulthood, with no evidence of progression in older MTLE patients.

CONCLUSION

These results on a large cohort of TLE patients demonstrate that emotion recognition deficits are common in MTLE patients and widespread across negative emotions. We confirm that early onset seizures with right or bilateral medial temporal dysfunction lead to severe deficits in recognizing facial expressions of emotions.

Name calling in the temporal lobe

Evidence for Cortical Reorganization of Language in Patients with Hippocampal Sclerosis. Hamberger MJ, Seidel WT, Goodman RR, Williams A, Perrine K, Devinsky O, McKhann GM 2nd. Brain 2007;130(Pt 11):2942–2950. Naming is mediated by perisylvian cortex in the left (language-dominant) hemisphere, and thus, left anterior temporal lobe resection for pharmacologically intractable temporal lobe epilepsy (TLE) carries risk for post-operative naming decline. Interestingly, this risk is lower in patients with hippocampal sclerosis (HS) relative to those without HS (non-HS). Although the hippocampus has traditionally been considered a critical structure for memory, without contribution to naming, this pattern might implicate direct hippocampal naming involvement. On the other hand, critical naming sites have been found in anterior, lateral temporal (i.e. extra-hippocampal) neocortex, the region typically removed with ‘standard’ TLE resection. We, therefore, speculated that the relative preservation of naming in post-operative HS patients might reflect cortical reorganization of language to areas outside this region. Using pre-resection electrical stimulation mapping, we compared the topography of auditory and visual naming sites in 12 patients with HS and 12 patients without structural brain pathology. Consistent with previous work, non-HS patients exhibited post-operative naming decline, whereas HS patients did not. As hypothesized, HS patients had proportionally fewer overall naming sites in anterior temporal cortex, the region typically removed with standard anterior temporal resection, whereas non-HS patients exhibited a more even distribution of naming sites in anterior and posterior temporal regions ( P = 0.03). Although both groups exhibited the previously reported pattern of auditory naming sites anterior to visual naming sites, auditory naming sites had a significantly more posterior distribution in HS patients ( P = 0.02). Additionally, non-HS patients exhibited a greater proportion of visual naming sites above the superior temporal sulcus, whereas visual naming sites in HS patients were scattered across superior and inferior temporal cortex. Results suggest that preserved naming ability in HS patients following anterior temporal resection might be attributable, at least in part, to intrahemispheric reorganization of language in response to the likely, early development of sclerosis in the medial temporal region. Furthermore, their more posterior distribution of naming sites is consistent with the more anterior propagation of EEG discharges in TLE. These results hold theoretical implications regarding the role of the dominant hippocampus in determining the cortical representation of semantic and lexical information, and raise questions regarding the specific roles of medial and lateral temporal cortex in targeted word retrieval. The different patterns of naming areas identified in patients with and without HS may also carry clinical implications, potentially improving efficiency during the time-constrained process of stimulation mapping.

Neuropsychological effects of antiepileptic drugs (carbamazepine versus valproate) in adult males with epilepsy

PURPOSE

To evaluate the effect of antiepileptic drugs (AEDs) on cognition and behavior in adult epileptic males controlled on treatment with conventional antiepileptic medications.

METHODS

Cognitive, mood, behavior and personality traits were assessed in 45 epileptic patients treated with carbamazepine and/or valproate and free of seizures for >/=1 year. Thirty-four newly diagnosed or untreated patients with epilepsy and 58 matched healthy subjects were also included for comparison. A battery of psychometric tests was utilized including Stanford-Binet (4th edition), Beck Inventory for Depression, Aggressive Scale and Eysenck Personality Questionnaire.

RESULTS

Compared to matched control subjects, treated and untreated epileptic patients had poor performance in different cognitive and behavioral functions testing. Treated patients had worse scores in memory for digits forward and backward, total short-term memory, extroversion and psychosis. The duration of AEDs intake was correlated with memory of objects (r = -0.323; P = 0.030), bead memory (r = -0.314; P = 0.036) and total nonverbal short-term memory (r = -0.346; P = 0.020). Treated and untreated epileptic patients had poor performance of similar extent in behavioral functions testing (depression, aggression and neurosis). The dose of AEDs was correlated with testing scores for neurosis (r = 0.307; P = 0.040), verbal aggression (r = 0.483; P = 0.001) and nonverbal aggression (r = 0.526; P = 0.000), and duration of drug intake was correlated with scores for depression (r = 0.384; P = 0.009), psychosis (r = 0.586; P = 0.0001) and nonverbal aggression (r = 0.300; P = 0.045).

CONCLUSIONS

This study provides support for the notion that AEDs can impair performance in cognition, mood and behavior. Duration of drug intake and the number of the utilized AEDs are the main confounding variables. This study did not provide clues on how to exclude the effect of epilepsy itself and psychosocial variables as additional important confounding variables.

Hippocampal NPY gene transfer attenuates seizures without affecting epilepsy-induced impairment of LTP

Recently, hippocampal neuropeptide Y (NPY) gene therapy has been shown to effectively suppress both acute and chronic seizures in animal model of epilepsy, thus representing a promising novel antiepileptic treatment strategy, particularly for patients with intractable mesial temporal lobe epilepsy (TLE). However, our previous studies show that recombinant adeno-associated viral (rAAV)-NPY treatment in naive rats attenuates long-term potentiation (LTP) and transiently impairs hippocampal learning process, indicating that negative effect on memory function could be a potential side effect of NPY gene therapy. Here we report how rAAV vector-mediated overexpression of NPY in the hippocampus affects rapid kindling, and subsequently explore how synaptic plasticity and transmission is affected by kindling and NPY overexpression by field recordings in CA1 stratum radiatum of brain slices. In animals injected with rAAV-NPY, we show that rapid kindling-induced hippocampal seizures in vivo are effectively suppressed as compared to rAAV-empty injected (control) rats. Six to nine weeks later, basal synaptic transmission and short-term synaptic plasticity are unchanged after rapid kindling, while LTP is significantly attenuated in vitro. Importantly, transgene NPY overexpression has no effect on short-term synaptic plasticity, and does not further compromise LTP in kindled animals. These data suggest that epileptic seizure-induced impairment of memory function in the hippocampus may not be further affected by rAAV-NPY treatment, and may be considered less critical for clinical application in epilepsy patients already experiencing memory disturbances.

A single early-life seizure impairs short-term memory but does not alter spatial learning, recognition memory, or anxiety

The impact of a single seizure on cognition remains controversial. We hypothesized that a single early-life seizure (sELS) on rat Postnatal Day (P) 7 would alter only hippocampus-dependent learning and memory in mature (P60) rats. The Morris water maze, the novel object and novel place recognition tasks, and contextual fear conditioning were used to assess learning and memory associated with hippocampus/prefrontal cortex, perirhinal/hippocampal cortex, and amygdala function, respectively. The elevated plus maze and open-field test were used to assess anxiety associated with the septum. We report that sELS impaired hippocampus-dependent short-term memory, but not spatial learning or recall. sELS did not disrupt performance in the novel object and novel place recognition tasks. Contextual fear conditioning performance suggested intact amydgala function. sELS did not change anxiety levels as measured by the elevated plus maze or open-field test. Our data suggest that the long-term cognitive impact of sELS is limited largely to the hippocampus/prefrontal cortex.

Memory outcome 2 years after anterior temporal lobectomy in patients with drug-resistant epilepsy

PURPOSE

Memory decline is often observed after anterior temporal lobectomy (ATL), particularly in patients with dominant hemisphere resections. However, the follow-up length has been 1 year or less in most studies. Our aims were to examine postoperative memory changes over a longer period and to identify baseline demographic and clinical predictors of memory outcome.

METHODS

We administered material-specific memory tests at baseline, and 1 and 2 years after surgery to 82 consecutive right-handed patients (52% males) who underwent ATL for drug-resistant temporal lobe epilepsy (TLE) (35 left, 47 right) after a non-invasive presurgical protocol. Repeated measures multivariate analysis of variance (RM-MANOVA) was used to examine the relationship between changes in memory tests scores over time and side of TLE and pathology. Also, standardized residual change scores were calculated for each memory test and entered in multiple linear regression models aimed at identifying baseline predictors of better memory outcome.

RESULTS

RM-MANOVA revealed a significant change in memory test scores over time, with an interaction between time and side of surgery, as 2 years after surgery patients with RTLE were improved while patients with LTLE were not worse as compared with baseline. Pathology was not associated with changes in memory scores. In multiple regression analysis, significant associations were found between right TLE and greater improvement in verbal memory, younger age and greater improvement in visuospatial memory, and male gender and greater improvement in both verbal and visuospatial memory.

CONCLUSIONS

Our results suggest that the long-term memory outcome of TLE patients undergoing ATL without invasive presurgical assessment may be good in most cases not only for right-sided but also for left-sided resections.

Outcomes of epilepsy surgery in adults and children

Surgery is widely accepted as an effective therapy for selected individuals with medically refractory epilepsy. Numerous studies in the past 20 years have reported seizure freedom for at least 1 year in 53-84% of patients after anteromesial temporal lobe resections for mesial temporal lobe sclerosis, in 66-100% of patients with dual pathology, in 36-76% of patients with localised neocortical epilepsy, and in 43-79% of patients after hemispherectomies. Reported rates for non-resective surgery have been less impressive in terms of seizure freedom; however, the benefit is more apparent when reported in terms of significant seizure reductions. In this Review, we consider the outcomes of surgery in adults and children with epilepsy and review studies of neurological and cognitive sequelae, psychiatric and behavioural outcomes, and overall health-related quality of life.

[Central nervous system neuromodulation for the treatment of epilepsy]

We present here a review of the work on neuromodulation - defined as application of an inhibitory or excitatory current - on intracranial structures for the treatment of drug-resistant epilepsy. Near 250 patients were treated using a neuromodulation technique of the cerebellum (paravermian cortex), the CM-pf nucleus of the thalamus, the hippocampus, epileptogenic foci, and anterior ventral nucleus of the thalamus, with a one- to 15-year follow-up. Four contact strips were used for cerebellar and functional region neuromodulation, and DBS-type depth electrodes were stereotactically implanted for CM-pf and anterior nuclei of the thalamus and hippocampal neuromodulation. Electric stimulation was cyclic in almost all trials, using low frequency (10-40 Hz) for excitation and high frequency (60-185 Hz) for inhibition. Seizure frequency reduction was variable, depending on the neuromodulation site and patient selection, although seizure duration decreased in most patients. Cerebellar neuromodulation was followed by a 78% reduction in tonic and tonic-clonic seizures, CM-pf neuromodulation by an 83% reduction in tonic-clonic seizures and atypical absence of Lennox-Gastaut syndrome, with a 17.2% seizure-free and drug-free patient rate. Hippocampal neuromodulation was followed by a 73% reduction in partial complex seizures, with a 33% seizure-free patient rate. Anterior ventral nucleus of the thalamus was followed by a 63% reduction in tonic-clonic, tonic and atonic seizures. Several prognostic factors were identified in order to improve future results. There was no mortality and morbidity was limited to skin erosion at the neurostimulator site. Seizure reduction was associated with improved neuropsychological performance and better quality of life. Neuromodulation is safe and effective for the treatment of epileptic seizures of various origins. Several targets may be associated in a single patient, especially when bilateral hippocampal seizure foci are present.

Magnetoencephalography for pediatric epilepsy: how we do it

Magnetoencephalography (MEG) is increasingly being used in the preoperative evaluation of pediatric patients with epilepsy. The ability to noninvasively localize ictal onset zones (IOZ) and their relationships to eloquent functional cortex allows the pediatric epilepsy team to more accurately assess the likelihood of postoperative seizure freedom, while more precisely prognosticating the potential functional deficits that may be expected from resective surgery. Confirmation of clinically suggested multifocality may result in a recommendation against resective surgery because the probability of seizure freedom will be low. Current paradigms for motor and somatosensory testing are robust. Paradigms allowing localization of those regions necessary for competent language function, though promising, are under continuous optimization. MR imaging white matter trajectory data, created from diffusion tensor imaging obtained in the same setting as the localization brain MR imaging, provide ancillary information regarding connectivity of the IOZ to sites of rapid secondary spread and the spatial relationship of the IOZ to functionally important white matter bundles, such as the corticospinal tracts. A collaborative effort between neuroradiology, neurology, neurosurgery, neuropsychology, technology, and physics ensures successful implementation of MEG within a pediatric epilepsy program.

Thalamic atrophy and cognition in unilateral temporal lobe epilepsy

This study examined quantitative magnetic resonance volumes of the thalamus and hippocampus and determined their relationship with cognitive function and clinical seizure characteristics in a sample of 46 unilateral temporal lobe epilepsy (TLE) subjects (20 left and 26 right) and 29 controls. The hippocampus and thalamus exhibited different patterns of volume abnormality, different associations with clinical seizure characteristics, and different patterns of relationship with cognitive measures. Hippocampal volume reduction was primarily ipsilateral to the seizure focus, and thalamic volume reduction was bilateral. Ipsilateral hippocampal volume was significantly correlated with both early neurodevelopmental features (age of seizure onset) and disease characteristics (duration of epilepsy), whereas thalamus integrity was related only to disease variables. Hippocampal volume showed a selective association with verbal memory performance. In contrast, both left and right thalamic volumes were significantly correlated with performance on both memory and nonmemory cognitive domains. These findings underscore the importance of thalamic atrophy in chronic TLE and its potential implications for cognition.

[Epilepsy: role of neuropsychological evaluation]

Cognitive deficits are frequent in epileptic patients and can be considered epileptic behavioural markers. They are assessed by neuropsychological exploration, which requires the use of standardized psychometric tests. The neuropsychological data obtained complement the information provided by other perisurgical investigations. In addition to the indications concerning lateralization and the extent of the cerebral dysfunction, neuropsychological findings can assist in anticipating the possible cognitive risks resulting from surgical treatment. Finally, these results are indispensable to implementing neuropsychological rehabilitation, which should be proposed before and/or after surgery, when necessary, to patients involved in a surgical program for epilepsy.

Use of preoperative functional MRI to predict verbal memory decline after temporal lobe epilepsy surgery

PURPOSE

Verbal memory decline is a frequent complication of left anterior temporal lobectomy (L-ATL). The goal of this study was to determine whether preoperative language mapping using functional magnetic resonance imaging (fMRI) is useful for predicting which patients are likely to experience verbal memory decline after L-ATL.

METHODS

Sixty L-ATL patients underwent preoperative language mapping with fMRI, preoperative intracarotid amobarbital (Wada) testing for language and memory lateralization, and pre- and postoperative neuropsychological testing. Demographic, historical, neuropsychological, and imaging variables were examined for their ability to predict pre- to postoperative memory change.

RESULTS

Verbal memory decline occurred in over 30% of patients. Good preoperative performance, late age at onset of epilepsy, left dominance on fMRI, and left dominance on the Wada test were each predictive of memory decline. Preoperative performance and age at onset together accounted for roughly 50% of the variance in memory outcome (p < 0.001), and fMRI explained an additional 10% of this variance (p <or= 0.003). Neither Wada memory asymmetry nor Wada language asymmetry added additional predictive power beyond these noninvasive measures.

DISCUSSION

Preoperative fMRI is useful for identifying patients at high risk for verbal memory decline prior to L-ATL surgery. Lateralization of language is correlated with lateralization of verbal memory, whereas Wada memory testing is either insufficiently reliable or insufficiently material-specific to accurately localize verbal memory processes.

The effects of cognitive rehabilitation on memory outcome after temporal lobe epilepsy surgery

OBJECTIVE

Epilepsy surgery is a valuable treatment option for patients with pharmacoresistant epilepsy, but seizure freedom is often achieved at the cost of cognitive impairments caused by surgery. The aim of this study was to investigate the short-term effects of cognitive rehabilitation on memory outcome after temporal lobe epilepsy surgery.

METHODS

Two groups of patients who underwent temporal lobe resection, one followed (n=55) and one not followed (n=57) by postoperative rehabilitation, were evaluated with respect to memory and attention before and 3 months after temporal lobe surgery. The groups came from different epilepsy centers, but were largely matched with respect to age, sex, type of surgery, and seizure outcome.

RESULTS

After surgery, 78% of the patients were seizure-free. Repeated-measures MANOVA revealed a significant "side x surgery" effect on verbal recognition and a "rehabilitation x surgery" effect on verbal learning and recognition. There were no effects for loss in verbal delayed recall or figural memory. Detailed analyses indicated gains as a result of rehabilitation, particularly after right temporal lobe surgery. Attention generally improved. The risk of manifesting losses in verbal memory was about four times higher without than with rehabilitation.

CONCLUSIONS

Rehabilitation can counteract the verbal memory decline that is normally seen after temporal lobe resection. Its positive effects were evident particularly with respect to the more cortically associated aspects of verbal learning rather than to the mesial aspects of long-term consolidation/retrieval. Figural memory was not affected at all, and attention improved independent of rehabilitation. Interestingly, left temporal lobe-resected patients, who were most in need of an efficacious rehabilitation, profited less than right temporal lobe-resected patients, indicating that left-sided surgery may reduce the capacity needed for efficient training of verbal memory. Thus, rehabilitation has a positive effect on memory outcome, but its usefulness for risk groups and the question of whether training should be performed after or possibly before surgery are debatable. Further research should also address different interventions, longer-term outcome, and the carryover effects on everyday functioning.

Cognitive outcome of status epilepticus in adults

There is no doubt that structural morphological brain lesions and malformations in epilepsy represent major etiological factors for the cognitive impairments seen in this disease. The role of epileptic activity and seizures for cognition and cognitive development, however, is less easily determined. Epileptic dysfunction ranges from interictal and periictal activity over self-terminating seizures to non-convulsive and convulsive status epilepticus, which appear the most severe conditions along this continuum. The decisive question in this regard is as to whether cognitive impairments observed in the acute epileptic condition are reversible or not. Impairments from interictal or postictal epileptic dysfunction are reversible and may interfere at most with brain maturation and cognitive development in the young patient. Seizures and ictal dysfunction in contrast, even when reversible, can leave a permanent trace which extends the phase of postictal recovery. As for status epilepticus and subsequent cognitive decline it often remains open whether the epileptic condition itself or the underlying clinical condition is causative for the aftermath. While there is evidence for both possibilities, group data from neuropsychological cross sectional and longitudinal studies indicate that more severe mental impairments, which in turn indicate more severe clinical conditions, appear to be a risk factor for sustaining status epilepticus, rather than that status epilepticus causes the cognitive decline. Reviewing the literature the cognitive condition in patients with status epilepticus varies with the type of epilepsy, the etiology of epilepsy, severity of the status, and the age of the patient.

Physiological studies of human dentate granule cells

The availability of human hippocampi obtained through surgery (usually for treatment of temporal lobe epilepsy) has allowed us to investigate the properties of the human dentate in a way that cannot be done with other brain regions. The dentate has been the primary focus of these studies because of its relative preservation in all patient specimens. Moreover, there is extensive synaptic reorganization of numerous neurotransmitter systems in this the fascia dentate (dentate gyrus and the hilus) in humans with specific forms of TLE. These changes are not evident in tissue from patients with seizure that begin outside the hippocampus, and, as a result, this tissue provides an invaluable resource for comparisons. Physiological data using both slices and acutely dissociated cells demonstrate that the granule cells have membrane properties similar to those of rodents although there are specific changes that appear to be associated with seizures. Similarly, in the non-sclerotic hippocampi, the synaptic properties are similar to those reported in rodents. There are also a number of parallels between the findings in humans and in status animal models of temporal lobe epilepsy. This review will cover analyses of membrane properties as well as of glutamatergic, GABAergic, and neuromodulatory systems. Thus, while there are a number of issues that invariably arise with studies of pathological human tissue, this tissue is ideally suited to verify and refine animal models of temporal lobe epilepsy. In addition, one can argue that human tissue provides the only resource to evaluate the ways that granule cells recorded from laboratory animals approximate human granule cell physiology.

THE CLINICAL COURSE AFTER STEREOTACTIC RADIOSURGICAL AMYGDALOHIPPOCAMPECTOMY WITH NEURORADIOLOGICAL CORRELATES

OBJECTIVE

Radiosurgical ablation of the mesial temporal lobe structures can be used in the treatment of intractable temporal lobe epilepsy associated with mesial temporal sclerosis. In this study, we analyzed the magnetic resonance imaging (MRI) and spectroscopic changes that follow the treatment and report the clinical sequelae of the procedure.

METHODS

Eight patients (five men and three women; age, 38 ± 15 yr [mean ± standard deviation]) with mesial temporal sclerosis were treated with radiosurgical amygdalohippocampectomy (25 Gy to the 50% isodose region with a mean target volume of 6.2 ± 0.7 cm3). MRI and magnetic resonance spectroscopy were performed sequentially during a 24-month period after treatment.

RESULTS

Patients were followed up clinically for 24 to 53 months. MRI scans revealed changes of marked temporal lobe swelling, with often markedly elevated apparent diffusion coefficients in keeping with vasogenic edema that became apparent 6 to 12 months after stereotactic radiosurgery. Spectroscopy of the target area revealed a progressive loss of N-acetylaspartate (the late evolution of lactate) and a peak in the choline-to-creatine ratio that seemed to coincide with the peak of the vasogenic edema in the temporal lobe surrounding the target area. Clinically, all patients showed some reduction in seizure frequency, although in two patients, this reduction was modest. The MRI changes in those patients were also modest, and three patients ultimately became free of seizures. However, there was a latency of 18 to 24 months before improvements in seizure control occurred, and during this period, seizures worsened or changed in four patients. Two patients also developed symptoms of increased intracranial pressure with mild dysphasia, which responded to administration of corticosteroid medication. However, no long-term clinical verbal memory decline was identified in any patient.

CONCLUSION

There are marked changes in MRI scans and magnetic resonance spectroscopic findings after patients undergo radiosurgery for temporal lobe epilepsy. Our initial findings suggest that some patients may have a period of distressing symptoms that accompany changes that are visualized on the MRI scans.

Extrahippocampal gray matter atrophy and memory impairment in patients with medial temporal lobe epilepsy

Memory impairment observed in patients with medial temporal lobe epilepsy (MTLE) is classically attributed to hippocampal atrophy. The contribution of extrahippocampal structures in shaping memory impairment in patients with MTLE is not yet completely understood, even though atrophy in MTLE extends beyond the hippocampus. We aimed to evaluate the neuropsychological profile of patients with MTLE focusing on memory, and to investigate whether gray matter concentration (GMC) distribution within and outside the medial portion of the temporal lobes would be associated with their neuropsychological performance. We performed a voxel based morphometry study of 36 consecutive patients with MTLE and unilateral hippocampal atrophy. We observed a significant simple regression between general and verbal memory performance based on Wechsler Memory Scale-Revised and the GMC of medial temporal and extratemporal structures in patients with left MTLE. We also performed a "regions of interest analysis" of the medial temporal lobe, and we observed that the GMC of the hippocampus, entorhinal, and perirhinal cortices were consistently associated with general and verbal memory performance in patients with MTLE. We also observed that the GMC of the cingulate and orbito-frontal cortex are independently associated with verbal and general memory performances. Our results suggest that general and verbal memory impairments in patients with left MTLE are associated with atrophy of the hippocampus, the entorhinal, and the perirhinal cortex. We also suggest that atrophy and dysfunction of limbic and frontal structures such as the cingulate and the orbito-frontal cortex contribute to memory impairment in MTLE.

Tractography of the parahippocampal gyrus and material specific memory impairment in unilateral temporal lobe epilepsy

INTRODUCTION

Temporal lobe epilepsy (TLE) is associated with disrupted memory function. The structural changes underlying this memory impairment have not been demonstrated previously with tractography.

METHODS

We performed a tractography analysis of diffusion magnetic resonance imaging scans in 18 patients with unilateral TLE undergoing presurgical evaluation, and in 10 healthy controls. A seed region in the anterior parahippocampal gyrus was selected from which to trace the white matter connections of the medial temporal lobe. A correlation analysis was carried out between volume and mean fractional anisotropy (FA) of the connections, and pre-operative material specific memory performance.

RESULTS

There was no significant difference between the left and right sided connections in controls. In the left TLE patients, the connected regions ipsilateral to the epileptogenic region were found to be significantly reduced in volume and mean FA compared with the contralateral region, and left-sided connections in control subjects. Significant correlations were found in left TLE patients between left and right FA, and verbal and non-verbal memory respectively.

CONCLUSION

Tractography demonstrated the alteration of white matter pathways that may underlie impaired memory function in TLE. A detailed knowledge of the integrity of these connections may be useful in predicting memory decline in chronic temporal lobe epilepsy.

A case study of long-term cognitive and social functioning following a right temporal lobectomy in infancy

We present the rare case of an adult patient, FS, who had a right anterior temporal lobe resection during infancy to treat intractable epilepsy, and underwent a cognitive evaluation 19 years later. Given the paucity of literature on long-term outcomes for infants who receive neurosurgery for epilepsy, this case provides valuable information for both clinicians and patients. What little literature exists on infant and child surgical outcomes for epilepsy suggests a variable course, with several areas of possible cognitive and social difficulty. FS's assessment at the age of 21 revealed only mild difficulties with memory, sequencing, and visual imagery, and spared intellectual functioning, working memory, problem-solving and social cognition, along with a high level of socioeconomic functioning. Thus, the case of FS suggests that neurosurgery during infancy is not necessarily associated with large-scale cognitive impairment, and furthermore, that high levels of functioning both educationally and vocationally are possible after surgical treatment of epilepsy in infancy.

Whole-brain voxel-based morphometry of white matter in medial temporal lobe epilepsy

PURPOSE

The purpose of this study was to analyze whole-brain white matter changes in medial temporal lobe epilepsy (MTLE).

MATERIALS AND METHODS

We studied 23 patients with MTLE and 13 age- and sex-matched healthy control subjects using voxel-based morphometry (VBM) on T1-weighted 3D datasets. The seizure focus was right sided in 11 patients and left sided in 12. The data were collected on a 1.5 T MR system and analyzed by SPM 99 to generate white matter density maps.

RESULTS

Voxel-based morphometry revealed diffusively reduced white matter in MTLE prominently including bilateral frontal lobes, bilateral temporal lobes and corpus callosum. White matter reduction was also found in the bilateral cerebellar hemispheres in the left MTLE group.

CONCLUSION

VBM is a simple and automated approach that is able to identify diffuse whole-brain white matter reduction in MTLE.

Voxel-based diffusion tensor imaging in patients with mesial temporal lobe epilepsy and hippocampal sclerosis

BACKGROUND

Mesial temporal lobe epilepsy (mTLE) with hippocampus sclerosis (HS) is an important cause for focal epilepsy. In this study, we explored the integrity of connecting networks using diffusion tensor imaging (DTI) and two whole-brain voxel-based methods: statistical parametric mapping (SPM) and tract-based spatial statistics (TBSS).

METHODS

Thirty-three consecutive patients with mTLE and HS undergoing presurgical evaluation were scanned at 3 T, a DTI data set was acquired and parametric maps of fractional anisotropy (FA) and mean diffusivity (MD) were calculated. Twenty-one patients had left hippocampal sclerosis (LHS) and 12 patients had right HS (RHS). These groups were compared to 37 normal control subjects using both SPM5 and TBSS.

RESULTS

The ipsilateral temporal lobe showed widespread FA reduction in both groups. The limbic system was clearly abnormal in the LHS group, also involving the arcuate fasciculus. In RHS, changes were more restricted but also showed involvement of the contralateral temporal and inferior frontal lobe. Increased MD was found in the ipsilateral hippocampus by SPM that was only marginally detected by TBSS. In white matter regions, however, TBSS was more sensitive to changes than SPM.

CONCLUSION

DTI detects extensive changes in mTLE with HS. The affected networks were principally in the ipsilateral temporal lobe and the limbic system but also the arcuate fasciculus. SPM and TBSS gave complementary information with higher sensitivity to FA changes using TBSS.

Cognitive and magnetic resonance volumetric abnormalities in new-onset pediatric epilepsy

This paper addresses the issue of cognitive morbidity and abnormalities in quantitative MR volumetric in children with new and recent onset idiopathic epilepsy. The available literature suggests that mild diffuse cognitive problems are evident in children with new onset epilepsy in the context of intact whole brain and lobar volumetrics. Subsets of children can be identified with salient academic and volumetric abnormalities. These findings represent the baseline upon which any subsequent effects of chronic epilepsy may accrue.

Growing old with epilepsy: the neglected issue of cognitive and brain health in aging and elder persons with chronic epilepsy

The purpose of this review is to examine what is known about cognitive and brain aging in elders with chronic epilepsy. We contend that much remains to be learned about the ultimate course of cognition and brain structure in persons with chronic epilepsy and concern appears warranted. Individuals with chronic epilepsy are exposed to many risk factors demonstrated to be associated with abnormal cognitive and brain aging in the general population, with many of these risk factors present in persons with chronic epilepsy as early as midlife. We suggest that a research agenda be developed to systematically identify and treat known modifiable risk factors in order to protect and promote cognitive and brain health in aging and elder persons with chronic epilepsy.

Cognitive progression in epilepsy

The issue of cognitive progression in people with epilepsy is of considerable interest and has important clinical and theoretical implications. In this paper, we review recent studies in both the adult and childhood epilepsy literature which have included a longitudinal test-retest design to examine this question. Several important methodological issues of this literature are highlighted and areas which require more investigation are identified.

Verbal cognition and attention deficits do not explain the verbal memory decline associated with pharmacoresistant partial epilepsy

The aim of this study was to explore whether change in verbal memory with time in patients with epilepsy is influenced by performance on tasks assessing verbal cognition or attention/processing speed. Thirty-six patients and twenty-five healthy controls were tested twice with median retest intervals of 4.8 and 3.1 years, respectively. Aspects of verbal memory, verbal cognition, and attention/processing speed were assessed. Decline in one verbal memory variable (Cronholm-Molander Memory Test Paired Associates -- Delayed Recall) was the strongest correlate of epilepsy. The second strongest correlate was a decrease in one attention/processing speed variable (Digit Symbol). The relationship between decline in verbal memory and epilepsy was not influenced by the decline in attention/processing speed, and the results did not support the notion that limited mental reserves as reflected in impaired verbal cognition or attention/processing speed can explain the relationship between verbal memory and epilepsy.