Diffusion Tensor Orientation as a Microstructural MRI Marker of Mossy Fiber Sprouting After TBI in Rats

Diffusion tensor imaging (DTI) metrics are highly sensitive to microstructural brain alterations and are potentially useful imaging biomarkers for underlying neuropathologic changes after experimental and human traumatic brain injury (TBI). As potential imaging biomarkers require direct correlation with neuropathologic alterations for validation and interpretation, this study systematically examined neuropathologic abnormalities underlying alterations in DTI metrics in the hippocampus and cortex following controlled cortical impact (CCI) in rats. Ex vivo DTI metrics were directly compared with a comprehensive histologic battery for neurodegeneration, microgliosis, astrocytosis, and mossy fiber sprouting by Timm histochemistry at carefully matched locations immediately, 48 hours, and 4 weeks after injury. DTI abnormalities corresponded to spatially overlapping but temporally distinct neuropathologic alterations representing an aggregate measure of dynamic tissue damage and reorganization. Prominent DTI alterations of were observed for both the immediate and acute intervals after injury and associated with neurodegeneration and inflammation. In the chronic period, diffusion tensor orientation in the hilus of the dentate gyrus became prominently abnormal and was identified as a reliable structural biomarker for mossy fiber sprouting after CCI in rats, suggesting potential application as a biomarker to follow secondary progression in experimental and human TBI.

Validity testing in veterans with epileptic seizures and psychogenic nonepileptic seizures

OBJECTIVE

Identification of clinically meaningful subgroups among patients with psychogenic nonepileptic seizures (PNES) or epileptic seizures (ES) is of potential value for assessing prognosis and predicting therapeutic response. Invalid performance on validity tests has been associated with noncredible complaints and worse cognitive test scores, and may be one such classification criteria. We studied invalid performance in Veterans with PNES or ES, and the association of invalid performance with cognitive test scores and subjective complaints.

METHODS

Patients were consecutive admissions to three veterans affairs (VA) epilepsy monitoring units. Evaluations included two validity tests: the Test of Memory Malingering (TOMM); and the Minnesota Multiphasic Personality Inventory-2-Restructured Form (MMPI-2-RF) over-reporting validity scales. We compared the frequency of invalid performance on the TOMM or MMPI-2-RF in patients diagnosed with PNES vs. ES. We evaluated the association of invalid performance with scores on the Repeatable Battery for Assessment of Neuropsychological Status (RBANS), and four subjective symptom measures including the Beck Depression Inventory-II, and Quality of Life in Epilepsy-31.

RESULTS

Invalid TOMM performance was found in 25.3% of Veterans diagnosed with PNES and 10.8% of those with ES (p = .03). Invalid reporting on the MMPI-2-RF was found in 35.9% of the PNES group vs. 15.3% of the ES group (p = .01). Effects of valid vs. invalid reporting on external measures were similar for ES and PNES groups. Patients with invalid vs. valid TOMM performance had lower scores on the RBANS (p < .001). Patients with invalid performance had greater complaints on all subjective measures, with largest effect sizes for the MMPI-2-RF validity scales (p < .001).

SIGNIFICANCE

In Veterans admitted for evaluation of poorly controlled seizures, invalid performance on validity tests was not uncommon. Cognitive test results and subjective reports from patients with invalid performance may not be credible. These observations have implications for the analysis of clinical trials, where primary and secondary outcomes often rely on self-report measures.

Nine-year prospective efficacy and safety of brain-responsive neurostimulation for focal epilepsy

OBJECTIVE

To prospectively evaluate safety and efficacy of brain-responsive neurostimulation in adults with medically intractable focal onset seizures (FOS) over 9 years.

METHODS

Adults treated with brain-responsive neurostimulation in 2-year feasibility or randomized controlled trials were enrolled in a long-term prospective open label trial (LTT) to assess safety, efficacy, and quality of life (QOL) over an additional 7 years. Safety was assessed as adverse events (AEs), efficacy as median percent change in seizure frequency and responder rate, and QOL with the Quality of Life in Epilepsy (QOLIE-89) inventory.

RESULTS

Of 256 patients treated in the initial trials, 230 participated in the LTT. At 9 years, the median percent reduction in seizure frequency was 75% (p < 0.0001, Wilcoxon signed rank), responder rate was 73%, and 35% had a ≥90% reduction in seizure frequency. We found that 18.4% (47 of 256) experienced ≥1 year of seizure freedom, with 62% (29 of 47) seizure-free at the last follow-up and an average seizure-free period of 3.2 years (range 1.04-9.6 years). Overall QOL and epilepsy-targeted and cognitive domains of QOLIE-89 remained significantly improved (p < 0.05). There were no serious AEs related to stimulation, and the sudden unexplained death in epilepsy (SUDEP) rate was significantly lower than predefined comparators (p < 0.05, 1-tailed χ2).

CONCLUSIONS

Adjunctive brain-responsive neurostimulation provides significant and sustained reductions in the frequency of FOS with improved QOL. Stimulation was well tolerated; implantation-related AEs were typical of other neurostimulation devices; and SUDEP rates were low.

CLINICALTRIALSGOV IDENTIFIER

NCT00572195.

CLASSIFICATION OF EVIDENCE

This study provides Class IV evidence that brain-responsive neurostimulation significantly reduces focal seizures with acceptable safety over 9 years.

Mesial temporal resection following long-term ambulatory intracranial EEG monitoring with a direct brain-responsive neurostimulation system

OBJECTIVE

To describe seizure outcomes in patients with medically refractory epilepsy who had evidence of bilateral mesial temporal lobe (MTL) seizure onsets and underwent MTL resection based on chronic ambulatory intracranial EEG (ICEEG) data from a direct brain-responsive neurostimulator (RNS) system.

METHODS

We retrospectively identified all patients at 17 epilepsy centers with MTL epilepsy who were treated with the RNS System using bilateral MTL leads, and in whom an MTL resection was subsequently performed. Presumed lateralization based on routine presurgical approaches was compared to lateralization determined by RNS System chronic ambulatory ICEEG recordings. The primary outcome was frequency of disabling seizures at last 3-month follow-up after MTL resection compared to seizure frequency 3 months before MTL resection.

RESULTS

We identified 157 patients treated with the RNS System with bilateral MTL leads due to presumed bitemporal epilepsy. Twenty-five patients (16%) subsequently had an MTL resection informed by chronic ambulatory ICEEG (mean = 42 months ICEEG); follow-up was available for 24 patients. After MTL resection, the median reduction in disabling seizures at last follow-up was 100% (mean: 94%; range: 50%-100%). Nine patients (38%) had exclusively unilateral electrographic seizures recorded by chronic ambulatory ICEEG and all were seizure-free at last follow-up after MTL resection; eight of nine continued RNS System treatment. Fifteen patients (62%) had bilateral MTL electrographic seizures, had an MTL resection on the more active side, continued RNS System treatment, and achieved a median clinical seizure reduction of 100% (mean: 90%; range: 50%-100%) at last follow-up, with eight of fifteen seizure-free. For those with more than 1 year of follow-up (N = 21), 15 patients (71%) were seizure-free during the most recent year, including all eight patients with unilateral onsets and 7 of 13 patients (54%) with bilateral onsets.

SIGNIFICANCE

Chronic ambulatory ICEEG data provide information about lateralization of MTL seizures and can identify additional patients who may benefit from MTL resection.

Health-related quality of life in Veterans with epileptic and psychogenic nonepileptic seizures

RATIONALE

Health-related quality of life (HRQoL) is compromised in civilians with epileptic seizures (ES) or psychogenic nonepileptic seizures (PNES). U.S. Veterans are a distinct patient group with regard to gender, age, and background. We studied HRQoL in Veterans and asked the following: (1) Is there a difference in HRQoL in Veterans with ES vs. PNES?; (2) What factors influence HRQoL in each group?; (3) What factors influenced the difference between seizure groups?

METHODS

We studied consecutive Veterans entering the epilepsy monitoring units (EMUs) of three VA Epilepsy Centers of Excellence. Patients underwent continuous video-EEG monitoring. Seizure diagnoses followed established criteria. Health-related quality of life was measured with the Quality of Life in Epilepsy Inventory-31 (QOLIE-31). Evaluations included the Structured Clinical Interview for Diagnostic and Statistical Manual-IV (DSM IV), the posttraumatic stress disorder (PTSD) Checklist (PCL), the Beck Depression Inventory II (BDI-II), and the Minnesota Multiphasic Personality Inventory-2 Restructured form (MMPI-2RF). Between-group differences were tested with Wilcoxon tests. Nested regression analysis was used to evaluate the influence of demographic, social, military, seizure-related, and psychological factors on QOLIE-31 scores.

RESULTS

The median QOLIE-31 total score was 14 points lower in Veterans with PNES vs. ES (p < 0.001; Cohen's d = 0.73). Within each seizure group, psychological factors accounted for ≥50% of the variance in QOLIE scores while combined demographic, social, and seizure-related factors accounted for 18% (group with ES) and 7% (PNES). Psychological measures, particularly PCL and the BDI-II scores, accounted for all of the difference in QOLIE-31 total scores between Veterans with ES and those with PNES.

CONCLUSIONS

Health-related quality of life as measured by the QOLIE-31 is worse in Veterans with PNES as compared with those with ES. Psychological factors account for the most of the variance in QOLIE-31 scores regardless of seizure type and also account for the difference between groups with PNES and ES. Demographic, military, social, and seizure-related factors have minimal influence on HRQoL. These results in U.S. Veterans are similar to those found in civilians despite differences in patient age, gender, and background.

Epilepsy Among Iraq and Afghanistan War Veterans - United States, 2002-2015

The age-adjusted prevalence of seizure disorder in United States veterans deployed in Iraq and Afghanistan conflicts (IAV) is 6.1 per 1,000 persons (1), compared with 7.1 to 10 per 1,000 persons in the general population (2,3). Persons with epilepsy are at risk of excess mortality in part because of comorbidity (4). Although patterns of comorbidity have been associated with mortality in IAV (5), the unique contribution of epilepsy to excess mortality in IAV is unknown. A cohort study was developed using inpatient, outpatient, and pharmacy data from the U.S. Department of Veterans Affairs, Veterans Health Administration (VA) to identify epilepsy, demographic characteristics, and baseline comorbidity for IAV who received VA care in 2010 and 2011. The VA's vital status records were used to identify 5-year mortality (2011-2015). The unadjusted Kaplan-Meier estimator and adjusted proportional hazards regression models tested the hypothesis that excess mortality is associated with epilepsy. IAV with epilepsy were more likely than those without epilepsy to have mental and physical comorbidity, and significantly higher mortality, even after controlling for demographic characteristics and other comorbid conditions (adjusted hazard ratio = 2.6; 95% confidence interval [CI] 2.1-3.2). IAV with epilepsy could benefit from evidence-based chronic disease self-management programs to reduce physical and psychiatric comorbidity, and linkages to VA clinical and other community health and social service providers.

Providing Quality Epilepsy Care for Veterans

Quality epilepsy care depends on balancing seizure control with medication adverse effects and on understanding a patient's medical history and anxieties related to the illness.

Delineating potential epileptogenic areas utilizing resting functional magnetic resonance imaging (fMRI) in epilepsy patients

Seizure localization includes neuroimaging like electroencephalogram, and magnetic resonance imaging (MRI) with limited ability to characterize the epileptogenic network. Temporal clustering analysis (TCA) characterizes epileptogenic network congruent with interictal epileptiform discharges by clustering together voxels with transient signals. We generated epileptogenic areas for 12 of 13 epilepsy patients with TCA, congruent with different areas of seizure onset. Resting functional MRI (fMRI) scans are noninvasive, and can be acquired quickly, in patients with different levels of severity and function. Analyzing resting fMRI data using TCA is quick and can complement clinical methods to characterize the epileptogenic network.

Attributing seizures to TBI: Validation of a brief patient questionnaire

PURPOSE

Traumatic brain injury (TBI) is an important cause of epilepsy and has also been associated with psychogenic nonepileptic seizures (PNES). We designed a brief questionnaire assessing patient beliefs regarding TBI as the cause of their seizures (Patient Seizure Etiology Questionnaire; PSEQ). This study reports content validity for the PSEQ.

METHODS

Ninety Veterans undergoing comprehensive evaluation at 3 VA epilepsy centers completed the PSEQ, a series of questions regarding possible causes for their seizures, including TBI. The PSEQ was scored as YES vs. NO for TBI as the proposed cause of seizures. For each patient, two expert reviewers independently completed a structured chart review to determine whether TBI was the proposed cause of seizures (n=180 reviews). Kappa statistic was used to assess agreement between the PSEQ and each chart review and between the PSEQ and combined chart reviews where both reviewers agreed on a TBI seizure etiology.

RESULTS

The PSEQ scored higher overall rates for a TBI seizure etiology than did expert chart reviews (40% vs. 28%; p<0.001). The PSEQ agreed with 82% of 180 independent chart reviews (sensitivity 88%; specificity 79%). Kappa statistic for agreement was 0.60. The two reviewers agreed on a probable TBI seizure etiology for 83% of chart reviews. The PSEQ sensitivity increased to 100% when both reviewers were in agreement.

CONCLUSION

The PSEQ provides a direct, standardized measure of patient beliefs regarding TBI as the cause of their seizures and has moderate-substantial agreement with expert chart reviews.

Long-term treatment with responsive brain stimulation in adults with refractory partial seizures

OBJECTIVE

The long-term efficacy and safety of responsive direct neurostimulation was assessed in adults with medically refractory partial onset seizures.

METHODS

All participants were treated with a cranially implanted responsive neurostimulator that delivers stimulation to 1 or 2 seizure foci via chronically implanted electrodes when specific electrocorticographic patterns are detected (RNS System). Participants had completed a 2-year primarily open-label safety study (n = 65) or a 2-year randomized blinded controlled safety and efficacy study (n = 191); 230 participants transitioned into an ongoing 7-year study to assess safety and efficacy.

RESULTS

The average participant was 34 (±11.4) years old with epilepsy for 19.6 (±11.4) years. The median preimplant frequency of disabling partial or generalized tonic-clonic seizures was 10.2 seizures a month. The median percent seizure reduction in the randomized blinded controlled trial was 44% at 1 year and 53% at 2 years (p < 0.0001, generalized estimating equation) and ranged from 48% to 66% over postimplant years 3 through 6 in the long-term study. Improvements in quality of life were maintained (p < 0.05). The most common serious device-related adverse events over the mean 5.4 years of follow-up were implant site infection (9.0%) involving soft tissue and neurostimulator explantation (4.7%).

CONCLUSIONS

The RNS System is the first direct brain responsive neurostimulator. Acute and sustained efficacy and safety were demonstrated in adults with medically refractory partial onset seizures arising from 1 or 2 foci over a mean follow-up of 5.4 years. This experience supports the RNS System as a treatment option for refractory partial seizures.

CLASSIFICATION OF EVIDENCE

This study provides Class IV evidence that for adults with medically refractory partial onset seizures, responsive direct cortical stimulation reduces seizures and improves quality of life over a mean follow-up of 5.4 years.

Reduced juvenile long-term depression in tuberous sclerosis complex is mitigated in adults by compensatory recruitment of mGluR5 and Erk signaling

A mouse model of the human genetic disorder tuberous sclerosis complex fails to undergo developmental down-regulation of mGluR5 expression and activation of Erk signaling, probably contributing to the aberrant plasticity and epilepsy in this disease.

Tuberous sclerosis complex (TSC) is a multisystem genetic disease that manifests with mental retardation, tumor formation, autism, and epilepsy. Heightened signaling through the mammalian target of rapamycin (mTOR) pathway is involved in TSC pathology, however it remains unclear how other signaling pathways are perturbed and contribute to disease symptoms. Reduced long-term depression (LTD) was recently reported in TSC mutant mice. We find that although reduced LTD is a feature of the juvenile mutant hippocampus, heightened expression of metabotropic glutamate receptor 5 and constitutively activated Erk signaling in the adult hippocampus drives wild-type levels of LTD. Increased mGluR5 and Erk results in a novel mTOR-independent LTD in CA1 hippocampus of adult mice, and contributes to the development of epileptiform bursting activity in the TSC2^+/− CA3 region of the hippocampus. Inhibition of mGluR5 or Erk signaling restores appropriate mTOR-dependence to LTD, and significantly reduces epileptiform bursting in TSC2^+/− hippocampal slices. We also report that adult TSC2^+/− mice exhibit a subtle perseverative behavioral phenotype that is eliminated by mGluR5 antagonism. These findings highlight the potential of modulating the mGluR5-Erk pathway in a developmental stage-specific manner to treat TSC.

Tuberous sclerosis complex (TSC) is a genetic disorder that afflicts around 1 in 6,000 people and results from a mutation in one of two genes, TSC1 or TSC2. TSC patients suffer a number of neuronal symptoms including various degrees of autism, mental retardation, and epilepsy, the latter found in more than 80% of cases within the first year of life. In the TSC mutant mice that are used to model the disease, a region of the brain called the hippocampus fails to undergo long-term depression (LTD), a neuronal process that is important for learning and memory. We find that while this is the case in juvenile mutant mice, adult mice appear to have fixed this deficit. The “fix” involves the ramping up of signaling pathways involving mGluR5 and Erk. Although increased mGluR5 and Erk signaling outwardly fixes the problem of diminished LTD in adulthood, it renders the brain insensitive to the cues and inputs that normally work to control LTD. Moreover, the hippocampus in adult TSC mice is prone to seizures and impaired in learning and memory tasks. We find that drugs that target mGluR5 or Erk signaling repair the problems with excitability and learning deficits.

EEG and epilepsy monitoring

PURPOSE OF REVIEW

This article reviews the utility of EEG and prolonged video-EEG telemetry in the diagnosis and management of a patient with epilepsy.

RECENT FINDINGS

The EEG can be the most helpful test to determine a diagnosis of epilepsy; it can also distinguish focal and generalized neurophysiologic correlates of epilepsy. Furthermore, when paired with video monitoring, EEG can not only define epileptic and nonepileptic events but also aid in localization of seizures in patients with epilepsy. Finally, when history and other imaging modalities are considered with the EEG, the epileptic syndrome can usually be defined and the treatment can be focused. In critically ill patients, continuous EEG monitoring can define subclinical seizures, although a variety of periodic patterns may also be identified.

SUMMARY

EEG is an invaluable tool in the diagnosis and management of a patient with epilepsy, and continuous EEG monitoring is useful in identifying subclinical seizures and nonconvulsive status epilepticus in critically ill patients.

Brain structure and aging in chronic temporal lobe epilepsy

PURPOSE

To characterize differences in brain structure and their patterns of age-related change in individuals with chronic childhood/adolescent onset temporal lobe epilepsy compared with healthy controls.

METHODS

Subjects included participants with chronic temporal lobe epilepsy (n = 55) of mean childhood/adolescent onset and healthy controls (n = 53), age 14-60 years. Brain magnetic resonance imaging (MRI) studies (1.5 T) were processed using FreeSurfer to obtain measures of lobar thickness, area, and volume as well as volumes of diverse subcortical structures and cerebellum. Group differences were explored followed by cross-sectional lifespan modeling as a function of age.

KEY FINDINGS

Anatomic abnormalities were extensive in participants with chronic temporal lobe epilepsy including distributed subcortical structures (hippocampus, thalamus, caudate, and pallidum), cerebellar gray and white matter, total cerebral gray and white matter; and measures of cortical gray matter thickness, area, or volume in temporal (medial, lateral) and extratemporal lobes (frontal, parietal). Increasing chronologic age was associated with progressive changes in diverse cortical, subcortical, and cerebellar regions for both participants with epilepsy and controls. Age-accelerated changes in epilepsy participants were seen in selected areas (third and lateral ventricles), with largely comparable patterns of age-related change across other regions of interest.

SIGNIFICANCE

Extensive cortical, subcortical, and cerebellar abnormalities are present in participants with mean chronic childhood/adolescent onset temporal lobe epilepsy implicating a significant neurodevelopmental impact on brain structure. With increasing chronologic age, the brain changes occurring in epilepsy appear to proceed in a largely age-appropriate fashion compared to healthy controls, the primary exception being age-accelerated ventricular expansion (lateral and third ventricles). These cumulative structural abnormalities appear to represent a significant anatomic burden for persons with epilepsy, the consequences of which remain to be determined as they progress into elder years.

The nature and extent of cerebellar atrophy in chronic temporal lobe epilepsy

PURPOSE

Research indicates that patients with chronic temporal lobe epilepsy (TLE) exhibit cerebellar atrophy compared to healthy controls, but the degree to which specific regions of the cerebellum are affected remains unclear. The purpose of this study was to characterize the extent and lateralization of atrophy in individual cerebellar lobes and subregions in unilateral TLE using advanced quantitative magnetic resonance imaging (MRI) techniques.

METHODS

Study participants were 46 persons with TLE and 31 age- and gender- matched healthy controls. All participants underwent high-resolution MRI with manual tracing of the cerebellum yielding gray and white matter volumes of the right and left anterior lobes, superior posterior lobes, inferior posterior lobes, and corpus medullare. The degree to which asymmetric versus generalized abnormalities was evident in unilateral chronic TLE was determined and related to selected clinical seizure features (age of onset, duration of disorder).

KEY FINDINGS

There were no lateralized abnormalities in cerebellar gray matter or white matter in patients with right or left TLE (all p's > 0.2). Compared with controls, unilateral TLE was associated with significant bilateral reductions in the superior (p = 0.032) and inferior (p = 0.023) posterior lobes, whereas volume was significantly increased in the anterior lobes (p = 0.002), especially in patients with early onset TLE, and not significantly different in the corpus medullare (p = 0.71). Total superior cerebellar tissue volumes were reduced in association with increasing duration of epilepsy.

SIGNIFICANCE

Patients with unilateral TLE exhibit a pattern of bilateral cerebellar pathology characterized by atrophy of the superior and inferior posterior lobes, hypertrophy of the anterior lobe, and no effect on the corpus medullare. Cross-sectional analyses show that specific aspects of cerebellar pathology are associated with neurodevelopmental (anterior lobe) or chronicity-related (superior posterior lobe) features of the disorder.

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.

A controlled prospective investigation of psychiatric comorbidity in temporal lobe epilepsy

Temporal lobe epilepsy patients (n = 48) and healthy controls (n = 69) underwent structured psychiatric interview at baseline and 4 years later to characterize the course of DSM-IV Axis I disorders. Adjusting for the influence of prior psychiatric history, epilepsy subjects exhibit significantly greater risk of interval episodes of Total Axis I Disorders and Mood Disorders, indicating a poorer prognosis for these comorbidities in the context of chronic temporal lobe epilepsy.

Cognitive phenotypes in temporal lobe epilepsy

The objective of this study is to determine if distinct cognitive phenotypes could be identified in temporal lobe epilepsy. Epilepsy patients (n = 96) and healthy controls (n = 82) underwent comprehensive neuropsychological assessment. Adjusted (age, gender, and education) test scores for epilepsy subjects were grouped into cognitive domains (intelligence, language, visuoperception, immediate and delayed memory, executive function, and cognitive/psychomotor speed). Cluster analysis revealed three distinct cognitive profiles types: (1) minimally impaired (47% of subjects); (2) memory impaired (24%); and (3) memory, executive, and speed impaired (29%). The three cluster groups exhibited different patterns of results on demographic, clinical epilepsy, brain volumetrics, and cognitive course over a 4-year interval. The specific profile characteristics of the identified cognitive phenotypes are presented and their implications for the investigation of the neurobehavioral complications of epilepsy are discussed.

Cognitive prognosis in chronic temporal lobe epilepsy

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.

Cerebellar atrophy in temporal lobe epilepsy affects procedural memory

The authors examined a cognitive function mediated by the cerebellum, classical eyeblink conditioning, and its relationship to cerebellar volume in healthy controls (n = 59) and temporal lobe epilepsy subjects (n = 77). Controls demonstrated better conditioning, larger cerebellar volumes, and an association between conditioning and cerebellar volume that was not observed in epilepsy patients. These findings provide support for the hypothesis that cerebellar atrophy in epilepsy affects procedural memory.

Ipsilateral and Contralateral MRI Volumetric Abnormalities in Chronic Unilateral Temporal Lobe Epilepsy and their Clinical Correlates

PURPOSE

To assess the presence, extent, and clinical correlates of quantitative MR volumetric abnormalities in ipsilateral and contralateral hippocampus, and temporal and extratemporal lobe regions in unilateral temporal lobe epilepsy (TLE).

METHODS

In total, 34 subjects with unilateral left (n = 15) or right (n = 19) TLE were compared with 65 healthy controls. Regions of interest included the ipsilateral and contralateral hippocampus as well as temporal, frontal, parietal, and occipital lobe gray and white matter. Clinical markers of neurodevelopmental insult (initial precipitating insult, early age of recurrent seizures) and chronicity of epilepsy (epilepsy duration, estimated number of lifetime generalized seizures) were related to magnetic resonance (MR) volume abnormalities.

RESULTS

Quantitative MR abnormalities extend beyond the ipsilateral hippocampus and temporal lobe with extratemporal (frontal and parietal lobe) reductions in cerebral white matter, especially ipsilateral but also contralateral to the side of seizure onset. Volumetric abnormalities in ipsilateral hippocampus and bilateral cerebral white matter are associated with factors related to both the onset and the chronicity of the patients' epilepsy.

CONCLUSIONS

These cross-sectional findings support the view that volumetric abnormalities in chronic TLE are associated with a combination of neurodevelopmental and progressive effects, characterized by a prominent disruption in ipsilateral hippocampus and neural connectivity (i.e., white matter volume loss) that extends beyond the temporal lobe, affecting both ipsilateral and contralateral hemispheres.

The nature and course of neuropsychological morbidity in chronic temporal lobe epilepsy

OBJECTIVE

To characterize the nature and degree of cognitive morbidity in patients with chronic temporal lobe epilepsy compared with healthy control subjects, determine the association between the duration of epilepsy and cognitive morbidity, and ascertain whether there are factors that moderate the association between duration of disorder and cognitive impairment.

METHODS

Temporal lobe epilepsy (n = 96) and healthy control (n = 82) subjects were assessed with a comprehensive neuropsychological battery. Test performances were adjusted for age, gender, and education and transformed to a common metric (z scores). Analyses included group comparisons and correlations of duration of epilepsy with cognitive morbidity.

RESULTS

Patients with temporal lobe epilepsy exhibited not only worse memory function (p < 0.05) but worse performance across measures of intelligence, language, executive function, and motor speed (p < 0.05). Chronicity of epilepsy was related to worsening mental status (r = 0.42, p < 0.001). This relationship was particularly evident among those individuals with less (r = 0.58, p < 0.001) compared with more (r = 0.25, NS) cerebral reserve, operationally defined by years of formal education.

CONCLUSIONS

Neuropsychological morbidity in chronic temporal lobe epilepsy is widespread in nature despite a focal epileptic process. Cross-sectional analyses demonstrate that increasing duration of epilepsy is associated with worsening mental status. Individuals with less educational attainment (low cerebral reserve) exhibit especially poor cognitive function in association with chronicity of epilepsy.

Epilepsy surgery outcome among US veterans

We retrospectively studied the outcome of anterior temporal lobectomy (ATL) among a population of veterans and evaluated outcome related to comorbidities. Veterans who underwent ATL between 1990 and 2001 at the Veterans Administration Hospital in Madison, Wisconsin, were included. Data related to postoperative seizure outcome, quality of life outcome, and employment outcome were collected. Factors associated with favorable outcome and outcome related to comorbidities were evaluated. Twenty-seven patients were entered into the study. The mean age at onset of seizures was 25 years (+/-10.2). History of a non-substance abuse psychiatric diagnosis, and substance abuse was present in 26% (7/27) and 30% (9/27), respectively, prior to surgery. While 66.6% (18/27) had a good outcome (Engel's Class I), no difference in the frequency of good outcome was seen among the patients with a history of substance abuse, other psychiatric diagnosis (71%), or no psychiatric diagnosis (67%). There was a significant correlation between seizure outcome and quality of life score (r(s)=0.67, p<0.001) and postoperative employment gains (r(s)=0.48, p=0.01). Outcomes among veterans that underwent ATL can be satisfactory even in the context of the late mean age of epilepsy onset and the psychiatric diagnoses that were present in this sample.

Spontaneous seizures and loss of axo-axonic and axo-somatic inhibition induced by repeated brief seizures in kindled rats

Repeated brief seizures evoked by kindling progressively increase seizure susceptibility and eventually induce spontaneous seizures. Previous studies have demonstrated that the initial seizures evoked by kindling increase paired-pulse inhibition at 15-25 msec interpulse intervals in the dentate gyrus and also induce apoptosis, progressive neuronal loss, mossy fiber sprouting, and neurogenesis, which could potentially alter the balance of excitation and/or inhibition and modify functional properties of hippocampal circuits. In these experiments, paired-pulse inhibition in the dentate gyrus was reduced or lost after approximately 90-100 evoked seizures in association with emergence of spontaneous seizures. Evoked IPSCs examined by single electrode voltage-clamp methods in granule cells from kindled rats experiencing spontaneous seizures demonstrated altered kinetics (reductions of approximately 48% in 10-90% decay time, approximately 40% in tau, and approximately 65% in charge transfer) and confirmed that decreased inhibition contributed to the reduced paired-pulse inhibition. The loss of inhibition was accompanied by loss of subclasses of inhibitory interneurons labeled by cholecystokinin and the neuronal GABA transporter GAT-1, which project axo-somatic and axo-axonic GABAergic inhibitory terminals to granule cells and axon initial segments. Seizure-induced loss of interneurons providing axo-somatic and axo-axonic inhibition may regulate spike output to pyramidal neurons in CA3 and could play an important role in generation of spontaneous seizures. The sequence of progressive cellular alterations induced by repeated seizures, particularly loss of GABAergic interneurons providing axo-somatic and axo-axonic inhibition, may be important in the development of intractable epilepsy.

Extratemporal quantitative MR volumetrics and neuropsychological status in temporal lobe epilepsy

Neuropsychological studies of temporal lobe epilepsy have focused heavily on the nature and extent of memory dysfunction and its relationship to the neuropathological status of the hippocampus and related mesial temporal lobe structures. In this study, we examined whole brain and lobar quantitative MRI volumes and comprehensive neuropsychological performance in 58 patients with temporal lobe epilepsy and 62 healthy controls in order to determine (1) the nature and degree of extratemporal structural abnormalities in localization-related temporal lobe epilepsy: (2) the nature and degree of cognitive abnormalities outside of anterograde memory function; and (3) the relationship of volumetric abnormalities to neuropsychological status. Temporal lobe epilepsy patients exhibited significant reduction in the volume of adjusted (age, gender, height) total cerebral tissue (-5.8%), more evident in white (-9.8%) compared to gray matter (-3.0%) tissue volumes. Significant volumetric reductions were evident across frontal, temporal and parietal but not occipital lobe regions. Subarachnoid but not total ventricular CSF was significantly increased in epilepsy patients. Neuropsychological abnormality was generalized in nature, consistent with the generalized nature of the morphometric abnormalities, and reductions in cerebral tissue volumes were directly associated with poorer cognitive performance. In summary, patients with temporal lobe epilepsy exhibited clinically significant structural and functional abnormalities that extended outside the epileptogenic temporal lobe. The degree to which these structural and cognitive abnormalities are due to factors that cause the epilepsy, as opposed to reflecting the consequences of chronic epilepsy (e.g., duration and severity of epilepsy), remain to be determined.

The neurodevelopmental impact of childhood-onset temporal lobe epilepsy on brain structure and function

PURPOSE

To characterize the neurodevelopmental correlates of childhood-onset temporal lobe epilepsy on brain structure and cognition compared with late-onset chronic temporal lobe epilepsy and healthy controls.

METHODS

Healthy controls (n = 62) and patients with early (n = 37) versus late (n = 16) age at onset of temporal lobe epilepsy were compared with high-resolution quantitative magnetic resonance imaging (MRI) volumetrics and comprehensive neuropsychological assessment.

RESULTS

Patients with childhood-onset temporal lobe epilepsy (mean onset age, 7.8 years) exhibited widespread compromise in neuropsychological performance and substantial reduction in brain tissue volumes extending to extratemporal regions compared with healthy controls and late-onset temporal lobe epilepsy patients (mean onset age, 23.3 years). Most evident was reduced total white-matter volume among the childhood-onset patients. Reduction in brain tissue volume, especially total white-matter volume, was associated with significantly poorer cognitive status, attesting to the clinical significance of the volumetric abnormalities.

CONCLUSIONS

Childhood-onset temporal lobe epilepsy appears to be associated with an adverse neurodevelopmental impact on brain structure and cognition that appears generalized in nature and especially evident in white-matter tissue volume.

Concomitant use of divalproex sodium and lamotrigine in developmentally disabled patients with epilepsy: a retrospective evaluation of efficacy and tolerability

Objective. Epilepsy in institutionalized severe developmentally disabled patients poses a therapeutic challenge. Frequently these patients have multiple seizure (sz) types that are often intractable. Both divalproex sodium (VPA) and lamotrigine (LTG) have demonstrated efficacy. We sought to examine the efficacy of this specific combination in a group of institutionalized, developmentally disabled patients with epilepsy.Methods. Medical and pharmacy records of all patients with developmental disabilities and intractable seizures were reviewed to identify those who had received VPA and LTG. This retrospective evaluation was structured with respect to time frame and outcome measure. Phase 1 consisted of baseline monotherapy with VPA. Phase 2 consisted of titration/dose escalation. Phase 3 was treatment observation period with the combination of both. Seizure frequency and adverse effect data were obtained from nursing or residential staff records. Primary outcome measures were change in seizure frequency between Phases 1 and 3. Additional measures were percentage of patients seizure-free and those with >75% reduction in seizures. A Wilcoxan signed rank test was used for statistical analysis.Results. Of 293 patients, 25 (12M/13F, 31.7+/-10.2 years) had VPA monotherapy following which LTG was added. Mean doses of VPA and LTG were 1474+/-728 and 165+/-111mg/day, respectively. Baseline seizure frequency ranged from 1 to 25 per month. Mean seizure frequency significantly decreased (6.5+/-vs2.0+/-4.0seizures/month, P<0.001). Sixty-four percent of these patients had >/=75% reduction in seizures 28% became seizure-free.Conclusions. The combination of VPA and LTG appears efficacious in this group of developmentally disabled patients with intractable seizures. Rash, which has been associated with this combination, was notably absent and this may reflect the slower titration schedule used.

Ipsilateral Reorganization of Language in Early-Onset Left Temporal Lobe Epilepsy

Purpose. Decline in confrontation naming ability occurs in a subset of temporal lobe epilepsy (TLE) patients following left (dominant) anterior temporal lobectomy (ATL). Patients with late age of onset of seizures are most vulnerable to such decline. In addition, object names typically acquired later in language development are the words most likely to be inaccessible after ATL. Early-onset left TLE patients may be at lower risk for post-ATL dysnomia either because they have a limited preoperative lexicon that does not include most late-age-of-acquistion names or they undergo early ipsilateral language reorganization, which results in a lexicon similar to that of late-onset TLE patients but offers protection from post-ATL naming decline.Methods. Sixty-five left hemisphere speech dominant left TLE patients who had undergone ATL were assessed pre- and postoperatively on the Boston Naming Test (BNT).Results. The early- and late-onset groups performed similarly across three BNT age-of-acquisition categories at the preoperative assessment. Words acquired relatively later in life were most likely to become inaccessible postoperatively for both groups, but the early-onset patients showed significantly less overall postoperative decline in naming ability compared with the late-onset group.Conclusions. The more stable pre- to postoperative naming performance exhibited by early-onset patients cannot be attributed to lack of acquisition of the words shown to be most vulnerable to postoperative decline (i.e., late-age-of-acquisition words). Their object naming stability suggests that early-onset left TLE patients undergo intrahemispheric reorganization of language early in life that provides protective benefits.

Negative symptoms in temporal lobe epilepsy

OBJECTIVE

This study examined the frequency of negative and positive symptoms in nonpsychotic patients with temporal lobe epilepsy and the relationship of negative and positive symptoms to cognition, quantitative magnetic resonance imaging (MRI) volumetrics, and depression.

METHOD

Eighty-four patients with temporal lobe epilepsy and 74 healthy comparison subjects were evaluated for negative and positive symptoms and underwent comprehensive neuropsychological evaluation, quantitative MRI volumetrics, and assessment of mood state and depression.

RESULTS

Negative symptoms were significantly more prevalent in the patients with temporal lobe epilepsy (31%) than in the comparison subjects (8%). There was no difference between groups in the rate of positive symptoms. Although the epilepsy patients as a group exhibited generalized cognitive impairment relative to the comparison subjects, the epilepsy patients with negative symptoms performed significantly worse than patients without negative symptoms and comparison subjects across measures of nonverbal intelligence, visuoperception, speeded visuomotor processing, and memory. The epilepsy patients with negative symptoms exhibited significantly greater diffuse atrophy than the healthy comparison subjects and higher CSF volumes than the epilepsy patients without negative symptoms. The epilepsy patients with and without negative symptoms had statistically equivalent Beck Depression Inventory scores and lifetime history of mood disorders, including major depression.

CONCLUSIONS

Negative but not positive symptoms were more prevalent in temporal lobe epilepsy patients than in healthy comparison subjects. Negative symptoms were independent of current and past depression and were associated with neuropsychological deficits exceeding the general cognitive morbidity associated with temporal lobe epilepsy and with quantitative MRI indices suggesting greater cerebral atrophy.

A protocol for status epilepticus in a long-term care facility using rectal diazepam (Diastat)

INTRODUCTION

A growing population of residents in long-term care facilities (LTCF) is likely to present with status epilepticus (SE), which requires rapid treatment to avoid permanent neuronal damage, associated morbidity, and mortality. The treatment of choice for SE is an intravenous benzodiazepine; however, this is not feasible in most LTCFs because of the training level of the personnel and the risk of respiratory depression. Transport to acute care facilities is often delayed and, in addition, many LTCF residents have "do not hospitalize" orders. As an alternative to an intravenous benzodiazepine, rectal delivery of diazepam has been shown to be effective in stopping prolonged seizures and is more easily accomplished in the LTCF setting.

METHODS

The Badger Prairie Health Care Center (BPHCC), a 132-bed LTCF in Verona, WI, developed a protocol for SE that uses a rectal diazepam gel preparation (Diastat) when intravenous access is unavailable. The protocol provides for initiation of long-term anticonvulsant therapy as a follow-up to the acute treatment of SE.

RESULTS

BPHCC staff successfully employed the protocol eight times from August 1999 to November 2000; this article describes the protocol and three representative cases.

Inter- and intra-subject variability in gabapentin absorption and absolute bioavailability

Gabapentin (GBP) is a non-metabolized, non-plasma protein bound, renally excreted antiepileptic drug that is actively absorbed via the system L amino acid transporter. Previous studies have demonstrated that gabapentin displays dose-dependent absorption.

OBJECTIVES

These studies were conducted to determine inter- and intra-subject variability of gabapentin absorption. Two prospective clinical studies in healthy adult volunteers were conducted. Coefficient of variation (CV) was used to express variability of gabapentin absorption.

METHODS

Study A: 400-mg single dose, randomized, cross-over study to assess bioavailability of four different gabapentin formulations (n=20, 9 males, 11 females; mean age and weight 41 years, 75.1 kg). Plasma was serially collected up to 48 h and bioavailability (F) calculated post-dose to determine concentration-time curves (AUC). All four formulations were bioequivalent, thus repeated measures analysis was performed to assess inter-and intra-subject variability. Study B: 600-mg single dose study (n=50, 15 males, 35 females; mean age and weight 31.1 years, 72.7 kg) was conducted to determine inter-subject variability in gabapentin F. Urine was collected over 48 h and bioavailability (F) calculated. Urine and plasma gabapentin concentrations were measured by HPLC-UV.

RESULTS

Study A: Overall mean (CV) of GBP AUC values was 34.1+/-24 ug/h per ml. Inter-subject CV for AUC was 22.5% and intra-subject CV was 12.1%. Study B: Overall mean (SD) GBP F was 49.3+/-13.6%. Inter-subject CV of F was 27.6%.

DISCUSSION

The inter-subject variability in gabapentin absorption is substantially less than that of the inter-subject variability. This indicates that one would expect a wide range in gabapentin absorption between subjects; however, a much smaller variability within a subject. The within subject variability of gabapentin is small enough that plasma drug monitoring may be used to assess gabapentin absorption for a given subject and the benefit of dose individualization.

Comorbid psychiatric symptoms in temporal lobe epilepsy: association with chronicity of epilepsy and impact on quality of life

Purpose. The goals of this work were to determine: (1) the nature and extent of differences in self-reported psychiatric symptoms between patients with temporal lobe epilepsy and matched healthy controls, (2) the relationship between chronicity (duration) of temporal lobe epilepsy and comorbid interictal psychiatric symptoms, and (3) the impact of comorbid psychiatric symptoms on self-reported health-related quality of life. Methods. Patients with temporal lobe epilepsy (n = 54) and healthy controls (n = 38) were administered the Symptom Checklist-90-Revised (SCL-90-R) to assess the nature and severity of psychiatric symptomatology and epilepsy patients completed the Quality of Life in Epilepsy-89 (QOLIE-89) to define health-related quality of life. Among epilepsy patients the SCL-90-R scales were examined in relation to chronicity of temporal lobe epilepsy as well as the impact of comorbid emotional-behavioral distress on health-related quality of life. Results. Compared with healthy controls, patients with epilepsy exhibited significantly higher (worse) scores across all but one of the 12 SCL-90-R scales. Among patients with epilepsy, increasing chronicity was associated with significantly higher (worse) scores across all SCL-90-R scales and increased emotional-behavioral distress was associated with lower (worse) scores across all 17 QOLIE-89 scales. Conclusion. Comorbid interictal psychiatric symptoms are elevated among patients with temporal lobe epilepsy compared with healthy controls and appear to be modestly associated with increasing chronicity (duration) of epilepsy. This comorbid emotional-behavioral distress is specifically associated with a significantly poorer health-related quality of life, and suggests that quality-of-life research should devote greater attention to the potential impact of comorbid psychiatric distress.

Efficacy of lamotrigine in institutionalized, developmentally disabled patients with epilepsy: a retrospective evaluation

The paper evaluates the efficacy of the newer anticonvulsant lamotrigine in a developmentally disabled patient population. A retrospective evaluation was done at two institutional centres to assess adjunctive lamotrigine (Lamictal) efficacy in a developmentally disabled population. Mean seizure frequency was compared between a 2-month pre-lamotrigine baseline period and a 2-month treatment period. A 3-month lamotrigine titration phase occurred between baseline and treatment periods. Seizure frequency data was obtained from standardized, daily seizure records. Adverse effect data was obtained from medical and nursing notes. An intent to treat analysis was performed. Data were analysed using Student's t-test for paired data. We evaluated 44 centre residents (25 male, 19 female, average age 33 +/- 11 years). Mean lamotrigine dose was 272 +/- 133 mg per day. A significant reduction in seizure frequency was noted. Seizure frequency (all seizures) was 10.1 +/- 11.2 during the baseline period vs. 5.8 +/- 7.9 seizures per month during the treatment period (P = 0.002). Thirty-two percent of patients (n = 14) had greater than a 75% reduction in seizure frequency. Twenty-three percent of patients (n = 10) had a 50-74% seizure reduction. Twenty-five percent of patients (n = 11) had less than a 50% reduction in seizures, while 20% (n = 9) had an increase in seizures. A significant reduction of 48% in generalized seizures (9.5 +/- 11.6 vs. 4.9 +/- 6.5 seizures per month, P = 0.013) was noted. Reductions in partial seizure frequency of 48% (7.9 +/- 10 vs. 4 +/- 6.6 seizures per month, P = 0.16) as well as in mixed-type seizures (19.9 +/- 9.3 was vs. 15 +/- 12.1 seizures per month, P = 0.11) were also seen; however, these changes did not reach significance. Overall, lamotrigine was well tolerated by the subject population. Adjunctive treatment with lamotrigine appears to be an efficacious and well-tolerated treatment for seizures in a significant percentage of developmentally disabled patients with epilepsy.

A 13-year-old with an acute change in mental status

A 13-year-old boy with Lennox-Gastaut syndrome characterized by absence, myoclonic, complex-partial, and secondarily generalized tonic-clonic seizures, presents with progressive obtundation and loss of motor and verbal skills over a 2-day period. Initial evaluation revealed therapeutic phenytoin serum concentrations. This article discusses the differential diagnosis and management approach used in this setting, as well as the appropriate interpretation of antiepileptic drug serum concentrations.

NMDA-dependent currents in granule cells of the dentate gyrus contribute to induction but not permanence of kindling

Single-electrode voltage-clamp techniques and bath application of the N-methyl-D-aspartate (NMDA) receptor antagonist 2-amino-5-phosphonovaleric acid (APV) were used to study the time course of seizure-induced alterations in NMDA-dependent synaptic currents in granule cells of the dentate gyrus in hippocampal slices from kindled and normal rats. In agreement with previous studies, granule cells from kindled rats examined within 1 wk after the last of 3 or 30-35 generalized tonic-clonic (class V) seizures demonstrated an increase in the NMDA receptor-dependent component of the perforant path-evoked synaptic current. Within 1 wk of the last kindled seizure, NMDA-dependent charge transfer underlying the perforant path-evoked current was increased by 63-111% at a holding potential of -30 mV. In contrast, the NMDA-dependent component of the perforant-evoked current in granule cells examined at 2.5-3 mo after the last of 3 or 90-120 class V seizures did not differ from age-matched controls. Because the seizure-induced increases in NMDA-dependent synaptic currents declined toward control values during a time course of 2.5-3 mo, increases in NMDA-dependent synaptic transmission cannot account for the permanent susceptibility to evoked and spontaneous seizures induced by kindling. The increase in NMDA receptor-dependent transmission was associated with the induction of kindling but was not responsible for the maintenance of the kindled state. The time course of alterations in NMDA-dependent synaptic current and the dependence of the progression of kindling and kindling-induced mossy fiber sprouting on repeated NMDA receptor activation are consistent with the possibility that the NMDA receptor is part of a transmembrane signaling pathway that induces long-term cellular alterations and circuit remodeling in response to repeated seizures, but is not required for permanent seizure susceptibility in circuitry altered by kindling.

Gabapentin bioavailability: effect of dose and frequency of administration in adult patients with epilepsy

Gabapentin (GBP) is a non-metabolized antiepileptic drug that is eliminated by renal excretion and displays saturable, dose dependent absorption. The recommended dosing schedule for GBP is t.i.d. At large daily doses, oral bioavailability (F) may be improved by giving the daily dose more frequently.

OBJECTIVE

To evaluate whether switching GBP dosage regimen from t.i.d. to q.i.d. results in increased oral bioavailability.

METHODS

This study consisted of two parts; a computer simulated pharmacokinetic model and a clinical pharmacokinetic study in nine adult epileptic patients receiving 3600 mg/day and 11 receiving 4800 mg/day. All patients were evaluated during both t.i.d. and q.i.d. regimens. F were determined by calculation of percent of dose excreted unchanged using steady-state 24-h urine collections and were compared using a paired t-test.

RESULTS

At 3600 mg/day, mean F following t.i.d. and q.i.d. dosing were 38.7+/-22.1% and 40.0+/-18.9%, respectively (P=0.738). At 4800 mg/day, mean F following t.i.d. and q.i.d. dosing were 29.2+/-16.2% and 35.6+/-17.6%, respectively (P=0.006).

DISCUSSION

Good agreement was observed between values from this study and predicted values based on the pharmacokinetic model. Improved GBP F at doses of 3600 mg/day was not achieved with more frequent drug administration, and thus is not warranted. At 4800 mg/day, a 22% increase in F was observed with more frequent drug dosing.

CONCLUSION

GBP F may be significantly increased by q.i.d. versus t.i.d. dosing, depending upon dose level. This increase in F however must be balanced against the inconvenience of more frequent dosing. Therapeutic drug level monitoring may aid in the evaluation of such pharmacokinetic maneuvers.

Effect of lamotrigine on carbamazepine epoxide/carbamazepine serum concentration ratios in adult patients with epilepsy

Although lamotrigine (LTG) appears to have a low propensity to cause pharmacokinetic interactions with other medications, it has been suggested that LTG may interfere with the elimination of carbamazepine 10,11-epoxide (CBZE), the active metabolite of carbamazepine (CBZ). Evidence for this pharmacokinetic interaction is inconclusive and conflicting, however. We evaluated CBZ apparent oral clearance and the steady-state CBZE/CBZ serum concentration ratios in nine patients (30.8 +/- 7.7 years) with epilepsy prior to and following the initiation of adjunctive treatment with LTG. Overall, CBZ oral clearance was unchanged following the introduction of LTG (5.58 +/- 1.60 vs. 5.81 +/- 1.74 1/h, P = 0.630). Likewise, CBZE to CBZ serum concentration ratios were not significantly different (0.241 +/- 0.082 vs. 0.232 +/- 0.082, P = 0.782). These observations suggest that the addition of LTG did not result in a significant pharmacokinetic interaction involving either CBZ or CBZE.

Lamotrigine pharmacokinetics in patients receiving felbamate

Drug interactions can significantly complicate the management of patients receiving multiple medications. It is essential therefore that potential pharmcokinetic interactions be evaluated as new antiepileptic medications are introduced. Lamotrigine (LTG) is a recently marketed medication whose pharmacokinetics are significantly influenced by concomitant drugs. Felbamate (FBM), another relatively new antiepileptic agent has been associated with multiple interactions including both enzyme induction and inhibition. The purpose of the present pilot study was to evaluate potential differences in lamotrigine kinetics in six patients concomitantly receiving FBM compared to five patients receiving lamotrigine as monotherapy. There was no statistically significant differences in either apparent LTG oral clearance (0.026 +/- 0.005 vs. 0.024 +/- 0.01 l/kg per h, respectively), or in mean elimination half-life (33.7 +/- 7.5 vs. 40.2 +/- 15.05 h, respectively). Oral clearance values in our patients are also consistent with data reported previously in the literature. Data from this pilot study suggest that a marked effect of FBM upon lamotrigine pharmacokinetics is unlikely.

Clinical features of Todd's post-epileptic paralysis

Two hundred and twenty nine patients with generalised tonic-clonic seizures were prospectively evaluated. Fourteen were identified who had transient focal neurological deficits thought to be Todd's post-epileptic paralysis (PEP). Eight of these 14 patients had underlying focal brain lesions associated with the postictal deficits. All patients with PEP were weak, but there was wide variation in the pattern (any combination of face, arm, leg), severity (plegia to mild), tone (spastic, flaccid, or normal), and reflexes (increased, decreased, or normal). Significant sensory loss occurred in only one patient. The only other signs of PEP were aphasia (in five patients all with underlying lesions) and gaze palsy (in four patients). Post-epileptic paralysis persisted from half an hour to 36 hours (mean of 15 hours). Post-epileptic paralysis may occur with the first seizure or after many years of seizures and does not appear after every seizure. The clinical features of PEP are thus heterogeneous.

Anatomical, physiological, and theoretical basis for the antiepileptic effect of vagus nerve stimulation

The vagus is a mixed nerve carrying somatic and visceral afferents and efferents. The majority of vagal nerve fibers are visceral afferents and have a wide distribution throughout the central nervous system (CNS) either monosynaptically or via the nucleus of the solitary tract. Besides activation of well-defined reflexes, vagal stimulation produces evoked potentials recorded from the cerebral cortex, the hippocampus, the thalamus, and the cerebellum. Activation of vagal afferents can depress monosynaptic reflexes, decrease the activity of spinothalamic neurons, and increase pain threshold. Depending on the stimulation parameters, vagal afferent stimulation in experimental animals can produce electroencephalographic (EEG) synchronization or desynchronization and has been shown to affect sleep states. The desychronization of the EEG appears to depend on activation of afferent fibers that have conduction velocities of less than or equal to 15 m/s. Vagal afferent stimulation can also influence the activity of interictal cortical spikes produced by topical strychnine application, and either attenuate or stop seizures produced by pentylenetetrazol, 3-mercaptoproprionic acid, maximal electroshock, and topical alumina gel. The mechanisms for the antiepileptic effects of vagal stimulation are not fully understood but probably relate to effects on the reticular activating system. The vagus provides an easily accessible, peripheral route to modulate CNS function.