Cardiac effects of seizures

Seizures frequently affect the heart rate and rhythm. In most cases, seizure-related cardiac changes are transient and do not appear to cause clinically significant abnormalities for the patient. Great interest in this area of research has been generated because of a possible connection with sudden unexpected death in epilepsy (SUDEP). While there are clear, but rare complications from seizure-related cardiac arrhythmias, such as ictal asystole that causes syncope, the overall risk of seizures on cardiac status and any potential connection between seizures and SUDEP still remain uncertain.

Genomic drift and copy number variation of chemosensory receptor genes in humans and mice

Recent studies about the structural variation of genomic sequences have shown that there is a large amount of copy number variations (CNVs) of genes within species. Analyzing Redon et al.'s (2006) crude data on copy number variable regions (CNVRs), we previously showed that CNVs are particularly high for chemosensory receptor genes in human populations. In this paper, we reanalyzed the CNVs of these genes using more refined data by Perry et al. (2008). The results showed that the extent of CNVs is somewhat lower in this dataset than in the previous one, but that the extent is still substantial for olfactory receptor (OR), vomeronasal receptor (VR), and taste receptor (TR) genes. We also studied the CNVs for chemosensory receptor genes in mice, using CNVR data obtained from inbred strains. It was found that the extent of CNVs is quite substantial but is lower than that for human populations. However, because the mouse data came from inbred strains and might be biased, this conclusion should be regarded as tentative. Despite this reservation, the distribution of gene copy number for the OR gene family was approximately normal in both humans and mice, suggesting that genomic drift caused by random duplication and deletion of genes plays important roles in determining the evolutionary change of chemosensation.

Characteristics and clinical significance of subclinical seizures

PURPOSE

To define characteristics of subclinical seizures (SCS) and their prognostic significance after epilepsy surgery.

METHODS

Reports from intracranial video-EEG monitoring were reviewed for patients who had epilepsy surgery between 1989 and 2003. Relationships between SCS and clinical seizures were categorized as either: complete colocalization (Group A), when both SCS and clinical seizures originated from the same single focus, or incomplete and no colocalization (Group B), when some or all SCS and clinical seizures originated from different foci in different lobes or hemispheres.

RESULTS

A total of 111 patients were included in this review. Seventy-one (64%) patients had 2,821 SCS and most SCS came from the mesial temporal lobe. The mean duration of SCS was shorter than complex partial seizures and generalized tonic-clonic seizures but similar to simple partial seizures. SCS rarely propagated beyond the site of origin and the majority of SCS had the same area of origin as clinical seizures. Sixty-five patients had both SCS and clinical seizures and underwent resective surgery. Group A patients had a higher seizure-free outcome rate (77.5%) than Group B patients (37.5%). The colocalization rate of SCS and clinical seizures may impact seizure-free outcome. The presence or absence of SCS, SCS duration, and extent of propagation of SCS did not influence surgical outcome.

CONCLUSION

SCS commonly originate from the same cortical area as clinical seizures and are related to postsurgical outcome. These findings suggest they should be viewed as having similar significance in the surgical decision process as clinical seizures.

Seizure-related injury and death

Epilepsy is associated with significantly increased morbidity and mortality from a variety of causes. Patients with epilepsy have approximately two to three times the risk of death from any cause compared with persons without epilepsy. Seizures may cause significant trauma, drowning, and accidental injury. Many of the deaths in persons with epilepsy are directly related to seizures, accidents and injuries arising from seizures, and the underlying condition resulting in seizures. This review focuses on recent data regarding seizure-related injury and mortality.

Corpus callosotomy in refractory idiopathic generalized epilepsy

RATIONALE

A small percentage of patients with idiopathic generalized epilepsy (IGE) do not respond to medical therapy. Generalized tonic-clonic (GTC) seizures are especially debilitating and can be associated with severe injuries. The benefit, safety and effect of corpus callosotomy (CC) in patients with IGE have not been studied.

METHODS

We reviewed patients with presumed IGE who underwent CC between 1991 and 2000. Criteria for selection included history, examination, brain imagining, interictal and ictal EEG. All patients had refractory and debilitating tonic-clonic seizures (GTCS) and had failed four or more antiepileptic drugs. Seizure frequency was calculated per month over the last year and pre-operative baseline was compared to last follow-up using paired t-tests. IQ, executive function, language and verbal, non-verbal memory and quality of life (QOL) was compared before and after surgery. Serial EEGs after surgery were reviewed.

RESULTS

There were nine patients (seven men), mean age 37.9 (range: 22-49), mean IQ 87.3 (range: 75-107). All had anterior CC. Mean follow-up time was 5.4 years (range: 0.6-10.3 years). One patient died from sudden death in epilepsy 9 months after surgery. There was a significant reduction of GTC seizures from 6.3 to 1.1 (p<0.005). Four patients had more than 80% and eight more than 50% reduction. Of five patients with absence seizures, two became seizure free and one had more than 80% reduction and two worsened slightly, and of three with myoclonic seizures one had more than 90% reduction. One patient had completion of the CC with improvement of myoclonus and absence seizures, but not of GTC seizures and suffered a disconnection syndrome. Another had right frontal focal resection without improvement after new seizures of focal onset. Cognitive testing showed a good outcome (improved or no change) in all cognitive domains. Post-surgical EEG showed new focal slowing and sharp waves. There was no change in QOL.

CONCLUSION

CC can be effective in reducing GTC, absence and myoclonic seizures in patients with refractory IGE. These findings suggest that interhemispheric communication of the cerebral cortices plays an important role in the generation of seizures in IGE. Anterior CC appears safe while complete callosotomy has a risk of disconnection syndrome.

Temozolomide Treatment of Refractory Epilepsy in a Patient with an Oligodendroglioma

A 40-year-old man with a left frontotemporal grade II oligodendroglioma developed seizures that were refractory to 14 antiepileptic medications, the ketogenic diet, and epilepsy surgery. With temozolomide therapy, his seizure frequency gradually changed from 30 partial seizures per day to a single simple partial seizure in 6 months. No additional therapeutic measures were introduced during this time. This reduction in seizure frequency appears attributable solely to temozolomide therapy.

Refractory generalized seizures: response to corpus callosotomy and vagal nerve stimulation

PURPOSE

The vagal nerve stimulator (VNS) and corpus callosotomy can reduce seizure frequency when seizures are refractory to medications. However, the efficacy and safety of these two procedures have not been compared. This study evaluates the two procedures for generalized seizures.

METHODS

All patients with refractory generalized seizures (generalized tonic-clonic, tonic, or atonic) who underwent a corpus callosotomy (anterior or complete) (n = 53) without other forms of epilepsy surgery and those who underwent VNS placement (n = 25) were evaluated for this study. Seizure response and procedure complications were evaluated.

RESULTS

For those with a corpus callosotomy and generalized tonic-clonic seizures (n = 50), 79.5% had >or=50% decrease in the frequency of generalized tonic-clonic seizures, and 60% had >or=80% seizure reduction. For those with a VNS and generalized tonic-clonic seizures (n = 21), 50% had >or=50% seizure reduction, and 33% had >or=80% seizure reduction. Tonic and atonic seizures decreased after either VNS or a corpus callosotomy. The complication rate for corpus callosotomy was higher (21% all complications, 3.8% permanent) than that for VNS (8%; none permanent), but complications for both corpus callosotomy and VNS were rarely permanent.

CONCLUSIONS

Both corpus callosotomy and VNS are effective in reducing generalized seizures. Corpus callosotomy is associated with greater efficacy but higher risk for complications, although these were generally transient.

Generalized tonic-clonic seizures detected by implantable loop recorder devices: diagnosing more than cardiac arrhythmias

BACKGROUND

Both syncope and seizures are important causes of recurrent, unexplained episodes of loss of consciousness. Implantable loop recorders have identified serious arrhythmias in patients with repeated syncope; however, implantable loop recorder detection of seizures is less well established.

OBJECTIVES

The purpose of this study was to provide in-depth analysis of a characteristic myopotential pattern recorded by implantable loop recorders during generalized tonic-clonic seizures.

METHODS

Fourteen patients with refractory, video-EEG-documented epilepsy (complex partial, atonic, tonic, or generalized tonic-clonic seizures) underwent implantable loop recorder placement as part of a study protocol evaluating cardiac rhythm abnormalities in patients at high risk for sudden unexpected death in epilepsy.

RESULTS

Twelve generalized tonic-clonic seizure episodes were detected by the implantable loop recorder in six patients. Implantable loop recorder and EEG recordings of generalized tonic-clonic seizures were identical and revealed a tonic phase (sustained, rapid, high-frequency myopotentials) transitioning to a clonic phase (periodic bursts of high-frequency myopotentials with a decelerating burst frequency from 3-6 Hz to 1-2 Hz) prior to seizure termination. With the nonprogrammable bandpass filter of 0.85 to 32 Hz in the implantable loop recorder, all generalized tonic-clonic seizure episodes had escaped automatic detection and required activation by family members. None of the 76 nongeneralized tonic-clonic seizure episodes recorded on the implantable loop recorder in the 14 patients exhibited the stereotypical tonic-clonic pattern that defines generalized seizures.

CONCLUSION

Recognizing this specific myopotential pattern on an implantable loop recorder might help diagnose generalized tonic-clonic seizures as a cause of recurrent, unexplained episodes of loss of consciousness. Having a programmable bandpass filter in the implantable loop recorder might increase its diagnostic yield for such patients.

Value of non-invasive testing when there are independent bitemporal seizures in the scalp EEG

We investigated the value of non-invasive data for predicting the outcome of intracranial EEG and anterior temporal lobectomy (ATL) (follow-up>1 year) in patients who have bitemporal independent seizures in the scalp EEG. No previous report has dealt with this patient group. Independent variables were duration of epilepsy, febrile seizures, interictal and ictal scalp EEG, ictal behavior, MRI, [18F]-fluorodeoxyglucose-PET (PET) and Wada test and dependent variables were surgical outcome (seizure free or not) and localized on intracranial EEG (finding all symptomatic seizures from one temporal lobe). Non-parametric statistics were used. Of 24 patients, 20 patients had IEEG, of which 12 were localized and 8 were not. Sixteen patients had ATL and, of these, 13 (81%) became seizure free and the remaining three improved. Lateralized findings on MRI and PET, a history of febrile convulsions and shorter duration of epilepsy were all associated with a focal onset on intracranial EEG, while there was a non-significant trend with ictal behavior. The non-invasive data did not predict surgical outcome. We conclude that some of these patients can do well with surgery. In most cases, intracranial EEG is necessary for localization of seizure focus, but if PET and MRI show focal abnormalities and there is a history of febrile convulsions no further evaluation could be needed. These findings need confirmation.

Mortality after Epilepsy Surgery

Mortality rates are higher in people with refractory epilepsy than in the general population. We assessed mortality rates in a prospectively followed cohort who had epilepsy surgery, to examine the factors related to mortality and to assess the relationship between seizure control and mortality. Five hundred eighty-three patients were evaluated. Mortality was strongly related to seizure control (p = 0.001), with 18 deaths observed in patients with recurrent seizures (mortality rate = 11.4 per 1,000 person-years) and 1 death in patients with no recurrent seizures (mortality rate = 0.85 deaths per 1,000 person-years). Patients with generalized epilepsy who had corpus callosotomy had a higher mortality rate than patients who had resective or transective surgery. The side of surgery and gender did not influence mortality rates. The standardized mortality ratio was 5.75 for patients with recurrent seizures and was significantly higher for females than males. These data show that the excess mortality associated with refractory epilepsy is eliminated after epilepsy surgery when seizures are abolished and suggest that epilepsy surgery reduces the risk of epilepsy-associated death.

A dissociation between implicit and explicit verbal memory in left temporal lobe epilepsy

PURPOSE

Temporal lobe epilepsy patients are well known to present deficits on explicit verbal memory procedures (e.g., recall, recognition). The integrity of implicit memory procedures in these patients is not established. Previous studies in this area used implicit memory measures contaminated by the effects of explicit memory.

METHODS

We examined the integrity of verbal implicit and explicit memory in left temporal lobe epilepsy (LTLE) patients and hypothesized that a clear dissociation in performance would be found with a relative preservation of implicit memory. TLE patients (n = 15) and age- and education-matched healthy normal patients (n = 15) were shown a 40-word study list, followed by a test phase requiring completion of word stems based on the study words or new/unseen words. Experimental conditions involved instructions to provide either the old (study) words or novel/nonlist words when completing the stem. Measures of automaticity and recollection provided uncontaminated indices of implicit and explicit memory, respectively.

RESULTS

The data showed a significant difference (p < 0.001) between the patients (Recollection, 0.12; SD, 0.18) and controls (0.50, SD, 0.15) on the measure of explicit memory. In contrast, the patients (Automaticity, 0.51; SD, 0.11) and controls (0.45, SD, 0.18) performed similarly on the implicit memory measure, with patient scores clearly at normative levels based on other Process Dissociation Procedure data.

CONCLUSIONS

The data demonstrate the integrity of implicit memory in LTLE patients. Finding a dissociation between the two forms of verbal memory in LTLE patients provides evidence that they rely on different neuroanatomic systems.

Linear IgA bullous dermatosis of neonatal onset: case report and review of the literature

Several small blisters were noticed on the forehead and the trunk of a newborn boy on day 1. The blisters gradually enlarged and spread over the whole body including the oral mucosa. A skin biopsy was performed twice and subepidermal bullae with polymorphonuclear and mononuclear cell infiltration were demonstrated. Direct immunofluorescence showed linear IgA, IgG and C3 depositions along the basement membrane zone and this finding led to a diagnosis of linear IgA bullous dermatosis. So far, internationally, only one case has ever been reported on the disease at neonatal onset. The skin lesions spontaneously regressed and the mucosal lesions were controlled with diaminodiphenylsulfone.

CONCLUSION

In neonates with prolonged blistering, autoimmune disease such as linear IgA bullous dermatosis should be considered within the differential diagnosis and an immunofluorescence study must be performed.

EEG and ECG in Sudden Unexplained Death in Epilepsy

PURPOSE

Sudden unexpected death in epilepsy (SUDEP) is a major cause of mortality for patients with epilepsy. Cardiac factors may be involved and were evaluated in this study.

METHODS

EEG and ECG data for 21 patients with definite (n = 6) or probable (n = 15) SUDEP were compared with data from a group of 43 patients with refractory partial epilepsy. ECG abnormalities and heart rate (HR) changes were correlated with clinical data.

RESULTS

Fourteen patients died in their sleep; two were awake. Ictal maximal HR (90 seizures from 16 of 21 patients) was significantly higher in SUDEP (mean, 149 beats/min, BPM) than in comparison patients (mean, 126 BPM; p < 0.001). Greater increases in HR were associated with seizures arising from sleep (78 BPM increase) than from wakefulness (47 BPM; p < 0.001) in SUDEP, as compared with the non-SUDEP group (52 BPM in sleep, 43 BPM in wakefulness; p = 0.27). Ictal cardiac repolarization and rhythm abnormalities occurred in 56% of SUDEP (including two atrial fibrillation, two ventricular premature depolarizations, two marked sinus arrhythmia, two atrial premature depolarizations, one junctional escape, one ST-segment elevation), and 39% of comparison patients (p = 0.39). No specific seizure onset (laterality or lobe) was associated with SUDEP.

CONCLUSIONS

This study reveals, for the first time, evidence of increased autonomic stimulation (as measured by HR) associated with seizures, particularly in sleep, in patients with SUDEP, as compared with a clinically similar group of patients with refractory epilepsy.

Reliabilities of parsimony-based and likelihood-based methods for detecting positive selection at single amino acid sites

The reliabilities of parsimony-based and likelihood-based methods for inferring positive selection at single amino acid sites were studied using the nucleotide sequences of human leukocyte antigen (HLA) genes, in which positive selection is known to be operating at the antigen recognition site. The results indicate that the inference by parsimony-based methods is robust to the use of different evolutionary models and generally more reliable than that by likelihood-based methods. In contrast, the results obtained by likelihood-based methods depend on the models and on the initial parameter values used. It is sometimes difficult to obtain the maximum likelihood estimates of parameters for a given model, and the results obtained may be false negatives or false positives depending on the initial parameter values. It is therefore preferable to use parsimony-based methods as long as the number of sequences is relatively large and the branch lengths of the phylogenetic tree are relatively small.

MEGA2: molecular evolutionary genetics analysis software

We have developed a new software package, Molecular Evolutionary Genetics Analysis version 2 (MEGA2), for exploring and analyzing aligned DNA or protein sequences from an evolutionary perspective. MEGA2 vastly extends the capabilities of MEGA version 1 by: (1) facilitating analyses of large datasets; (2) enabling creation and analyses of groups of sequences; (3) enabling specification of domains and genes; (4) expanding the repertoire of statistical methods for molecular evolutionary studies; and (5) adding new modules for visual representation of input data and output results on the Microsoft Windows platform.

AVAILABILITY

http://www.megasoftware.net.

CONTACT

s.kumar@asu.edu

Vagal nerve stimulation: adjustments to reduce painful side effects

Vagal nerve stimulation is an approved adjunctive treatment for medically intractable epilepsy. Although it is generally well tolerated, some patients experience pain, coughing, or hoarseness during stimulation. Lowering the pulse width in these patients alleviates pain and reduces voice alteration without loss of efficacy. This allows more optimal programming of stimulation intensities.

ADAPTSITE: detecting natural selection at single amino acid sites

ADAPTSITE is a program package for detecting natural selection at single amino acid sites, using a multiple alignment of protein-coding sequences for a given phylogenetic tree. The program infers ancestral codons at all interior nodes, and computes the total numbers of synonymous (c(S)) and nonsynonymous (c(N)) substitutions as well as the average numbers of synonymous (s(S)) and nonsynonymous (s(N)) sites for each codon site. The probabilities of occurrence of synonymous and nonsynonymous substitutions are approximated by s(S) / (s(S) + s(N)) and s(N) / (s(S) + s(N)), respectively. The null hypothesis of selective neutrality is tested for each codon site, assuming a binomial distribution for the probability of obtaining c(S) and c(N).

AVAILABILITY

ADAPTSITE is available free of charge at the World-Wide Web sites http://mep.bio.psu.edu/adaptivevol.html and http://www.cib.nig.ac.jp/dda/yossuzuk/welcome.html. The package includes the source code written in C, binary files for UNIX operating systems, manual, and example files.

Evolutionary dynamics of the T-cell receptor VB gene family as inferred from the human and mouse genomic sequences

The diversity of T-cell receptors is generated primarily by the variable-region gene families, each of which is composed of a large number of member genes. The entire genomic sequence of the variable region (VB) of the T- cell receptor beta chain from humans and mice has become available. To understand the evolutionary dynamics of the VB gene family, we conducted a phylogenetic analysis of all VB genes from humans and mice, as well as a detailed analysis of internal DNA duplications in the human genomic VB region. The phylogenetic tree obtained shows that human and mouse VB genes intermingle extensively rather than forming two separate clusters and that many gene duplications occurred both before and after the divergence between primates and rodents. Analyzing the genomic maps of transposable elements (e.g., LINEs and SINEs) and relic VB genes in the VB gene region, we present evidence that a 20-kb VB region duplicated tandemly four times in the human lineage during the last 32 Myr, and 6 out of the 15 VB genes in this region have become nonfunctional during this period. Our results show that the VB gene family is subject to evolution by a birth-and-death process rather than to concerted evolution.

Estimation of divergence times from multiprotein sequences for a few mammalian species and several distantly related organisms

When many protein sequences are available for estimating the time of divergence between two species, it is customary to estimate the time for each protein separately and then use the average for all proteins as the final estimate. However, it can be shown that this estimate generally has an upward bias, and that an unbiased estimate is obtained by using distances based on concatenated sequences. We have shown that two concatenation-based distances, i.e., average gamma distance weighted with sequence length (d(2)) and multiprotein gamma distance (d(3)), generally give more satisfactory results than other concatenation-based distances. Using these two distance measures for 104 protein sequences, we estimated the time of divergence between mice and rats to be approximately 33 million years ago. Similarly, the time of divergence between humans and rodents was estimated to be approximately 96 million years ago. We also investigated the dependency of time estimates on statistical methods and various assumptions made by using sequence data from eubacteria, protists, plants, fungi, and animals. Our best estimates of the times of divergence between eubacteria and eukaryotes, between protists and other eukaryotes, and between plants, fungi, and animals were 3, 1.7, and 1.3 billion years ago, respectively. However, estimates of ancient divergence times are subject to a substantial amount of error caused by uncertainty of the molecular clock, horizontal gene transfer, errors in sequence alignments, etc.

Purifying selection and birth-and-death evolution in the ubiquitin gene family

Ubiquitin is a highly conserved protein that is encoded by a multigene family. It is generally believed that this gene family is subject to concerted evolution, which homogenizes the member genes of the family. However, protein homogeneity can be attained also by strong purifying selection. We therefore studied the proportion (p(S)) of synonymous nucleotide differences between members of the ubiquitin gene family from 28 species of fungi, plants, and animals. The results have shown that p(S) is generally very high and is often close to the saturation level, although the protein sequence is virtually identical for all ubiquitins from fungi, plants, and animals. A small proportion of species showed a low level of p(S) values, but these values appeared to be caused by recent gene duplication. It was also found that the number of repeat copies of the gene family varies considerably with species, and some species harbor pseudogenes. These observations suggest that the members of this gene family evolve almost independently by silent nucleotide substitution and are subjected to birth-and-death evolution at the DNA level.

Efficiencies of fast algorithms of phylogenetic inference under the criteria of maximum parsimony, minimum evolution, and maximum likelihood when a large number of sequences are used

In phylogenetic inference by maximum-parsimony (MP), minimum-evolution (ME), and maximum-likelihood (ML) methods, it is customary to conduct extensive heuristic searches of MP, ME, and ML trees, examining a large number of different topologies. However, these extensive searches tend to give incorrect tree topologies. Here we show by extensive computer simulation that when the number of nucleotide sequences (m) is large and the number of nucleotides used (n) is relatively small, the simple MP or ML tree search algorithms such as the stepwise addition (SA) plus nearest neighbor interchange (NNI) search and the SA plus subtree pruning regrafting (SPR) search are as efficient as the extensive search algorithms such as the SA plus tree bisection-reconnection (TBR) search in inferring the true tree. In the case of ME methods, the simple neighbor-joining (NJ) algorithm is as efficient as or more efficient than the extensive NJ+TBR search. We show that when ME methods are used, the simple p distance generally gives better results in phylogenetic inference than more complicated distance measures such as the Hasegawa-Kishino-Yano (HKY) distance, even when nucleotide substitution follows the HKY model. When ML methods are used, the simple Jukes-Cantor (JC) model of phylogenetic inference generally shows a better performance than the HKY model even if the likelihood value for the HKY model is much higher than that for the JC model. This indicates that at least in the present case, selecting of a substitution model by using the likelihood ratio test or the AIC index is not appropriate. When n is small relative to m and the extent of sequence divergence is high, the NJ method with p distance often shows a better performance than ML methods with the JC model. However, when the level of sequence divergence is low, this is not the case.