Rufinamide

Rufinamide is a new antiepileptic drug that is effective in acute animal seizure models and also in the kindling model of epilepsy with a high protective index. Its mechanism of action is largely unknown; studies suggest an effect at voltage-gated sodium channels, but whether this is its main mode of action remains to be determined. Rufinamide can be administered twice daily and has minimal drug interactions (it does, however, interact with the contraceptive pill). Food markedly increases absorption, which may complicate clinical use. Trials indicate that rufinamide is effective as adjunctive therapy in partial epilepsy and the Lennox-Gastaut syndrome with minimal adverse effects including headache, dizziness and fatigue. In addition, rufinamide has a favorable cognitive side-effect profile. However, it remains uncertain whether rufinamide offers significant advantages over other current antiepileptic drugs, and the results of further clinical trials are awaited.

Regulation and role of REST and REST4 variants in modulation of gene expression in in vivo and in vitro in epilepsy models

Repressor element-1 silencing transcription factor (REST) is a candidate modulator of gene expression during status epilepticus in the rodent. In such models, full-length REST and the truncated REST4 variant are induced and can potentially direct differential gene expression patterns. We have addressed the regulation of these REST variants in rodent hippocampal seizure models and correlated this with expression of the proconvulsant, substance P encoding, PPT-A gene. REST and REST4 were differentially regulated following kainic acid stimulus both in in vitro and in vivo models. REST4 was more tightly regulated than REST in both models and its transient expression correlated with that of the differential regulation of PPT-A. Consistent with this, overexpression of a truncated REST protein (HZ4, lacking the C-terminal repression domain) increased expression of the endogenous PPT-A gene. Similarly the proximal PPT-A promoter reporter gene construct was differentially regulated by the distinct REST isoforms in hippocampal cells with HZ4 being the major inducer of increased reporter expression. Furthermore, REST and REST4 proteins were differentially expressed and compartmentalized within rat hippocampal cells in vitro following noxious stimuli. This differential localization of the REST isoforms was confirmed in the CA1 region following perforant path and kainic acid induction of status epilepticus in vivo. We propose that the interplay between REST and REST4 alter the expression of proconvulsant genes, as exemplified by the PPT-A gene, and may therefore regulate the progression of epileptogenesis.

Do seizures in patients with refractory epilepsy vary between wakefulness and sleep?

AIM

To determine the effects of sleep and wakefulness on seizures in patients with refractory epilepsy recorded while undergoing video-electroencephalography (EEG) telemetry.

METHODS

The video-EEG data of patients who had two or more seizures during video-EEG telemetry (n = 270) were reviewed. Fifty seven patients who had seizures both in wakefulness and sleep were identified. The video and ictal EEG data were reviewed, paying specific attention to type of seizures, duration, semiology, lateralisation and number of seizures.

RESULTS

Three hundred and sixty two seizures were recorded; 237 seizures while awake and 125 while sleeping. Secondary generalisation occurred more often in sleep than in wakefulness (p < 0.01). Overall, there was no significant effect of sleep on the duration of seizures or ictal EEG change. Sleep and awake seizures differed in only eight patients.

CONCLUSION

Secondary generalisation occurred more often in sleep than in wakefulness, perhaps due to the facilitated spread of seizures during sleep. For the most part, however, seizures recorded during sleep did not differ from those recorded during wakefulness.

Treatment of seizure emergencies: Convulsive and non-convulsive status epilepticus

Status epilepticus (SE), defined as recurrent epileptic seizures without complete recovery between seizures, is one of the most serious manifestations of epilepsy. Generalized convulsive status epilepticus (GCSE) is the most common and most life-threatening form of SE, and aging increases the mortality risk. In a recent study of treatment of GCSE, 226 of 518 evaluable patients (43.6%) were of age 65 or older. In the 157 elderly patients with overt GCSE, phenobarbital was successful as first-line treatment in 71.4%, lorazepam in 63%, diazepam and phenytoin in 53.3%, and phenytoin alone in 41.5%. Phenobarbital and lorazepam were more successful than phenytoin alone. In the 69 elderly patients with subtle GCSE, success as the first treatment was 30.8% for phenobarbital, 14.3% for lorazepam, 11.8% for phenytoin, and 7.7% for diazepam and phenytoin. Overall, the results were similar to those reported for the entire study. Lorazepam, because of ease of use, is probably the best drug for the initial treatment of overt GCSE in the elderly; phenobarbital may be the best drug for subtle GCSE in this group, but more data are needed. The term "nonconvulsive SE" has been used to include complex partial SE and absence SE - both of which present as an "epileptic twilight state" - and SE in comatose patients. The diagnosis can be challenging, particularly in the elderly, as overlapping clinical features and electroencephalogram patterns can be seen in SE and in a variety of encephalopathic conditions. There is a suggestion that aggressive treatment of elderly patients with nonconvulsive SE may worsen prognosis. Clearly, there is a need for more data to better understand management of elderly patients with both convulsive and nonconvulsive SE.

Heparin for pregnant women with acquired or inherited thrombophilias

BACKGROUND

Thrombophilias, which are associated with a predisposition to thrombotic events, have been implicated in adverse obstetrical outcomes such as intrauterine growth restriction, stillbirth, severe early onset pre-eclampsia, and placental abruption. Heparin administration in pregnancy may reduce the risk of these events.

OBJECTIVES

The objective of this review was to assess the effects of heparin on pregnancy outcomes for women with a thrombophilia.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group trials register (July 2002), MEDLINE, EMBASE, CINAHL, Scidex (via OVID Technologies - July 2002) and reference lists and personal files.

SELECTION CRITERIA

Randomized controlled trials comparing heparin with placebo or no treatment, or randomized controlled trials comparing any two treatments. Quasi randomized studies would be included.

DATA COLLECTION AND ANALYSIS

Data would be abstracted from identified studies and recorded on a paper form by two reviewers.

MAIN RESULTS

No studies were included.

REVIEWER'S CONCLUSIONS

There are no completed trials to determine the effects of heparin on pregnancy outcomes for women with a thrombophilia.

Disease modification in partial epilepsy

With the growth in antiepileptic drug treatment, the question arises as to what extent we are merely treating the symptom (i.e. the seizures) rather than the underlying disease process (i.e. epileptogenesis). Epileptogenicity can be considered as the process whereby structural and functional changes occur following an insult that in some cases result in epilepsy. Epileptogenicity also describes some of the changes and processes that contribute to the progression observed in some epilepsies. These processes have been modelled in animals mostly by the kindling model of epilepsy, in which repetition of subconvulsive stimuli results in a progressive epileptic state and eventually leads to spontaneous seizures. However, it is not clear that kindling has a human correlate, so models in which an initial insult (status epilepticus, hyperthermia, hypoxia, trauma) is followed by the development of lowered seizure threshold and, in some instances, spontaneous seizures have been used. These models seem to support the "second hit" hypothesis, in which there is an initial insult resulting in lowered seizure threshold, and then a later insult, the "second hit", that results in the expression of epilepsy. These models also support the concept of a latent period during which there could be targeted therapies to prevent the epileptogenic process. Although the occurrence of neuronal damage is one such target, neuronal damage is not necessary for epileptogenesis, and other mechanisms are at play. At the present time, it is not known whether targeted therapies may also affect compensatory processes, such as brain repair. Clearly, this would be a potential risk of such strategies. Epidemiological evidence and trials indicate that our present antiepileptic drugs are not effective in preventing epileptogenesis; antiepileptic drugs were, however, not designed for this purpose. Data from animal experiments suggest that treatment of non-convulsive status epilepticus following specific insults may prevent epileptogenesis. The relevance of this for the human condition remains uncertain, but non-convulsive status epilepticus is probably an under-recognized and probably under-treated condition. Perhaps one of the most salutary findings has been the observation of decreased childhood epilepsy with improved neonatal care. This highlights the importance of medical care at the time of an insult, and of prevention of the insults. This review discusses the data that support the concepts underlying epileptogenesis and the model systems that are presumed to reflect the human condition. Particular attention is paid to the potential for interrupting the processes underlying epileptogenesis.

Diagnosis and treatment of nonconvulsive status epilepticus

Nonconvulsive status epilepticus (SE) is not uncommon and comprises at least one-third of all cases of SE. However, nonconvulsive SE consists of very different syndromes, a common feature being the difficulty in making the diagnosis. In this review, nonconvulsive SE is divided into typical absence SE, complex partial SE, nonconvulsive SE in patients with learning difficulties (including electrical SE during sleep, atypical absence SE and tonic SE), and nonconvulsive SE in coma. These conditions have different prognoses and treatments. The diagnosis of these conditions is critically dependent on EEG. When the EEG demonstrates typical ictal patterns, the diagnosis is usually straightforward. However, in many circumstances the EEG has to be differentiated from encephalopathic patterns, and this differentiation can prove troublesome, although the clinical and electrographic response to treatment can prove helpful. Nonconvulsive SE in patients with learning difficulties possibly provides the greatest diagnostic difficulty; the clinical presentation can be subtle resulting in the diagnosis being frequently missed. Whether the neuronal damage that occurs in convulsive SE and in animal models of limbic SE also occurs in nonconvulsive SE in humans is still a matter of debate. There are critical differences between the animal models and the human condition. Indeed, the prognosis of nonconvulsive SE is usually dependent on the underlying aetiology rather than the persistence of electrographic discharges. Because of these doubts, a more conservative approach to the treatment of particular types of nonconvulsive SE (those with a better prognosis) has been taken in this article. Thus, in most instances, oral benzodiazepines for the treatment of typical absence SE and complex partial SE are recommended. In some circumstances intravenous medication is necessary, but in neither condition is anaesthetic coma recommended. This contrasts with nonconvulsive SE in coma in which a more aggressive approach is suggested. Until there are more relevant animal models, and controlled trials of conservative versus more aggressive treatment, treatment regimens for nonconvulsive SE will remain largely speculative.

Postprandial venous ammonia concentrations in the diagnosis of hepatobiliary disease in dogs

A postprandial ammonia tolerance test (PPATT) was performed on normal dogs and dogs with signs that suggested they may have liver disease. All dogs underwent transcolonic scintigraphy, liver biopsy, or both and were assigned to extrahepatic disease, primary hepatocellular, and congenital portosystemic vascular anomalies (PSVA) groups. Each dog was fed a chicken and rice diet providing 25% of its estimated daily metabolizable energy requirement (MER) as an ammonia challenge. This is practical in patients with liver disease because ammonium chloride administration often causes vomiting or ammonia toxicity. Venous ammonia concentrations were measured before feeding and every 2 hours after feeding for 8 hours. No difference in mean ammonia concentrations between dogs with extrahepatic disease and control dogs was found. Therefore, the specificity of the PPATT was 100%. Dogs with hepatocellular disease showed no change in mean ammonia concentration at any time point, before or after feeding, but sensitivity was greatest when venous ammonia was measured 6 hours after feeding (sensitivity before feeding, 28%, and after feeding, 36%). Among dogs with congenital PSVA, mean ammonia concentrations were higher than the reference range at all time points before and after feeding, and peak mean ammonia concentration occurred 6 hours after feeding. In this group, the sensitivity of the PPATT was 81% before feeding and 91% 6 hours after feeding. This study demonstrates that the measurement of venous ammonia concentration is a useful test to detect congenital PSVA, and the sensitivity of the test may be improved by sampling 6 hours after feeding. The PPATT has poor sensitivity in detecting primary hepatocellular disease.

A three-step kinetic mechanism for selective inhibition of cyclo-oxygenase-2 by diarylheterocyclic inhibitors

Cyclo-oxygenase (COX) enzymes are the targets for non-steroidal anti-inflammatory drugs (NSAIDs). These drugs demonstrate a variety of inhibitory mechanisms, which include simple competitive, as well as slow binding and irreversible inhibition. In general, most NSAIDs inhibit COX-1 and -2 by similar mechanisms. A unique class of diarylheterocyclic inhibitors has been developed that is highly selective for COX-2 by virtue of distinct inhibitory mechanisms for each isoenzyme. Several of these inhibitors, with varying selectivity, have been utilized to probe the mechanisms of COX inhibition. Results from analysis of both steady-state and time-dependent inhibition were compared. A generalized mechanism for inhibition, consisting of three sequential reversible steps, can account for the various types of kinetic behaviour observed with these inhibitors.

The attitude of courts in England to compensation for post-traumatic epilepsy

The attitudes of courts in England to the assessment of damages for post-traumatic epilepsy have dramatically changed over the last 20-30 years. In assessing damages for post-traumatic epilepsy the courts are faced with a number of considerations: epilepsy can appear several years after the injury; epilepsy is not a homogeneous condition; the eventual prognosis is unknown; the epilepsy may not have been directly due to the trauma; and epilepsy affects life expectancy and employment. Damages were originally fixed at the point of compensation, and these rather crude calculations led to both over- and under-compensation. This situation was improved in 1985, when courts were permitted to award damages on the assumption that epilepsy would not occur or worsen, and further damages should these assumptions prove to be incorrect. The courts in England still depend, however, upon the evidence of expert witnesses chosen by the plaintiff and defendant. A tension thus exists between the duty of expert witnesses to the court and the understandable inclination of expert witnesses to support the party that has instructed them. The Woolf report has led to changes in the responsibilities of expert witnesses, and will hopefully remedy many of the inconsistencies and inequities that occur.

Monosynaptic GABAergic signaling from dentate to CA3 with a pharmacological and physiological profile typical of mossy fiber synapses

Mossy fibers are the sole excitatory projection from dentate gyrus granule cells to the hippocampus, where they release glutamate, dynorphin, and zinc. In addition, mossy fiber terminals show intense immunoreactivity for the inhibitory neurotransmitter GABA. Fast inhibitory transmission at mossy fiber synapses, however, has not previously been reported. Here, we show that electrical or chemical stimuli that recruit dentate granule cells elicit monosynaptic GABA(A) receptor-mediated synaptic signals in CA3 pyramidal neurons. These inhibitory signals satisfy the criteria that distinguish mossy fiber-CA3 synapses: high sensitivity to metabotropic glutamate receptor agonists, facilitation during repetitive stimulation, and NMDA receptor-independent long-term potentiation. GABAergic transmission from the dentate gyrus to CA3 has major implications not only for information flow into the hippocampus but also for developmental and pathological processes involving the hippocampus.

Propofol in subanesthetic doses terminates status epilepticus in a rodent model

Status epilepticus is commonly refractory to first-line therapy, and thus better treatments are needed. We have investigated an experimental model of drug-resistant self-sustaining status epilepticus (SSSE) induced by 2 hours of perforant path stimulation. Propofol in subanesthetic doses administered shortly after the end of stimulation and also after a further 3 hours of SSSE terminated the SSSE without recurrence. This finding calls for a trial of propofol in refractory status epilepticus and also raises the possibility of using it as first-line therapy.

Maternal plasma homocysteine levels in women with preterm premature rupture of membranes

Homocysteine is a sulfur-containing amino acid produced by the breakdown of methionine. Plasma homocysteine levels can be elevated due to a variety of genetic and nutritional factors. Poor nutrition from diets low in folate and vitamin B12 can lead to hyperhomocysteinemia. Mildly elevated levels of homocysteine have been implicated in a number of disease processes such as atherosclerotic vascular disease and adverse obstetrical outcomes. High levels of plasma homocysteine are also associated with abnormal collagen cross-linking. Due to homocysteine's effects on connective tissue integrity, it is hypothesized that hyperhomocysteinemia in pregnancy is associated with preterm premature rupture of membranes (PPROM). Hyperhomocysteinemia, therefore, could be a treatable cause of this important public health concern.

The role of mammalian ionotropic receptors in synaptic plasticity: LTP, LTD and epilepsy

Synaptic plasticity is the foremost candidate mechanism to explain the rapid acquisition of memories. In the mammalian brain, the NMDA subclass of glutamate receptors plays a central role in the induction of several forms of use-dependent plasticity. The finding that modifications in synaptic strength are largely expressed by receptors of the AMPA subclass has focused attention on molecular mechanisms that affect their function and targeting. Receptor plasticity has also been reported in pathological situations, notably in animal and human forms of epilepsy. Which of these changes are causally implicated in the generation of seizures, and which may be compensatory or neuroprotective adaptations, has not been fully resolved.

Comparison of serum, cerebrospinal fluid and brain extracellular fluid pharmacokinetics of lamotrigine

We investigated the rate of penetration into and the intra-relationship between the serum, cerebrospinal fluid (CSF) and regional brain extracellular fluid (bECF) compartments following systemic administration of lamotrigine in rat. The serum pharmacokinetics were biphasic with an initial distribution phase, (half-life approximately 3 h), and then a prolonged elimination phase of over 30 h. The serum pharmacokinetics were linear over the range 10 - 40 mg kg(-1). Using direct sampling of CSF with concomitant serum sampling, the calculated penetration half-time into CSF was 0.42+/-0.15 h. At equilibrium, the CSF to total serum concentration ratio (0.61+/-0.02) was greater than the free to total serum concentration (0.39+/-0.01). Using in vivo recovery corrected microdialysis sampling in frontal cortex and hippocampus with concomitant serum sampling, the calculated penetration half-time of lamotrigine into bECF, 0.51+/-0.11 h, was similar to that for CSF and was not area or dose dependent. At equilibrium, the bECF to total serum concentration ratio (0.40+/-0.04) was similar to the free to total serum concentration (0.39+/-0.01), and did not differ between hippocampus and frontal cortex. The species specific serum kinetics can explain the prolonged action of lamotrigine in rat seizure models. Lamotrigine has a relatively slow penetration into both CSF and bECF compartments compared with antiepileptic drugs used in acute seizures. Furthermore, the free serum drug concentration is not the sole contributor to the CSF compartment, and the CSF concentration is an overestimate of the bECF concentration of lamotrigine.

Large-scale purification of myeloperoxidase from HL60 promyelocytic cells: characterization and comparison to human neutrophil myeloperoxidase

A large-scale purification procedure was developed for the isolation of myeloperoxidase from HL60 promyelocytic cells in culture. Initial studies showed the bulk of peroxidase-positive myeloperoxidase activity to be located in the cetyltrimethylammonium bromide solubilized particulate fraction of cell homogenates. The myeloperoxidase was then chromatographically purified using concanavalin A followed by gel filtration. SDS-PAGE analysis of the final preparation showed the presence of only two proteins with molecular masses of approximately 55 and 15 kDa, corresponding to the large and small subunits of myeloperoxidase. These data, along with Reinheit Zahl (RZ) values (A(430)/A(280)) of greater than or equal to 0.72, indicate that the myeloperoxidase prepared by this method is apparently homogeneous. Preparations routinely yielded 12-20 mg of pure myeloperoxidase per 10 ml of cell pellet. The HL60 myeloperoxidase was shown to be indistinguishable from purified human neutrophil myeloperoxidase by size exclusion chromatography, analytical ultracentrifugation, SDS-PAGE, Western blot, and NH(2)-terminal sequence analysis. The activities of the two myeloperoxidase samples, as measured using either the tetramethylbenzidine or the taurine chloramine assay, were indistinguishable. Finally, both enzymes responded identically to dapsone and aminobenzoic acid hydrazide, known inhibitors of myeloperoxidase. A protocol is presented here for the rapid, large-scale purification of myeloperoxidase from cultured HL60 cells, as well as evidence for the interchangeability of this myeloperoxidase and that purified from human neutrophils.

Multiple endocrine neoplasia type 1 in a crossbred dog

Multiple endocrine neoplasia type 1 was diagnosed in a 12-year-old male crossbred dog. Relevant history included polyuria and polydipsia of four months' duration. Physical examination revealed abdominal enlargement, seborrhoea and polypnoea. Diagnostic tests indicated hypercalcaemia, elevated serum alkaline phosphatase and alanine aminotransferase, an exaggerated response to adrenocorticotropic stimulation of the adrenal gland, lack of cortisol suppression with a low dose dexamethasone suppression test and suppression of cortisol secretion with a high dose dexamethasone test. An enlarged right parathyroid gland was removed surgically and confirmed histopathologically to be a parathyroid adenoma. The pituitary-dependent hyperadrenocorticism was treated successfully with mitotane for 14 months before the patient was euthanased for an unrelated problem.

Vertebral physitis with epiphyseal sequestration and a portosystemic shunt in a Pekingese dog

Vertebral physitis with bone sequestration and a portosystemic shunt were diagnosed in an 18-month-old female Pekingese dog. The latter was determined by the presence of low blood urea nitrogen, elevated serum bile acids, microhepatica and an increased portosystemic shunt fraction. It was managed with a home-cooked low protein diet. Vertebral physitis and bone sequestration was diagnosed by the presence of thoracolumbar hyperaesthesia, radiographic and scintigraphic changes, isolation of Staphylococcus intermedius from blood and the third lumbar vertebra, and histopathological examination of a surgical biopsy. A partial sequestrectomy was performed and a six-month course of amoxycillin-clavulanate was prescribed. The dog was pain-free and showed partial resolution of the radiographic signs four months after the discontinuation of antibiotics.

A canarypox vaccine expressing multiple human immunodeficiency virus type 1 genes given alone or with rgp120 elicits broad and durable CD8+ cytotoxic T lymphocyte responses in seronegative volunteers

Induction of CD8+ cytotoxic T cells is considered one of the important correlates for the protective efficacy of candidate human immunodeficiency virus type 1 (HIV-1) vaccines. To induce CD8+ cytotoxic T lymphocytes (CTLs) along with neutralizing antibody and CD4+ T cell help, a live canarypox virus construct expressing gp120, transmembrane gp41, the gag and protease genes, and sequences containing CTL epitopes in nef and pol was given simultaneously with, or followed by, rgp120 SF2. CD8+ CTLs were detected in 61% of volunteers at some time during the trial. Three to 6 months after the last immunization, the gene-specific responses were gag, 26/81; env, 17/77; nef, 12/77; and pol, 3/16. Simultaneous immunization with the canarypox vector and the subunit, beginning with the initial immunization, resulted in earlier antibody responses. In summary, a strategy of immunization with a canarypox vector expressing multiple genes of HIV-1 given with gp120 results in durable CD8+ CTL responses to a broad range of epitopes.