Immunization with envelope subunit vaccine products elicits neutralizing antibodies against laboratory-adapted but not primary isolates of human immunodeficiency virus type 1. The National Institute of Allergy and Infectious Diseases AIDS Vaccine Evaluation Group

Phase I studies of volunteers not infected with human immunodeficiency virus type 1 (HIV-1) have shown that immunization with envelope subunit vaccine products elicits antibodies that neutralize laboratory-adapted (prototype) HIV-1 strains in vitro. Prototype strains are adapted to grow in continuous (neoplastic) cell lines and are more susceptible to neutralization than are primary isolates cultured in human peripheral blood mononuclear cells. In this study, 50 sera from nine phase I vaccine trials and 16 from HIV-1-infected persons were evaluated for neutralizing antibody activity against 3 laboratory-adapted and 5 primary HIV-1 isolates. Of 50 sera, 49 neutralized at least 1 of the prototype strains; however, none displayed neutralizing activity against primary isolates of HIV-1. Serum from most HIV-1-infected persons neutralized both laboratory-adapted and primary HIV-1 isolates. These data demonstrate a qualitative, or large quantitative, difference in the neutralizing antibody response induced by envelope subunit vaccination and natural HIV-1 infection.

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.

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.

Immune responses to human immunodeficiency virus (HIV) type 1 induced by canarypox expressing HIV-1MN gp120, HIV-1SF2 recombinant gp120, or both vaccines in seronegative adults. NIAID AIDS Vaccine Evaluation Group

A safety and immunogenicity trial was conducted in vaccinia-immune and vaccinia-naive human immunodeficiency virus (HIV)-uninfected adults who were randomized to receive 10(6) or 10(7) TCID50 of canarypox (ALVAC) vector expressing HIV-1MN gp160 or 10(5.5) TCID50 of ALVAC-rabies virus glycoprotein control at 0 and 1 or 2 months and ALVAC-gp160 or 50 microg of HIV-1SF2 recombinant (r) gp120 in microfluidized emulsion at 9 and 12 months; others received rgp120 at 0, 1, 6, and 12 months. All vaccines were well-tolerated. Neither vaccinia-immune status before vaccination nor ALVAC dose affected HIV immune responses. HIV-1MN and HIV-1SF2 neutralizing antibodies were detected more often (100%) in ALVAC-gp160/rgp120 recipients than in recipients of ALVAC-gp160 (<65%) or rgp120 (89%) alone. ALVAC-gp160/rgp120 also elicited more frequent HIV V3-specific and fusion-inhibition antibodies, antibody-dependent cellular cytotoxicity, lymphoproliferation, and cytotoxic CD8+ T cell activity than did either vaccine alone. Trials with ALVAC expressing additional HIV components and rgp120 are underway.

Changes in homocysteine levels during normal pregnancy

OBJECTIVE

The objective of this study was to determine the changes in total plasma homocysteine concentration that occur during normal pregnancy.

STUDY DESIGN

In this cross-sectional study homocysteine was measured in 155 normal women in the first, second, and third trimesters and in nonpregnant controls. In addition, albumin, serum B12, serum folate, and red blood cell folate concentrations were measured and correlated to homocysteine values.

RESULTS

The mean homocysteine concentration (in micromoles per liter) was 5.6 (95% confidence interval 3.9-7.3) at 8-16 weeks' gestation, 4.3 (95% confidence interval 3.5-5.3) at 20-28 weeks' gestation, 5.5 (95% confidence interval 3.3-7.5) at 36-42 weeks' gestation, and 7.9 (95% confidence interval 6.2-9.6) in the nonpregnant control group. Homocysteine was significantly lower in all 3 trimesters of pregnancy compared with nonpregnant controls (P <.001). Homocysteine levels were directly correlated with albumin levels, which decreased during pregnancy. Homocysteine concentrations were decreased in subjects taking folic acid supplementation.

CONCLUSION

Serum concentrations of homocysteine decrease during pregnancy. This occurs in association with the physiologic fall in albumin during pregnancy, as well as with folic acid supplementation.

Structure-activity relationships in the oxidation of benzylamine analogues by bovine liver mitochondrial monoamine oxidase B

The influence of para and meta substitution of benzylamine on its interaction with bovine liver mitochondrial monoamine oxidase B (MAO B) has been investigated by steady-state and reductive half-reaction anaerobic stopped-flow kinetic approaches. Steady-state kinetic properties of each benzylamine analogue suggest that para or meta substitution does not alter the mechanistic pathway of catalysis [Husain, M., et al. (1982) Biochemistry 21, 595-600]. All analogues tested exhibited Dkcat values ranging from 5.5 to 8.9 and D[kcat/Km(amine)] values ranging from 3.3 to 8.1 D[kcat/Km(O2)] values of approximately 1 are observed for all substrate analogues. Values for Kd were calculated from steady-state isotope effect data [Klinman, J.P., & Matthews, R.G. (1985) J. Am. Chem. Soc. 107, 1058-1060] and are in good agreement with Ks values determined from analysis of the rate of MAO B reduction as a function of benzylamine analogue concentration in reductive half-reaction experiments. A linear correlation of benzylamine analogue Kd values with the hydrophobicity parameter (phi) is observed for the para-substituted analogues where the binding affinity increases with increasing hydrophobicity of the substituent. Statistical treatment of the correlation shows a small negative contribution to binding by the van der Waals volume (VW) of the para substituent. meta-Substituted benzylamine analogues show a decreased binding affinity with the VW of the substituent and no correlation with the hydrophobicity value of the substituents tested. No spectral evidence was found for any flavin radical intermediates during the time course of MAO B flavin reduction in anaerobic reductive half-reduction stopped-flow experiments with any of the alpha,alpha-diprotio- or alpha,alpha-dideuteriobenzylamine analogues tested. The limiting rates of enzyme reduction exhibit large Dk values (6.5-14.1) for all of the analogues tested. para-Substituted benzylamine analogues reduce MAO B with limiting rates that correlate with the steric influence (Es value) of the substituent. Statistical analysis shows the rate of MAO B reduction by para-substituted analogues to be retarded by increased values of Es and, with a smaller contribution, by the hydrophobicity value of the substituent. The rate of MAO B reduction by meta-substituted benzylamine analogues is essentially independent of the nature of the substituent. No evidence was found for any electronic contribution to the rate of MAO B flavin reduction by any of the analogues tested. These data demonstrate the steric orientation of the substrate to be important in the rate of amine oxidation by MAO B and that ring meta substituents favor this orientation.(ABSTRACT TRUNCATED AT 400 WORDS)

Seizure activity results in calcium- and mitochondria-independent ROS production via NADPH and xanthine oxidase activation

Seizure activity has been proposed to result in the generation of reactive oxygen species (ROS), which then contribute to seizure-induced neuronal damage and eventually cell death. Although the mechanisms of seizure-induced ROS generation are unclear, mitochondria and cellular calcium overload have been proposed to have a crucial role. We aim to determine the sources of seizure-induced ROS and their contribution to seizure-induced cell death. Using live cell imaging techniques in glioneuronal cultures, we show that prolonged seizure-like activity increases ROS production in an NMDA receptor-dependent manner. Unexpectedly, however, mitochondria did not contribute to ROS production during seizure-like activity. ROS were generated primarily by NADPH oxidase and later by xanthine oxidase (XO) activity in a calcium-independent manner. This calcium-independent neuronal ROS production was accompanied by an increase in intracellular [Na(+)] through NMDA receptor activation. Inhibition of NADPH or XO markedly reduced seizure-like activity-induced neuronal apoptosis. These findings demonstrate a critical role for ROS in seizure-induced neuronal cell death and identify novel therapeutic targets.

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.

Effects of antibody to rotavirus on protection of adults challenged with a human rotavirus

Effects of preinoculation rotavirus antibody titers on the probability of infection and illness were evaluated in adults challenged orally with different doses of a virulent human rotavirus (CJN strain). Preinoculation titers considered were serum neutralizing antibody, serum rotavirus IgA, serum rotavirus IgG, jejunal neutralizing antibody, jejunal rotavirus IgA, and stool rotavirus IgA. Doses of virus of either 9 x 10(1) or 9 x 10(3) focus-forming units were administered to 19 subjects each. Twenty-six were infected; 15 experienced illness. The probability of either outcome was unrelated to dose. Stool rotavirus IgA titers could not be correlated to either infection or illness, but the mean titers of the other five antibodies were significantly or nearly significantly lower in subjects infected or ill, when compared with those negative for either outcome. When analyzed by stepwise logistic regression, only serum rotavirus IgG remained significantly (P = .005) related to the probability of infection, and only jejunal neutralizing antibody remained significantly (P = .01) related to the probability of illness.

Changes in activated protein C resistance during normal pregnancy

OBJECTIVE

The objective of this study was to determine the changes in activated protein C resistance that occur during normal pregnancy.

STUDY DESIGN

In this cross-sectional study activated protein C was measured in 128 women with normal pregnancies in the first, second, and third trimesters and in nonpregnant control subjects with 24 to 39 women in each group. In addition, factor V, factor VIII, free protein S, and functional protein C were measured and correlated with activated protein C levels. Polymerase chain reaction for factor V Leiden mutation was performed.

RESULTS

There was a significant fall in the activity of activated protein C in the second and third trimesters of pregnancy (p < 0.05). This was related to increased factor VIII and decreased free protein S levels (p = 0.002, R2 = 0.20). The prevalence of the factor V Leiden mutation was 7.3%.

CONCLUSION

Resistance to activated protein C is increased in the second and third trimesters of pregnancy. This is related to the alterations in other coagulation proteins, a phenomenon normally occurring during pregnancy.

Clinical pharmacokinetics of new antiepileptic drugs

We have reviewed the pharmacokinetics of six antiepileptic drugs that are marketed (felbamate, gabapentin, lamotrigine, oxcarbazepine, vigabatrin, and zonisamide) and six drugs that are undergoing evaluation (levetiracetam, ralitoline, remacemide, stiripentol, tiagabine, and topiramate). In addition, we have compared the prodrugs eterobarb and fosphenytoin and the controlled-release formulations of valproic acid and carbamazepine with their parent compounds. Finally, we have devised a scoring system to compare the pharmacokinetics of new antiepileptic drugs. Using this system, vigabatrin, levetiracetam, gabapentin, and topiramate appea to have the most favourable pharmacokinetic profiles, whilst ralitoline and stiripentol have the least favourable.

Difficulties in extrapolating from clinical trial data to clinical practice: the case of antiepileptic drugs

Effective new antiepileptic drugs (AEDs) are needed for the treatment of those with refractory epilepsy. However, with the growing number of these drugs being licensed and marketed, a rational approach to the treatment of epilepsy is becoming essential. New AED trials can determine appropriate use of AEDs but ultimately fail to determine the best use of AEDs and their exact role in treating patients. New AED trials rarely use clinically applicable measures of efficacy, and it is difficult to extrapolate the data from populations used in AED trials to the wider population of patients with epilepsy. Furthermore, AED trials ignore the factors that are most likely to determine prognosis: the etiology, seizure types, and epilepsy syndrome. To resolve these issues, we need large multicenter studies in well-defined populations with well-characterized seizures, epilepsy syndromes, and etiologies. Being seizure free should be the primary measure of efficacy rather than meta-analyses and guidelines based upon incomplete data.

Summary report: workshop on the potential risks of antibody-dependent enhancement in human HIV vaccine trials

Concern that ADE of HIV infection could occur in vivo, as a result of HIV immunization, has arisen for several reasons. Immune-mediated disease enhancement occurs in several human and animal viral diseases, including lentiviral diseases. Tropism for host M/M cells is a common characteristic in these diseases. Sera from naturally infected, and possibly HIV-immunized, individuals have been shown to contain infection enhancing antibodies in vitro. Finally, there is considerable genetic, and potentially antigenic, diversity among HIV-1 isolates. This workshop was convened to evaluate these concerns regarding ADE of HIV infection in human HIV vaccine trials and to propose studies that would address this potential risk. Although there is currently no evidence that immune-mediated enhancement of disease occurs in HIV, there is clearly a need for carefully designed experiments to further evaluate this issue. As there are several notable diseases for which in vitro ADE does not correlate with ADE in vivo, in vitro data are insufficient to deter development of current HIV-1 vaccine candidates. In vivo correlates of protection/enhancement are necessary to evaluate the ADE risk accurately. The development of an HIV animal model that would allow testing of vaccine candidates is of primary importance.

Association of caesarean delivery for first birth with placenta praevia and placental abruption in second pregnancy

OBJECTIVE

To quantify the risk of placenta praevia and placental abruption in singleton, second pregnancies after a caesarean delivery of the first pregnancy.

DESIGN

Retrospective cohort study.

SETTING

Linked birth and infant mortality database of the USA between 1995 and 2000.

POPULATION

A total of 5,146,742 singleton second pregnancies were available for the final analysis after excluding missing information.

METHODS

Multiple logistic regressions were used to describe the relationship between caesarean section at first birth and placenta praevia and placental abruption in second-birth singletons.

MAIN OUTCOME MEASURES

Placenta praevia and placental abruption.

RESULTS

Placenta praevia was recorded in 4.4 per 1000 second-birth singletons whose first births delivered by caesarean section and 2.7 per 1000 second-birth singletons whose first births delivered vaginally. About 6.8 per 1000 births were complicated with placental abruption in second-birth singletons whose first births delivered by caesarean section and 4.8 per 1000 birth in second-birth singletons whose first births delivered vaginally. The adjusted odds ratio (95% CIs) of previous caesarean section for placenta praevia in following second pregnancies was 1.47 (1.41, 1.52) after controlling for maternal age, race, education, marital status, maternal drinking and smoking during pregnancy, adequacy of prenatal care, and fetal gender. The corresponding figure for placental abruption was 1.40 (1.36, 1.45).

CONCLUSION

Caesarean section for first live birth is associated with a 47% increased risk of placenta praevia and 40% increased risk of placental abruption in second pregnancy with a singleton.

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.

Diagnosis and treatment of status epilepticus on a neurological intensive care unit

Status epilepticus refractory to first-line therapy is associated with a high morbidity and mortality. Correct diagnosis and adequate treatment of this condition require electrographic monitoring and anaesthetic facilities available in specialist intensive care units (ICUs). We carried out an audit of 26 patients admitted to a neurological ICU with a diagnosis of status epilepticus, to identify deficiencies in diagnosis and management prior to transfer to the ICU, and examine the effectiveness of ICU management. Or transfer, only 14 (54%) were in status epilepticus; six were in drug-induced coma or were encephalopathic, and six had pseudostatus epilepticus, of whom four had been intubated. The commonest treatments prior to transfer were benzodiazepines, chlormethiazole and phenytoin; the loading dose of phenytoin was adequate in at least 7/16 cases. All those in status epilepticus on transfer had their seizures successfully controlled, but ten required general anaesthesia with thiopentone, propofol, ketamine or midazolam. Two died--one had a severe encephalitis and the other had had a cardiac arrest prior to treatment. This study highlights deficiencies in the initial diagnosis and management of status epilepticus, the role of specialist neurological intensive care, and the importance of early referral.

Ascorbate and glutamate release in the rat hippocampus after perforant path stimulation: a "dialysis electrode" study

Excitatory amino acids have been proposed to play a critical role in the development and maintenance of epileptic seizures and in the development of neuronal damage. Previous animal studies of glutamate during seizures, however, have often failed to measure any rise in glutamate. We have overcome many of the problems of these studies by using an animal model in which epileptic afterdischarges are induced by stimulation of the perforant path, and glutamate and ascorbate are measured using a newly developed microdialysis electrode that combines the advantages of microdialysis and in vivo electrochemistry. We have successfully shown (1) a rise in glutamate after an epileptic afterdischarge, (2) a concomitant initial fall and then a later rise in ascorbate, and (3) progressive dwindling of this effect when afterdischarges are repeated within minutes, despite similar electroencephalographic responses. The possible mechanisms of these effects are discussed and include ascorbate/glutamate heteroexchange, reversal of the glutamate uptake mechanism, and augmentation of glutamate uptake after a seizure.

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.

Complex partial status epilepticus: a recurrent problem

Twenty patients with complex partial status epilepticus were identified retrospectively from a specialist neurology hospital. Seventeen patients experienced recurrent episodes of complex partial status epilepticus, often occurring at regular intervals, usually over many years, and while being treated with effective anti-epileptic drugs. No unifying cause for the recurrences, and no common epilepsy aetiologies, were identified. In spite of the frequency of recurrence and length of history, none of the patients showed any marked evidence of cognitive or neurological deterioration. Complex partial status epilepticus is more common than is generally recognised, should be differentiated from other forms of non-convulsive status, and is often difficult to treat.

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.

Case of simple partial status epilepticus in occipital lobe epilepsy misdiagnosed as migraine: clinical, electrophysiological, and magnetic resonance imaging characteristics

An 31-year-old man had a unique form of occipital lobe epilepsy. Since age 13 years, he has had episodes of simple partial status epilepticus (SE) occurring twice a month. These typically consisted of elementary visual hallucinations of flashing lights obscuring his left visual field for a period of 2 days, associated with a severe frontal headache initially diagnosed as migraine. These episodes of simple partial SE then evolved to a complex partial seizure (CPS) or secondarily generalized seizure. There were unique EEG features, including: (a) the perception of a flash of light in the left visual field with a single sharp/slow wave discharge over the right occipital lobe, (b) right occipital lobe epileptiform activity during the prolonged aura, and (c) an abnormal response to photic stimulation, with occipital lobe discharges during low rates of stimulation (3-5 Hz), time-locked to the stimulus. High-resolution magnetic resonance imaging (MRI) with quantitative morphometry demonstrated that the right hemisphere and right caudate nucleus were smaller than those on the left. An abnormal gyral pattern was also noted over the right parietal region. Occasionally, distinguishing occipital lobe epilepsy from migraine may be difficult.

The intensive care treatment of convulsive status epilepticus in the UK. Results of a national survey and recommendations

Six hundred and ninety-four members of the Intensive Care Society working in the UK were surveyed by postal questionnaire between May and November 1993 to determine their management of convulsive status epilepticus resistant to initial therapy with intravenous diazepam and phenytoin. Four hundred and eight forms were completed and returned (58.8%). The survey revealed that, following failure of initial management, a benzodiazepine infusion (35%) or anaesthetic induction agent (32%) were the preferred second lines of treatment in intensive care units. In paediatric intensive care units, phenobarbitone (31%) was the agent of choice. Most respondents (57%) gave anaesthetic induction agents within 60 min of the start of status epilepticus, the majority choosing thiopentone (82%). Patients were usually monitored using clinical assessment only (45%), except in paediatric intensive care units and specialist neurological or neurosurgical units where the majority used a cerebral function monitor. Only 12% of the respondents were aware of a protocol for status epilepticus in their intensive care units. The most frequently used therapeutic and monitoring strategies in the management of refractory status epilepticus in the UK are insufficient and need re-evaluation.

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.