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R D Elwes

Publications and source records attributed to R D Elwes.

At least 37 records · Page 2Linked to original sources
PubMed1997

Origin and propagation of interictal discharges in the acute electrocorticogram. Implications for pathophysiology and surgical treatment of temporal lobe epilepsy.

Although acute electrocorticography (ECoG) is routinely performed during epilepsy surgery there is little evidence that the extent of the discharging regions is a useful guide to tailoring the resection or that the findings are predictive of outcome or pathology. Patterns of discharge propagation have, however, rarely been considered in assessing the ECoG. We hypothesize that regions where discharges show earliest peaks ('leading regions') are located in the epileptogenic zone, whereas sites in which late, secondary, propagated activity occurs have less epileptogenic potential and do not need to be excised. To allow intraoperative topographic ECoG analysis, a computer program has been developed to identify leading regions and the sites showing greatest rates or amplitudes of spikes. Their topography has been compared retrospectively with pathology and seizure control in 42 consecutive patients following temporal lobe surgery. Leading regions were most often found in the hippocampus, the subtemporal cortex and the superior temporal gyrus. The most common propagation patterns were from hippocampus to subtemporal cortex and vice versa. There was no association between seizure outcome and the location of regions with greatest incidence or amplitude of spikes or location of leading regions. There was, however, a strong and significant association between poor outcome and non-removal of leading regions other than those in the posterior subtemporal cortex. All leading regions (other than posterior subtemporal) were resected in 27 patients of whom 25 had a favourable outcome. Leading regions (other than posterior subtemporal) remained in 14 patients of whom only four had a good outcome. One patient had no epileptiform activity in the ECoG and good outcome. Persistent posterior subtemporal leading regions remained in nine subjects; all had favourable outcome (Grades I or II) but only three were seizure free. These results suggest that: (i) interictal epileptiform discharges may originate from a complex interaction between separate regions, resulting in propagation and recruitment of neuronal activity along specific neural pathways; (ii) removal of all discharging areas appears unnecessary to achieve seizure control provided that leading regions (other than posterior subtemporal) are removed; and (iii) identification of such leading regions could be used to tailor resections in order to improve seizure control and reduce neurological, neuropsychological and psychiatric post-surgical morbidity.

Adolescent↗
PubMed1996

Clinical pharmacokinetics of newer antiepileptic drugs. Lamotrigine, vigabatrin, gabapentin and oxcarbazepine.

The clinical pharmacokinetics of the 4 antiepileptic drugs lamotrigine, vigabatrin, gabapentin and oxcarbazepine have been reviewed in this paper. All the drugs have linear kinetics and reliable absorption, although the saturation of transport across the gut may occur at high doses with gabapentin. All the drugs can be conveniently given as a twice daily dosage apart from gabapentin, which has a short half-life and a midday dose is needed. Unlike many of the older drugs, lamotrigine, vigabatrin and gabapentin have a predominantly renal excretion and are not metabolised through the cytochrome P450 system. They do not induce their own metabolism or that of other commonly used anticonvulsants. Similarly, clinically important interactions with other major classes of drugs metabolised this way, such as anticoagulants or steroid hormones, do not occur. Oxcarbazepine, however, can cause oral contraceptive pill failure. Oxcarbazepine is immediately metabolised to a hydroxy metabolite and could be considered a prodrug. It appears to have fewer pharmacokinetic interactions than carbamazepine. Valproic acid (sodium valproate) inhibits the glucuronidation of lamotrigine and increases its half-life; when used together, dosage modification of lamotrigine is needed to avoid toxicity.

Acetates↗
PubMed1995

Power spectrum and intracranial EEG patterns at seizure onset in partial epilepsy.

Intracranial electroencephalographic patterns of seizure onset during preoperative assessment with intracerebral and subdural electrodes have been correlated with surgical outcome in 15 patients with partial epilepsy assessed for surgery. The presence and topography of electrodecremental events, high frequency activity, irregular sharp waves intermixed with slow activity, spike-wave activity and rhythmic ictal transformation at seizure onset were studied in a total of 78 complex partial seizures. Raw traces from intracerebral and subdural recordings were assessed visually in conjunction with changes in the following spectral variables (calculated for consecutive 1.28 sec epochs): amplitude (sum of amplitude of all components within a frequency band), activity, mobility, and complexity. The time course of these variables during preictal and ictal periods was displayed and assessed. This technique proved effective for detecting low-amplitude high-frequency activity and subtle electrodecremental events. It was concluded that: (a) most patients (12/15) showed early electrodecremental events, generalised or local, mainly involving frequencies below 40 Hz; (b) generalised electrodecremental events at onset did not imply poor outcome; (c) localised high-frequency activity, between 20 and 80 Hz, was associated with a good outcome.

Adolescent↗
PubMed1995

Phenobarbitone, phenytoin, carbamazepine, or sodium valproate for newly diagnosed adult epilepsy: a randomised comparative monotherapy trial.

Recent studies have shown that most newly diagnosed epileptic patients can be satisfactorily treated with a single antiepileptic drug. We therefore undertook a prospective randomised pragmatic trial of the comparative efficacy and toxicity of four major antiepileptic drugs, utilised as monotherapy in newly diagnosed epileptic patients. Between 1981 and 1987 243 adult patients aged 16 years or over, newly referred to two district general hospitals with a minimum of two previously untreated tonic-clonic or partial with or without secondary generalised seizures were randomly allocated to treatment with phenobarbitone, phenytoin, carbamazepine, or sodium valproate. The protocol was designed to conform with standard clinical practice. Efficacy was assessed by time to first seizure after the start of treatment and time to enter one year remission. The overall outcome with all of the four drugs was good with 27% remaining seizure free and 75% entering one year of remission by three years of follow up. No significant differences between the four drugs were found for either measure of efficacy at one, two, or three years of follow up. The overall incidence of unacceptable side effects, necessitating withdrawal of the randomised drug, was 10%. For the individual drugs phenobarbitone (22%) was more likely to be withdrawn than phenytoin (3%), carbamazepine (11%), and sodium valproate (5%). In patients with newly diagnosed tonic-clonic or partial with or without secondary generalised seizures, the choice of drug will be more influenced by considerations of toxicity and costs.

Adolescent↗
PubMed1995

Multiple subpial transection: a review of 21 cases.

Multiple subpial transection (MST) is a novel technique in surgery for epilepsy, employed in patients where some or all of the epileptogenic zone cannot be resected because it lies in a vital cortical area. Twenty one patients subjected to MST were reviewed. Eighteen patients had medically intractable epilepsy and three patients had Landau-Kleffner syndrome. Their ages ranged from 6 to 47 (mean 15-9) and duration of epilepsy ranged from 0.33 to 42 (mean 8.6) years. Preoperative MRI showed focal abnormalities in eight cases. Detailed electrophysiological examination was carried out on all patients. Brain resection was performed in addition to MST in 12 patients. A further six patients underwent brain biopsy. Three patients with Landau-Kleffner syndrome were subjected neither to resection nor to biopsy. Histopathological examination showed Rasmussen's syndrome in six patients, cortical dysplasia in six, cerebral tumour in one, and non-specific changes in five. Multiple subpial transection was carried out mainly in precentral and postcentral regions. Eighteen patients have been followed up for one to five years, and three for 10 months. The three patients with Landau-Kleffner syndrome were mute before operation and have shown substantial recovery of speech. Of the other 18, 11 showed a worthwhile decrease in seizure frequency. None of the patients developed chronic neurological deficits attributable to MST. It is concluded that MST leads to worthwhile seizure control without major neurological deficit in patients who would otherwise be inoperable.

Adolescent↗
PubMed1994

Utility of stereoelectroencephalography in preoperative assessment of temporal lobe epilepsy.

Of 269 consecutive patients entered into a preoperative assessment programme for possible surgical treatment of epilepsy, 33 had intracranial recording (SEEG) with combined subdural and depth electrodes for the purpose of localising a suspected temporal site of seizure onset. The findings in these patients are analysed with particular reference to: 1) the criteria of selection for SEEG and their validity; 2) information on SEEG compared with that obtained by less invasive means, including foramen ovale telemetry; 3) information on the use of intracerebral electrodes compared with subdural placements; 4) possible predictors of failure of localisation by SEEG and of surgical outcome. It was concluded that SEEG had usefully contributed to the management of 69% of the patients in whom it was used, establishing a previously unidentified site of seizure onset in 33%, correcting an erroneous localisation in 15%, and establishing inoperability in 21% of patients. No predictors of failure of SEEG or of surgery emerged; thus there was no evidence of unnecessary use of this procedure. Five patients were found with incorrect lateralisation of seizure onset on foramen ovale recording (of a total of 192 foramen ovale telemetries). Localisation of the ictal onset zone either by the distribution of inter-ictal discharges or by the initial ictal changes at subdural electrodes was unreliable, confirming the need for ictal, depth recordings.

Adult↗
PubMed1994

Intracerebral propagation of interictal activity in partial epilepsy: implications for source localisation.

The hypothesis that focal scalp EEG and MEG interictal epileptiform activity can be modelled by single dipoles or by a limited number of dipoles was examined. The time course and spatial distribution of interictal activity recorded simultaneously by surface electrodes and by electrodes next to mesial temporal structures in 12 patients being assessed for epilepsy surgery have been studied to estimate the degree of confinement of neural activity present during interictal paroxysms, and the degree to which volume conduction and neural propagation take part in the diffusion of interictal activity. Also, intrapatient topographical correlations of ictal onset zone and deep interictal activity have been studied. Correlations between the amplitudes of deep and surface recordings, together with previous reports on the amplitude of scalp signals produced by artificially implanted dipoles suggest that the ratio of deep to surface activity recorded during interictal epileptiform activity on the scalp is around 1:2000. This implies that most such activity recorded on the scalp does not arise from volume conduction from deep structures but is generated in the underlying neocortex. Also, time delays of up to 220 ms recorded between interictal paroxysms at different recording sites show that interictal epileptiform activity can propagate neuronally within several milliseconds to relatively remote cortex. Large areas of archicortex and neocortex can then be simultaneously or sequentially active via three possible mechanisms: (1) by fast association fibres directly, (2) by fast association fibres that trigger local phenomena which in turn give rise to sharp/slow waves or spikes, and (3) propagation along the neocortex. The low ratio of deep-to-surface signal on the scalp and the simultaneous activation of large neocortical areas can yield spurious equivalent dipoles localised in deeper structures. Frequent interictal spike activities can also take place independently in areas other than the ictal onset zone and their interictal propagation to the surface is independent of their capacity to trigger seizures. It is concluded that: (1) the deep-to-surface ratios of electromagnetic fields from deep sources are extremely low on the scalp; (2) single dipoles or a limited number of dipoles are not adequate for surgical assessment; (3) the correct localisation of the onset of interictal activity does not necessarily imply the onset of seizures in the region or in the same hemisphere. It is suggested that, until volume conduction and neurophysiological propagation can be distinguished, semiempirical correlations between symptomatology, surgical outcome, and detailed presurgical modeling of the neocortical projection patterns by combined MEG, EEG, and MRI could be more fruitful than source localization with unrealistic source models.

Adult↗
PubMed1991

Outcome following resective surgery for temporal lobe epilepsy: a prospective follow up study of 102 consecutive cases.

The long term outcome has been assessed in a consecutive series of 102 cases undergoing resective temporal lobe surgery because of medically intractable epilepsy. Patients were followed prospectively for a median of 61 months. Actuarial statistics were used to measure the temporal patterns of remission and stability of outcome over prolonged periods of observation. The probability of achieving one year remission was 57% by one year, 70% by two years, and 77% by seven years. Once a patient was in one year remission the probability of remaining seizure free was 90%. This rose to 94% after two consecutive years of being seizure free. The majority of patients who remit following surgery have done so by two years of follow up. Outcome at the end of the second post operative year is a good predictor of long term prognosis.

Adolescent↗
PubMed1991

Epilepsy and employment. A community based survey in an area of high unemployment.

A community based survey was undertaken to assess the work record of patients with epilepsy in an area of high unemployment. One hundred and thirty seven epileptic patients were identified from a population of 23,837 persons of employable age registered with three urban group practices in North East England. The unemployment rate for economically active patients with epilepsy was 46% compared with 19% for an age and sex matched control population (p less than 0.01). Fifty nine per cent of patients with active epilepsy were unemployed. In those with an associated neurological or psychiatric handicap and those who were unskilled manual workers the unemployment rates were 79% and 77%, respectively. Patients with epilepsy were less likely to leave school with qualifications or undergo subsequent training or apprenticeships. They were more likely to be unskilled manual workers, single and living in rented accommodation. In an area of high unemployment patients with epilepsy have disproportionately greater difficulty finding work. High unemployment rates among patients with epilepsy are only one aspect of a spectrum of social and economic disadvantage.

Adolescent↗
PubMed1989

Treatment of narcolepsy with L-tyrosine: double-blind placebo-controlled trial.

A randomised, double-blind, placebo-controlled study of L-tyrosine was done in ten subjects with narcolepsy and cataplexy. Of twenty-eight visual analogue scales rating mood and arousal, the subjects' ratings in the tyrosine treatment (9 g daily) and placebo periods differed significantly for only three (less tired, less drowsy, more alert). Ratings of daytime drowsiness, cataplexy, sleep paralysis, night-time sleep, overall clinical response, and measurements of multiple sleep latency and tests of speed and attention did not differ significantly between tyrosine and placebo periods. Dietary supplementation with tyrosine 9 g daily for 4 weeks seems to have a mild stimulant action on the central nervous system but this effect is not clinically significant in the treatment of the narcoleptic syndrome.

Adult↗
PubMed1988

The course of untreated epilepsy.

As little is known about the course of untreated epilepsy the time intervals between untreated tonic clonic seizures were examined retrospectively in a series of 183 patients presenting to a neurological department having had two to five seizures. After the first seizure a second attack had occurred within one month in 56 patients, within three months in 93, and within one year in 159. The median interval between the first two seizures was 12 weeks (95% confidence interval 10 to 18 weeks), between the second and third eight weeks (four to 12 weeks), between the third and fourth four weeks (two to 20 weeks), and between the fourth and fifth three weeks (one to four weeks). When patients who had had three, four, or five untreated seizures were considered separately a similar pattern of decreasing intervals was seen. Successive intervals between seizures could be compared in 82 patients. In 48 the interval decreased, in 16 it did not change, and in 18 it increased. These results suggest that in many patients there is an accelerating disease process in the early stages of epilepsy.

Adolescent↗
PubMed1986

Subacute combined degeneration of the cord due to folate deficiency: response to methyl folate treatment.

Subacute combined degeneration of the cord is a rare complication of folate deficiency. Disturbance of methylation reactions in nervous tissue probably underlie subacute combined degeneration of the cord arising from folate as well as vitamin B12 deficiency. Methyl tetrahydrofolate is the form in which folic acid is transported into the CNS. Therefore methyl tetrahydrofolate treatment of the neurological and psychiatric manifestations of folate deficiency would seem to be theoretically advantageous. A case of subacute combined degeneration of the cord due to dietary folate deficiency and associated with an organic brain syndrome is reported. There was striking haematological, neurological and psychiatric response to methyl folate treatment.

Female↗
PubMed1985

Prognosis after a first untreated tonic-clonic seizure.

The prognosis for seizure recurrence was assessed in 133 patients who presented at a median of 1 day after a first-ever tonic-clonic seizure. The cumulative probability of recurrence was 20% by 1 month, 28% by 2 months, 32% by 3 months, 46% by 6 months, 62% by 1 year, and 71% by 3 and 4 years. After a first seizure epilepsy is likely to develop in the majority of patients.

Adolescent↗