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Biomedical subjects

C D Binnie

Publications and source records attributed to C D Binnie.

At least 91 records · Page 5Linked to original sources
PubMed1994

Electroencephalography.

Notwithstanding recent advances in neuroimaging, EEG remains a major technique for investigation of the brain. Its main applications are in assessment of cerebral function rather than for detecting structural abnormalities. The principal clinical applications are in epilepsy, states of altered consciousness including postanoxic and traumatic coma, the parasomnias, dementias, toxic confusional states, cerebral infections, and various other encephalopathies. Abnormalities in EEG reflect general pathophysiological processes, raised intracranial pressure, cerebral anoxia, or oedema, epileptogenesis etc, and show little specificity for a particular disease. Consequently, they need to be interpreted in a particular clinical context; the use of routine EEG examination for screening purposes is rarely of value. Conversely, the investigation becomes most cost effective when applied to specific problems--for instance, monitoring serial changes in postanoxic coma or during open heart surgery, differential diagnosis (by telemetric ictal recordings) of epileptic and non-epileptic attacks, and providing early prediction of outcome after stroke. High technological standards and an individualised problem solving approach are prerequisites of a cost effective, reliable clinical EEG service. These are most likely to be achieved by a considered, selective referral policy, the use where necessary of prolonged complex procedures such as telemetry, and the avoidance of routine examinations of dubious clinical relevance.

Acquired Immunodeficiency Syndrome↗
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↗
PubMed1994

Cognitive impairment--is it inevitable?

Neuropsychological dysfunction in children and adults with epilepsy is common and has several possible interrelated causes, including the underlying pathophysiology, possible cerebral pathology, the effects of subclinical discharges, sleep disorders, status epilepticus and drug therapy. Of these factors the effects of subclinical discharges and those of medication are potentially remediable. In up to 50% of patients with subclinical epileptiform EEG discharges, these are associated with transitory cognitive impairment. When the discharges are focal, the cognitive deficits usually reflect the normal neuropsychological functions of the affected brain region. Most antiepileptic drugs, with the exception of the benzodiazepines (which themselves adversely affect cognition) and lamotrigine, do not suppress inter-ictal discharges. Although well-designed clinical trials of the effects of antiepileptic drugs are difficult to perform, there is convincing evidence that phenobarbitone and phenytoin cause cognitive impairment. Drugs which control both the seizures and inter-ictal discharges should improve cognitive function, provided the drugs themselves do not have a cognitive penalty. Lamotrigine provides effective control of both overt and subclinical seizures, without adversely affecting cognition.

Anticonvulsants↗
PubMed1993

MEG and EEG in epilepsy: is there a difference?

Interictal epileptiform activity recorded by scalp EEG, foramen ovale electrodes and MEG is discussed. Gross differences in waveform between the electric and magnetic records are discussed in the light of intracranial depth recordings.

Electroencephalography↗
PubMed1993

Effects of transitory cognitive impairment on psychosocial functioning of children with epilepsy: a therapeutic trial.

The authors report a trial of the use of anti-epileptic medication to treat possible cognitive deficits due to subclinical epileptiform EEG discharges in 10 children with psychosocial and educational problems associated with epilepsy. Medication intended to suppress the EEG discharges was added to the children's existing drug regime. In all instances, epileptiform activity, assessed by 24-hour periods of ambulatory monitoring, was reduced on active medication compared with placebo. In general, there was improvement of psychosocial function on active treatment: eight children improved, there was no change in one and one deteriorated. No psychosocial deterioration attributable to adverse effects of the medication was detected in those completing the trial. Despite possible confounding factors, the findings are in accordance with the view that subclinical EEG discharges can impair psychosocial function, which may be ameliorated by anti-epileptic medication.

Adolescent↗
PubMed1993

Surgical treatment of epilepsy due to cortical dysplasia: clinical and EEG findings.

Seventeen patients with cortical dysplasia who had surgical resection for medically intractable partial epilepsy were studied. Compared with two groups of surgically treated patients with intractable epilepsy due to tumour (n = 20) and mesial temporal sclerosis (n = 40), patients with cortical dysplasia showed significantly more frequent extratemporal lesions, more frequent non-epileptiform EEG abnormalities and less favourable surgical outcome for seizure control. Patients with cortical dysplasia were younger at onset of seizures and had a lower detection rate of CT abnormalities compared with the tumour group, and lower IQ compared with the mesial temporal sclerosis group. MRI was abnormal in five of seven patients. Six patients became seizure-free or almost seizure-free but eight did not experience relief of seizures. Surgical outcome related to the extent of pathology but not to the histological abnormality. Lesions outside the temporal and frontal lobes were correlated with poor surgical outcome, as were generalised interictal EEG abnormalities, which may reflect extensive or multiple lesions. Ictal intracranial recordings were not useful for presurgical evaluation of cortical dysplasia.

Adolescent↗
PubMed1992

Cognitive correlates of interictal discharges.

Interictal discharges can occur silently without apparent simultaneous clinical manifestations. Nevertheless, formal testing during electroencephalographic (EEG) recording may demonstrate transitory cognitive impairment (TCI). The probability of demonstrating TCI is related to the nature of the test employed and the type of epileptiform discharge. Difficult tasks are more useful to detect TCI, and working memory and language tests may be particularly sensitive. Generalized 3-Hz spike-wave bursts lasting at least 3 s are most likely to produce demonstrable TCI, but they can also be found during briefer and even focal discharges. The latter exhibit some specificity: left-sided focal spiking more frequently produces errors in verbal tasks, whereas right-sided discharges are more often accompanied by impairment in handling nonverbal material. TCI may adversely affect the patient's psychosocial functioning in daily life, as has been shown by some studies pointing out an impairment of educational skill in epileptic children and of driving performance in motorists. Our study on benign childhood epilepsy with Rolandic spikes also detected TCI in the majority of the patients. Nevertheless, it is not possible to claim that everyone with subclinical EEG discharges has TCI that adversely affects their psychosocial functioning. It may be possible to treat TCI by antiepileptic drugs.

Anticonvulsants↗
PubMed1991

Predictive value of intraoperative electrocorticograms in resective epilepsy surgery.

The preresection and postresection intraoperative electrocorticograms of 76 consecutive patients undergoing resective surgery for intractable epilepsy were analyzed to see if location, configuration, and discharge rate of epileptiform activity correlated with type and location of pathology of the resected specimens and outcome in regard to seizure control. The location of the predominant spike focus did not correlate with either type of location of pathology or with seizure outcome from temporal lobe surgery (n = 58). The presence of spontaneous or activated spikes outside the resected area did not correlate with outcome from any surgery type. Positive spikes recorded from the amygdala and anterior hippocampus (n = 37) were not associated with type or location of pathology, but bursts of fast repetitive spikes on these needle recordings tended to associate with mesiotemporal pathology (p = less than 0.02) and with mesial temporal sclerosis (p = less than 0.04). A preresection spike discharge rate of 1 per 4 minutes or less was associated with a poor outcome in 5 of 6 patients (p = 0.03), whereas a rate of 18 or more per minute was associated with a good outcome in 15 of 18 patients (p less than 0.06). Persistence of 50% or more of the preresection epileptiform activity in the postresection electrocorticogram after temporal lobectomy correlated with poor outcome in 80% (p = less than 0.03), although the absolute amount of epileptiform activity remaining in the postresection electrocorticogram did not correlate with outcome. Further studies are needed to define the role of intraoperative electrocorticograms in resective epilepsy surgery.

Action Potentials↗
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↗
PubMed1990

Combined use of subdural and intracerebral electrodes in preoperative evaluation of epilepsy.

For intracranial recording of partial seizures considered to originate from one of the temporal or frontal lobes, the team in the Utrecht Academic Hospital has used subdural, multicontact, flexible electrodes since 1972. These are introduced through bilateral, frontocentral trephine holes and are manipulated under fluoroscopy to cover most of the cerebral convexity. It became evident that in many patients, additional placements to record from intracerebral structures were indispensable. Therefore, using the same trephine holes, an additional 2 to 4 depth electrodes were stereotactically implanted in the mesial temporal and/or frontal structures, as appropriate. An extensive intra- and extracerebral spatial representation of the epileptogenic zone was thus obtained. We report here the methods for manufacturing and applying these electrodes and our clinical experience with 28 patients. The results obtained so far stress the value of combining subdural and depth electroencephalographic monitoring in the presurgical selection of patients suffering from medically refractory complex partial seizures. By miniaturizing the electrodes, extensive areas of the brain can be investigated without craniotomy or multiple burr holes.

Adult↗
PubMed1990

Learning disabilities in epilepsy: neurophysiological aspects.

Subclinical generalized spike-wave discharges are often accompanied by transitory cognitive impairment, demonstrable by psychological testing during EEG recording. Transitory cognitive impairment is demonstrated most readily by difficult tasks and during generalized regular spike-wave bursts lasting for more than 3 s, but can also be found during briefer and even focal discharges. That this is not simply a consequence of global inattention is shown by the fact that focal discharges exhibit some specificity: left-sided focal spiking is more likely to produce errors on verbal tasks, for instance, whereas right-sided discharges are more often accompanied by impairment in handling nonverbal material. Both learning difficulties in general and specific abnormal patterns of cognitive functioning are well documented in children with epilepsy and are most pronounced in those with frequent interictal discharges. However, there is now evidence that intermittent cognitive impairment due to the discharges themselves contributes significantly to such neurophysiological abnormalities. The significance of transitory cognitive impairment accompanying subclinical EEG discharges for everyday functioning is uncertain, but there is experimental evidence that subclinical discharges may be accompanied by disruption of educational skills in children or by impairment of driving performance in motorists. In some individuals, suppression of discharges by antiepileptic drugs has demonstrably improved psychological function, but further work is required to determine the indications for such treatment.

Animals↗
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↗