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Biomedical subjects

W Van Emde Boas

Publications and source records attributed to W Van Emde Boas.

5 recordsLinked to original sources
PubMed1998

Light diffusion in photosensitive epilepsy.

Photosensitivity is usually tested by intermittent photic stimulation. Photoparoxysmal responses in the EEG are enhanced when the eyes remain closed during stimulation. We tested the hypothesis that this is due to diffusion of light by the eyelids. In 25 photosensitive patients, conditions 'eye closure', 'eyes closed', 'eyes open' and 'eyes open with diffuser' were tested for frequencies of 2-60 Hz. Additional influences of a red filter and fixation were also examined. The photosensitivity range was maximal in the condition 'eyes open with diffuser', due to an increase of the upper limit to a median 60 Hz (range 25-60), from 35 (15-50) Hz with eyes open, 37.5 (25-60) Hz with eyes closed and 40 (23-60) Hz with eye closure (P = 0.0002). This effect was attenuated in patients on valproic acid and with the use of a red or white filter. Testing with a diffuser was more sensitive than without, except for one patient who was photosensitive only in the eye closure condition. The influence of the eyelids on photosensitivity can be explained by diffusion of light, attentuated by an intensity loss. Use of a diffuser may simplify testing for photosensitivity in the EEG laboratory. The diffusion effect may explain seizure susceptibility in front of 50 and 60 Hz television screens.

Adolescent↗
PubMed1987

Seven day administration of lamotrigine in epilepsy: placebo-controlled add-on trial.

A double-blind placebo-controlled trial of 7 days administration of lamotrigine as add-on therapy was performed in 10 patients with frequent therapy-resistant, chiefly partial, seizures. Dosage was adjusted on the basis of estimated half-life. Six patients showed a 50% seizure reduction on lamotrigine and two an increase. Side effects (ataxia, dizziness and apathy) occurred in 3 patients, but only at blood levels above 3 micrograms/ml, and were rapidly relieved when the dose was reduced in two. EEG spike counts were significantly reduced on lamotrigine. There was no evidence of interactions with co-medication.

Adolescent↗
PubMed1987

Electroencephalographic findings in antiepileptic drug trials: a review and report of 6 studies.

A recent survey has shown that the EEG is of doubtful value as an outcome variable in clinical antiepileptic drug (AED) trials. Analysis of findings in 6 trials shows that in only two no consistent effect was seen; that in two power spectral analysis provided additional information to confirm changes in background activity; that in one a close relationship could be established between reduction in frequency of epileptiform discharges and administration of the trial drug (lamotrigine), and that in one, even though no correlation was apparent during use of the AED, there was an increase in frequency of both discharges and seizures on withdrawal (CGP 11952). In general the EEG would appear to be unsuitable as an outcome variable for assessing drug efficacy in AED trials. On the other hand it may give insight into the mode of drug action. Conceivably more efficient use could be made of the EEG if the methodology--including patient selection, consideration of circadian rhythms and of combination AED therapy, and standardized long-term recording--were to be improved and automation and quantification techniques used.

Adolescent↗
PubMed1985

Geniculate spikes during epileptic seizures induced in dogs by pentylenetetrazol and bicuculline.

Previous studies have indicated that in cats generalized seizures induced by pentylenetetrazol (PTZ) or bicuculline (BIC) may be preceded by high frequency multi-unit activity in brain-stem structures. This activity is not readily demonstrable using conventional EEG recording bandwidths and precedes the onset of spikes and spikes-wave activity in thalamo-cortical systems. Recording with chronic subdural and depth electrodes during PTZ and BIC-induced seizures in 18 dogs essentially replicated these results. However, a new and consistent finding was that the high frequency discharges accompanying seizure onset were most often seen, and most often appeared first, in the lateral geniculate body, neocortex and hippocampus being involved later. The findings are considered to suggest a significant role for subcortical structures in this particular model of generalized cortico-reticular epilepsy.

Animals↗