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Biomedical subjects

C D Binnie

Publications and source records attributed to C D Binnie.

At least 145 records · Page 8Linked to original sources
PubMed1981

Interhemispheric differences in photosensitive epilepsy. I. Pattern sensitivity thresholds.

A group of 15 volunteers with both photosensitive epilepsy and pattern sensitivity were shown patterns of stripes in the left and right visual hemifields. In the majority of patients the resulting paroxysmal epileptiform EEG activity was maximal in the posterior temporal and occipital regions contralateral to the stimulus. Patterns in the upper and lower hemifields were also presented and in two patients there was a difference in the vertical distribution of the response such as to suggest that in these patients the discharges were largely confined to the striate and prestriate cortex. The probability with which paroxysmal activity was evoked was usually different for the two lateral hemifields. This difference between the hemifields (which was dramatic in some patients) was mirrored in a lateralisation of the responses to diffuse intermittent photic stimulation. The association between the asymmetries in pattern sensitivity and in the responses to photic stimulation suggests that the two cerebral hemispheres often differed in hyperexcitability. It is therefore interesting that the putative differences in hyperexcitability were observed in patients with primary generalised epilepsy as well as those with other types.

Electroencephalography↗
PubMed1981

Interhemispheric differences in photosensitive epilepsy. II. Intermittent photic stimulation.

Of a consecutive series of 138 photosensitive epileptic patients 57 showed a unilateral preponderance of asymmetrical discharges on IPS, significant in each individual at the 5% level. There was no association between asymmetry of IPS-induced discharges and clinical evidence of cerebral pathology (partial or secondary generalized epilepsy, neurological deficit, left handedness, etc.). It is concluded that these results, together with our previous findings of asymmetrical pattern sensitivity suggest that the cortical hyperexcitability postulated in primary cortico-reticular epilepsy is not uniformly distributed.

Adult↗
PubMed1981

Evaluation of a simple spike-wave recognition system.

A simple analogue system for recognition of spike-wave discharges is described. During an evaluation study of 81 h recording from 23 patients the mean error rates were 4.7% false negatives and 5.2% false positives.

Computers, Analog↗
PubMed1981

Telemetric EEG and video monitoring in epilepsy.

We report a clinical evaluation of EEG and video monitoring. In 181 consecutive records, the most common clinical indications were differentiation of epileptic and nonepileptic events (99), seizure recordings for locating a possible focus (23), seizure frequency determination (32), and investigation of possible trigger factors (19). Overall, useful information was obtained in 72% and the clinical question was answered in 67% of records. Prolonged EEG and video monitoring is therefore an important diagnostic aid in patients with proven or suspected epilepsy.

Electroencephalography↗
PubMed1980

EEG sensitivity to television: effects of ambient lighting.

The effect of ambient lighting on EEG sensitivity to television has been tested in 16 photosensitive epileptic patients. Those who were not sensitive to 50 Hz IPS responded to TV at a viewing distance of 1 m or less and showed a consistent increase of EEG activation by television when the room was brightly lit. Most of those who were sensitive to 50 Hz IPS were also TV-sensitive at viewing distances greater than 1 m and the effect was most marked with lights off. The results are discussed in the context of previous work showing that some patients with TV epilepsy respond to the raster pattern of the screen and some, at greater distance, to 50 Hz flicker.

Adolescent↗
PubMed1980

The effect of background illumination on sensitivity to intermittent photic stimulation.

Sensitivity to intermittent photic stimulation (IPS) was tested in 23 photosensitive epileptic subjects under conditions of normal and reduced ambient lighting. Darkening the room to 20 lux did not increase either the incidence of photosensitivity or the effective range of flash frequencies. It is concluded that for routine clinical EEG examination there is no advantage in the current practice of darkening the room during IPS. For exhaustive testing of photosensitivity it is, however, necessary to perform IPS both in light and darkness.

Adolescent↗
PubMed1980

The self-induction of epileptic seizures by eye closure.

Of 22 consecutive epileptic patients sensitive to intermittent photic stimulation, 7 were found to induce paroxysmal activity and/or seizures by a slow closure of the lids accompanied by eye rolling, which in 6 of the 7 was totally different from the movement normally carried out on voluntary eye closure to command. To identify the syndrome it may be necessary to monitor the EEG and oculogram for some 10 min or longer with the eyes open in a well-lit environment.

Adult↗
PubMed1980

Seizure prognosis in long-stay mentally subnormal epileptic patients: interrater EEG and clinical studies.

Two groups of long-stay mentally subnormal epileptic patients, those with a chronically high seizure frequency and those who had become seizure-free, were studied for clinical and EEG factors relating to the prognosis of seizures. The mean period of observation was 20 and 22 years, respectively. All patients had a detailed clinical examination including psychometric testing, and for each, two EEG records were selected for blind semi-quantitative interrater analysis: an admission EEG and an EEG obtained within 6 months of the start of the study. Early onset of seizures, a high initial seizure frequency, multiple seizure types, upper motor neuron signs, and severe mental retardation characterized the seizure group. Significant admission EEG findings in this group included an absence of posterior dominant rhythmic activity, generalized delta activity, and frequent generalized paroxysmal discharges. Results of a linear discriminant analysis confirm that the admission EEG and clinical findings provide a basis for predicting outcome with a reliability on the order of 80%.

Adult↗
PubMed1980

Self-induction of epileptic seizures by eyeclosure: incidence and recognition.

Self-induction of epileptic seizures is generally regarded as a rarity, chiefly observed in patients of subnormal intelligence. During EEG recordings with open eyes in a consecutive series of 48 photosensitive patients, however, 13 subjects induced paroxysmal activity of seizures by eyeclosure with forced upward deviation of the eyes. Eyeclosure on command produced a different type of oculographic artefact and induced paroxysmal activity in only one subject. Two patients were of subnormal intelligence but all displayed psychiatric or psychosocial problems. The incidence of induced paroxysmal activity was reduced by reduction of ambient lighting. Eight patients admitted self-induction of seizures. We conclude that this phenomenon occurs more often than was previously supposed and can be recongnized by the recording in photosensitive patients of prolonged EEGs with eyes open and in a brightly lit environment.

Adolescent↗
PubMed1979

Visual and computer-assisted assessment of the EEG in epilepsy of late onset.

A study was made of 275 patients presenting with suspected epilepsy after the age of 20 years. In 122 it was concluded that the attacks were non-epileptic. In 60 others cerebral pathology was found. If the EEG was visibly abnormal the risk of cerebral pathology was 8 times greater than when the record was normal. The EEGs were also assessed by an automatic pattern recognition technique, which classified them as abnormal by reference to a control population of 300 volunteers. 90% of EEGs from patients with pathology were classified as abnormal and, conversely, 86% of patients with abnormal records (as assessed by the automatic analysis) had pathology.

Adult↗
PubMed1979

Television epilepsy--the role of pattern.

Patients with photosensitive epilepsy were asked to view normally functioning 625-line televisions while the EEG was monitored. In the first of two studies paroxysmal EEG activity was reliably induced by television at a viewing distance related to a patient's sensitivity to intermittent photic stimulation (IPS); patients who were sensitive to diffuse IPS at 50 Hz were sensitive to the television at greater viewing distances than those who were not. No such relationship was obtained with patterned IPS. On the other hand, patterned IPS was generally more epileptogenic than diffuse IPS with the same luminance. In the second study, where the angular subtense of the television screen and the subtense of its lines were manipulated independently, the convulsive response was found to be a function of both factors, the relative contribution of each depending on the viewing distance at which the patient was sensitive. For patients sensitive at normal viewing distances, where 50 Hz diffuse flicker appeared to be responsible for the induction of paroxysmal activity, the probability with which paroxysmal activity was induced was closely related to the subtense of the screen. For patients sensitive only at closer viewing distances the probability was influenced not by the subtense of the screen but by the subtense of its lines, suggesting that the paroxysmal activity was induced by the 25 Hz pattern alternation produced by the scan. A television with a small screen was considerably less epileptogenic than one with a large screen for all patients, presumably due to the reduced contribution of both diffuse flicker and pattern alternation.

Adolescent↗
PubMed1979

Neurophysiological aspects of pattern-sensitive epilepsy.

The capacity of striped patterns (square-wave gratings) to induce paroxysmal EEG activity in a group of pattern-sensitive epileptic patients is shown to depend on: 1. The spatial frequency of the pattern. The optimum spatial frequency lies between 1 and 4 cycles/degree in every patient tested. 2. The orientation of the pattern. Although, for the patient group as a whole, no one orientation is consistently more likely to induce paroxysmal activity than any other, the responses of individual patients can show marked orientation selectivity. 3. The brightness contrast of the pattern. The probability of paroxysmal EEG activity increases dramatically as contrast is increased from 0.2 to 0.4. Red/green gratings at isoluminance fail to induce paroxysmal activity. 4. The size of the pattern. There is considerable variation between patients in the subtense of a centrally-fixated circular pattern necessary to induce paroxysmal activity with a given probability. However, for every patient an increase in the probability of paroxysmal activity from near zero to near unity is effected by an increase in the angular subtense of the pattern by a factor of two. Patterns other than square-wave gratings are capable of inducing paroxysmal activity but, in general, patterns that stimulate more than one orientation system are less epileptogenic. The above findings are compatible with the hypothesis of a seizure trigger in the striate cortex and are incompatible with a trigger confined to the lateral geniculate nucleus of the thalamus. Further evidence against a geniculate trigger is obtained from an investigation of the response of a pattern-sensitive patient to a diffuse (unpatterned) flickering field in which it is shown that the effects of counter-phase interocular flicker implicate binocular mechanisms.

Adolescent↗
PubMed1979

The delayed effect of sodium valproate on the photoconvulsive response in man.

The acute effect of a single oral dose of sodium valproate on the photoconvulsive response has been studied. In 7 of 9 patients naive to this drug photosensitivity was abolished or reduced. A similar effect was seen in only 2 of 7 already receiving chronic sodium valproate therapy. The effect appeared 1 to 5 hr (mean, 3 hr) after attainment of peak sodium valproate concentration and lasted up to 5 days.

Adolescent↗
PubMed1979

Fluorescent lighting and epilepsy.

Fluorescent tubes flash at twice the mains frequency (100 Hz in Europe). With aging, 50-Hz brightness modulation appears. A survey of tubes used in our institute showed that 42% exhibited brightness modulation up to a depth of 20% or occasionally 30%. The effects of fluorescent lighting on the EEGs of 20 patients with photosensitive epilepsy have been studied. In no patient did the 100-Hz flicker of normally functioning tubes elicit paroxysmal activity. In 8 of 13 subjects sensitive to 50 Hz, IPS paroxysmal discharges were evoked by 50-Hz brightness modulation, but only at modulation depths of 50% or more. It is concluded that as paroxysmal activity could not be elicited by normally functioning tubes nor at those depths of modulation occurring in practice, fluorescent lighting is unlikely to present a hazard to photosensitive patients.

Adolescent↗
PubMed1979

Sodium valproate: serial monitoring of EEG and serum levels.

The clinical and electroencephalographic (EEG) effects of sodium valproate were studied in four patients by means of serial 24-hour EEG recordings and simultaneous hourly determinations of serum drug concentrations. The patients all had frequent clinical seizures and generalized spike-wave discharges. Valproate appeared to reduce diurnal paroxysmal discharges (PD) and clinical seizures, but the effect on nocturnal PD was less marked. The extent and duration of the depression of PD and seizures varied. Altering the distribution of the total daily dose may change the pattern of clinical seizures and PD. Valproate concentrations fluctuated widely over 24 hours, and the significance of single estimations often cited in the literature appears dubious. Peak serum concentrations above 100 micrograms per milliliter may be necessary in some patients to achieve clinical and EEG improvement.

Adolescent↗
PubMed1978

Computer-assisted interpretation of clinical EEGs.

A multivariate pattern recognition technique has been developed, to distinguish the EEGs of patients with cerebral pathology from those of normal controls and to localize any abnormalities detected. Two methods of feature extraction have been used, power spectral density and slope descriptor analysis, together with various types of feature compression. These techniques have been evaluated on EEGs from 63 patients with proven pathology. Spectral analysis proved more reliable than slope descriptor analysis and predicted the site of cerebral pathology more accurately than did visual assessment of the EEGs. This apparent improvement over the diagnostic reliability of visual analysis in considered to justify further development and evaluation of this technique.

Adult↗
PubMed1977

Television epilepsy and pattern sensitivity.

Properly functioning domestic television sets may induce seizures in epileptic patients (TV epilepsy). We investigated the effects of different types of visual stimuli on paroxysmal electroencephalographic (EEG) activity in 32 patients known to be sensitive to intermittent photic stimulation (stroboscopic light). We monitored sensitivity to patterns of horizontal and vertical lines, both stationary and vibrated (pattern sensitivity), and to normal broadcasts on a domestic, black and white (405- or 625-line) TV receiver (TV sensitivity). Twenty-three of the 32 patients were sensitive to pattern. Twenty-two were sensitive to vibrated patterns, and 11 to static patterns (P less than 0-01), All patients sensitive to pattern were also sensitive to TV; The association between sensitivity to pattern and to TV was significant. Clinical history of TV epilepsy (16 out of 32 patients) and laboratory evidence of pattern or TV sensitivity were not significantly associated. The high incidence of pattern sensitivity among flicker-sensitive patients and its association with TV sensitivity suggests that linear patterns produced by the raster of a black and white set as it scans, or "line-jitter" produced by the raster in areas of low TV-signal strength may contribute to the epileptogenic effect of TV.

Adolescent↗