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Biomedical subjects

P B Fenwick

Publications and source records attributed to P B Fenwick.

At least 19 recordsLinked to original sources
PubMed1992

The relationship between mind, brain, and seizures.

The medical model of epilepsy suggests that seizures arise at random or in response to precise physiological events. Little weight is given to the part that ongoing brain activity may play in either precipitating or inhibiting seizures. In the focal epilepsies, the presence of damaged neurons that fire in the epileptic mode continuously and are called pacemaker cells has been demonstrated in both animal models and human epilepsy. If these pacemaker cells are firing all the time, why then do seizures arise only spasmodically? Behavior can be thought of as changes in the excitation and inhibition of populations of neurons. Therefore, it is likely that these excitatory and inhibitory waves will either increase or decrease the likelihood of seizures arising. The conditioning of the neurons to fire in volleys in a biofeedback paradigm, the conditioning of seizures in a classic Pavlovian sense, and the occurrence of seizures in response to behavioral changes has been shown in animal models of epilepsy and in humans. There is now evidence that children can both inhibit and generate their own seizures spontaneously. Many adult patients have behavioral strategies that they use either to inhibit or to stop the spreading seizures. In patients who have difficulties in coping with the stresses in their life, the voluntary generation of seizures may come to form a response to difficult situations. Thus, any complete epilepsy program must consider the patient, the behavior, and the relationship between seizures and behavior.

Animals↗
PubMed1992

Antiepileptic drugs and their psychotropic effects.

Antiepileptic drugs (AEDs) are still the main treatment for epilepsy. The first drugs such as the bromides, phenobarbital (PB), and related barbituates were all found to be anticonvulsant by chance. They also all carried to some extent the disadvantages of slowing thinking and motor behavior. Bromides are now seldom used and (PB) is only used when other drugs fail, although it is an important drug in the third world because of its low cost. Carbamazepine (CBZ), valproate (VPA), and phenytoin (PHT) are the current first-line AEDs. All of these drugs vary in the extent of their effect on mood. These drugs have also all been used in the treatment of psychiatric disorders. CBZ has been used mainly as a mood normalizer and has had some success in treating hypermanic episodes. VPA has been used successfully in the treatment of cyclical psychoses, whereas PHT, although it had a vogue in the 1940s for the treatment of psychosis, is little used as a psychological treatment now.

Affect↗
PubMed1991

Metabolic clearance rate of testosterone in male epileptic patients on anti-convulsant therapy.

There are several reports which state that male epileptics on anti-convulsant therapy have reduced sexual activity. We and others have shown that, although total testosterone is raised, the free testosterone concentration is reduced in this patient population. This could be a result of an increased metabolic clearance rate (MCR) of testosterone, inadequate secretion of LH to stimulate testosterone synthesis or inappropriately low testosterone production by the Leydig cells. We have examined these possibilities by measuring the MCR of testosterone in 15 male epileptics on anti-convulsant therapy. In this group of patients, the mean LH (9.3 +/- 5.9 IU/l) and sex-hormone binding globulin (SHBG) (54.5 +/- 22.9 nmol/l) concentrations were significantly greater than those of five normal control subjects (4.7 +/- 1.11 IU/l and 26.0 +/- 7.0 nmol/l respectively). Mean total testosterone concentrations of the two groups were not significantly different but the mean percentage of free testosterone and free testosterone concentration were significantly lower in the patient population (2.06 +/- 0.43 vs 2.98 +/- 0.27 and 0.56 +/- 1.1 vs 0.79 +/- 0.07 pmol/l). The MCR of testosterone was significantly lower in the patients (773 +/- 322 vs 1354 +/- 443 l/day) and showed a positive correlation with the percentage of free testosterone. Therefore, our results suggest that the lowered free testosterone in male epileptics on anti-convulsant therapy is not due to an increased MCR of testosterone. The increased LH concentration suggests primary hypogonadism. This, in turn, could be responsible for low free testosterone levels in the presence of normal testosterone.

Adult↗
PubMed1990

Behavioural treatment of epilepsy.

There is abundant evidence of the close interrelation between the induction and inhibition of seizure activity and the patient's thoughts, feelings and behaviour. The detailed knowledge that we now have of the epileptic focus and the way that it is connected to the surrounding cerebral mechanisms, makes it possible for many patients with focal epilepsy to establish a significant degree of seizure control by altering their thinking and behaviour.

Cognitive Behavioral Therapy↗
PubMed1989

Evoked and psychogenic epileptic seizures. I. Precipitation.

The precipitation of seizures by external stimulation (evoked seizures) is well known. Less well known is the precipitation of seizures by a change in the patient's thinking or feelings. This artick uses Lockhart's monkey model of focal epilepsy to propose that there is a close relationship between seizures and ongoing brain activity. Thus, seizures precipitated by both voluntary and spontaneous changes in behaviour and thinking must commonly occur. Clinical examples of such seizure precipitation is described.

Adult↗
PubMed1989

Evoked and psychogenic epileptic seizures: II. Inhibition.

The inhibition of seizure activity by behavioural methods is becoming more popular. Lockhart's monkey model of focal epilepsy suggests a theoretical approach to behavioural seizure inhibition. Behaviour, by changing the pattern of excitation and inhibition surrounding a focus, is thus able to inhibit seizure activity. This article describes single case studies in which the behavioural methods of cued arousal, covert desensitization and relaxation have brought about a decrease in seizure frequency.

Adult↗
PubMed1988

Effects of nitrous oxide on auditory cortical evoked potentials and subjective thresholds.

This study has examined the effects of inhaled nitrous oxide on the N1 and P2 components of the cortical auditory evoked potentials (AEP) in the latency interval 80-300 ms after the stimulus. The amplitudes, latencies and thresholds of the AEP were measured at a range of end-tidal nitrous oxide concentrations (0%, 10%, 20%, 40%) in 10 subjects with normal hearing. Systematic decreases in amplitude and latency were observed with an increase in threshold. A study of the effect of stimulus intensity on AEP amplitude showed that the amplitude change with nitrous oxide was accounted for largely by systematic increase in evoked potential threshold. Subjective pure tone thresholds were not affected by the concentrations of nitrous oxide used, indicating that the AEP changes were independent of subjective hearing level.

Adolescent↗
PubMed1988

The aetiology of aggression in temporal-lobe epilepsy.

A retrospective case-note survey was carried out on 31 subjects admitted with temporal-lobe epilepsy to the Maudsley hospital from 1974-1983 inclusive. Fourteen aggressive subjects were compared with the non-aggressive patients on 95 organic, developmental, and social variables. Aggressive behaviour was associated with male sex, early onset of seizures, and a history of long-standing behavioural problems. Aggressive subjects had lower mean IQ scores and poorer occupational records than controls. No relationship was found between aggression and the presence of specific EEG or CAT scan findings, or a history of psychosis. The results demonstrate the complex interplay between organic and socially mediated factors underlying aggressive behaviour in temporal-lobe epilepsy.

Adolescent↗
PubMed1987

Effect of oestrogen and testosterone implants on psychological disorders in the climacteric.

In a double-blind trial oestradiol, oestradiol/testosterone, or placebo implants were assessed for their effects on psychological symptoms in women attending a menopause clinic. After two months, women receiving active treatment scored better than the placebo group on a self-rating scale of distress, on anxiety, and on depression (p less than 0.05). Postmenopausal but not perimenopausal women improved after placebo, and at 4 months the scores in the three groups no longer differed significantly.

Adult↗
PubMed1986

Nocturnal penile tumescence and serum testosterone levels.

Ten patients with chronic epilepsy were selected; five had high and five had low total serum testosterone levels. Each patient slept for two nights in the sleep laboratory. EEG monitoring and measurements of nocturnal penile tumescence were carried out during sleep. A clear relationship between both total and free serum testosterone levels were found with nocturnal penile tumescence. FSH, LH, SHBG, and prolactin showed no relationship. The five patients with low serum testosterone levels all showed reduced sexual activity.

Adolescent↗
PubMed1986

Epilepsy and handicap from birth to age 36.

Fifty-five subjects with epilepsy were identified in the first 36 years of the 1946 birth cohort study. In 37 cases there was neither evident cause for the epilepsy nor associated brain-damage and these are referred to as 'uncomplicated', the rest as 'complicated'. Subjects with epilepsy came from poorer social backgrounds than the rest of the cohort. Mortality for both the complicated and uncomplicated groups was high. The educational and occupational achievements, marriage and parenthood, self-esteem and psychiatric morbidity of those surviving to adult life were compared with individually matched controls drawn from the same population. For the uncomplicated group there was no evidence of handicap at age 26, but 10 years later handicap was evident in this group in the economic sphere and in self-esteem.

Adult↗
PubMed1985

Sexual behaviour in a centre for epilepsy.

The sexual behaviour and hormonal profiles in 97 patients with chronic epilepsy from an epilepsy centre were studied. Sexual behaviour relating to numbers of sexual contacts, orgasms, spontaneous erections, and early morning erections, whether there was difficulty in obtaining or maintaining an erection, or in ejaculation, was assessed at interview. Hormonal profiles consisted of LH, FSH, prolactin, total testosterone, free testosterone, and SHBG. Information was obtained relating to type of seizure, seizure frequency, age of onset, likely pathology, IQ, and medication. The study showed that this patient group was profoundly hyposexual and had a high level of sexual dysfunction. Serum free testosterone levels were low, and it is suggested that the high level of sexual dysfunction and lack of sexual interest may well have a hormonal basis. The reasons for this are discussed.

Adolescent↗
PubMed1978

The contingent negative variation in antisocial behaviour: a pilot study of Broadmoor patients.

Using a classical click/flash paradigm, the CNV was recorded from the following three groups of subjects at Broadmoor Hospital: (1) 14 'psychopathic' patients selected by use of the 4/9 MMPI profile and confirmed by independent clinical diagnosis; (2) 15 'non psychopathic' patients, all psychotic and mainly schizophrenic; (3) 14 healthy staff control subjects. All three groups were matched for age and sex; the two patients groups were also matched for length of stay. Two series of 32 paired stimuli were used, separated by an interval of 30 minutes. The mean CNV voltage was significantly lower in the 'non-psychopathic' patients. The amplitude of the 'psychopath's' CNV response did not differ significantly from that of the staff controls, but the response variability between the first and second series of trials was much greater in the 'psychopathic' patients than in the other two subject groups. The 'psychopathic' subjects tended to show more rapid initial development of the CNV.

Adult↗
PubMed1977

Relationship between amplitude of pattern displacement and visual evoked potentials.

Thirteen subjects looked at a 7 mm2 black and white checkerboard which was displaced through 0.25, 0.50, 0.75 and full pattern displacement. One hundred and twenty eight averages were taken for each displacement and the peak to peak amplitude of the visual evoked potential was measured. This showed a linear relationship between pattern displacement and size of the evoked potential. Latency was unaffected for 0.25, 0.50 and 0.75 displacement but was significantly longer for the full pattern stimulation.

Adolescent↗
PubMed1977

Metabolic and EEG changes during transcendental meditation: an explanation.

Two experiments were conducted to measure the oxygen uptake (Experiment II) and the carbon dioxide production (Experiment I) during transcendental meditation. A control group of non-meditators and a few meditators listening to music was used for both experiments. In Experiment I, a controlled group of fasting meditators was also included. A drop in oxygen consumption and carbon dioxide production, found by previous authors during transcendental meditation, was confirmed. It was, however, possible to show that these drops were physiologically of small significance, and were of the magnitude to be expected from muscle relaxation. EEG recordings were taken during Experiment II in the meditating group. The EEG results showed transcendental meditation to be a method of holding the mediator's level of consciousness at stage 'onset' sleep. No evidence could be found to suggest that meditation produced a hypometabolic state beyond that produced by muscle relaxation and there was no evidence that the EEG changes were different from those observed in stage 'onset' sleep. No support was found for the idea that transcendental meditation is a fourth stage of consciousness.

Analysis of Variance↗