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Biomedical subjects

J S Duncan

Publications and source records attributed to J S Duncan.

At least 19 recordsLinked to original sources
PubMed1992

Lamotrigine-induced carbamazepine toxicity: an interaction with carbamazepine-10,11-epoxide.

We report an interaction between lamotrigine (LTG), a new antiepileptic drug (AED), and carbamazepine (CBZ) and its primary metabolite CBZ-10,11-epoxide (CBZ-E) in 9 consecutive patients (5 male, 4 female, aged 19-31 years). After introduction of LTG (median daily dose 200 mg, range 100-300 mg) the mean serum CBZ-E concentration increased by 45% (P less than 0.01) and the CBZ-E/CBZ ratio increased by 19% (P less than 0.02). In 4 patients these changes were associated with clinical toxicity (dizziness, nausea, diplopia). The possibility of an increase in serum CBZ-E concentrations needs to be considered if toxicity symptoms develop when LTG is added to CBZ therapy.

Adult↗
PubMed1991

The Chalfont Seizure Severity Scale.

Seizure severity has been largely neglected in studies of patients with epilepsy and the evaluations of treatment. A seizure severity scale, that measures the components of seizures that cause patients the most disturbance, is presented with an assessment of the scale's validity and reliability.

Anticonvulsants↗
PubMed1991

Modern treatment strategies for patients with epilepsy: a review.

Of patients who develop epilepsy 70-80% will become seizure free, the remaining 20% are the most difficult to treat satisfactorily. Eighty per cent of patients are best treated with a single drug. Stepwise treatment plans for the treatment of newly diagnosed patients and for the evaluation of patients with chronic epilepsy are suggested. There is a lack of consensus regarding the rate at which to taper antiepileptic drugs being discontinued in patients with active epilepsy. There are arguments for making drug changes rapidly; these arguments and strategies for managing the withdrawal of individual drugs are presented.

Anticonvulsants↗
PubMed1991

Reinforcement of linear structure using parametrized relaxation labeling.

An approach for reinforcing underlying linear structure while suppressing unwanted noise, useful for analysis of medical images, has been presented. The method utilizes principles previously presented with regard to relaxation labeling processes, but differ in that the label set is now considered to be continuous and the distribution of label preference values for each object (pixel) parametrized by a single vector. Due to this parametrization, the total number of computations per pixel in the new method is now dependent only on the number of neighbors used in the computation, and not on the number of labels as well, as in previous methods. Thus, for a general reinforcement problem with m labels and n neighbors being considered for each pixel, the time complexity per object (pixel) per iteration goes as O (nm2) for the prototypical algorithm (e.g. (Zucker, et. al., 1977)) and is reduced by the approach presented here to O (n). The method uses a new approach for deciding local neighborhood influence and making a decision between reinforced linear structure with some magnitude and orientation and a no-structure condition based on the nonlinear (sigmoidal) thresholding of a linear vector sum. It should be noted that there is a similarity between this sigmoidal thresholding function and similar functions used in artificial neural networks (Hopfield, 1984). Ongoing work is being performed to further investigate such overlap. Also, it is planned to extend the approach in several ways. These include the ability to reinforce co-circularity, as well as to reinforce underlying planar structure by updating surface normals in true three-dimensional diagnostic imagery.

Image Enhancement↗
PubMed1991

Measurement of left ventricular wall motion from contour shape deformation.

This paper has presented the formulation and initial results for a new algorithm aimed at estimating and quantifying the trajectories of points on the left ventricular wall of the heart based on two- dimensional image-derived shape information. The algorithm is based on first automatically estimating the LV contour for two frames and then sampling the contours and tracking the motion of each sample point. Work is currently in progress to evaluate and compare each of three shape-based matching criteria, and to extend the algorithm to multiple frames. Future work will extend the approach to three spatial dimensions, capitalizing on the idea that all of the basic concepts, including curvature measurement, can be readily adapted for the higher dimensional problem.

Algorithms↗
PubMed1990

Suppression of inter-ictal spikes by CM40907. A double-blind placebo-controlled investigation and review of spike counting as a methodology for assessing the antiepileptic effect of drugs.

To assess the efficacy of CM40907--a new antiepileptic drug--in suppressing inter-ictal spikes, 6 patients with severe intractable epilepsy and frequent spikes in their inter-ictal EEGs were entered in a double-blind placebo-controlled trial. The results show that CM40907 is efficacious in reducing spike counts in the first hour after oral administration. The results of the study are presented and inter-ictal spike counting as a method is discussed.

Adolescent↗
PubMed1989

Zonisamide usage.

Explore the source record for details and available documents.

Epilepsies, Myoclonic↗
PubMed1988

Effect of the removal of individual antiepileptic drugs on antipyrine kinetics, in patients taking polytherapy.

1. Antipyrine (AP) clearance, half-life and volume of distribution were determined in 52 patients, taking one or more antiepileptic drug (AED), before and 4 weeks after the complete removal of phenytoin (PHT, n = 20), carbamazepine (CBZ, n = 15) and sodium valproate (VPA, n = 17). 2. PHT removal was associated with a mean 13% fall in AP clearance and a mean 16% increase in AP half-life, in patients who were also taking CBZ with or without barbiturates. There was no significant difference between patients who did, and did not, take barbiturates, in addition to CBZ. 3. CBZ removal was associated with a mean 45% fall in AP clearance and a mean 69% increase in AP half-life, if there was no inducing AED comedication, but had no effect on AP clearance and half-life if PHT and/or barbiturates were also being taken. 4. Removal of VPA had no effect on AP clearance or half-life. 5. The removal of PHT, CBZ and VPA had no significant effect on AP volume of distribution. 6. PHT appears to be a more powerful inducer of hepatic enzyme activity, as measured by the AP test, than is CBZ.

Adolescent↗
PubMed1988

Withdrawal symptoms from phenytoin, carbamazepine and sodium valproate.

A prospective, double-blind, placebo-controlled investigation of possible withdrawal symptoms from phenytoin, carbamazepine and sodium valproate is reported in patients with active epilepsy, on combination therapy. There was an increase in seizures on reduction and withdrawal of carbamazepine, but there was no convincing evidence of withdrawal symptoms from any of these drugs.

Adolescent↗
PubMed1986

Regional myocardial dysfunction during coronary angioplasty: evaluation by two-dimensional echocardiography and 12 lead electrocardiography.

Balloon inflation performed during percutaneous transluminal coronary angioplasty causes transient total occlusion of the coronary artery and thus provides a model for evaluation of the regional myocardial responses to transient ischemia. Twenty patients with normal left ventricular function undergoing angioplasty of isolated stenosis of the proximal left anterior descending coronary artery were studied. In group A (14 patients) analysis of one inflation-deflation sequence per patient was performed. Group B (six patients) had multiple (greater than 5) inflations; the first and last sequences were analyzed. Assessment included continuous two-dimensional echocardiography with computerized quantitative analysis of regional left ventricular wall motion, and continuous 12 lead electrocardiographic recordings. The mean duration of inflation in group A was 62 +/- 6 seconds (mean +/- SD). The onset of regional left ventricular dysfunction was 12 +/- 5 seconds after inflation. Profound dysfunction was noted in all patients. After 60 seconds of balloon occlusion of the coronary artery, 29% of patients had severe hypokinesia of the ischemic region and 71% had akinesia or dyskinesia. With deflation there was prompt recovery of regional function, with full recovery at 43 +/- 17 seconds. Comparison of data from first and last inflations in group B revealed no significant differences in time to onset of dysfunction, magnitude of dysfunction or time to complete recovery of function. The onset of ischemic electrocardiographic changes lagged behind the onset of wall motion abnormalities, with only 64% of patients showing evidence of ischemia on 12 lead electrocardiograms at 20 seconds of inflation. After 60 seconds, 86% had ischemia detectable by electrocardiography. Thus, balloon inflation during coronary angioplasty leads to profound but reversible regional left ventricular dysfunction. Repeated occlusions of the coronary artery during angioplasty do not have a cumulative ischemic effect. It may be hazardous to apply these findings to patients who have underlying major left ventricular dysfunction and in whom the reversibility of dysfunction and lack of cumulative ischemic effect may not be assured.

Adult↗
PubMed1978

Studies of louping-ill virus (Flavivirus group) in wild red grouse (Lagopus lagopus scoticus).

Studies were made to find evidence of louping-ill virus infection in free-living red grouse and relate this to their breeding success. In areas where ticks were abundant 61 (84%) adult grouse had antibody to the virus compared with 1 (10%) in areas where ticks were relatively scarce. Of 162 chicks tested 25 were shown to be viraemic. Infected chicks were of significantly less weight than comparably aged uninfected birds and the probability that they died was much greater than that of uninfected birds. It is concluded that the relatively poor breeding success in areas of high tick numbers was principally due to infection with louping-ill virus. The susceptibility of the red grouse to infection is discussed.

Animal Population Groups↗
PubMedDate not supplied

Antiepileptic drugs and the electroencephalogram.

The usefulness of electroencephalography (EEG) as an aid to diagnosis of seizure disorders is established, but its role as a guide to monitoring treatment is much less certain. For those patients with classical absences and 3-s spike wave activity there is a very close correlation between control of clinically detected seizures and EEG events. In some, but not all, patients with other seizure disorders there is a positive correlation between numbers of seizures and amount of interictal epileptiform activity (IEA). Intravenous benzodiazepines and phenytoin result in both acute seizure control and suppression of IEA. For seizures other than absences, and antiepileptic drugs (AEDs) given in the medium and long term, there is generally not a clear relationship between control of seizures and IEA. In studies of children whose epilepsy is in remission, persistent IEA has been associated with a higher risk of seizure relapse should AEDs be discontinued, but in adults the relevance of persistent IEA appears to be much less certain. Benzodiazepines and barbiturates result in increased fast activity. All AEDs may result in slowing of the dominant rhythm and increased slow activity. Carbamazepine, in particular, is often associated with apparent deterioration of background activity, even in the face of clinical improvement. Further studies are necessary to determine the mechanisms and significance of AED-induced changes in EEG background activity.

Anti-Anxiety Agents↗
PubMedDate not supplied

Effects of the removal of phenytoin, carbamazepine, and valproate on the electroencephalogram.

We report the EEG changes that occurred on discontinuance of phenytoin (PHT), carbamazepine (CBZ), and valproate (VPA) in patients with active epilepsy. Discontinuation of CBZ was associated with an increase in mean frequency of dominant rhythm and reduction in amount of slow activity. Patients who had a marked increase in seizures on discontinuation of an antiepileptic drug had a slower mean dominant rhythm at baseline than did patients who did not have an increase in seizures. Subsequent EEGs, during and at the end of drug reduction, showed an increase in bursts of interictal epileptiform activity (IEA) and in slow activity in patients who had a marked increase in seizures. The amount of slow activity and IEA did not alter in patients who did not have an increase in seizures. No patients developed photosensitivity.

Adolescent↗