Exploring the evaluation of antiepileptic drug change in people with intellectual disabilities and high-frequency epileptic seizures: seizure control and sustained responsiveness to the environment
Introduction
There are a number of people within the general population who experience difficulties in communication, such as very young children, people with Alzheimer's disease, and people with intellectual disabilities. Where such problems are acute, personal well-being and state of mind are largely inferred from people's observable behavior, with reliance on second-hand reporting from family or carers being common. Such reliance can call into question the validity of the information gathered on the efficacy of professional intervention [1]. This problem has been particularly highlighted where epilepsy and intellectual disabilities occur together due to the high prevalence of the condition among people with intellectual disability and the additional difficulties that this comorbidity causes.
The frequency of epilepsy occurring in people with intellectual disability is much higher than in the general population and seems to increase with the severity of disability [2], [3], [4]. Epidemiological studies suggest that as many as one-fifth of the population of people with intellectual disabilities have epilepsy [5], [6], [7], [8] and reported that people with such a “dual disability” showed poorer life skills than their peers without epilepsy, and that behavioral disturbances, such as aggression and self-injury, were particularly associated with frequent seizures and with antiepileptic polytherapy. The coexistence of epilepsy and intellectual disability also seems, as one would expect, to be a factor associated with the impact of caring. Espie et al. [9] found that carers experience strain and that family carers may be particularly prone to experience clinically significant levels of anxiety and depression.
Both conditions predispose to earlier mortality [10]. People with an intellectual disability are known to have a lower life expectancy than the general population with an estimated standardized mortality ratio (SMR) of 1.6 [11]. The probability of survival decreases as the severity of intellectual disability increases [12]. This higher risk of mortality is increased for people with coexisting epilepsy whose SMR may be as high as 5 [11], [13], [14]. With a condition occurring with such frequency and with such consequences for those concerned, it is possible to see why investigation in this area is badly needed.
The introduction of new medication is a particular issue for professionals and families alike because of the fear of undesirable side effects, such as suppression of arousal [15]. In treating epilepsy, doctors strive to prescribe the right type and level of medication to be successful in reducing seizures but with minimal adverse effects on other aspects of the patients' lives, such as their level of awareness or ability to concentrate. However, achieving such a balance in managing epilepsy in people with intellectual disabilities is made more difficult because of a number of problems.
It is common for there to be a higher than desirable frequency and severity of seizures refractory to treatment [16]. This may mean that patients have a greater vulnerability to any cognitive side effects if dosages are increased to maximize seizure control. The situation is further complicated by the high prevalence of psychiatric and behavioral disturbance in people with intellectual disabilities [17]. A large proportion of people with intellectual disabilities experience long-term exposure to drug treatment for behavioral problems [18], [19], [20], [21]. This may lead to involuntary body movements, such as tardive dyskinesia, which can look like seizure activity [22].
Moreover, the assessment of the efficacy of medication can be hampered by confusion between general behavioral abnormalities and behavior problems caused by epilepsy or the antiepileptic medication itself [3], [23]. Early observations found that approximately two-thirds of people with severe intellectual disabilities living in institutions displayed stereotypical behavior including head movements, rocking, and jerking [24], [25]. Differentiating this behavior from the pattern of behavior typically seen in complex partial seizures, particularly when there are associated ictal or postictal automatisms, is complex.
Current measures used to assess the effectiveness of medication, such as seizure diaries and seizure severity scales, make it comparatively easy to judge whether improvements have occurred in the number and level of seizures a person has experienced. However, it is often less easy for carers to notice other, more subtle changes in the person's state of alertness and behavior. It is unlikely that the commonly used primary outcome measure, seizure reduction, adequately assesses such quality-of-life outcomes. A way of measuring a patient's responsiveness to environmental stimuli would complement existing evaluation approaches and give practitioners a more accurate overview of medication effects.
Observational methods for studying human behavior and the interactions people have with others have made a substantial contribution to the evaluation of services for people with severe intellectual disability [26], [27]. The extent to which people are engaged in activity has been measured reliably. The measure has been shown to discriminate between institutional and community services [26], day services and work [28], and people with lower and higher assessed adaptive behavior [29]. Observed activity has also been shown to correlate significantly with scores on staff reported activity scales [30]. In addition, observational methods have been used to evaluate the impact on resident activity of changes in the way staff attend to residents brought about by staff training [31], [32].
The application of palmtop computers to behavioral measurement has permitted real-time multiple-category observation to be undertaken in real-world settings [33]. Sequential analysis [34] allows behavior occurring in a period of time to be analyzed in relation to the environmental states that precede or follow it. A person's response to a defined environmental stimulus can be represented by the conditional probabilities of the response occurring or not given the occurrence and nonoccurrence of the stimulus in question [35]. Such probabilities divided one by the other constitute an odds ratio, a measure of the size of effect that the stimulus has on the person's behavior. For example, Felce et al. [36] were interested in whether staff became more effective at assisting residents to engage in activities after they had been given training. The odds ratio of resident engagement in activity given the receipt of assistance after training was compared with that before training. A significant increase was interpreted as showing that staff had become more effective at assisting residents. In other words, a changed quality of assistance had caused an increased probability of the resident response, engagement in activity.
This approach to evaluating the responsiveness of people with intellectual disabilities may have application beyond analyzing the impact of changed environmental stimuli. Responsiveness to unchanged environmental stimuli but under different types or levels of medication may provide a methodology for assessing the behavioral impact of drug treatment in this population. The purpose of this study was to explore the application of this approach to studying the behavioral consequences of antiepileptic medication review among adults with intellectual disabilities and severe epilepsy.
The aims of the present study were (1) to assess the impact of antiepileptic drug change in terms of not only seizure control but also sustained responsiveness to environment stimuli, and (2) to explore the association between change in seizure frequency and such responsiveness.
Section snippets
Participants and settings
A specialist outpatient epilepsy unit at the University of Wales College of Medicine served a population of approximately 1.5 million people in South Wales and received referrals of adults with intellectual disability and severe epilepsy. It was intended to recruit 20 participants, a number determined by practical considerations concerning volume of data collection and power to demonstrate statistical significance. Participants were recruited prospectively during a 12-month period using the
Results
At baseline, Yule's Q for engagement occurring given carer interaction was positive for 18 of the 19 participants, indicating that carer attention made participant engagement in activity more likely (baseline mean, 0.77; range, −0.20–0.99). Five months following drug intervention Yule's Q had increased for 10 of the 19 participants, stayed the same for 2, and decreased for 6. Yule's Q was not calculable for 1 person. Overall, change in Yule's Q 5 months after antiepilepetic drug change was not
Discussion
The aim of this study was to explore whether the response of adults with severe learning disabilities and high-frequency epileptic seizures to receipt of attention from carers could be used as a sensitive means of representing their responsiveness to the environment when change in antiepileptic medication was undertaken to review the effectiveness of seizure control. Sequential analysis was used to calculate the likelihood of participant engagement in activity following receipt of carer
Acknowledgements
This study was funded by Wellcome Trust Project Grant #M/98/366.
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