Treatment of memory disorders in epilepsy

The Spontaneous Incidence of Neurological Clinical Signs in Preclinical Species Using Cage-side Observations or High-definition Video Monitoring: A Retrospective Analysis

When conducting toxicology studies, the interpretation of drug-related neurological clinical signs such as convulsions, myoclonus/myoclonic jerks, tremors, ataxia, and salivation requires an understanding of the spontaneous incidence of those observations in commonly used laboratory animal species. The spontaneous incidence of central nervous system clinical signs in control animals from a single facility using cage-side observations or high definition video monitoring was retrospectively analyzed. Spontaneous convulsions were observed at low incidence in Beagle dogs and Sprague-Dawley rats but were not identified in cynomolgus monkeys and Göttingen minipigs. Spontaneous myoclonic jerks and muscle twitches were observed at low incidence in Beagle dogs, cynomolgus monkeys, and Sprague-Dawley rats but were not seen in Göttingen minipigs. Spontaneous ataxia/incoordination was identified in all species and generally with a higher incidence when using video monitoring. Salivation and tremors were the two most frequent spontaneous clinical signs and both were observed in all species. Data from the current study unveil potential limitations when using control data obtained from a single study for toxicology interpretation related to low incidence neurological clinical signs while providing historical control data from Beagle dogs, cynomolgus monkeys, Sprague-Dawley rats, and Göttingen minipigs.

Memory dysfunctions

Since the seminal work on the patient HM, who in his adulthood presented an acquired amnesic syndrome following the resection of the bilateral temporal lobe, other research has described several cases of isolated memory dysfunction in children. This chapter presents developmental and long-lasting memory disorders emerging from an organic or neurologic cause at birth or in infancy. More notably, we focus on developmental amnesic syndrome caused by neonatal bihippocampal damage and memory dysfunction caused by medial temporal developmental epilepsy. We describe these two pediatric populations and present the consequences of hippocampal/medial temporal lobe damage in the development of memory systems. We review episodic memory deficits in children with developmental amnesia and temporal lobe epilepsy and highlight their impact on new learning, personal memories, and independent life. Finally, we provide a brief overview of some of the insights and debates emerging from classic work and recent advances in the context of episodic memory dysfunction displayed by children with hippocampal/medial temporal lobe amnesia and propose new perspectives in child neuropsychology of memory, suggesting new avenues for more ecologic memory assessment and rehabilitation.

Memory Rehabilitation in Patients with Epilepsy: a Systematic Review

Memory failure is a common clinical concern of patients with epilepsy and is associated with significant functional impairments. Thus, memory rehabilitation is of critical clinical importance. In this article, we aimed to systematically evaluate the efficacy of memory rehabilitation in patients with epilepsy. The Preferred Items for Systematic Reviews and Meta-Analyses (PRISMA) was used to guide searches, extraction and reporting of data in this review. PsycINFO, Medline and PsychBITE searches yielded 95 studies. Twelve papers met inclusion criteria, reporting outcomes of cognitive or behavioural interventions that specifically targeted the rehabilitation of memory in patients with epilepsy. Methodological rigour was rated using the Single-Case Experimental Design (SCED) scale for single-case studies and a modified version of the Downs and Black checklist for group studies. Twelve prospective studies, nine group (six pre-post design, one waitlist crossover, two randomised controlled trials) and three single-case studies were identified. Eleven of the studies included adults, eight of which involved adults with temporal lobe epilepsy (TLE). One paediatric study was identified. The quality of group studies ranged from 36% (poor) to 72% (good), using the modified Downs and Black checklist. Single-case studies were assessed using the SCED scale and assessed to range in quality from four to seven out to 11. Overall, memory rehabilitation was associated with improved memory function in all studies. Verbal memory outcomes were most commonly examined and associated with improvements. This review found that the level of evidence available to support rehabilitation of memory in patients with epilepsy was generally weak and inconsistent. Nevertheless, studies conducted to date, albeit of limited methodological quality, offer preliminary evidence that memory rehabilitation is associated with improvements in verbal memory in patients with temporal lobe epilepsy. Little is known about the efficacy of memory rehabilitation in patients with non-TLE, children, and other aspects of memory difficulties. Guidelines for future research are proposed.

Neurocognitive problems in epilepsy

Cognitive dysfunction is one of the major contributors to the burden of epilepsy. It can significantly disrupt intellectual development in children and functional status and quality of life in adults. Epilepsy affects cognition through a number of mechanisms in complex interrelationship. Cognitive deficits in epilepsy may be treated indirectly through aggressive seizure control using anti-epileptic drugs or surgery, and by treating comorbid conditions such as depression. The beneficial effects of reducing seizures may offset the adverse cognitive side-effects of these therapies. Direct treatment of cognitive impairment in epilepsy mainly involves memory rehabilitation. Other direct treatments are mostly experimental and their evidence base is currently poor.

Cognitive training to improve memory in individuals undergoing electroconvulsive therapy: Negative findings

Although electroconvulsive therapy (ECT) remains the most effective treatment for severe depression, some patients report persistent memory problems following ECT that impact their quality of life and their willingness to consent to further ECT. While cognitive training has been shown to improve memory performance in various conditions, this approach has never been applied to help patients regain their memory after ECT. In a double-blind study, we tested the efficacy of a new cognitive training program called Memory Training for ECT (Mem-ECT), specifically designed to target anterograde and retrograde memory that can be compromised following ECT. Fifty-nine patients with treatment-resistant depression scheduled to undergo ultra-brief right unilateral ECT were randomly assigned to either: (a) Mem-ECT, (b) active control comprised of nonspecific mental stimulation, or (c) treatment as usual. Participants were evaluated within one week prior to the start of ECT and then again within 2 weeks following the last ECT session. All three groups improved in global function, quality of life, depression, and self-reported memory abilities without significant group differences. While there was a decline in verbal delayed recall and mental status, there was no decline in general retrograde memory or autobiographical memory in any of the groups, with no significant memory or clinical benefit for the Mem-ECT or active control conditions compared to treatment as usual. While we report negative findings, these results continue to promote the much needed discussion on developing effective strategies to minimize the adverse memory side effects of ECT, in hopes it will make ECT a better and more easily tolerated treatment for patients with severe depression who need this therapeutic option.

Epilepsy, cognition and behavior

Epilepsy is defined as two or more unprovoked seizures. Epileptic patients have intellectual disability and behavioral co-morbidities to the tune of up to 25 and 75% respectively. Various factors like underlying etiology, socioeconomic environment at home, age at onset, seizure semiology, seizure descriptors like duration, severity and frequency, therapy related adverse effects secondary to antiepileptic drugs and epilepsy surgery have been implicated for the causation of cognitive and behavioral impairment in epilepsy. Cognitive epilepsy has emerged as a specific entity. This may manifest as a transient behavioral or cognitive change, insidous onset subacute to chronic encephalopathy or more catastrophic in the form of nonconvulsive status epilepticus. Cognitive impairment seen in epileptic children include difficulties in learning, memory, problem solving as well as concept formation. Anxiety, depression and attention deficit hyperkinetic disorders are the most common psychiatric co-morbidities seen. Investigating a child with epilepsy for cognitive and behavioral impairment is difficult as these tests would require cooperation from the patient's side to a significant extent. A rational approach towards treatment would be judicious selection of antiepileptic drugs, treatment of underlying cause, appropriate management of behavioral co-morbidities including psychopharmacotherapy and a trial of immunotherapy (particularly in cognitive epilepsies), wherever appropriate.

Multifactorial determinants of the neurocognitive effects of electroconvulsive therapy

For many patients with neuropsychiatric illnesses, standard psychiatric treatments with mono or combination pharmacotherapy, psychotherapy, and transcranial magnetic stimulation are ineffective. For these patients with treatment-resistant neuropsychiatric illnesses, a main therapeutic option is electroconvulsive therapy (ECT). Decades of research have found ECT to be highly effective; however, it can also result in adverse neurocognitive effects. Specifically, ECT results in disorientation after each session, anterograde amnesia for recently learned information, and retrograde amnesia for previously learned information. Unfortunately, the neurocognitive effects and underlying mechanisms of action of ECT remain poorly understood. The purpose of this paper was to synthesize the multiple moderating and mediating factors that are thought to underlie the neurocognitive effects of ECT into a coherent model. Such factors include demographic and neuropsychological characteristics, neuropsychiatric symptoms, ECT technical parameters, and ECT-associated neurophysiological changes. Future research is warranted to evaluate and test this model, so that these findings may support the development of more refined clinical seizure therapy delivery approaches and efficacious cognitive remediation strategies to improve the use of this important and widely used intervention tool for neuropsychiatric diseases.

Comparison of remedial and compensatory approaches in memory dysfunction: a comprehensive literature review

ABSTRACT Memory is a cognitive process of information storage and retrieval that is essential to performing daily functional activities efficiently. Occupational therapists regularly help individuals with memory impairment to manage their memory deficits. The purpose of this paper was to review the main memory strategies and instructional methods used to improve or manage memory. Studies were identified by searching for the relevant literature published between 1980 and 2007 through the use of several databases with the inclusion criteria that the study must identify at least one specific memory rehabilitation method with an outcome measure representative of the specific method. The reviewed studies included three reviews, 10 randomized control trials, 17 quasi-experimental studies, and five single subjects' designs. The results suggest that there is empirical evidence to support the effectiveness of certain remedial and compensatory memory rehabilitation methods with healthy populations, but weaker evidence can be identified for the memory-impaired populations. In general, remedial methods are effective in lab settings with primarily healthy populations, yet effectiveness in daily activities is less clear. Compensatory methods are generally more efficient than remedial ones and more easily generalized to daily activities, even with memory-impaired populations.

Slow oscillation state facilitates epileptiform events in the hippocampus

In mesial temporal lobe (MTL) epilepsy, which typically involves the hippocampus (HPC), epileptiform events are enhanced during slow wave sleep (SWS). It remains unclear how and why the electroencephalographic (EEG) states that constitute SWS might predispose the HPC to this type of pathological activity. Recently our laboratory has described a novel state of deactivated hippocampal EEG activity that occurs during both SWS and urethan anesthesia: the slow oscillation (SO). This activity is characterized by a high-amplitude approximately 1-Hz signal, high synchrony within the hippocampus, and a dynamic coordination with neocortical SO. To assess how this activity state might influence epileptiform discharges, we studied the properties of stimulation-evoked and spontaneous epileptiform events elicited in the HPC of urethan-anesthetized rats. We compared those elicited during the SO to those occurring during the theta rhythm. The average duration but not the amplitude of evoked afterdischarges (ADs) was consistently larger during the SO. In addition, spontaneous epileptiform events were more frequent and of higher amplitude during the SO. Last, the bilateral propagation of both ADs and spontaneous events in the hippocampus was enhanced during the SO. These results imply that the threshold for the generation and propagation of epileptiform activity in the hippocampus is lowered during the SO and that this state may be a seed for the initiation, maintenance, and generalization of MTL epilepsy. Further examination of the pathophysiology of sleep-epilepsy interactions in the HPC will be of benefit for an understanding of the mechanisms, prognosis, and therapy for this form of epilepsy.

Amygdaloid kindling is anxiogenic but fails to alter object recognition or spatial working memory in rats

Kindling in rats produces enduring behavioral changes that parallel the psychobehavioral disturbances frequently accompanying temporal lobe epilepsy. Some evidence suggests that the site of kindling is an important determinant of the type of behavioral changes observed following kindling, although this variable has not been systematically investigated. In the present experiments, the effects of amygdaloid kindling were assessed on a battery of behavioral tests we used previously to assess the effects of kindling in dorsal hippocampus or perirhinal cortex. Three generalized seizures were kindled with stimulation in or near the basolateral amygdala. One week later, rats were tested successively on measures of anxiety, activity, object recognition memory, and spatial working memory over a period of 3 weeks. Amygdaloid kindling produced increased anxiety, but spared all other behaviors assessed. This pattern of results is partially distinct from the previously described effects of perirhinal cortical kindling, which increases anxiety but also impairs object recognition memory, and is completely distinct from dorsal hippocampal kindling, which selectively increases activity and impairs spatial working memory. The observations suggest that kindling of distinct highly interconnected temporal lobe sites produces distinct patterns of behavioral comorbidity. The underlying mechanisms are thus most likely localized to intrinsic circuits at the site of seizure origination.

The use of self-generation procedures facilitates verbal memory in individuals with seizure disorders

The efficacy of a self-generation encoding procedure in facilitating the encoding and retrieval of verbal memories was compared with the didactic presentation of information in individuals with seizure disorders. Through a within-subject design, 87 patients (25 left temporal seizure onset, 29 right temporal, 8 frontal, and 25 psychogenic nonepileptic seizures) received a self-generation learning condition and a didactic learning condition and were subsequently tested for verbal paired associate free recall, cued recall, and recognition memory. All patient groups benefited from the use of the self-generation condition relative to the didactic condition. Better performance occurred with the self-generation procedure for cued recall and recognition memory test performance, but not free recall. Individuals with a left temporal seizure onset (patients with the poorest memory performance on the didactic condition) benefited the most from the self-generation condition. A memory encoding strategy that actively involves patient participation enhances memory performance.

Memory, emotional and vocational impairments before and after anterior temporal lobectomy for complex partial seizures

PURPOSE

To assess the pre- and postsurgical frequency of memory, emotional, and vocational impairments in patients who underwent anterior temporal lobectomy (ATL), and to assess the relationship between emotional disturbance and memory abilities after ATL.

METHODS

Retrospective analysis of data was performed on 90 patients with medically intractable complex partial seizures who underwent ATL between 1981 and 2003. Patients were evaluated an average of 5 months before surgery and 11.3 months after surgery.

RESULTS

A moderate to high frequency of memory impairment (44.4%; verbal or nonverbal), emotional disturbance (38.9%) and unemployment (27.8%) existed in the same individuals both before and after surgery. There were small to moderate rates of new onset memory (18.9%), emotional (11.1%), and vocational (7.8%) difficulties after surgery often regardless of seizure control outcome. Patients who underwent left-ATL and had emotional disturbance after surgery had the lowest verbal memory test scores.

CONCLUSIONS

Results highlight the importance of taking into account emotional status when assessing memory abilities after ATL. Results replicate the finding of moderate to high frequencies of memory impairment, emotional disturbance, and unemployment both before and after ATL. Results provide support for the rationale that cognitive, psychiatric and vocational interventions are indicated to mitigate the problems that exist before and persist after ATL.

Response inhibition and set shifting in patients with frontal lobe epilepsy or temporal lobe epilepsy

Patients with frontal lobe epilepsy (FLE), patients with temporal lobe epilepsy (TLE), and matched controls were administered a test of response inhibition and set shifting (switching) (Color Word Interference Test, CWIT). Patients with FLE were impaired relative to the controls across all conditions of the CWIT, with the FLE patients showing disproportionate impairment in the Inhibition and Inhibition/Switching conditions. In contrast, the TLE patients did not differ from controls. Further analysis of the patient groups revealed that patients with left FLE were impaired relative to those with right FLE, left TLE, and right TLE in the Inhibition condition. In the Inhibition/Switching condition, patients with left FLE and left TLE were impaired relative to their right-sided counterparts. Finally, performance by the TLE group in the Inhibition/Switching condition was correlated with seizure frequency. These data suggest that patients with FLE, but not TLE, show impaired inhibition and set shifting relative to controls. In addition, side of the seizure focus and seizure frequency may contribute to executive dysfunction in patients with epilepsy.

Therapy for neurobehavioral disorders in epilepsy

Neurobehavioral disorders commonly affect patients with epilepsy. In addition to the behavioral changes during and immediately after seizures, the epileptogenic disorder of function often extends further into the postictal and interictal period. Cognitive impairments commonly affect attention, memory, mental speed, and language, as well as executive and social functions. Reducing seizure frequency and the antiepileptic drug burden can reduce these problems. Attentional deficits may respond to therapies for attention-deficit/hyperactivity disorder, but apart from patients with this comorbid disorder, their efficacy is unproven in other epilepsy patients. No effective therapies are established for other cognitive problems, but pragmatic, compensatory strategies can be helpful. Behavioral disorders include fatigue, depression, anxiety, and psychosis. Many of these disorders usually respond well to pharmacotherapy, which can be supplemented by psychotherapy. Cognitive and behavioral disorders can be the greatest cause of morbidity and impaired quality of life, often overshadowing seizures. Yet these problems often go unrecognized and, even when identified, are often undertreated or untreated.

Epilepsy and sleep disturbance

Sleep disturbance is common in epilepsy, the nature of sleep disturbances in epilepsy is diverse, and the etiologies are complex. Evidence suggests that having epilepsy and the occurrence of seizures, as well as some AEDs, are associated with significant sleep disruption. The occurrence of seizures can have profound effects on sleep architecture lasting much longer than the postictal period. Persistent daytime drowsiness in patients with epilepsy is not always due to the side effects of some AEDs and may be independently linked with sleep fragmentation. Significant sleep disruption in epilepsy has been associated with impaired quality of life and impaired seizure control. All aspects of sleep medicine are important in the management of epilepsy and are confounded by the occurrence of seizures, the location of seizures, and the beneficial and detrimental effects of AEDs. Sleep should be proactively evaluated, and sleep disturbances should be treated as part of the total care of patients with epilepsy.

Epilepsy and cognition

Patients with epilepsy are more prone to cognitive and behavioral deficits. Epilepsy per se may induce or exacerbate an underlying cognitive impairment, a variety of factors contribute to such deficits, i.e., underlying neuropathology, seizure type, age of onset, psychosocial problems, and treatment side effects. Epilepsy treatment may offset the cognitive and behavioral impairments by stopping or decreasing the seizures, but it may also induce untoward effects on cognition and behavior. The neurocognitive burden of epilepsy may even start through in utero exposure to medications. Epilepsy surgery can also induce certain cognitive deficits, although in most cases this can be minimized. Clinicians should consider cognitive side effect profiles of antiepileptic medications, particularly in extreme age groups. While no effective treatments are available for cognitive and behavioral impairments in epilepsy, comprehensive pretreatment evaluation and meticulous selection of antiepileptic drugs or surgical approach may minimize such untoward effects.