The Frontal Lobes, Epilepsy, and Behavior

Cognitive flexibility impairment in temporal lobe epilepsy: The impact of epileptic foci lateralization on executive functions

INTRODUCTION

Temporal Lobe Epilepsy (TLE) has been associated with memory impairments, which are typically linked to hippocampal and mesial temporal cortex lesions. Considering the presence of extensive bidirectional frontotemporal connections, it can be hypothesized that executive dysfunction in TLE is modulated by the lateralization of the epileptic foci.

MATERIAL AND METHODS

A comprehensive neuropsychological executive functions protocol was administered to 63 participants, including 42 individuals with temporal lobe epilepsy (20 with right-TLE and 22 with left-TLE) and 21 healthy controls aged 20-49.

RESULTS

The results indicate that TLE patients exhibit poorer executive performance compared to healthy controls in working memory (F(2,60) = 4.18, p <.01), planning (F(2,60) = 4.71, p <.05), set shifting (F(2,60) = 10.1, p <.001), phonetic verbal fluency (F(2,60) = 11.71, p <.01) and semantic verbal fluency (F(2,60) = 9.61, p <.001. No significant differences were found in cognitive inhibition. Furthermore, right-TLE patients showed lower performance than left-TLE in set shifting (F(1,61) = 6.45, p <.05), while no significant differences were observed in working memory, planning, inhibition, and verbal fluency.

CONCLUSIONS

This research emphasize the importance of considering the lateralization of the temporal lobe focus to achieve a more accurate neuropsychological characterization. The cognitive differences between left and right TLE patients highlight the need for individualized approaches in their treatment and care.

Verbosity with retelling: Narrative discourse production in temporal lobe epilepsy

To examine micro- and macrolinguistic underpinnings of circumstantiality in temporal lobe epilepsy (TLE), we examined the elicited narrative output of 15 individuals with TLE and 14 controls. To replicate and extend Field and colleagues' (2000) work, participants were asked to produce five immediately consecutive elicitations of an eight-frame cartoon "Cowboy Story" (Joanette et al., 1986). Following transcription and coding, detailed multi-level discourse analysis demonstrated a typical pattern of compression in controls. The narratives produced by individuals with TLE were less fluent, cohesive, and coherent across trials: producing fewer novel units and more repetitive and extraneous content. Significant group by trial interactions in sample length, spontaneous duration, and statements, were not explained by seizure burden, age, or lexical retrieval deficits. These findings suggest that they do not benefit from repeated engagement with a narrative in the same manner as controls. Disturbed social cognition and pragmatics in TLE might underpin communication inefficiencies.

Neuroimaging of memory in frontal lobe epilepsy

In a large percentage of epilepsies, seizures have focal onset. These epilepsies are associated with a wide range of behavioral and cognitive deficits sometimes limited to the functions encompassed within the ictal onset zone but, more frequently, expanding beyond it. The presence of impairments associated with neuroanatomical areas outside of the ictal onset zone suggests distal propagation of epileptic activity via brain networks and interconnected whole-brain neural circuitry. In patients with frontal lobe epilepsy (FLE), using functional magnetic resonance imaging (fMRI) to identify deficits in working, semantic, and episodic memory may provide a lens through which to understand typical and atypical network organization. A network approach to focal epilepsy is relevant in these patients because of the frequently noted early age of seizure onset. Early seizure-related disruption in healthy brain development may result in a significant brain reorganization, development of compensation-related mechanisms of dealing with function abnormalities and disruptions, and the propagation of epileptic activity from the focus to widespread brain areas (functional deficit zones). Benefits of a network approach in the study of focal epilepsy are discussed along with considerations for future neuroimaging studies of patients with FLE.

Neuropsychology of frontal lobe epilepsy in children and adults: Systematic review and meta-analysis

Frontal lobe epilepsy (FLE) is associated with cognitive problems, especially in areas related to frontal lobe functioning as executive functions, attention, and motor skills, but with impact on memory and psychosocial adaptation. Deficits are similar in both adults and children with FLE, although no studies have compared adult and pediatric performance in the same study. The aim of this research was to analyze the existing evidence concerning the cognition in adults and children with FLE. A random effect meta-analysis was used using Cohen's d, and the confidence interval for each cognitive factor was calculated. The results in the meta-analysis show a general pattern of cognitive dysfunction in FLE, especially in functions related to the frontal lobe, with an influence of the duration and the age at onset of epilepsy, as well as the age of the sample used. In addition, researches in this type of epilepsy are heterogeneous, with too many different sampling and methodological characteristics, which is not a standard format for reporting clinical sample characterization, making it difficult to study FLE in depth.

Depression symptoms as a function of duration of intractable or controlled epilepsy

We examined if depression symptoms in patients with intractable (IE) or controlled epilepsy (CE) differ and how long after onset of epilepsy these effects would be most pronounced. The NDDI-E was administered to all outpatients (n=358) seen in a comprehensive epilepsy program clinic over a two-year period. Patients who met inclusion criteria (n=223) completed a total of 431 NDDI-E surveys over this time. Patients with a diagnosis of IE (n=72) or CE (n=151) were compared as a function of time since their epilepsy onset, segmented into 10-year epochs. Depression symptoms were higher in patients with IE compared to CE at 10-<20 years and did not differ at other time points. This study reveals differences in depression symptoms as a function of duration of epilepsy. Attending to the dynamic nature of depression symptoms in different epochs of epilepsy may be an important treatment target in patients with epilepsy.

Extratemporal functional connectivity impairments at rest are related to memory performance in mesial temporal epilepsy

Mesial temporal lobe epilepsy (MTLE) is the most frequent form of focal epilepsy. At rest, there is evidence that brain abnormalities in MTLE are not limited to the epileptogenic region, but extend throughout the whole brain. It is also well established that MTLE patients suffer from episodic memory deficits. Thus, we investigated the relation between the functional connectivity seen at rest in fMRI and episodic memory impairments in MTLE. We focused on resting state BOLD activity and evaluated whether functional connectivity (FC) differences emerge from MTL seeds in left and right MTLE groups, compared with healthy controls. Results revealed significant FC reductions in both patient groups, localized in angular gyri, thalami, posterior cingulum and medial frontal cortex. We found that the FC between the left non-pathologic MTL and the medial frontal cortex was positively correlated with the delayed recall score of a non-verbal memory test in right MTLE patients, suggesting potential adaptive changes to preserve this memory function. In contrast, we observed a negative correlation between a verbal memory test and the FC between the left pathologic MTL and posterior cingulum in left MTLE patients, suggesting potential functional maladaptative changes in the pathologic hemisphere. Overall, the present study provides some indication that left MTLE may be more impairing than right MTLE patients to normative functional connectivity. Our data also indicates that the pattern of extra-temporal FC may vary as a function of episodic memory material and each hemisphere's capacity for cognitive reorganization.

The effects of perceived emotional distress on language performance in intractable epilepsy

We evaluated the potential moderating effect of emotional distress (Minnesota Multiphasic Personality Inventory 2, scales D and Pt) on language functioning (i.e., Boston Naming Test, phonemic paraphasic error production on the Boston Naming Test, Controlled Oral Word Association Task, Animal Naming, Token Test) in patients with left (N=43) and right (N=34) mesial temporal lobe epilepsy (MTLE) and frontal lobe epilepsy (FLE) (N=30). Video/EEG and brain imaging results confirmed localization. Logistic regression models revealed that perceived emotional distress moderated language performance. Performance of patients with left MTLE and that of patients with FLE were equally poor across language measures. Performance of patients with right MTLE was intact. Depression and anxiety differentially moderated performance. Anxiety was associated with better performance in patients with FLE on classically temporal lobe-mediated tasks (Boston Naming Test). Depression was associated with worse language performance on measures for which impaired performance was traditionally intrinsic to the underlying epileptogenic lesion (word fluency in FLE). Emotional distress influences language performance. Adequate treatment of mood should be considered when managing pharmacoresistant epilepsy.

Executive deficits in generalized and extrafrontal partial epilepsy: long versus short seizure-free periods

OBJECTIVE

The goal of this study was to examine the influence of seizure freedom on executive function in outpatients with generalized epilepsy and extrafrontal partial epilepsy. Recent investigations of cognitive function in epilepsy have revealed executive deficits in persons with focal temporal as well as generalized epilepsies. Additional studies have suggested an influence of seizure freedom on cognitive function.

METHODS

Thirty-five consecutive outpatients were divided into seizure free <or= 3 months (n=18) and seizure free >3 months (n=17). The neuropsychological tests administered included: verbal fluency tasks, the Cognitive Estimation Test, the Hayling and Brixton Test, and the Behavioural Assessment of the Dysexecutive Syndrome (BADS) battery. Both patient groups were compared with matched healthy controls (n=16).

RESULTS

The extensive testing revealed significant differences between patients with shorter seizure-free periods and healthy controls with respect to overall errors and phonemic verbal fluency, response suppression, and BADS overall profile scores. Subjects seizure free >3 months exhibited a trend toward impairment in the phonemic fluency task only.

CONCLUSIONS

The results suggest that deficits in executive function were present in patients with extrafrontal partial epilepsy and generalized epilepsy, indicating the potential influence of epileptic activity on the ability to focus on relevant information and switch attention to other relevant information, to plan tasks and subtasks, and to check on and encode working memory content. The results also suggest that those deficits may be more pronounced in patients with relatively short seizure-free periods.

Reversible nonfluent aphasia and left frontal hypoperfusion during topiramate treatment

We report the case of a patient with complex partial seizures who developed a nonfluent aphasia when topiramate was added to his therapy. This emergent adverse effect appeared to be reversible, as language performance improved after discontinuation of topiramate. Interictal SPECT performed when the patient was aphasic revealed a focal perfusion reduction in the left lateral and mesial frontal cortex, which was no longer evident at a follow-up study after language recovery.

Palpitations: could they be neurogenic? A case report

BACKGROUND

Palpitations usually occur in patients with arrhythmias of cardiac origion, in conditions associated with increased catecholamine levels, and in psychiatric disorders. A rare etiology of palpitations is seizures with autonomic features.

REVIEW SUMMARY

We report a 24-year-old man with a several-week history of episodic palpitations, weakness, dizziness, and presyncopal phenomena. Subsequent events included loss of consciousness, with postevent confusion and tonic movements. A low-grade astrocytoma was diagnosed in the right frontal lobe.

CONCLUSION

This case emphasizes the importance of detailed history in the diagnosis of epilepsy.

Frontoparietal activation during delayed visuospatial recall in patients with epilepsy due to hippocampal sclerosis

We hypothesized that brain activation during encoding and retrieval of visual material differed between epilepsy patients with hippocampal sclerosis (HS) and healthy controls. Eleven patients with epilepsy and HS and nine age- and education-matched control subjects were tested during functional MRI recording. A three-block design for visuospatial memory encoding and retrieval and an interference interval longer than 1 minute without memory tasks were used. All subjects revealed parietal, occipital, and prefrontal activation patterns during encoding. Interference revealed parietal more than occipital activation, whereas retrieval revealed asymmetrical frontal and parietal activation. Patients demonstrated a relative increase in occipitoparietal versus frontal cortical activation as compared with controls. Memory performance did not differ between patients and controls. The increased activation in occipitoparietal versus frontal areas in the patients suggests cortical reorganization of visuospatial recognition memory in epilepsy patients with HS. The study is limited by other factors that may contribute to the results, for example, antiepileptic drugs, effects of greater cognitive effort allocated in patients than controls, and possibly subclinical epileptic activity. However, normal visuospatial memory performance in our patients with HS suggests successful network plasticity.

Cognitive problems related to epilepsy syndromes, especially malignant epilepsies

Neurocognitive impairment is frequent in epilepsy patients. Causes are multiple, and may be influenced by several factors including the epilepsy syndrome. Most cognitive complaints in adult patients are mental slowness, memory difficulties and attention deficits. In children, cognitive problems are more diffuse, responsible for language troubles, learning difficulties, poor academic outcome, behavior problems and finally unfortunate socio-professional prognosis. The most devastating epilepsy syndromes such as epileptic encephalopathies are nearly exclusively described in infancy and childhood. This paper will review the major cognitive complaints in relation to the epilepsy syndrome, with a more detailed interest for the malignant epilepsies in infancy and childhood such as Ohtahara and West syndrome, Lennox-Gastaut syndrome and epileptic encephalopathis with continuous spike-and-wase during slow wave sleep. The impact of surgery on cognition will be briefly discussed in adults and youger patients.

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.

Idiopathic epileptic syndromes and cognition

Epilepsy is frequently associated with cognitive impairments which result from various interacting factors. The present paper deals with the contribution of neuropsychology to the characterization of the type of epilepsy and the possible mechanisms underlying idiopathic epileptic syndromes. The non-lesional, so-called idiopathic epilepsies, constitute an interesting model for assessing the relationship between epileptiform EEG discharges and cognition. Among the idiopathic generalized epilepsies, disorders of social integration and personality have been frequently reported in juvenile myoclonic epilepsy (JME). Since similar disturbances are observed in frontal-lobe-lesioned patients, impairments in other frontal lobe functions (e.g. executive functions) might be expected in JME. This gives rise to speculation about the possible underlying pathophysiological mechanisms in JME. With regard to partial idiopathic epilepsies, benign childhood epilepsy with centrotemporal spikes (BCECTS) may provide a useful model for the study of the relationship between epileptiform EEG discharges in the peri-sylvian region and language functions. Furthermore, the description of mild cognitive dysfunctions in BCECTS, and their persistence into adulthood, can provide information about compensatory mechanisms and may allow for the generation of remedial strategies. Thus, 'lesional' neuropsychology has given way to 'dynamic' neuropsychology based on specific postulates. By using the cognitive profile to specify the mechanism underlying the behavioral disturbances observed in different types of epilepsy, neuropsychology may eventually contribute to a revision of the present classification of epileptic syndromes. In addition, the neuropsychological data may help predict the extent and limits of functional recovery and cerebral plasticity.

Deficit of preparatory attention in children with frontal lobe epilepsy

We compared the performance of a sustained attention task by children with epilepsy in either the frontal or temporal lobe. In a new simple task that specifically measures preparatory attention, developed recently by LaBerge, Auclair, and Siéroff [LaBerge, D., Auclair, L., & Siéroff, E. (2000). Preparatory attention: Experiment and theory. Consciousness and Cognition, 9, 396-434], patients responded to a target presented in the centre of the display and ignored a distracter presented at locations to the right or the left side of the target. The distracter was presented prior to the onset of the target and the relative frequency of the distracter to target was varied within a block of trials (from 0% to 67%). Children with frontal lobe epilepsy showed a higher mean slope of response time to the target as a function of distracter probability compared to children with temporal lobe epilepsy or compared to the response time slope of control subjects. The response time slope of children with temporal lobe epilepsy did not differ from that of control subjects. These results indicate that the presence of frontal lobe epilepsy selectively affects the capacity of these patients to resist the interference a distracter.

Neuropsychological aspects of epilepsy surgery

Neuropsychological evaluation of a patient's cognitive capabilities before and after epilepsy surgery is essential in elective epilepsy surgery. On the one hand, neuropsychology provides accessory information regarding the localization and lateralization of epilepsy-associated cognitive impairment; on the other hand, it is a useful tool for quality and outcome control of epilepsy surgery which helps to make surgery more effective and safe. Evaluation of the adequacy of the brain tissues to be resected and of the patient's mental reserve capacities allows for a prediction of the postoperative cognitive development. Successful surgery can stop mental decline due to chronic epilepsy and it can reverse this negative trend by release of functions and capacities that were secondarily affected before surgery. However, surgery bears the risk of additional impairments which, in interaction with normal or even pathological processes of mental aging, may accelerate cognitive decline at an older age. From a neuropsychological point of view, early recognition of pharmacoresistance is important along with early and complete seizure control with maximal sparing of functional tissues.

The prefrontal cortex regulates lateral amygdala neuronal plasticity and responses to previously conditioned stimuli

The amygdala plays a role in learning and memory processes that involve an emotional component. However, neural structures that regulate these amygdala-dependent processes are unknown. Previous studies indicate that regulation of affect may be imposed by the prefrontal cortex (PFC) and its efferents to the amygdala. The presentation of conditioned affective stimuli enhances activity of neurons in the lateral nucleus of the amygdala (LAT), which is thought to drive conditioned affective responses. Moreover, plasticity of LAT neuronal responses to stimuli during the course of conditioning is believed to underlie affective learning. This study examines the role of the PFC in the regulation of affective behaviors by evaluating how the PFC affects LAT neuronal plasticity and activity that is evoked by previously conditioned stimuli. In vivo intracellular recordings were performed from the LAT of anesthetized rats during pavlovian conditioning and during the presentation of stimuli that were conditioned in the awake rat before recording. Train stimulation of the PFC suppressed LAT neuronal activity that was evoked by both previously conditioned and neutral stimuli. In addition, PFC stimulation blocked LAT neuronal plasticity associated with an affective conditioning procedure. These results indicate that the PFC has the potential to regulate affective processes by inhibition of the LAT. Patients with disruptions of the PFC-LAT interaction often display an inability to regulate affective responses. This may be attributable to the loss of PFC-imposed inhibition of the emotional response to a stimulus but may also include the formation or diminished extinction of inappropriate associations.

Behavioral Aspects of Frontal Lobe Epilepsy

There is growing interest in disorders of behavior, personality, and mood associated with focal epilepsies, though the neuropsychological and behavioral or psychiatric aspects of epilepsy have usually been treated separately. The causes of behavioral disorders in patients with focal epilepsies are multifactorial, though the positive effects of seizure control on behavior suggest that state dependency is a major contributing factor. Patients with temporal lobe epilepsy manifest depression, anxiety, neuroticism, and social limitations, as well as impaired memory. By contrast, studies of cognitive function in patients with frontal lobe epilepsy show executive dysfunctions in response selection/initiation and inhibition, as well as cognitive impairment, hyperactivity, conscientiousness, obsession, and addictive behaviors.