Faculty Bibliography

This paper describes ten core features of a neuropsychological assessment with the aim of helping neurologists understand the unique contribution the evaluation can make within the wider context of diagnostic methods in epilepsy. The possibilities, limitations and cautions associated with the investigation are discussed under the headings below: 1. A neuropsychological assessment is a collaborative investigation. 2. Assessment prior to treatment allows for the accurate assessment of treatment effects. 3. The nature of an underlying lesion and its neurodevelopmental context play an important role in shaping the associated neuropsychological deficit. 4. Cognitive and behavioural impairments result from the essential comorbidities of epilepsy which can be considered as much a disorder of cognition and behaviour as of seizures. 5. Patient's subjective complaints can help us understand objective cognitive impairments and their underlying neuroanatomy, resulting in improved patient care. At other times, patient complaints reflect other factors and require careful interpretation. 6. The results from a neuropsychological assessment can be used to maximise the educational and occupational potentials of people with epilepsy. 7. Not all patients are able to engage with a neuropsychological assessment. 8. There are limitations in assessments conducted in a second language with tests that have been standardized on different populations to that of the patient. 9. Adequate intervals between assessments maximise sensitivity to meaningful change. 10. Patients should be fully informed about the purpose of the assessment and have realistic expectations of the outcome prior to referral.

In our first paper in this series (Epilepsia 2015; 56(5): 674-681), we published recommendations for the indications and expectations for neuropsychological assessment in routine epilepsy care. This partner paper provides a comprehensive overview of the more specialist role of neuropsychological assessment in the pre and postoperative evaluation of epilepsy surgery patients. The paper is in two parts. The first part presents the framework for the mandatory role of neuropsychologists in the presurgical evaluation of epilepsy surgery candidates. A preoperative neuropsychological assessment should be comprised of standardised measures of cognitive function in addition to wider measures of behavioural and psychosocial function. The results from the presurgical assessment are used to: (1) establish a baseline against which change can be measured following surgery; (2) provide a collaborative contribution to seizure characterization, lateralization and localization; (3) provide evidence-based predictions of cognitive risk associated with the proposed surgery; and (4) provide the evidence base for comprehensive preoperative counselling, including exploration of patient expectations of surgical treatment. The second part examines the critical role of the neuropsychologist in the evaluation of postoperative outcomes. Neuropsychological changes following surgery are dynamic and a comprehensive, long-term assessment of these changes following surgery should form an integral part of the postoperative follow-up. The special considerations with respect to pre and postoperative assessment when working with paediatric populations and those with an intellectual disability are also discussed. The paper provides a summary checklist for neuropsychological involvement throughout the epilepsy surgery process, based on the recommendations discussed.

Magnetic resonance imaging (MRI)-negative temporal lobe epilepsy (TLE) may be a distinct syndrome from TLE with mesial temporal sclerosis (TLE-MTS). Imaging and neuropsychological features of TLE-MTS are well-known; yet, these features are only beginning to be described in MRI-negative TLE. This study examined whether a quantitative measure of cortical gray and white matter blurring (GWB) was elevated in the temporal lobes ipsilateral to the seizure onset zone of individuals with MRI-negative TLE relative to TLE-MTS and healthy controls (HCs) and whether GWB elevations were associated with neuropsychological comorbidity. Gray-white matter blurring from 34 cortical regions and hippocampal volumes were quantified and compared across 28 people with MRI-negative TLE, 15 people with TLE-MTS, and 51 HCs. Declarative memory was assessed with standard neuropsychological tests and the intracarotid amobarbital procedure (IAP). In the group with MRI-negative TLE (left and right onsets combined), hippocampal volumes were within normal range but GWB was elevated, relative to HCs, across several mesial and lateral temporal lobe regions ipsilateral to the seizure onset zone. Gray-white matter blurring did not differ between the groups with TLE-MTS and HC or between the groups with TLE-MTS and MRI-negative TLE. The group with MRI-negative TLE could not be distinguished from the group with TLE-MTS on any of the standard neuropsychological tests; however, ipsilateral hippocampal volumes and IAP memory scores were lower in the group with TLE-MTS than in the group with MRI-negative TLE. The group with left MRI-negative TLE had lower general cognitive abilities and verbal fluency relative to the HC group, which adds to the characterization of neuropsychological comorbidities in left MRI-negative TLE. In addition, ipsilateral IAP memory performance was reduced relative to contralateral memory performance in MRI-negative TLE, indicating some degree of ipsilateral memory dysfunction. There was no relationship between hippocampal volume and IAP memory scores in MRI-negative TLE; however, decreased ipsilateral IAP memory scores were correlated with elevated GWB in the ipsilateral superior temporal sulcus of people with left MRI-negative TLE. In sum, GWB elevations in the ipsilateral temporal lobe of people with MRI-negative TLE suggest that GWB may serve as a marker for reduced structural integrity in regions in or near the seizure onset zone. Although mesial temporal abnormalities might be the major driver of memory dysfunction in TLE-MTS, a loss of structural integrity in lateral temporal lobe regions may contribute to IAP memory dysfunction in MRI-negative TLE.

Objective/UNASSIGNED:Assessment of performance validity is a necessary component of any neuropsychological evaluation. Prior research has shown that cutoff scores of ≤6 or ≤7 on Reliable Digit Span (RDS) can detect suboptimal effort across numerous adult clinical populations; however, these scores have not been validated for that purpose in an adult epilepsy population. This investigation aims to determine whether these previously established RDS cutoff scores could detect suboptimal effort in adults with epilepsy. Method/UNASSIGNED:Sixty-three clinically referred adults with a diagnosis of epilepsy or suspected seizures were administered the Digit Span subtest of the Wechsler Adult Intelligence Scale (WAIS-III or WAIS-IV). Most participants (98%) passed Trial 2 of the Test of Memory Malingering (TOMM), achieving a score of ≥45. Results/UNASSIGNED:Previously established cutoff scores of ≤6 and ≤7 on RDS yielded a specificity rate of 85% and 77% respectively. Findings also revealed that RDS scores were positively related to attention and intellectual functioning. Given the less than ideal specificity rate associated with each of these cutoff scores, together with their strong association to cognitive factors, secondary analyses were conducted to identify more optimal cutoff scores. Preliminary results suggest that an RDS cutoff score of ≤4 may be more appropriate in a clinically referred adult epilepsy population with a low average IQ or lower. Conclusions/UNASSIGNED:Preliminary findings indicate that cutoff scores of ≤6 and ≤7 on RDS are not appropriate in adults with epilepsy, especially in individuals with low average IQ or below.

Several methods for identifying suboptimal effort on Spanish neuropsychological assessment have been established. The purpose of this retrospective study was to determine whether recognition data from the WHO-AVLT could be employed for determination of malingering in a Spanish-speaking sample. Sixteen subjects in litigation, 25 neurological patients, and 14 healthy controls completed neuropsychological testing. All subjects completed the Test of Memory Malingering (TOMM). Inclusion criteria for neurological patients and controls included performance above the standard TOMM cutoff. Subjects in litigation were classified as probable malingering, through lower than cutoff performance on the TOMM and at least one other performance validity measure. Cut-off scores for classification of malingering were determined based on the number of recognition hits on the WHO-AVLT. The probable malingering group performed significantly worse than both groups on recognition hits. A score <10 was determined to be the optimal group cutoff, with 56.25% sensitivity and specificity greater than 92%. A combination score of 14 increased sensitivity to 68.75%. These findings provide initial validation of a new malingering index, based on the number of hits on the WHO-AVLT recognition trial. This index will provide valuable information to neuropsychologists conducting forensic or clinical evaluations on Spanish-speaking individuals.

In this study, we employed a kernel support vector machine to predict epilepsy localization and lateralization for patients with a diagnosis of epilepsy (n = 228). We assessed the accuracy to which indices of verbal memory, visual memory, verbal fluency, and naming would localize and lateralize seizure focus in comparison to standard electroencephalogram (EEG). Classification accuracy was defined as models that produced the least cross-validated error (CVϵ). In addition, we assessed whether the inclusion of norm-based standard scores, demographics, and emotional functioning data would reduce CVϵ. Finally, we obtained class probabilities (i.e., the probability of a particular classification for each case) and produced receiver operating characteristic (ROC) curves for the primary analyses. We obtained the least error assessing localization data with the Gaussian radial basis kernel function (RBF; support vectors = 157, CVϵ = 0.22). There was no overlap between the localization and lateralization models, such that the poorest localization model (the hyperbolic tangent kernel function; support vectors = 91, CVϵ = 0.36) outperformed the strongest lateralization model (RBF; support vectors = 201, CVϵ = 0.39). Contrary to our hypothesis, the addition of norm, demographics, and emotional functioning data did not improve the accuracy of the models. Receiver operating characteristic curves suggested clinical utility in classifying epilepsy lateralization and localization using neuropsychological indicators, albeit with better discrimination for localizing determinations. This study adds to the existing literature by employing an analytic technique with inherent advantages in generalizability when compared to traditional single-sample, not cross-validated models. In the future, class probabilities extracted from these and similar analyses could supplement neuropsychological practice by offering a quantitative guide to clinical judgements.