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Neuropsychological tools

General intellectual functioning

The majority of the tests used in the standard neuropsychological assessment remain pencil
and paper desktop tasks, though the use of computerised tasks is becoming more widespread.2
Almost all assessments will include the current gold-standard measure of general intellectual
functioning in adults, the Wechsler Adult Intelligence Scale – Fourth Edition (WAIS-IV UK,
2010). The most recent incarnation of the Wechsler Intelligence Scale has dispensed with the
traditional distinction between verbal (VIQ) and performance IQ (PIQ) and now provides
four index scores, including the verbal comprehension index (VCI), the perceptual reasoning
index (PRI), the perceptual organisation index (POI) and the working memory index (WMI).
The full-scale IQ (FSIQ) has been retained and an additional general ability index (GAI) has
also been added. The distributions of all the indices are constructed to have a mean of 100
and a standard deviation of 15 IQ points. An index score of 100 therefore defines the
performance of an average, healthy, adult at that age. Approximately two-thirds of the adult
population obtain scores between 115 and 85, one standard deviation above and below the
mean, respectively. Any IQ between 80 and 119 is usually classified as falling within the
average range (Table 1).

Table 1. IQ Index Classifications used in the Wechsler Intelligence Scales

IQ Index score ranges Qualitative description Percent of cases

Below 69 Extremely low 2.2
70-79 Borderline 6.7
80-89 Low average 16.1
90-109 Average 50
110-119 High average 16.1
120-129 Superior 6.7
Above 130 Very superior 2.2

Measures of FSIQ may underestimate the intellectual abilities of a significant proportion of
people with epilepsy (40%). Reductions in FSIQ are correlated with the number of AEDs
taken and duration of epilepsy. Individual AEDs also differentially interfere with the
expression of underlying intellectual ability in this group, via their selective actions on
processing speed and working memory.3

Memory

Memory tests are most frequently divided into three groups: verbal, visual and behavioural
memory tasks. The most frequently used verbal memory tests include story recall and list-
learning tasks. In these tests the patient is typically read a short local-news type story and
asked to recall as much detail as they can immediately after they have heard it and again
following a delay of between 30 minutes and an hour. List-learning tasks typically test an
individual’s ability to learn a list of 1520 words over a number of trials and frequently
include recall and/or recognition conditions following distraction or a delay. Analogous tasks
involving non-verbal material include complex figure-recall tasks and design-learning tasks.
In the former an individual is required to copy a complex geometric figure and then reproduce
as much as they can immediately afterwards and again following a delay of up to an hour.
There is a growing consensus that these complex figure-recall tasks may have limited validity
in the assessment of epilepsy. Behavioural memory tests are generally thought to be more