Unilateral brain damage and patterns of age-corrected WAIS subtest scores

Relative subtest scatter on the WAIS-IV in a clinical sample referred for outpatient neuropsychological evaluation

OBJECTIVE

The primary aim of this study was to examine relative inter-subtest variability, or scatter, on the Wechsler Adult Intelligence Scale-Fourth Edition (WAIS-IV) in a clinical sample of patients referred for neuropsychological evaluation and compare the findings to corresponding data from the scale's standardization sample.

METHOD

Participants were 638 individuals diagnosed primarily with neurological, psychiatric, or neurodevelopmental disorders who completed the 10 core subtests of the WAIS-IV as part of a comprehensive assessment battery.

RESULTS

Mean participant scores on the WAIS-IV Full Scale IQ and all index composites were within the average range, overall, but were significantly below those of the standardization sample. The correlation between scatter range and highest subtest scaled score was significant, r = .65, indicating a greater degree of subtest scaled score variability in participants with higher than average peak subtest scaled scores than participants with average or below peak subtest scaled scores. Mean variability by highest subtest scaled score was, in most cases, larger in this clinical sample relative to the scale's standardization sample. Exploratory secondary analyses also revealed specific differences in relative scatter based on diagnostic group classification.

CONCLUSIONS

Subtest scatter on the WAIS-IV is common among both healthy individuals and clinical patients. Although somewhat higher in this investigation's clinical sample, the significance of this finding generally appears to be of nominal value during interpretation of individual cases but may have some utility in formulating hypotheses when considered in conjunction with reliability data and other approaches for analyzing test scores. High scatter is not pathognomonic of abnormality, and at least some degree of caution is warranted when interpreting subtest scaled score differences on the WAIS-IV.

A hierarchical analysis of block design errors in children with early focal brain damage

This study investigated the differential effects of very early damage to the left hemisphere (LH) or right hemisphere (RH) on visuospatial processing. Twenty-two children who had suffered either LH or RH strokes in the pre- or perinatal period were included in the study. The Block Design subtest of the Wechsler Intelligence Scale for Children-Revised (Wechsler, 1974) was used. Each missed item was coded as either a global error (e.g., broken configuration), local error (e.g., incorrect details), or time fail error (i.e., not completed within the allotted time). Results showed that the LH lesion and RH lesion groups had similar full scale IQs, verbal IQs, and performance IQs and were within the average to low average range. Block Design scaled scores were also within the average to low average range and did not significantly differ between the 2 lesion groups. Error analysis revealed, however, that the RH focal lesion group produced a significantly higher percentage of global errors than did the LH lesion group, whereas the LH lesion group produced a significantly higher percentage of local errors than did the RH lesion group. The groups did not differ on their percentage of time fail errors. These results are consistent with previous findings that suggest that the RH is involved in more global aspects of visual processing, whereas the LH mediates the more detailed, local aspects of visual information. The fact that these differences in processing are present after such early focal damage implies that hemispheric specialization for visuospatial processing occurs very early in brain development.

Base rates of the WAIS-R intersubtest scatter and VIQ-PIQ discrepancy in normal elderly

This study provides base rates for WAIS-R VIQ-PIQ discrepancy and for 3 indices of intersubtest scatter in a sample of high functioning normal elderly. High correlations between indices of scatter, such as (1) range of scatter; (2) Profile Variability Index; and (3) number of subtest scores that significantly deviated from the individual's own mean, indicate that easy-to-compute range can be used as an adequate measure of scatter in many clinical settings. The results suggest that bright elderly individuals display a large degree of scatter. The clinician should base judgment regarding abnormality of the WAIS-R indices on the rarity of the value demonstrated by the individual with respect to the sample of comparable age and intelligence level.

Differences in neuropsychological performance in psychiatric, anterior- and posterior-cerebral dysfunctioning groups

The neuropsychological performance of psychiatric, anterior- and posterior-cerebral dysfunctioning groups was compared using both raw scores and scores statistically adjusted for the effects of age, education, gender, and overall level of intellectual functioning. Between 5% and 37% of the variance of the subtests of the WAIS-R and between 9% and 58% of the variance associated with the neuropsychological variables was accounted for by the demographic variables. Using raw scores, ten of the twenty-five tests showed significant overall differences among the groups, while only five of the contrast using adjusted scores were significant. Anterior- and posterior-cerebral dysfunctioning groups generally were significantly more impaired than the psychiatric group. Memory and problem-solving variables were the most sensitive to the removal of demographic variance, while psychomotor test scores were the most robust. Differences among cerebrally impaired and psychiatric groups may be obscured by demographic variables or levels of general intellectual functioning.

IQ patterns in affective disorder, lateralized and diffuse brain damage

Meta-analysis of 38 studies compared Wechsler IQ scores in affective disorder (A), lateralized right (RH), left (LH) and bilateral/diffuse (BI) brain damage. A, RH, and BI had lower PIQ than VIQ. In A and BI groups the PIQ/VIQ ratio was identical, whereas each differed significantly from the RH group which revealed a much lower PIQ/VIQ ratio. Similarity of neuropsychological profiles of A and RH patients is often interpreted as indicating predominant right-hemisphere involvement in affective disorder. The present findings suggest an alternative interpretation is possible: i.e., the presence of bilateral/diffuse CNS involvement in affective disorder. We do not believe that our findings strongly support one interpretation over the other. In future research, both possibilities should be considered.

Base rates of WAIS-R subtest scatter as a guide for clinical and neuropsychological assessment

Data from the WAIS-R standardization sample (N = 1880, ages 16-74) were analyzed to determine normal base rates of subtest scatter and to discover whether the amount of scatter is related significantly to various stratification variables. Two indices of scatter were computed for the Verbal, Performance, and Full Scales: range (highest minus lowest scaled score) and number of subtests that deviated significantly from a person's own mean. ANOVAs conducted with the range statistic showed that scatter on all three WAIS-R IQ scales was related significantly to education level; that Blacks had less scatter than Whites on the Verbal and Full Scale; and that females had less scatter than males on the Verbal scale. Base rate normative tables of subtest scatter were presented for five different levels of Full Scale IQ. Implications of these tables for clinical and neuropsychological assessment were discussed.

The neuropsychological significance of a verbal-performance discrepancy with the Wechsler Intelligence Scale for Children-Revised

This study examined the neuropsychological significance of the Wechsler Intelligence Scale for Children-Revised (Wechsler, 1974) Verbal-Performance discrepancy using a large learning-disabled sample taken from a school population. A simple index was formed to allow the Verbal-Performance discrepancy to be considered as a continuous variable. In an attempt to consider the neuropsychological significance of the Verbal-Performance discrepancy, measures of the Halstead-Reitan Neuropsychological Battery for older children (HRNB) (Reitan, 1969) were regressed against the index. Some 9% of the variance in Verbal-Performance differences was explained by five neuropsychological measures of the HRNB. The practical significance of this relationship was questioned. It was concluded that the Verbal-Performance discrepancy is a poor general indicator of neuropsychological functioning in learning-disabled students in the school setting.

Lateralized brain damage, sex differences, and the Wechsler Intelligence Scales: a reexamination of the literature

Recent reviews have suggested that males and females show different patterns of intellectual impairment following lateralized brain injury. As the percentage of males in such studies increases, the magnitude of the difference between Verbal and Performance IQs increases. The present review reexamines this literature. Although the association between patient sex, pattern of intellectual deficit, and lateralized brain injury is reconfirmed for studies which used the Wechsler-Bellevue Intelligence Scale, there was no such relationship in those which used the more recent Wechsler Adult Intelligence Scale. In addition, it is shown that, in studies which used the former measure, the percentage of males may be highly correlated with other variables, a relationship which could have an effect on the pattern of intellectual loss following brain injury.

Late effects of unilateral brain lesions sustained before and after age one

Forty-eight children with unilateral cerebral lesions, incurred before or after the first year of life, were given the Wechsler Intelligence Scale for Children, with an average delays of 4 and 8 1/2 yr for the late and early injuries, respectively. Thirty-one of their siblings were chosen as controls. Results are as follows: early and late right-hemisphere lesions significantly lower only Performance IQ. Early left lesions impair equally Verbal and Performance IQ, while late left-hemisphere lesions do not significantly affect Verbal or Performance IQ relative to controls.

The development of spatial and class relations in four young children with right-cerebral-hemisphere damage: evidence for an early spatial constructive deficit

This study followed the development of four children with right-hemisphere injury on a series of manipulative classification tasks to determine whether and how early brain injury affects the development of spatial and class relations. The children were first tested at about 2 years of age. Their data were compared with previously collected data from 18- to 42-month-old normal children, and with data from four young children with left-hemisphere injury. The results showed the children with right-hemisphere injury do not generate a particular spatial relation (next to) in their spatial groupings with the same frequency as normal or left-hemisphere damaged children, although they do generate in and on relations with normal frequency. An apparent deficit in the development of class relations is shown to be secondary to the spatial deficit, in that it is evident only in tasks that require spatial grouping.

Wechsler VIQ versus PIQ differences in cerebral dysfunction: a literature review with emphasis on sex differences

For the past three decades neuropsychologists have published results which indicated that left-sided cerebral dysfunction affected the Wechsler Verbal Scale whereas right-sided dysfunction affected the Performance Scale. Recent investigations have indicated that the effects of cerebral dysfunction on performance of the Wechsler Scales may be different for males and females. In view of these reports, the present review considered 24 studies (28 samples) which have reported Wechsler IQ scores in patients with unilateral or bilateral cerebral dysfunction. Eight studies (10 samples) used the Wechsler-Bellevue I, whereas 16 studies (18 samples) employed the WAIS. In these 28 published samples, there were four exceptions to the hypothesis of lower mean VIQ in patients with left-hemisphere lesions, and lower mean PIQ in patients with right-hemisphere dysfunction. Of the four exceptions to this "rule", two samples contained only women, while a third contained only patients with missile wounds of the frontal lobe. One sample appeared to be a true exception, and could not be accounted for by lesion location or sexual composition of the sample. The studies reviewed appear to add additional support to the hypothesis of sex differences in the effects of unilateral lesions. Therefore, insofar as published mean values for the Wechsler Scales are concerned, the specific effects on Verbal versus Performance IQ appear more prominently in males.

Lateralized psychological impairment associated with CT lesions in head injured patients

Twenty-six adult patients with CT scans were given the Wechsler Adult Intelligence Scale (WAIS) during recovery from an acute head injury. Focal lesions were observed on the initial CT scans of 24 patients. These included 13 in the right hemisphere, 8 in the left hemisphere and 3 in both hemispheres. Diffuse cerebral swelling was observed in the remaining 2 patients. Both the standard WAIS examination (11 subtests) and a shorter version described by McFie (7 subtests) were used to assess psychological impairment associated with CT documented lesions. The McFie method involved a special scoring procedure that utilized reference subtests as an index of premorbid functioning. When mean algebraic differences between Verbal and Performance subtests were used, both methods differentiated left and right-sided lesions to a highly significant degree (p less than .001). Lateralized lesions yielded significant differences on 3 individual subtests (1 Verbal and 2 Performance) with the McFie method and on 6 individual subtests (all Verbal) with the standard WAIS procedure. Wechsler's Deterioration Quotient did not discriminate between groups. It was concluded that the traditional distinction between Verbal and Performance subtests on the WAIS was valid for CT documented lesions, and the shorter McFie version was as effective as the standard WAIS in lateralizing psychological dysfunction. Acknowledgements. This research was supported by Contract NS 5-2316 and Grant NS 08803 from the National Institutes of Health. We are grateful to Drs. Thomas A. Gennarelli and Howard I. Hurtig for patient referrals and neurological evaluations.

Constructional apraxia in patients with discrete missile wounds of the brain

Sixty patients with missile wounds confined to one of the four quadrants of the brain were investigated. All patients had neurosurgical verification of the limits of their lesions. The incidence and severity of constructional apraxia was studied using the WAIS Block Design and Object Assembly subtests, and the Bender Gestalt Test. A uniformly significant caudality effect was obtained with more posteriorly localized lesions resulting in more severe constructional apraxia. A significant laterality effect was obtained on two of three criterion measures with uniformly inferior performance by patients with right hemisphere lesions. The magnitude of the laterality effect, however, was less than that of the caudality effect for all criterion variables. The degree of severity of constructional apraxia in patients with right posterior lesions was uniformly greater than that of patients with other quadrant loci. The incidence of constructional apraxia in the four quadrants varied as expected with the left anterior lesion sample showing very little evidence of constructional apraxia, while the right posterior sample showed a high incidence of such deficits. The absolute incidence of significant constructional apraxia in all samples was suprisingly low. This finding might be partially accounted for by the age and general good health of the subjects studied, the relative absence of general cognitive impairment in the majority of subjects, and the discrete nature of the lesions.

Cognitive recovery after severe head injury. 1. Serial testing on the Wechsler Adult Intelligence Scale

The Wechsler Adult Intelligence Scale was administered serially to 40 severely head-injured adults, and the results compared with a matched group of 40 non-injured men. The scores on the verbal subtests showed less initial impairment and were faster to recover to the level of the comparison group than were the non-verbal subtest scores. Verbal IQ of the head-injury group approached that of the comparison group within about one year of injury, while recovery of Performance IQ continued over about three years.

Cognitive effects of unilateral brain lesions secondary to penetrating missile wounds

The WAIS verbal and nonverbal subtest performance of Ss with unilateral brain lesions secondary to penetrating missile wounds was examined and compared with that of normal controls. The performance of matched right- and left-hemisphere lesion Ss differed significantly on only two verbal and one nonverbal measures, however, all performance differences were in the direction hypothesized. The performance of right-hemisphere lesioned and control Ss differed significantly on all measures, with consistently lower scores by brain-injured Ss, while the performance of left-hemisphere and control Ss differed significantly on the three verbal measures and WAIS Full Scale IQ. These results are in general agreement with previous reports using a similar research design and tend to support the hypothesis of differential impairment of verbal and nonverbal test performance in Ss with unilateral brain lesions.

Memory and paired-associated learning of patients with unilateral brain lesions

Wechsler Memory Scale scores and paired-associate learning performance were compared in matched samples of Ss with right- and left-hemisphere brain lesions secondary to penetrating missile wounds and normal controls. Wechsler Memory Quotient, easy paired-associate learning scores, and difficult paired-associate learning scores for left-hemisphere Ss were significantly lower than those for normal controls; while the mean scores for right-hemisphere and normal control Ss did not differ significantly. For the latter Ss the Wechsler Memory Quotient and the difficult paired-associate learning task differed significantly with lower mean scores for left-hemisphere Ss. Significant relationships were obtained between Wechsler Memory Quotient and all paired-associate learning scores and between WAIS IQ and Wechsler Memory Quotient, total and easy paired-associate learning scores.