Comparison of Neuropsychological and Balance ...

Applied Neuropsychology: Adult

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Comparison of Neuropsychological and Balance Performance Validity Testing Patrick Armistead-Jehle, Beth J. Lange & Paul Green To cite this article: Patrick Armistead-Jehle, Beth J. Lange & Paul Green (2016): Comparison of Neuropsychological and Balance Performance Validity Testing, Applied Neuropsychology: Adult, DOI: 10.1080/23279095.2015.1132219 To link to this article: http://dx.doi.org/10.1080/23279095.2015.1132219

Published online: 14 Apr 2016.

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Date: 14 April 2016, At: 14:24

APPLIED NEUROPSYCHOLOGY: ADULT 2016, VOL. 00, NO. 00, 1–8 http://dx.doi.org/10.1080/23279095.2015.1132219

Comparison of Neuropsychological and Balance Performance Validity Testing Patrick Armistead-Jehlea, Beth J. Langeb and Paul Greenc a

Downloaded by [74.222.206.8] at 14:24 14 April 2016

c

Concussion Clinic, Munson Army Health Center, Fort Leavenworth, Kansas; bNeurovestibular Program, University of Calgary, Alberta, Canada; Private Practice, Edmonton, Alberta, Canada ABSTRACT

KEY WORDS

Performance validity testing in the context of neuropsychological assessment is well established. While such measures are also available with balance testing, little research has investigated these two domains in concert. The purpose of this study was to compare scores on two measures of performance validity across cognitive and balance modalities. Seventy-eight subjects independently evaluated by a neuropsychologist and an otolaryngologist in the context of disability evaluations were administered the Word Memory Test and Computerized Dynamic Posturography. Results of the measures were significantly correlated (rφ ¼ 0.35, p ¼ .002) and demonstrated 70.5% agreement. These data suggest that if symptom exaggeration occurs within one modality, other modalities may also be exaggerated and should be independently evaluated.

Computerized dynamic posturography; disability seeking; performance validity testing; symptom exaggeration; word memory test

Introduction In order for any medical professional to draw accurate diagnostic conclusions, it is necessary that the patient or examinee report symptoms and demonstrate signs in a valid manner. However depending on the evaluation context, symptom exaggeration can be fairly commonplace. This is particularly evident in select settings such as disability and forensic evaluations (Ardolf, Denney, & Houston, 2007; Chafetz, 2008). The evolution of measures and procedures developed to objectively assess response validity has burgeoned in the relatively recent past and now crosses domains (Martin, Schroeder, & Odland, 2015). Performance validity testing in the discipline of neuropsychology is well established and has become the recommended standard of practice regardless of evaluation context (Bush et al., 2005; Heilbronner et al., 2009). Performance validity tests (PVT) typically work to establish poor effort on behalf of the examinee by demonstrating illogically low or inconsistent performances on tasks that can generally be passed without difficulty by those with notable neurologic impairment. Base rates of failure on performance validity testing vary as a function of evaluation context, but can approach or exceed 40% depending on the study (Ardolf et al., 2007; Armistead-Jehle, 2010; Chafetz, Prentkowski, & Rao, 2011; Larrabee, Millis, & Meyers, 2009). The importance of recognizing poor effort and symptom exaggeration via PVTs is highlighted by the numerous studies that CONTACT Patrick Armistead-Jehle Leavenworth, KS 66027, USA. © 2016 Taylor & Francis

[email protected]

demonstrate the notable impact that poor effort has on artificially diminishing scores across cognitive ability measures (Armistead-Jehle & Buican, 2012; Fox, 2011; Green, 2007; Green, Rohling, Lees-Haley, & Allen, 2001; Lange, Iverson, Brooks, & Rennison, 2010; Meyers, Volbrecht, Axelrod, & Reinsch-Boothby, 2011). Performance validity testing has also been introduced and studied within the realm of balance assessments. One’s ability to maintain balance results from the integration of inputs from the visual, somatosensory, and vestibular systems. Improper functioning in any of these three distinct systems can lead to loss of balance, gait abnormalities, dizziness, vertigo, and/or postural instability. Computerized Dynamic Posturography (CDP) is an assessment technique that separates the influences of each of these systems in examinees with reported balance and dizziness problems. With CDP testing, the examinee stands on a movable force-plate support surface that is located within a modifiable enclosure. The force plate can move within a horizontal plane and thus alter the angle on which the examinee stands; while the enclosure can be altered to manipulate the visual surround of the examinee. Standard protocols subject the examinee to different variations of support surface and/or visual stimuli and subsequently measure postural stability and motor reactions. Various patterns of performance have been associated with different pathologies related to the visual, somatosensory, and vestibular systems (Monsell, Fumman, Herdman, Konrad, & Shepard, 1997). Concussion Clinic, Munson Army Health Center, 550 Pope Ave., Fort


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P. ARMISTEAD-JEHLE, B. J. LANGE, & P. GREEN

Of the standardized CDP protocols available, the Sensory Organizational Test (SOT) has been employed to examine vestibular system dysfunction versus nonorganic or aphysiologic patterns of performance. The SOT protocol evaluates the amount of anteriorposterior sway across various conditions of increasing difficulty that alter the platform on which the examinee is standing and/or the visual input to which the examinee is exposed. Three trials of six subtests each lasting 20 seconds are employed in the SOT protocol (Figure 1). Performances in each condition are calculated based on the amount of sway demonstrated by the examinee, with scores ranging from 0 (a patient fall) to 100 (no sway, perfect stability). With condition 1 the support surface is fixed and eyes are open. As all three sensory systems are available a high score (i.e., close to 100) is expected. Under condition 2, the examinee stands on a fixed support with eyes closed. With condition 3 the support is still fixed and eyes are open, but the visual surround moves with changes in the examinee’s center of gravity as sensed by the platform. Under condition 4, the examinee’s eyes are open and the visual surround is fixed; however, the platform responds to changes in the examinee’s center of gravity. Condition five matches condition four except the examinee’s eyes are closed. Under condition 6, the examinee’s eyes remain open and both the visual surround and the platform respond to changes in the examinee’s center of gravity. With the latter conditions (i.e., conditions 5 and 6), it becomes increasingly more difficult for vestibular deficient patients to maintain balance, as they are not able to rely on accurate visual and proprioceptive information.

Conceptually, a non-organic or aphysiologic pattern on CDP is thought to be present when performances are relatively better with the more difficult conditions. The neurologic research generally terms this a “functional” deficit; however, in the neuropsychological lexicon this is akin to symptom exaggeration. Several studies have evaluated this construct via CDP, with the original work by Cevette, Puetz, Marion, Wertz, and Muenter (1995). Here the authors compared 22 patients with aphysiologic CDP patterns who presented with unusual symptoms of gait unsteadiness, imbalance, or vertigo with 22 age-matched patients with vestibular dysfunction CDP patterns and 22 age-matched patients with normal CDP patterns. The aphysiologic group demonstrated significantly better performances relative to the vestibular dysfunction group on the most challenging conditions (i.e., 5 and 6) and significantly worse performances on the least challenging conditions (i.e., 1–4). Moreover, the aphysiologic group evidenced greater inter-trial variability compared with subjects in the vestibular and normal groups. The authors employed a stepwise linear discriminant analysis to detect a set of conditions that were able to distinguish among the three groups and in turn identified three equations for classifying patients. These equations were 95.6% accurate in classifying the sample. A subsequent study by Morgan, Beck, and Dobie (2002) sought to evaluate if subjects could better feign vestibular weakness if they were given information on CDP. Sixty participants were divided into two equal groups; one received no information on CDP (naïve faking) and the other was given some limited information

Figure 1. The six conditions of the CDP sensory organization test. (1) Eyes open, fixed surface and visual surround. (2) Eyes closed and fixed surface. (3) Eyes open, fixed surface, and sway referenced visual surround. (4) Eyes open, sway referenced surface, and fixed visual surround. (5) Eyes closed and sway referenced surface. (6) Eyes open, sway referenced surface, and visual surround. Image courtesy of Natus Medical Incorporated.


APPLIED NEUROPSYCHOLOGY: ADULT

about CDP with the indication that those with balance disorders tended to do more poorly only when the test became more challenging (informed faking). The Cevette et al. (1995) scoring criteria correctly classified about two thirds of the naïve and informed faking groups and it was conclude that educating subjects about CDP prior to test administration did not improve their ability to successfully fake a vestibular dysfunction. Another method for determining aphysiologic response was crafted by Goebel et al. (1997). These authors include information from the SOT as well as the Motor Control Test (MCT) of the CDP assessment. The MCT protocols assess the examinee’s automatic reactions to unanticipated rapid movements of the support surface (see Figure 2). Three magnitudes of movements are evaluated in both the forward and backward directions. Logically, lower magnitude movements of the support surface have been shown to produce lesser responses than higher magnitude movements. Additionally, it has been shown that responses to the surface movements have a high degree of intra-subject reliability, even in those with impaired motor function. Findings to the contrary in any single examinee could then suggest symptom exaggeration. Goebel et al. evaluated seven rationally-derived criteria thought to suggest aphysiologic sway in 122 normal subjects, 347 subjects with known or suspected balance disorders, and 72 subjects told to feign a balance problem. Three of these criteria (one from the SOT and two from the MCT protocols) were successful at identifying the malingering group. An ensuing study by Kemple and Dobie (1998) sought, in part, to evaluate the abilities of the Cevette et al. (1995) and Goebel et al. (1997) criteria to successfully identify patients in one of three conditions (normal, malingering, and vestibular induced weakness via bilateral caloric irrigation). The authors concluded that CDP was able to discriminate the malingering group from the normal and induced vestibular weakness group, with the Cevette criteria about 75% accurate.

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As with efforts to evaluate cognitive performance validity testing, select studies have sought to determine base rates of symptom exaggeration in patients with possible secondary gain. Gianoli, McWilliams, Soileau, and Belafsky (2000) conducted a retrospective chart review of 100 patients to compare the incidence of nonorganic sway patterns on CDP among those with and without potential secondary gain. The authors found a non-organic sway pattern, suggesting symptom exaggeration, in 76% of the patients with potential secondary gain, but only 8% of the patients without obvious secondary gain. These data can be taken to suggest that evaluation context is an important variable. Analogous findings have been reported with cognitive performance validity testing. Chafetz et al. (2011) compared three groups with equivalently low FSIQs below 80 (social security claimants seeking compensation for inability to work, individuals seeking custody of their children, and claimants from rehabilitation services seeking a return to work). The group seeking disability demonstrated a far higher rate of PVT failure relative to the other two groups despite the low FSIQ across the totality of the sample. It was thus concluded that low IQ was not a factor in these results and this work demonstrates that evaluation context is a notable factor in the outcomes of performance validity testing. There are then reliable methods of detecting exaggerated symptoms in both cognitive and balance testing and there is a high incidence of exaggeration in select groups. To the author’s collective knowledge however, no study to date has evaluated the co-occurrence of symptom exaggeration across cognitive and balance domains. The aim of the current study was to retrospectively review disability evaluations where neuropsychological assessments that included performance validity testing in addition to balance testing with CDP were conducted. It was hypothesized that there would be a high rate of agreement among effort testing in each domain.

Figure 2. CDP motor control test. Image courtesy of Natus Medical Incorporated.

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Methods


Sample A retrospective review of consecutive charts was completed for patients independently evaluated by both a neuropsychologist (P.G.) and otolaryngologist (B.L.) in the context of disability evaluations. The total sample size was 78. Ninety-two percent of the sample were male with an average age of 44.5 years (SD ¼ 12.7). Most subjects (n ¼ 47) were referred for evaluation following a mild traumatic brain injury (TBI)/mild head injury as defined by a GCS of 13 to 15 and Post Traumatic Amnesia less than 24 hours. While all subjects in this group reported some period of altered consciousness (thus meeting the American Congress of Rehabilitation Medicine criteria for mild traumatic brain injury [American Congress of Rehabilitation Medicine [ACRM], 1993], it was clear with neuropsychological assessment that select subjects were exaggerating symptoms. These subjects’ self-report regarding injury must then be regarding with skepticism as they may not have validly stated their mental status after their reported injury and if there was no alteration of consciousness they did not actually experience a TBI. This group is therefore conservatively categorized as mild TBI/mild head injury. Other diagnoses included Moderate TBI (n ¼ 7), as defined by a GCS of 9–12 or post traumatic amnesia (PTA) of 1–24 hours; Severe TBI (n ¼ 14), as defined by a GCS of less than 9 or a period of PTA of more than 24 hours; TBI of unknown severity (N ¼ 3); and other orthopedic injury or neurologic conditions (N ¼ 7). PTA was determined by a review of the medical records when available. When this was not clearly delineated in the records, the length of PTA was determined on clinical interview. The three subjects in the TBI of unknown severity group all self-reported a remote history of severe TBI; however, there were no medical records (i.e., documented LOC, PTA, brain imaging, or neurological status following the claimed injury) that could be consulted to verify this claim. Rather than include these subjects in the severe TBI group, which all had at least some medical documentation to support the diagnosis, these subjects were categorized as severity unknown. All subjects were evaluated by both the otolaryngologist and neuropsychologist 1 year or more after the injury. Measures Each subject was administered the Word Memory Test (WMT; Green, Allen, & Astner, 1996; Green, 2003) as part of a comprehensive neuropsychological battery administered by the third author (P.G.). The WMT is

a computer administered measure with multiple subtests designed to assess verbal memory, effort, and response consistency. Twenty semantically related word pairs are presented twice for examinees to learn. Directly after the learning trials Immediate Recognition (IR) is tested. Following a delay, Delayed Recognition (DR) is assessed. This is then followed by a series of subtests comprising Multiple Choice (MC), Paired Associate (PA), and Free Recall (FR) formats. In addition to these five subtests, a consistency (CNS) score is calculated to gauge recall consistency across select trials. Failure on the WMT was defined as performance below the cut score on the IR, DR, and/or CNS subtests as defined in the test manual. A number of studies have demonstrated the utility of this measure in the discrimination between those with genuine memory impairment and those simulating impairment in a range of patient samples (e.g., Green, Flaro, & Courtney, 2009; Green, Lees-Haley, & Allen, 2002; Hartman, 2002; Wynkoop & Denney, 2005). Subjects were also evaluated on independent referral by the second author (B.L.) for balance testing and assessed via CPD (see above for a description of this technology). Standard protocols for SOT and MCT were administered on Equitest manufactured by Neurocom. Goebel et al. (1997) criteria were used as a template to define non-organic or aphysiologic performances. This consisted of the following: 1. SOT 1 performance below 75 percentile and inconsistent with observed normal walking balance. 2. SOT 2 performance better than SOT 1 performance. 3. Large variability (i.e., falls alternating with normal results) between trials of any single SOT condition (particularly in the easier conditions of 1–4). 4. Large antero-posterior and lateral sway that are outside of normal limits (with or without falls) as calculated by the CDP force platform. 5. Large amplitude responses (with early or delayed responses), which fall outside of the normal limits on the small perturbations of the MCT. 6. Large trial to trial variability in MCT, alternating between falls and normal balance. 7. Immediate falls within 1–2 seconds of platform movement. 8. Clinical correlation as defined by normal walking balance and performance below the 75th percentile on SOT 1. A performance that consisted of three or more of any of the above criteria was considered to be non-organic in nature. All subjects also underwent videonystagmography (VNG) and demonstrated normal results. This procedure analyzes eye movements across various conditions designed to assess how well the eyes respond to information relayed from the vestibular system. The primary purpose of VNG is to determine if reported

APPLIED NEUROPSYCHOLOGY: ADULT

balance problems are secondary to inner ear disease. As all subjects had normal results (via interpretation by a neurotologist or neurologist with subspecialty training in vestibular disorders), inner ear problems were ruled out as a likely cause of the reported dizziness and balance problems. With abnormal VNG specific SOT patterns are typically demonstrated, which would not be considered aphysiologic in nature. As such, even with abnormal VNG aphysiologic responses would still warrant scrutiny; however, as no subjects in the current study had an abnormal VNG such concerns do not apply.


Statistical analysis Performances on both the CDP and WMT were coded dichotomously for passing or failing based on the aforementioned criteria. Results were compared via Spearman Rho correlations and a chi-squared analyzes.

Results Thirty-five percent of the total sample failed the WMT. Table 1 outlines the WMT scores for those passing and failing the WMT. Five of the 21 subjects with a history of moderate to severe TBI (23.8%) failed the WMT effort measures and of these two had a Genuine Memory Impairment Profile (GMIP). Of those with a history of mTBI/mild head injury, 18 (38.3%) failed the WMT and eight demonstrated a GMIP. However, none of the subjects in the sample were diagnosed with a current condition that would render them unsafe for independent living and all were living without assistance at the time of evaluation. As such, the GMIP was inapplicable and WMT failure in all cases was deemed Table 1.

secondary to poor effort. Thirty six percent of the sample demonstrated an aphysiologic pattern on CDP assessment. Across the entire sample, thirty-nine subjects passed both the WMT and the CDP and 16 failed both. Eleven subjects failed the WMT, but passed the CDP, while 12 subjects passed the WMT but failed the CDP (Table 2). There was a 70.5% agreement between these two measures, which were significantly correlated (rφ ¼ 0.35, p ¼ .002). Chi-squared was statistically significant (χ2 ¼ 9.8, p ¼ .002). When the sample was separated by TBI diagnosis, findings were similar. Among the subjects who experienced a mTBI/mild head injury (N ¼ 47), 22 (46.8%) passed both the WMT and the CDP, while 10 (21.3%) failed both. Nine mTBI/mild head injury subjects (19.1%) failed the WMT, but passed the CDP, while 6 (12.8%) mTBI/mild head injury subjects failed the CDP, but passed the WMT. There was a 68.0% agreement between the measures, which was significantly correlated (rφ ¼ .32, p ¼ .03), with a significant Chi-squared of 4.9 (p ¼ .03). Across those experiencing a moderate to severe TBI (N ¼ 21), 11 subjects (52.4%) passed and five (23.8%) failed both measures. Four moderate to severe TBI subjects (19.0%) passed the WMT, but failed the CDP, while 1 (4.8%) failed the WMT and passed the CDP. There was a 76% agreement between the WMT and the CDP. Spearman Rho Correlations and Chi-Squared analyses were each statistically significant (rφ ¼ 0.52, p ¼ .02 and χ2 ¼ 5.6, p ¼ .03). It is of note that similar percentages of patients in the mild and moderate to severe TBI groups failed both measures (21 and 23%, respectively). Across the entire sample WMT scores were also examined as a function of CDP performance. As shown

Scores for those passing and failing the WMT.

Pass WMT (N ¼ 51)

Fail WMT (N ¼ 27)

WMT scores IR DR CNS MC PA FR Easy Subtests Hard Subtests IR DR CNS MC PA FR Easy Subtests Hard Subtests Easy-Hard Subtests

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Mean scores in % correct 95.7 96.7 93.7 83.4 81.1 49.2 95.4 72.4 78.0 77.0 71.2 58.5 51.3 28.5 75.4 45.8 29.1

Std. Dev. 3.9 3.3 4.3 17.6 17.9 13.6 3.1 13.3 14.8 13.5 10.8 16.3 17.6 9.3 11.6 11.9 8.1

Note. WMT ¼ Word Memory Test; IR ¼ Immediate Recognition; DR ¼ Delayed Recognition; CNS ¼ Consistency; MC ¼ multiple choice; PA ¼ Paired Associates; FR ¼ Free Recall. Easy-Hard subtest differences in those passing the WMT were not reported as this statistic is only examined in individuals who fail the easy subtests (Green, 2003).

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Table 2. CDP and WMT comparison in total sample. WMT – Pass

WMT – Fail

39 12

11 16

CDP – Pass CDP – Fail

Note. CDP ¼ Computerized Dynamic Posturography; WMT ¼ Word Memory Test.

Table 3.

WMT subtest scores as a function of CDP validity performance.

WMT Subtest

CDP Pass

Immediate Recognition Delayed Recognition Consistency Multiple Choice Paired Associates Free Recall

92.6 92.7 89.4 83.4 77.4 45.5

(10.8) (11.2) (11.2) (17.6) (20.5) (14.1)

CDP Fail 84.3 84.9 79.7 64.3 58.5 35.2

(13.7) (13.4) (13.8) (18.0) (22.0) (16.8)

F (df) 8.8 7.6 11.5 20.5 13.9 7.9

(1.76) (1.76) (1.76) (1.75) (1.74) (1.73)

p .004 .007 .001