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Forensic Neuropsychology in Personal Injury Cases II

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  1. Forensic Neuropsychology in Personal Injury Cases II Russell M. Bauer, Ph.D. July 20, 2006

  2. “Noninjury” Contributors to Neuropsychological Impairment in MHI • Adversarial patient-examiner relationship • Exaggeration or poor effort • Impairment as communication • Frank malingering for gain; financial incentives • Factitious disorders • Fatigue, pain, other physical factors • Psychiatric disturbance (e.g., psychosis, anxiety, depression) • Pre-existing factors affecting neuropsychological performance (e.g., learning disability, limited education) • Occupational/life experience factors

  3. Financial Incentives and Disability • Binder & Rohling (AJP, 1996, 153, 7-10) • Meta-analytic review of financial incentives and symptoms • 18 study groups, 2,353 subjects • Weighted mean effect size of difference between groups with and without financial incentives was 0.47 • More late-onset symptoms in compensation-seeking groups

  4. Checks against False Positives: Consistency Analysis • Consistency of results between/within domains • Consistency with known syndromes • example: “hemi-anomia” • Consistency with injury severity • Consistency with other aspects of behavior • e.g. memory abilities during vs. apart from formal testing

  5. Post-Concussion Syndrome

  6. Post-Concussion Syndrome: DSM-IV Definition • “acquired impairment in cognitive functioning, accompanied by specific neurobehavioral symptoms, that occurs as a consequence of closed head injury of sufficient severity to produce a significant cerebral concussion” (LOC, PTA, etc.)

  7. PCS: DSM-IV Criteria • Hx of head trauma that has caused significant cerebral concussion • Evidence from NP testing or quantified cognitive assessment of difficulty in attention or memory • Three (or more) of the following occur shortly after trauma and last at least 3 months: • easy fatigue • disordered sleep • headache • dizziness/vertigo • irritability or aggression with little/no provocation • anxiety, depression, or affective lability • changes in personality • apathy or lack of spontaneity

  8. PCS: DSM-IV Criteria (cont’d) • Symptoms begin after head trauma or else represent a worsening of pre-existing symptoms • Significant impairment in social or occupational function; decline from previous functional level • Do not meet criteria for dementia and are not better accounted for by another mental disorder

  9. PCS-Like Complaints of NP Dysfunction • Common • Nonspecific • Potentially related to non-neurological factors (anxiety, depression, fatigue, stress) • Correlate better with distress than with objective indicators of CNS injury • Easy to feign or exaggerate

  10. Complaints as “Evidence” • In the absence of objective neuro-psychological deficit, complaints are often taken to indicate the existence of occult disease • There is a difference between symptoms (subjective evidence)and signs (objective evidence) of illness • Symptom reports subject to cognitive distortions and attributional processes

  11. Problems with Using Complaints as Evidence of MHI • Mittenberg et al. (1992, 1997): “expectation as etiology” • ‘imaginary concussion’produces symptom complaint cluster identical to that reported by patients with ‘real’ head injury • patients with minor TBI significantlyunderestimatedegree of pre-injury problems

  12. Major PCSSymptoms “Imaginary concussion” produces a pattern of symptom reports virtually identical to that seen after MHI

  13. MHT patients significantly underestimate preinjury symptoms compared to a noninjured control group

  14. Conclusions • You don’t have to have had a head injury to have post-concussion symptoms • Once something bad has happened to you, you tend to attribute more of your problems to it • Complaints reflect the subjective, not necessarily the objective, consequences of MTBI

  15. Implications for Understanding PCS • 5% of MHI patients have persistent deficits • Physiogenic causes likely operative in the first 1-3 months • Psychogenic causes important thereafter • Complaints have low specificity for MHI • Baserate issues important • Attributional processes important • Suggests need for a scientific approach to assessing persistent complaints after MHT

  16. Assessment of Malingering and Poor Effort • Issues with definition • Intentional (intention) • Fabrication or exaggeration (action) • For purposes of gain (motive) • Explanatory models (Rogers, 1997) • Pathological (mental disorder) • Criminological (fake) • Adaptational (meeting adversarial demands) • Cognitive vs. Somatic Malingering

  17. Effort, Motivation, & Response Styles Frederick et al., 2000

  18. Slick (1999) • Considers evidence from NP and self report • NP criteria • Definite or probable response bias • Discrepancies/inconsistencies between NP data and patterns of brain functioning, collateral reports, reports of past functioning

  19. DEFINITE MND Presence of financial incentive Definite negative response bias Behaviors that meet criteria for negative response bias that are not fully accounted for by psychiatric, neurological, or developmental factors PROBABLE MND Presence of financial incentive Two or more types of evidence from NP, excluding definite response bias, or one piece of evidence from NP and one from self-report Slick et al, 1999 (cont’d)

  20. Malingering Research Literature • Case study • Simulation studies • Interpretive issues • Appropriate designs • Differential prevalence design • contrasting high and low baserate groups • Known-groups design • Selecting groups on the basis of malingering criteria (e.g., Slick, et al)

  21. Selecting Specialized Cognitive Effort Tests • Ease of use • Credibility of rationale • Operating Characteristics • Incremental validity • TBI vs. PPCS • Coaching issues • Not likely to be a “best” test

  22. Commonly Used Specialized Tests • Portland Digit Recognition • Digit Memory Test • Computerized Assessment of Response Bias (CARB) • Word Memory Test (WMT) • Victoria Symptom Validity Test • Test of Memory Malingering • Validity Indicator Profile • Rey 15-Item Test • Dot Counting Test

  23. Why being a knowledgeable neuropsychologist is important • You know likely patterns of impairment • You know psychometric relationships among tests • You know course of recovery • You know about contributory factors (e.g., LD, depression, etc.) • You can compare what you see to what you expect

  24. Common “suspect” neuropsychological signs on NP testing • Recognition << recall (hits, discriminability) • Extremely poor DS in the context of normal auditory comprehension (RDS) • Motor slowing (e.g., reduced tapping) relative to overt motor disability • Excessive failures-to-maintain-set on WCST • Discrepancies between test level and level during informal interaction • Other “impossible” signs • Hemi-anomia

  25. Detecting Somatic Malingering • Symptom report, as well as cognitive performance, can be controlled by the litigant • Use of MMPI-2 • F-scale, F(p) • VRIN, TRIN • Subtle-Obvious • F-K index • Revised Dissimulation Scales • These scales may not be sufficiently sensitive to TBI-related claims, despite neuropsychological differences

  26. Lees-Haley FBS • Model of goal-directed behavior: • Want to appear honest • Want to appear psychologically normal except for the influence of injury • Avoid admitting longstanding problems • Minimize pre-existing complaints • Minimizing pre-injury antisocial or illegal behavior • Presenting plausible injury severity

  27. Lees-Haley FBS (cont’d) • 18 “True” , 25 “False” • Does not correlate very strongly with F-scale derivatives • Most scale items overlap with “neurotic” side of MMPI • Cut-off mid 20’s, with varying false positive rates; increasing security with scores > 25-27