معیارهای کمی تمارض حافظه درباره مقیاس حافظه وکسلر؛نسخه سوم در طرفین آسیب سر خفیف

Wechsler Memory Scale—Third edition (WMS-III) performance in 25 mild traumatic brain injury (TBI) litigants who met the criteria for probable malingered neurocognitive dysfunction (MND) was compared with 50 nonmalingering subjects. The base rate for probable MND in the population studied was 27%. Overall, malingerers showed globally depressed memory function. They returned significantly poorer scores than nonmalingerers on all WMS-III indexes and subtests, and on selected WMS-III index difference scores and intelligence–memory difference scores. Using the minimum score returned in the nonmalingerers as the cut-off for malingering, the delayed auditory recognition memory tasks were highly effective in detecting malingering. Raw scores below 43 on the auditory recognition-delayed (AR-D) subtest or below 18 on word list II-recognition, identified around 80% of the malingerers. In a group of 50 severe TBI litigants, only a very small proportion (i.e., <10%) returned scores below the cut-offs for malingering for the mild TBI subjects.

Various definitions and criteria for malingering have been proposed, those of the Diagnostic and Statistical Manual of Mental Disorders—Fourth edition (DSM-IV) probably being the most widely used (American Psychiatric Association, 1994). In an attempt to facilitate both clinical practice and systematic research in relation to malingering in neuropsychology, Slick, Sherman, and Iverson (1999) have proposed a set of diagnostic criteria for possible, probable, and definite malingering of cognitive dysfunction based on psychometric, behavioural, and collateral data. “Probable” malingering of neurocognitive dysfunction (MND) requires a substantial incentive to fabricate cognitive dysfunction, the presence of evidence strongly suggesting volitional exaggeration or fabrication of cognitive dysfunction, and the absence of plausible alternative explanations. The prevalence of conscious and intentional faking of cognitive impairment on neuropsychological assessment is unknown. Malingerers rarely identify themselves and foolproof methods of detecting malingering remain to be found. Base rates for malingering of cognitive impairment in litigants remain speculative, but appear to be quite high. A meta-analysis of studies evaluating the impact of financial incentives on persistent symptomatology after closed head injury reported a particularly strong effect size (of 1.47 S.D.) in the mild head injury group (Binder & Rohling, 1996). These researchers concluded that “money matters” and they recommended that malingering be considered in all medico-legal cases. Actual estimates of malingering in the population of head injury litigants are reported to vary considerably, allegedly from 1 to 50% (Reynolds, 1998). The present study assessed the prevalence of probable MND, with particular emphasis on feigned memory impairment, in a mild head injury litigant population. Base rate information is important in clinical practice and is critical in interpreting the sensitivity and specificity of malingering measures (Bianchini, Mathias, & Greve, 2001; Gouvier, Hayes, & Smiroldo, 1998).