Differentiating poor validity from probable impairment on the medical symptom validity test: a cross-validation study

Aims: In neuropsychological evaluations, it is often difficult to ascertain whether poor performance on measures of validity is due to poor effort or malingering, or whether there is genuine cognitive impairment. Dunham and Denney created an algorithm to assess this question using the Medical Symptom Validity Test (MSVT). We assessed the ability of their algorithm to detect poor validity versus probable impairment, and concordance of failure on the MSVT with other freestanding tests of performance validity.

Methods: Two previously published datasets (n?=?153 and n?=?641, respectively) from outpatient neuropsychological evaluations were used to test Dunham and Denney’s algorithm, and to assess concordance of failure rates with the Test of Memory Malingering and the forced choice measure of the California Verbal Learning Test, two commonly used performance validity tests.

Results: In both datasets, none of the four cutoff scores for failure on the MSVT (70%, 75%, 80%, or 85%) identified a poor validity group with proportionally aligned failure rates on other freestanding measures of performance validity. Additionally, the protocols with probable impairment did not differ from those with poor validity on cognitive measures.

Conclusions: Despite what appeared to be a promising approach to evaluating failure on the easy MSVT subtests when clinical data are unavailable (as recommended in the advanced interpretation program, or advanced interpretation [AI], of the MSVT), the current findings indicate the AI remains the gold standard for doing so. Future research should build on this effort to address shortcomings in measures of effort in neuropsychological evaluations.     

Magnetic resonance elastography with guided pressure waves

Magnetic resonance elastography aims to non-invasively and remotely characterize the mechanical properties of living tissues. To quantitatively and regionally map the shear viscoelastic moduli in vivo, the technique must achieve proper mechanical excitation throughout the targeted tissues. Although it is straightforward, ante manibus, in close organs such as the liver or the breast, which practitioners clinically palpate already, it is somewhat fortunately highly challenging to trick the natural protective barriers of remote organs such as the brain. So far, mechanical waves have been induced in the latter by shaking the surrounding cranial bones. Here, the skull was circumvented by guiding pressure waves inside the subject's buccal cavity so mechanical waves could propagate from within through the brainstem up to the brain. Repeatable, reproducible and robust displacement fields were recorded in phantoms and in vivo by magnetic resonance elastography with guided pressure waves such that quantitative mechanical outcomes were extracted in the human brain.     

Predictors of gastric emptying in Parkinson''s disease

Predictors of gastric emptying (GE) in patients with idiopathic Parkinson's disease (PD) of a solid and liquid meal are not well defined. For measurement of GE 80 patients with PD were randomly assigned to receive either a solid meal (250 kcal) containing 13C-octanoate (n = 40) or a liquid meal (315 kcal) with 13C-acetate (n = 40). All patient groups were off medication affecting motility and were matched for age, gender, body mass index, disease duration and severity, using Unified Parkinson's Disease Rating Scale (UPDRS). Gastric emptying was compared with a healthy control group (n = 40). Multiple regression analysis was used to determine predictors of gastric emptying. Exactly 88% and 38% of PD patients had delayed GE of solids and liquids respectively. Solid and liquid emptying was similar in women and men. There were no differences in GE in PD patients < 65 years of age when compared with patients > or = 65 years. Multiple regression analysis showed that motor handicaps such as rigour and action tremor are independent predictors of solid GE (r = 0.68, P < 0.001). The severity of motor impairment, but not any other neurological symptom, as assessed by UPDRS is associated with gastroparesis in PD and solid emptying is more likely to be delayed.     

Postinfectious gastroparesis related to autonomic failure: a case report

BACKGROUND AND AIM: Severe dysautonomia may be secondary to viral infections, resulting in impaired autoimmune, cardiovascular, urinary and digestive dysfunction. Herein, we present a case of a 31-year-old white female patient who had severe gastroparesis related to autonomic failure following an episode of acute gastroenteritis. This seems to be the first report providing thorough assessment of the enteric and autonomic nervous system by analysis of full-thickness small intestinal biopsies, cardiovagal testing and autopsy. HOSPITAL COURSE: This patient affected by a severe gastroparesis was treated with antiemetics, prokinetics, analgesics and gastric electrical stimulation to control symptoms. Nutritional support was made using jejunal feeding tube and, in the final stage of disease, with total parenteral nutrition. Autonomic studies revealed minimal heart rate variability and a disordered Valsalva manoeuvre although the enteric nervous system and the smooth muscle layer showed a normal appearance. Hospital courses were complicated by episodes of bacteraemia and fungemia. Serum antiphospholipid antibodies were noted but despite anticoagulation, she developed a pulmonary embolism and shortly thereafter the patient died. Autopsy revealed acute haemorrhagic Candida pneumonia with left main pulmonary artery thrombus. Sympathetic chain analysis revealed decreased myelinated axons with vacuolar degeneration and patchy inflammation consistent with Guillain-Barre syndrome. The evaluation of the enteric nervous system in the stomach and small bowel revealed no evidence of enteric neuropathy or myopathy. CONCLUSION: A Guillain-Barre-like disease with gastroparesis following acute gastroenteritis is supported by physiological and autonomic studies with histological findings.     

Measuring behaviour: The tools and the strategies

Animal behaviour can be viewed as a stream of elements, which, once accurately described, can be counted and timed. Data acquisition techniques and tools are reviewed, and some strategies for collection and analysis of data using PC computers are suggested. Automated instruments are not satisfactory for the study of complex behaviour and as such systemic observation remains irreplaceable. IBM PC-type computers, with a wide range of analytical software (e.g., spreadsheets, statistical packages, technical graphics), are practical for data acquisition. Several systems which can satisfy different applications are reviewed. Some systems can communicate with a videorecorder, a facility which remarkably increases the accuracy of measurement; this is essential for meaningful analyses of the internal structure of behavioural streams (sequences, time patterns) or communication processes. The power of new tools enables behavioural measurement with the necessary complexity to allow a whole new set of questions to be addressed. However, it also increases demands for meaningful content and analysis of data.