Abnormal flash visual evoked potentials in malnourished infants: an evaluation using principal component analysis.

OBJECTIVE: To characterize the morphology of flash visual evoked potentials (fVEPs) obtained from infants hospitalized with severe, chronic malnutrition (marasmus). METHODS: A covariance-based principal component analysis with Promax factor rotation was applied to fVEPs obtained from malnourished infants and age-matched control subjects. RESULTS: The analysis suggests the presence of a late positive complex in the fVEP, with at least one of its components being significantly diminished in marasmic infants. The N3 component was also diminished in marasmic infants. Following remediation, the marasmic group no longer differed with respect to these components. However, an abnormally large late, positive deflection was evident at discharge. CONCLUSIONS: The fVEP morphology of infants hospitalized with severe malnutrition was found to be significantly different from age-matched controls. Moreover, although there was evidence of recovery following remediation, fVEPs continued to show abnormality at discharge, suggesting the possibility that nutritional rehabilitation did not fully eliminate the physiological deficit. SIGNIFICANCE: Malnourishment during early infancy results in altered neurophysiological functioning, possibly in cortical areas responsible for higher order visual processing.

Detection of feigned tactile sensory loss using a forced-choice test of tactile discrimination and other measures of tactile sensation.

OBJECTIVE: Intentional exaggeration of disability is a risk in work injuries but is hard to reliably detect clinically. This study examined the accuracy of tactile sensory threshold and forced-choice discrimination measures in detecting feigned sensory loss. METHODS: Participants (n = 80) were randomly assigned to one of four sensory loss groups: (1) none; (2) partial; (3) full; or (4) feigned. Sensory data were collected for the upper extremities. RESULTS: Tactile thresholds greater than 0.5 g, discriminability less than 0.50, or forced-choice scores less than 90% were associated with a very low probability of false-positive errors. CONCLUSIONS: Below-chance scores are definitive evidence that the sensory loss is intentionally feigned. Scores beyond cut-offs should raise the clinician's suspicion of malingering if there is no physical basis for sensory loss.