Neurobehavioral Toxicology

The adverse effects of exposure to neurotoxic chemicals on the brain manifest themselves behaviorally as changes inmood and in cognitive function. Neuropsychological testing has emerged as a means of documenting and measuring these changes. This methodology has several advantages for use in both the clinical diagnosis of chemically induced disorders and the epidemiologic investigation of neurotoxicant exposure–outcome relationships. These advantages include the documented validity and reliability of neuropsychological tests and their known sensitivity for detecting the effects of cerebral pathology and for localizing the probable specific anatomical sites associated with many neuropathological and neurodegenerative processes. In addition, methods of neuropsychological testing used to estimate premorbid intellectual abilities allow investigators to uncover acquired changes in cognitive functioning associated with brain insults, including the effects of exposure to neurotoxicants. The pathological effects following brain insults that may produce measurable deficits on formal neuropsychological testing may ormay not be detectable by conventionalmagnetic resonance imaging (MRI), computed tomography (CT), and electroencephalography studies. Although the newer imaging technologies [i.e., positron emission tomography (PET), single photon emission computed tomography (SPECT), functional MRI (fMRI), and magnetic resonance spectroscopy (MRS)] can provide additional objective evidence of an organic basis of the neurobehavioral manifestations, formal neuropsychological assessment nevertheless remains the principal means for documenting impaired function among patients exposed to neurotoxicants. This article discusses the neurobehavioral syndromes related to neurotoxicant exposure and presents a reviewof the clinical diagnostic approaches most utilized in their evaluation.