Neuropsychological assessment for detecting adverse effects of volatile organic compounds on the central nervous system

Because there are no direct biological markers for the substances implicated in indoor air exposure, it is impossible to directly measure if an individual or group of individuals has been exposed to a potentially neurotoxic substance in the workplace. Behavioral changes may be the earliest and only manifestation of central nervous system (CNS) effects and are often too subtle to be revealed by routine physical or neurological examination. Neuropsychological techniques are sensitive to subtle behavioral/cognitive changes that can result from exposure to neurotoxins. These techniques consist of oral and written tests that are administered by a trained examiner on a one-to-one basis. In general, a wide variety of cognitive domains are evaluated. The typical battery generally includes assessing orientation, attention, intelligence, language, visual memory, verbal memory, perception, visuoconstruction, simple motor speed, psychomotor speed, and mood. As with most assessment techniques, the neuropsychological methods have limitations. One major drawback is the availability of appropriate norms that are used to compare the results of a specific individual. Because these tasks are greatly affected by age, intelligence, and in some instances sex, the availability of appropriate norms is mandatory to determine if the CNS has been effected. Although neuropsychological tests are sensitive to the presence of CNS involvement, they are not specific. Patterns of performance seen with specific instances of neurotoxic exposure may also be seen with a number of other diseases of the CNS such as dementia, cerebrovascular disease, hydrocephalus, or normal aging. In addition, neuropsychiatric symptoms such as anxiety and/or depression are often manifested as cognitive difficulties that will mimic the cognitive dysfunction seen with toxicity of the CNS. Some of the more sensitive neuropsychological tests are presented. Interpretations of test performance as they relate to toxic effects on the CNS are discussed.