The usual evaluation of neurologic function involves the clinical neurologic examination in conjunction with several testing procedures. The neurologic examination is a five-part battery of tests performed by a physician that systematically evaluates cerebral (mental status), cranial nerve, motor, sensory, and cerebellar/gait functions. Special ancillary tests that can be performed by additional professionals (physicians, neuropsychologists, or technicians) may include detailed neuropsychological evaluations with standardized and validated test protocols, electromyography (EMG) and nerve conduction studies for PNS function, neuroimaging for identifying CNS anatomic lesions, and neurophysiology tests such as electroencephalography (EEG) for the assessment of epilepsy and metabolic disorders.
The neuropsychologic battery of tests chosen depends on the age of the patient and the type of behavioral alterations being evaluated. Although there are literally hundreds of standardized tests available for neuropsychological assessment, a few of the most commonly used are the Wechsler Adult Intelligence Scales (WAIS) and its revised version (WAIS-R), the Minnesota Multiphasic Personality Inventory (MMPI), and the Self-Report Symptom Inventory (known as SCL-90). The WAIS and WAIS-R assess general intelligence as well as verbal and nonverbal cognitive abilities using 11 different subtests. The MMPI, a standardized 566-item questionnaire, provides objective assessment of personality characteristics and psychopathology (Green, 1980). The MMPI consists of three validity scales and ten clinical scales; test norms are based on scores of a sample of Minnesota men who took the test before World War II. The SCL-90 is a 90-question, self-administered checklist that examines various personality characteristics, psychiatric disorders, health-related concerns, anxiety, and depression.
Although the neurologic examination and the specialty tests described above are widely available, they are not all uniformly standardized and their results can be affected by a number of factors. They are often able to detect neurologic dysfunction but cannot always distinguish it from the effects of abnormal emotional states or diseases outside the nervous system that can alter a patient's function. For example, body temperature can modify EMG data, examiner style and native intelligence can affect patient performance on neuropsychologic tests, and fatigue or medications can profoundly affect EEG patterns. For these reasons, rigorous methodology and maximally matched control or comparison populations are especially important for the scientific study of the causes of neurologic and behavioral alterations.
Case identification in neurology is also often difficult. Despite the advances in neuroimaging, many types of neurologic alternations are biochemical and show no abnormalities on scanning tests. The nervous system is not usually accessible for biopsy, so pathologic confirmation is not feasible