An accurate history and thorough physical and neurologic examinations are necessary to evaluate a problem involving the nervous system. An understanding of functional neuroanatomy, neurophysiologic concepts, and mechanisms of disease is a prerequisite for accurate interpretation of clinical findings. Based on the initial clinical assessment, 1) the anatomic location(s) of disease can be determined, and 2) the problem may be defined as diffuse, multifocal, or focal; symmetric or asymmetric; painful or nonpainful; progressive, regressive, waxing and waning, or static; and mild, moderate, or severe. The potential mechanisms of disease must also be considered to determine differential diagnoses. Further diagnostic tests include clinicopathologic tests (on serum, blood, urine, feces, and CSF), diagnostic imaging (including plain and contrast radiography, CT, and MRI), and electrodiagnostic testing.