A general classification of the disorders or diseases that impact upon the nervous system. An understanding of diseases of the nervous system should include not only the type of lesion and reaction to injury, but also the site of involvement. Indeed, exquisite localization of function is a key distinguishing feature between the nervous system and other organs of the body. Further important considerations include age and sex. With regard to the sites affected, one important regional division is between the central nervous system (CNS), which includes the brain, spinal cord, and their coverings (meninges), and the peripheral nervous system (PNS), which includes the motor, sensory, and autonomic components of nerves that traverse the body.