Disorder of the peripheral nervous system .
It may be genetic or acquired, progress quickly or slowly, involve motor, sensory, and/or autonomic (see autonomic nervous system ) nerves, and affect only certain nerves or all of them. It can cause pain or loss of sensation, weakness, paralysis , loss of reflex es, muscle atrophy , or, in autonomic neuropathies, disturbances of blood pressure, heart rate, or bladder and bowel control; impotence; and inability to focus the eyes. Some types damage the neuron itself, others the myelin sheath that insulates it. Examples include amyotrophic lateral sclerosis , {{link=poliomyelitis">poliomyelitis , and shingles . Causes include diseases (e.g., diabetes mellitus , leprosy , syphilis ), injury, toxin s, and vitamin deficiency (e.g., beriberi ). See also neuralgia ; neuritis .