Autonomic neuropathies

Many peripheral neuropathies affect autonomic fibers in isolation or in addition to somatic sensory and motor fibers. When involvement of autonomic fibers is prominent, the term autonomic neuropathy is used. The most commonly encountered autonomic neuropathies are listed in this chapter. Other neuropathies, inherited or acquired, specifically target autonomic fibers. The current understanding of the autonomic neuropathies has improved due to better understanding of the molecular basis of the inherited autonomic neuropathies, development of objective and noninvasive tests of autonomic function, and recognition of an immunological basis for many cases of subacute acquired autonomic neuropathy. The natural history of autonomic distal neuropathies due to toxins and drugs is more favorable. The brunt of the pathology is manifested at the distal ends of the longest nerve fibers. Although the cell body can be affected, its involvement is usually partial and capable of recovery. Following withdrawal of the toxin or cessation of the drug, slow recovery is expected. The natural history of positive somatic and autonomic symptomatology is complex. Recovery is typical but not invariable. Part of the incomplete recovery relates to the incompleteness of fiber regeneration. However, there can be functional alterations.