One can infer relatively little about the cause of a peripheral nerve disorder from the symptoms and signs alone. A second distinctive feature of the PNS is its accessibility. Unlike the brain and the spinal cord, which are well protected by bony cases, most of the major peripheral nerves reside for much of their course only a short distance beneath the skin. This simplifies direct study of their electrical and histologic characteristics. Clinical evaluation of PNS diseases has been greatly facilitated by nerve conduction studies and nerve biopsy, which can be performed with essentially no risk to the patient.
Regenerative capacities differ between the peripheral nervous system and central nervous system.
In the mature CNS, little or no regrowth of axons occurs after injury. However, an injured peripheral nerve can often regenerate over long distances and reestablish functional connections. Thus, many peripheral nerve disorders have potential for significant recovery of function with treatment. The difference in regenerative capacity was long thought to be related to some intrinsic property of PNS neurons. However, recent evidence suggests that the critical factor lies in their supporting tissues.