Abnormal sensory finding may have a peripheral nervous system (PNS) or a central nervous system (CNS) cause.The neuropathies of diabetes , malnutrition,and vascular problems are due to a PNS cause and generally involve the entire extremity or both extremities.Damage to a specific spinal nerve may not result in significant sensory loss because the spinal nerves overlap.Injury to several adjacent spinal nerves is manifested as decreased or absent sensation in the dermatomes of those nerves.