Diagnosis

Peripheral neuropathy has many potential causes. Besides a physical exam, which may include blood tests, diagnosis usually requires:

• A full medical history. Your doctor will review your medical history, including your symptoms, lifestyle, exposure to toxins, drinking habits and a family history of nervous system (neurological) diseases.
• Neurological examination. Your doctor might check your tendon reflexes, your muscle strength and tone, your ability to feel certain sensations, and your posture and coordination.

Tests

Your doctor may order tests, including:

• Blood tests. These can detect vitamin deficiencies, diabetes, abnormal immune function and other indications of conditions that can cause peripheral neuropathy.
• Imaging tests. CT or MRI scans can look for herniated disks, pinched (compressed) nerves, tumors or other abnormalities affecting the blood vessels and bones.

• Nerve function tests. Electromyography (EMG) records electrical activity in your muscles to detect nerve damage. A thin needle (electrode) is inserted into the muscle to measure electrical activity as you contract the muscle.

  At the same time your doctor or an EMG technician obtains an electromyogram, he or she typically performs a nerve conduction study. Flat electrodes are placed on the skin and a low electric current stimulates the nerves. Your doctor will record your nerves' responses to the electric current.

• Other nerve function tests. These might include an autonomic reflex screen that records how the autonomic nerve fibers work, a sweat test that measures your body's ability to sweat, and sensory tests that record how you feel touch, vibration, cooling and heat.
• Nerve biopsy. This involves removing a small portion of a nerve, usually a sensory nerve, to look for abnormalities.
• Skin biopsy. Your doctor removes a small portion of skin to look for a reduction in nerve endings.