Nerve and muscle biopsy are usually done simultaneously.
Nerve biopsy can help differentiate axonal from demyelinating polyneuropathies when other tests are inconclusive. A nerve supplying the affected area should be chosen. Nerve biopsy can also reveal rare infections, such as leprosy.
If polyneuropathy may be caused by vasculitis, the sample should include skin to increase the chances of finding a characteristic vascular abnormality.
If the biopsy shows that nerve endings are lost, skin punch biopsy can help confirm small-fiber polyneuropathy.
Muscle biopsy can help confirm myopathies.
