Peripheral neuropathies may affect One nerve (mononeuropathy) Several discrete nerves (multiple mononeuropathy, or mononeuritis multiplex) Multiple nerves diffusely (polyneuropathy) A plexus (plexopathy) A nerve root (radiculopathy) More than one site can be affected; eg, in the most common variant of Guillain-Barré syndrome, multiple segments of cranial nerves, usually the 2 facial nerves, may be affected.