Test selection is based on anatomic location of the suspected cause: Peripheral nerves or nerve roots: Nerve conduction studies and electromyography (electrodiagnostic testing) Brain or spinal cord: MRI Electrodiagnostic tests can help differentiate between neuropathies and plexopathies (lesions distal to the nerve root) and more proximal lesions (eg, radiculopathies) and between types of polyneuropathies (eg, axonal and demyelinating, hereditary and acquired).