Electrodiagnostics (Nerve and Muscle Testing)
- Electromyography (EMG)
- Motor and sensory nerve conduction studies (NCV)
- Auditory brainstem evoked response (BAER)
- Repetitive nerve stimulation
- Special testing for myasthenia gravis (SFEMG)
- Somatosensory evoked potentials
EMG is the recording of activity of the muscle. During the test a small specialized needle is inserted into the muscle and the activity recorded. EMGs are performed on a patient under deep sedation or more commonly, general anesthesia therefore no pain is felt during examination and it can’t be skewed from the movement.
Normal resting muscle is generally electrically silent. In contrast, the sick muscle has spontaneous activity which can be documented during the electromyographic examination and can help confirm the existence of disease of the peripheral nervous system and distinguish between primary nerve and muscle disease. It says precisely if the muscle atrophy is because of disease of the muscle or nerve or because of because of too little activity.
Nerve Conduction Studies
Nerve conduction studies evaluate the function of the peripheral nerves. In the clinical practice, the function of the motor nerves is the most commonly evaluated. The most commonly tested nerves in dogs and cats are the peroneal and the tibial nerves in the pelvic (back) limbs and the ulnar and the radial nerves in the thoracic (front) limbs.
Changes in the nerve conduction velocity indicate damage to the nerve (the axon, myelin, or both). Nerve conduction velocity helps to confirm the presence of the peripheral nerve disease and to helps to choose the right nerve for the further investigation, such as nerve biopsy.