Electromyography (EMG)

Electromyography is the recording of electrical activity from muscle tissue. Motor neurons generate action potentials when electrically stimulated or under pathological conditions. An electromyograph detects these changes in electrical activity and represents an important diagnostic tool to monitor nerve root function and muscle cell activity.

Electromyography recording

EMG activity can be recorded using different types of electrodes, including monopolar needles, concentric needles, bipolar needles, and single-fiber needles. Without the use of high and low frequency filters, EMG signals would be very noisy and difficult to interpret. The low frequency filter should be set to 10-30 Hz and the high frequency filter to 10-20 kHz, for example.

1. Spontaneous EMG. After the recording electrodes are inserted into the muscle tissue, the background EMG activity is stable and quiet under healthy conditions. Spontaneous EMG activity generated by the motor cell or by the muscle fiber occurs in the presence of an injury or a pathology. Examples of spontaneous activity arising from the muscle fiber include fibrillation potentials, positive sharp waves, myotonic discharges, and complex repetitive discharges. Examples of spontaneous activity arising from the motor cell include neuromyotonic tonic discharges, myokymic discharges, and tremors.
2. Stimulated EMG. Electrically stimulated EMG activity is a very useful diagnostic test and is performed in a variety of surgical procedures that require IONM.
3. Single Fiber EMG

Cranial Nerves

1. Facial Nerve
2. Cranial Nerve III IV and VI
3. Other Cranial Nerves

Intraoperative Monitoring

1. Pedicle screws
2. Peripheral Nerves
3. Brachial Plexus
4. Dorsal Rhizotomy
5. Skull Base Tumor
6. Others

Anesthesia and Other Factors

1. Anesthesia Methods
2. Muscle Relaxants
3. Temperature
4. Tourniquet
5. Others