Intraoperative Neuromonitoring: Insurance for Nerve Protection

Real-time monitoring of the functions of the brain, spinal cord, and peripheral nerves during surgery is called intraoperative neuromonitoring (IONM). It aims to prevent permanent neurological deficits by alerting the surgeon before nerve damage develops.

Basic Modalities

SEP (Somatosensory Evoked Potentials): The peripheral nerve is stimulated, and the response is recorded from the brain cortex. It monitors the integrity of the sensory pathways.

MEP (Motor Evoked Potentials): The brain's motor cortex is stimulated, and muscle responses are recorded. It monitors the integrity of the motor pathways. It is the most critical modality in spinal cord surgery.

EMG (Electromyography): Directly monitors muscle activity. Spontaneous EMG evaluates nerve root irritation, while triggered EMG evaluates the safety of screw placement.

BAEP (Brainstem Auditory Evoked Potentials): Monitors the function of the auditory nerve and brainstem. It is used in acoustic neuroma and posterior fossa surgery.

D-Wave: Motor response from the spinal cord via direct cortical stimulation. It is one of the primary methods for monitoring motor pathways in intramedullary tumour surgery.^1,2

Clinical Importance

With the use of IONM, the risk of recurrent laryngeal nerve damage in thyroid surgery is significantly reduced (up to 80% in some studies)^3,4; in scoliosis surgery, the risk of adverse neurological outcomes such as paraplegia can be reduced.⁵

Alerting the surgeon before nerve damage develops is the key to preventing permanent neurological deficits.

Alarm Criteria

A 50% decrease in SEP amplitude is a warning criterion according to current guidelines.⁶ Loss of MEP: urgent warning — surgery is paused. Continuous train activity in EMG: risk of nerve root damage.

→ Next page: S69 — Stem Cell and Regenerative Neurosurgery