Intraoperative Neuromonitoring (IONM) During Spinal Surgery

Intraoperative Neuromonitoring (IONM) During Spinal Surgery

Intraoperative neuromonitoring (IONM) consist of a subcontinuou1s evaluation of spinal cord sensory - motor functions by using electrophysiological methods such as electromyography (EMG), evoked potentials [somatosensory evoked potentials (SSEP), motor evoked potentials (MEP)], transcranial motor evoked potential (tcMEPs). IONM is reliable, safer and valid for use during spinal surgery to reduce postoperative neurological complication. 

IONM is used to localise neural structures, to test function of structures, for early detection of intraoperative injury allowing for immediately. 

During surgery on any spinal column, there is some risk to spinal column. By evoke potential monitored spinal cord function by stimulating a nerve distal to surgery. A baseline is obtained and there are no significant changes, the assumption is that spinal cord has not been injured. If significant changes occur, corrective measures can be taken. 

These all allow the reduction in incidence of neurological complications like paraplegia, brachial plexus injury, lumbosacral plexus injury during spinal cord surgery. The EMG assesses the integrity of cranial/spinal nerve roots and indirectly peripheral nerves from the site of stimulation to the muscle. SSEPs monitor the integrity of sensory pathways from peripheral nerves to the sensory cortex. Disruption along any part of this pathway may disrupt normal SSEP responses. MEPs involve transcranial motor cortex stimulation to elicit a response from muscles and thereby assess the integrity of motor pathways. TcMEP used to evaluate pyramidal motor pathways by stimulate motor cortex and descending motor axons and get response in both hand and legs.

IONM can be used during spinal surgeries like correction of spinal deformity, Vertical Expandable Prosthetic Titanium Rib surgery, Vertebral column resection and the initial implantation of expandable spinal rods (growing rods) for early-onset spinal deformity. There are many conditions in which IONM cannot be used or used with precaution. Like somatosensory evoked potentials (SSEPs) and transcutaneous motor evoked potentials (TcMEPs) may not be attainable in ages below 18 months, and SSEP may not be obtainable below age 6 months. As normal neural pathways develop steadily during the first approximately 18 months of age. Progressive my elinisation occurs during this period and in part determines responsiveness to externally delivered stimuli.

Dr. Parul Rakholiya (MPT in musculoskeletal and sports)
Assistant Professor