Transcranial Motor Evoked Potential (TcMEP): Monitoring for Scoliosis, Orthopedic Spine Surgery, and More

Transcranial motor evoked potentials (TcMEP) are currently the most effective means of evaluating the pyramidal motor pathways and are used during orthopedic spine and scoliosis surgery, as well as neurosurgery where the motor pathways are at risk.

TcMEP monitoring is performed by stimulating the motor cortex and descending motor axons using transcranial electric stimulation,or a very mild electric current on the scalp. These currents are not painful for the patient, and are used only to stimulate a muscle response, typically in both the hands and legs. The motor potentials can then be recorded by electrodes that are placed over the spinal cord or from electrodes in distal muscle groups. Due to the large amplitude of these responses, feedback can be obtained almost instantaneously.

Any changes in muscle response are reported at a greater than 50 percent decrease in amplitude. TcMEP changes of this nature indicate a possible interruption of motor pathways, which may result in a negative post operative outcome.

Types of Surgeries that Use TcMEP Monitoring

TcMEP monitoring is recommended for all spinal surgeries that place the motor pathways at risk, including:

• orthopedic spine surgery
• scoliosis surgery
• thoracic fusions
• anterior cervical fusions
• any other cervical or thoracic procedure for fractures or an unstable spine

Advantages of TcMEP

There are advantages to TcMEP monitoring, including the fact that it gives direct feedback on the integrity of the corticospinal (motor) tracts of the spinal cord. It is also the most effective means of evaluating the pyramidal motor pathways. Therefore, if the motor pathways are interrupted during procedures where the spinal cord is at risk, such as during orthopedic spine surgery or scoliosis surgery, our neural monitoring technologists will be alerted and steps can be taken immediately to prevent a permanent injury.

Disadvantages of TcMEP

One disadvantage of TcMEP monitoring is that it is not sensitive to lumbosacral nerve root damage, so another form of monitoring such as somatosensory evoked potentials would be needed as well. In addition, TcMEPs are affected by high anesthetic levels and muscle relaxants. The lack of muscle response that occurs due to these factors can mimic "real" changes and thus require additional interpretation. However, if muscle relaxants are not taken before surgery, and anesthetic levels are monitored, our neural monitoring technologists may be able to effectively record potentials.

If you need transcranial motor evoked potential ( TcMEP) monitoring for a procedure where the motor pathways are at risk, such as in orthopedic spine surgery or scoliosis surgery, contact Biotronic. Our neural monitoring technologists come highly recommended by surgeons and hospitals that have used our services in the past. We provide quality neuromonitoring and can protect your patients better than anyone else in the business.