Intraoperative Neurophysiological Monitoring

While complications associated with North American Spine’s minimally invasive surgical techniques are rare, risks are associated with all surgical procedures.  In an effort to reduce an already low complication rate, North American Spine utilizes state of the art neurodiagnostic monitoring techniques during all spinal procedures. Below is a general description of how intraoperative neurophysiological monitoring (IONM) takes place and, most importantly, how patients benefit with our IONM procedures.

Logistics

  • A certified/registered IONM technician travels to the hospital where the surgical procedure is scheduled with his/her neuromonitoring equipment
  • The technician connects the IONM computer with our board certified neurologists’ computer via satellite modem
  • The technician places the appropriate monitoring electrodes on the sedated patient and begins the neuromonitoring process
  • The neurologist receives all neuromonitoring data in real time before, during, and after the surgical procedure

Techniques

  • Somatosensory or “mixed nerve” evoked potentials transmit electrical potentials from the extremities to the somatosensory cortex of the brain for analysis. Therefore, electrical potentials travel across the location of the surgical site. When electrical resistance in the form of mechanical blockade or nerve fiber destruction is encountered at the surgical site, the evoked potentials are delayed or even lost. The mixed nerve evoked potentials are generated throughout the surgical process and the potentials are monitored by the neurologist for changing waveform characteristics.
  • Motor evoked potentials (MEP) are electrical impulses generated at the motor cortex that travel to musculature within the extremities. As with mixed nerve evoked potentials, the motor evoked potentials travel across the site of the surgical procedure and detect the presence of mechanical blockade and/or nerve fiber destruction. A baseline MEP is obtained after the patient is sedated but prior to the surgical procedure. A follow-up MEP is performed after the surgical procedure but before the patient gains consciousness. If nerve structure compression related to the surgical process has developed, the surgeon is alerted by the neurologist allowing the issue to be corrected by the surgeon before closing.
  • “Free run” EMG monitoring gives the surgeon the ability to be informed when a potentially harmful mechanical disruption of a nerve structure has taken place in real time. Electrical potentials known as “burst” or “train” EMG patterns are generated at the site of the potentially harmful nerve structure insult and are recorded within muscles that are innervated by the nerve fibers involved with the mechanical event. The surgeon is notified by the neurologist when burst or train activity has developed and he/she can actually hear the electrical potentials in the operating room. Free run EMG affords the surgeon the ability to implement corrective technical procedures before permanent damage has occurred.
  • Pudendal nerve MEP’s and free run EMG monitoring is performed during lumbar spine procedures. The surgical complication rate of incontinence and erectile dysfunction is dramatically reduced when the pudendal nerves are monitored throughout the surgical procedure.
  • EEG activity is monitored throughout the course of the surgical procedure in an effort to provide the anesthesiologist with valuable information pertaining to the patient’s sedation level in real time. The anesthesiologist uses the level of EEG activity to alter his/her course and level of sedation; customized with the patient’s needs.

Complications related to spinal surgery which have reduced rates with comprehensive intraoperative neurophysiological monitoring

  • Muscular weakness such as post operative foot drop
  • Failed back syndrome
  • Persistent or worsening of extremity paresthesias
  • Persistent or worsening of extremity pain levels
  • Fecal incontinence
  • Erectile Dysfunction
  • Surgical positioning ischemic compression neuropathies such as post operative brachial plexopathy, crossed leg palsy, and cubital tunnel syndrome