Intraoperative Neurophysiologic Monitoring Program

Stanford University Medical Center is renowned for its premier program in intraoperative neurophysiologic monitoring (IONM), which was one of the first to obtain formal accreditation nationwide.  The comprehensive clinical service is very active, led by a dedicated team of five neurologists that assist in a wide diversity of surgeries for both pediatric and adult populations.

Monitoring the state of the nervous system in “real-time” during surgery alerts surgeons of potential evolving neurologic injury and may allow for corrective actions to be implemented to prevent permanent deficits, thus improving safety and surgical outcomes.  Surgeons have traditionally been reliant on such measures as monitoring blood pressure, pulse, respiration, and blood gas content, to gauge the general health of the patient during surgery.   Following such parameters has allowed for some limited interventions.  However, intraoperative neurophysiologic monitoring extends this principle specifically to the neuraxis, providing the surgical team with real-time feedback during surgeries that involve the brain, spinal cord, or peripheral nervous system (either directly or indirectly).   This has allowed for prompt interventions intraoperatively that have been shown to reduce post-surgical incidence of paralysis, muscle weakness, sensory deficits, hearing loss, as well as other new neurologic deficits.

Intraoperative neurophysiologic monitoring is performed using a variety of neurophysiologic techniques, including EEG (electroencephalogram), SSEPs (somatosensory evoked potentials), EMG (electromyography), and transcranial motor evoked potentials (tcMEPs), which are then interpreted by physicians to assess the integrity of neural pathways.   At Stanford University Medical Center, a group of seven technologists that are specially trained in IONM work with fellowship-trained neurologists on-site to provide clinical services for a diversity of surgical cases.  Each surgical case is directly supervised by an IONM attending neurologist.  In addition, IONM services are available 24/7, 365 days per year.

What is IONM and its purpose?

• Ongoing assessment and monitoring of neurologic function via neurophysiologic studies

• Goal is to minimize peri- and postoperative morbidity, and to optimize patient outcomes

• Provide ongoing feedback to the surgeon during procedures that may place neural structures at risk

• Requires dynamic interaction with colleagues across multiple disciplines

Modalities of Testing

• EEG     (electroencephalogram)

• SSEP   (somatosensory evoked potentials)

• tcMEP  (transcranial motor evoked potentials)
• BAEP   (brainstem auditory evoked potentials)
• EMG    (electromyography)
• NAP     (nerve action potential)
• Direct cortical stimulation
• Direct subcortical stimulation
• Awake testing

Diversity of cases monitored at Stanford include: