Neuromonitoring

The scientific practice of neuromonitoring takes place in the surgical suite (OR). It aims to 1) reduce the risk to the patient of iatrogenic damage to the nervous system, and/or 2) provide functional guidance to the surgeon. To accomplish this, a specially trained member of the surgical team, for example a neurophysiologist, obtains and co-interprets triggered and spontaneous electrophysiologic signals from the patient as their surgery proceeds. Patients who benefit from neuromonitoring are those undergoing surgeries which involve the nervous system or which pose risk to it. Neuromonitoring is also known as surgical neurophysiology, intraoperative neurologic monitoring, or simply intraoperative monitoring. Acronyms include IOM and IONM.

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Licensure - Certification - Credentialing

In the US, IONM licensure has not been legislated at the state or federal level. Issues of licensure are discussed in ASET's 68 page White Paper on Occupation Regulation. Worldwide, there are at least two private certifications available: the technologist level CNIM and the professional level D.ABNM. Though not governmentally regulated, certain health care facilities have internal regulations pertaining to neuromonitoring certifications. The more fundamental issue is that demand for trained intraoperative neurophysiologists continues to be greater than their number (2007).

Certification for Neurophysiological Intraoperative Monitoring (Technologist Certification)

The CNIM [1] is awarded by the American Board of Electroencephalographic and Evoked Potential Technicians [2]. As of 2007-02, minimum requirements include 1) a B.A., B.S. or another health care credential, and 2) an experience base of 100 surgeries. ABRET has scheduled for 2008 major changes to these requirements. The $350, 250 question, 4 hour multiple choice written exam is offered twice a year.

Diplomat of the American Board of Neurophysiologic Monitoring (Professional Board Certification)

The D.ABNM [3] is awarded by the American Board of Neurophysiological Monitoring [4]. As of 2007-02, the minimum requirements include 1) an M.S. or M.A. in a health science related field, Most have an MD, PhD, AuD, ScD or a DC. 2) an experience base of 300 surgeries that spans at least 3 years of primary responsibility, and 3) two surgeon-signed attestation forms. The exam includes a written portion, which must be passed first, and an oral portion. The $600, 250 question, 4 hour written exam is offered twice a year, as is the $800 oral exam. As 2007-02, there are 104 D.ABNM certified individuals.

Methods

Neuromonitoring employs various electrophysiologic modalities, such as extracellular single unit and local field recordings, SSEP, TCeMEP, EEG, EMG, and ABR. For a given surgery, the set of modalities used in depends on which neural structures are at risk.

In general, a trained neurophysiologist or technologists attaches a computer system to the patient using stimulating and recording electrodes. Interactive software running on the system carries out 2 tasks. The system 1) selectively activates stimulating electrodes with appropriate timing, and 2) processes and displays the electrophysiologic signals as they are picked up by the recording electrodes.

See video of the equipment used [5]

The neurophysiologist can thus observe and document the electrophysiologic signals in realtime in the operating during the surgery. The signals change according to a various factors, including anesthesia, tissue temperature, surgical stage, and tissue stresses. Various factors exert their influence on the signals with various tissue-dependent timecourses. Differentiating the signal changes along these lines - with particular attention paid to stresses - is the joint task of the surgical triad: surgeon, anesthesiologist, and neurophysiologist.

Transcranial Doppler Imaging is becoming more widely used to detect vascular emboli. TCDI can be used in tandem with EEG during vascular surgery.

IONM techniques have significantly reduced the rates of morbidity and mortality without introducing additional risks. By doing so, IONM techniques reduce health care costs.

Surgical Procedures

Patients benefit from neuromonitoring during certain surgical procedures, including:

• acoustic neuroma
• anterior cervical diskectomy
• anterior corpectomy
• anterior vertebrectomy
• arteriovenous malformations
• brachial plexus or distal peripheral nerve injury
• cardiopulmonary bypass and hypohermia
• carotid body tumor
• carotid endarterectomy
• cauda equina tumors
• cerebral and spinal aneurysms
• cervical laminectomy
• cochlear implant
• correction of coarctation
• cranial base tumors
• DBS - deep brain stimulation
• embolization of traumatic cavernous sinus fistula
• epilepsy surgery (localization and mapping of eloquent cortex)
• extracranial vascular reconstruction
• femoral lengthening
• fronto-temporal tumors (motor cortex mapping)
• glomus tumor
• instrumentation for spinal instability
• intramedullary or extramedullary spinal cord tumors
• lumbosacral decompression
• microvascular decompression
• neuroma-in-continuity
• occlusion of brain-supplying arteries
• parotidectomy
• pedicle and lateral mass screw placement
• pelvic hip arthroplasty
• percutaneous transluminal angioplasy
• peripheral nerve surgery
• posterior fossa tumors
• pterygian band release
• radical head & neck surgery
• repair of thoracic aortic aneurysm
• revision mastoidectomy
• rhizotomy/ganglionectomy
• scoliosis correction
• selective dorsal rhizotomy
• spinal angiography
• spinal arteriovenous malformations
• spinal cord untethering
• spinal fusion
• stabilization of odontoid/dens fracture
• subclavian-carotid bypass
• syringomyelia
• temporo-parietal tumors
• thermal capsulorrhaphy
• thoracic laminectomy
• thyroidectomy
• vestibular nerve section

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