Intraoperative neurophysiological monitoring

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Intraoperative neurophysiological monitoring (IONM) or intraoperative neuromonitoring is the use of electrophysiological methods such as electroencephalography (EEG), electromyography (EMG), and evoked potentials to monitor the functional integrity of certain neural structures (e.g., nerves, spinal cord and parts of the brain) during surgery. The purpose of IONM is to reduce the risk to the patient of iatrogenic damage to the nervous system, and/or to provide functional guidance to the surgeon and anesthesiologist.

Contents

Methods

Neuromonitoring employs various electrophysiologic modalities, such as extracellular single unit and local field recordings, SSEP, transcranial electrical motor evoked potentials (TCeMEP), EEG, EMG, and auditory brainstem response (ABR). For a given surgery, the set of modalities used depends in part on which neural structures are at risk. Transcranial Doppler imaging (TCDI) is also 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.[ citation needed ]

To accomplish these objectives, a member of the surgical team with special training in neurophysiology obtains and co-interprets triggered and spontaneous electrophysiologic signals from the patient periodically or continuously throughout the course of the operation. Patients who benefit from neuromonitoring are those undergoing operations involving the nervous system or which pose risk to its anatomic or physiologic integrity. In general, a trained neurophysiologist attaches a computer system to the patient using stimulating and recording electrodes. Interactive software running on the system carries out two tasks:

  1. selective activation of stimulating electrodes with appropriate timing, and
  2. processing and displaying of the electrophysiologic signals as they are picked up by the recording electrodes.

The neurophysiologist can thus observe and document the electrophysiologic signals in realtime in the operating area during the surgery. The signals change according to 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.

Surgical procedures

Patients benefit from neuromonitoring during certain surgical procedures, namely any surgery where there is risk to the nervous system. Most neuromonitoring is utilized by spine surgeons, but neurosurgeons, vascular, orthopedic, otolaryngologists, and urology surgeons have all utilized neuromonitoring as well.

The most common applications are in spinal surgery; selected brain surgeries; carotid endarterectomy; ENT procedures such as acoustic neuroma (vestibular schwannoma) resection, parotidectomy; and nerve surgery. Motor evoked potentials have also been used in surgery for thoracic aortic aneurysm. Intraoperative monitoring is used to :

For example, during any surgery on the thoracic or cervical spinal column, there is some risk to the spinal cord. Since the 1970s, SSEP (somatosensory evoked potentials) have been used to monitor spinal cord function by stimulating a nerve distal to the surgery, and recording from the cerebral cortex or other locations rostral to the surgery. A baseline is obtained, and if there are no significant changes, the assumption is that the spinal cord has not been injured. If there is a significant change, corrective measures can be taken; for example, the hardware can be removed. More recently, transcranial electric motor evoked potentials (TCeMEP) have also been used for spinal cord monitoring. This is the reverse of SSEP; the motor cortex is stimulated transcranially, and recordings made from muscles in the limbs, or from spinal cord caudal to the surgery. This allows direct monitoring of motor tracts in the spinal cord. EEG electroencephalography is used for monitoring of cerebral function in neurovascular cases (cerebral aneurysms, carotid endarterectomy) and for defining tumor margins in epilepsy surgery and some cerebral tumors.

EEG measures taken during anesthesia exhibit stereotypic changes as anesthetic depth increases. These changes include complex patterns of waves with frequency slowing accompanied by amplitude increases which typically peak when loss of consciousness occurs (loss of responses to verbal commands; loss of righting reflex). As anesthetic depth increases from light surgical levels to deep anesthesia, the EEG exhibits disrupted rhythmic waveforms, high amplitude burst suppression activity, and finally, very low amplitude isoelectric or 'flat line' activity. Various signal analysis approaches have been used to quantify these pattern changes and can provide an indication of loss of recall, loss of consciousness and anesthetic depth. Monitors have been developed using various algorithms for signal analysis and are commercially available, but none have as yet proven 100% accurate. This is a difficult problem and an active area of medical research.

EMG is used for cranial nerve monitoring in skull base cases and for nerve root monitoring and testing in spinal surgery. ABR (a.k.a. BSEP, BSER, BAEP, etc.) is used for monitoring of the acoustic nerve during acoustic neuroma and brainstem tumor resections.

Licensure, certification, credentialing, and evidence

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 occupational regulation. [1] Worldwide, there are at least two private certifications available: CNIM (Certified in Neurophysiological Intraoperative Monitoring) and D.ABNM (Diplomate of the American Board of Neurophysiological Monitoring). Though not governmentally regulated, certain health care facilities have internal regulations pertaining to neuromonitoring certifications (see below). The CNIM is a more widely known credential throughout the United States. The Certification for Neurophysiological Intraoperative Monitoring (CNIM) is awarded by the American Board of Electroencephalographic and Evoked Potential Technologists. As of 2010, minimum requirements include 1) a B.A., B.S. [Path 2] 2) R.EP.T or R.EEG.T Credential [Path 1] 3) A minimum of 150 surgeries. Path 1 is a 200 question exam costing $600. Path 2 is a 250-question exam. A 4-hour multiple-choice computer-based exam is offered twice a year. Currently, there are a little over 3500 board certified clinicians.

Audiologists may received board certification in neurophysiological intraoperative monitoring via AABIOM. The exam has 200 multiple choice questions covering 6 areas: Anesthesia, Neuroscience, Instrumentation, Electro-physiology, Human physiology / anatomy, Surgical Applications. [2]

There are several organisations that certify MDs in the field including the American Clinical Neurophysiology Society (www.acns.org) and the American Board of Electrodiagnostic Medicine. The optimal practice model is under discussion at the present time (2013) as is the relevant qualifications for supervision.

Outside the US there many different styles of IOM.

The evidence-based support for IOM is growing. There is a debate over whether IOM required controlled studies such as randomized trials, [3] or whether expert consensus suffices. [4]

Related Research Articles

<span class="mw-page-title-main">Neurology</span> Medical specialty dealing with disorders of the nervous system

Neurology is the branch of medicine dealing with the diagnosis and treatment of all categories of conditions and disease involving the nervous system, which comprises the brain, the spinal cord and the peripheral nerves. Neurological practice relies heavily on the field of neuroscience, the scientific study of the nervous system.

Clinical neurophysiology is a medical specialty that studies the central and peripheral nervous systems through the recording of bioelectrical activity, whether spontaneous or stimulated. It encompasses both research regarding the pathophysiology along with clinical methods used to diagnose diseases involving both central and peripheral nervous systems. Examinations in the clinical neurophysiology field are not limited to tests conducted in a laboratory. It is thought of as an extension of a neurologic consultation. Tests that are conducted are concerned with measuring the electrical functions of the brain, spinal cord, and nerves in the limbs and muscles. It can give the precise definition of site, the type and degree of the lesion, along with revealing the abnormalities that are in question. Due to these abilities, clinical neurophysiology is used to mainly help diagnose diseases rather than treat them.

<span class="mw-page-title-main">Anesthesia</span> State of medically-controlled temporary loss of sensation or awareness

Anesthesia or anaesthesia is a state of controlled, temporary loss of sensation or awareness that is induced for medical or veterinary purposes. It may include some or all of analgesia, paralysis, amnesia, and unconsciousness. An individual under the effects of anesthetic drugs is referred to as being anesthetized.

Local anesthesia is any technique to induce the absence of sensation in a specific part of the body, generally for the aim of inducing local analgesia, i.e. local insensitivity to pain, although other local senses may be affected as well. It allows patients to undergo surgical and dental procedures with reduced pain and distress. In many situations, such as cesarean section, it is safer and therefore superior to general anesthesia.

An evoked potential or evoked response is an electrical potential in a specific pattern recorded from a specific part of the nervous system, especially the brain, of a human or other animals following presentation of a stimulus such as a light flash or a pure tone. Different types of potentials result from stimuli of different modalities and types. Evoked potential is distinct from spontaneous potentials as detected by electroencephalography (EEG), electromyography (EMG), or other electrophysiologic recording method. Such potentials are useful for electrodiagnosis and monitoring that include detections of disease and drug-related sensory dysfunction and intraoperative monitoring of sensory pathway integrity.

<span class="mw-page-title-main">General anaesthesia</span> Medically induced loss of consciousness

General anaesthesia (UK) or general anesthesia (US) is a method of medically inducing loss of consciousness that renders a patient unarousable even with painful stimuli. This effect is achieved by administering either intravenous or inhalational general anaesthetic medications, which often act in combination with an analgesic and neuromuscular blocking agent. Spontaneous ventilation is often inadequate during the procedure and intervention is often necessary to protect the airway. General anaesthesia is generally performed in an operating theater to allow surgical procedures that would otherwise be intolerably painful for a patient, or in an intensive care unit or emergency department to facilitate endotracheal intubation and mechanical ventilation in critically ill patients. Depending on the procedure, general anaesthesia may be optional or required. Regardless of whether a patient may prefer to be unconscious or not, certain pain stimuli could result in involuntary responses from the patient that may make an operation extremely difficult. Thus, for many procedures, general anaesthesia is required from a practical perspective.

Awareness under anesthesia, also referred to as intraoperative awareness or accidental awareness during general anesthesia (AAGA), is a rare complication of general anesthesia where patients regain varying levels of consciousness during their surgical procedures. While anesthesia awareness is possible without resulting in any long-term memory of the experience, it is also possible for victims to have awareness with explicit recall, where they can remember the events related to their surgery.

<span class="mw-page-title-main">Bispectral index</span>

Bispectral index (BIS) is one of several technologies used to monitor depth of anesthesia. BIS monitors are used to supplement Guedel's classification system for determining depth of anesthesia. Titrating anesthetic agents to a specific bispectral index during general anesthesia in adults allows the anesthetist to adjust the amount of anesthetic agent to the needs of the patient, possibly resulting in a more rapid emergence from anesthesia. Use of the BIS monitor could reduce the incidence of intraoperative awareness during anaesthesia. The exact details of the algorithm used to create the BIS index have not been disclosed by the company that developed it.

<span class="mw-page-title-main">Nerve conduction study</span> Diagnostic test for nerve function

A nerve conduction study (NCS) is a medical diagnostic test commonly used to evaluate the function, especially the ability of electrical conduction, of the motor and sensory nerves of the human body. These tests may be performed by medical specialists such as clinical neurophysiologists, physical therapists, physiatrists, and neurologists who subspecialize in electrodiagnostic medicine. In the United States, neurologists and physiatrists receive training in electrodiagnostic medicine as part of residency training and in some cases acquire additional expertise during a fellowship in clinical neurophysiology, electrodiagnostic medicine, or neuromuscular medicine. Outside the US, clinical neurophysiologists learn needle EMG and NCS testing.

<span class="mw-page-title-main">Nerve block</span> Deliberate inhibition of nerve impulses

Nerve block or regional nerve blockade is any deliberate interruption of signals traveling along a nerve, often for the purpose of pain relief. Local anesthetic nerve block is a short-term block, usually lasting hours or days, involving the injection of an anesthetic, a corticosteroid, and other agents onto or near a nerve. Neurolytic block, the deliberate temporary degeneration of nerve fibers through the application of chemicals, heat, or freezing, produces a block that may persist for weeks, months, or indefinitely. Neurectomy, the cutting through or removal of a nerve or a section of a nerve, usually produces a permanent block. Because neurectomy of a sensory nerve is often followed, months later, by the emergence of new, more intense pain, sensory nerve neurectomy is rarely performed.

<span class="mw-page-title-main">Electrocorticography</span> Type of electrophysiological monitoring

Electrocorticography (ECoG), a type of intracranial electroencephalography (iEEG), is a type of electrophysiological monitoring that uses electrodes placed directly on the exposed surface of the brain to record electrical activity from the cerebral cortex. In contrast, conventional electroencephalography (EEG) electrodes monitor this activity from outside the skull. ECoG may be performed either in the operating room during surgery or outside of surgery. Because a craniotomy is required to implant the electrode grid, ECoG is an invasive procedure.

<span class="mw-page-title-main">Laminoplasty</span>

Laminoplasty is an orthopaedic/neurosurgical surgical procedure for treating spinal stenosis by relieving pressure on the spinal cord. The main purpose of this procedure is to provide relief to patients who may have symptoms of numbness, pain, or weakness in arm movement. The procedure involves cutting the lamina on both sides of the affected vertebrae and then "swinging" the freed flap of bone open thus relieving the pressure on the spinal cord. The spinous process may be removed to allow the lamina bone flap to be swung open. The bone flap is then propped open using small wedges or pieces of bone such that the enlarged spinal canal will remain in place.

Cardiothoracic anesthesiology is a subspeciality of the medical practice of anesthesiology, devoted to the preoperative, intraoperative, and postoperative care of adult and pediatric patients undergoing cardiothoracic surgery and related invasive procedures.

<span class="mw-page-title-main">Scoliosis Research Society</span> International professional organization

The Scoliosis Research Society (SRS) is a non-profit, professional, international organization made up of physicians and allied health personnel, whose purpose is to "care for those with spinal deformity throughout life by patient care, education, research and patient advocacy." It was founded in 1966 with 37 members, and now has grown to include over 1300 spinal deformity surgeons and allied health personnel in 41 countries, with a primary focus on providing continuing medical education for health care professionals, and funding/support for research in spinal deformities. Among the founding members were Dr. Paul Randall Harrington, inventor of the Harrington rod treatment for scoliosis, and Dr. David B. Levine, spine surgeon at Hospital for Special Surgery. Harrington later served as President of the SRS from 1972 to 1973, and Levine was President of the Society from 1978 to 1979. Current membership primarily includes spinal deformity surgeons, as well as some researchers, physician assistants, and orthotists who are involved in research and treatment of spinal deformities. Strict membership criteria ensure that the individual SRS Fellows are dedicated to the highest standards of care for adult and pediatric spinal deformities, utilizing both non-operative and operative techniques.

The TESSYS method is a minimally-invasive, endoscopic spinal procedure for the treatment of a herniated disc. It was a further development of the YESS method by the Dutch Dr Thomas Hoogland in the Alpha Klinik in Munich in 1989 and was first called THESSYS. The procedure involves performing a small foramenotomy and removal of soft tissue compressing the nerve root.

Clinical Electrophysiological Testing is based on techniques derived from electrophysiology used for the clinical diagnosis of patients. There are many processes that occur in the body which produce electrical signals that can be detected. Depending on the location and the source of these signals, distinct methods and techniques have been developed to properly target them.

Electrodiagnosis (EDX) is a method of medical diagnosis that obtains information about diseases by passively recording the electrical activity of body parts or by measuring their response to external electrical stimuli. The most widely used methods of recording spontaneous electrical activity are various forms of electrodiagnostic testing (electrography) such as electrocardiography (ECG), electroencephalography (EEG), and electromyography (EMG). Electrodiagnostic medicine is a medical subspecialty of neurology, clinical neurophysiology, cardiology, and physical medicine and rehabilitation. Electrodiagnostic physicians apply electrophysiologic techniques, including needle electromyography and nerve conduction studies to diagnose, evaluate, and treat people with impairments of the neurologic, neuromuscular, and/or muscular systems. The provision of a quality electrodiagnostic medical evaluation requires extensive scientific knowledge that includes anatomy and physiology of the peripheral nerves and muscles, the physics and biology of the electrical signals generated by muscle and nerve, the instrumentation used to process these signals, and techniques for clinical evaluation of diseases of the peripheral nerves and sensory pathways.

Bioelectromagnetic medicine deals with the phenomenon of resonance signaling and discusses how specific frequencies modulate cellular function to restore or maintain health. Such electromagnetic (EM) signals are then called "medical information" that is used in health informatics.

Aage R. Møller was an American professor of cognition and neuroscience. He was the Founders Professor and Distinguished Lecturer at the University of Texas at Dallas School of Behavioral and Brain Sciences. The Aage and Margareta Møller Distinguished Professorship at The University of Texas at Dallas is named after him.

Pierre Stagnara was a French spinal surgeon. He has been described as a "pioneer" in the study of spinal deformities, "one of the greatest figures of French spinal surgery." Stagnara was born in January 16, 1917 in Loriol-sur-Drôme, France. He studied medicine in the city of Lyon. During World War II he was drafted into the French army. After the war, he worked in a variety of hospitals throughout Lyon. In 1959 he became the Chief of the Centre des Massues and served in this position until his retirement in 1982. Whilst working at the institution he pioneered many orthopedic techniques. Including the non-surgical management of scoliosis.

References

  1. ASET's White Paper on Occupation Regulation
  2. AABIOM FAQ Retrieved 24 January 2017. Archived 24 March 2018 at the Wayback Machine
  3. Howick J, Cohen BA, McCulloch P, Thompson M, Skinner SA (Jul 2015). "Foundations for evidence-based intraoperative neurophysiological monitoring". Clin Neurophysiol. 127 (1): 81–90. doi:10.1016/j.clinph.2015.05.033. PMID   26268581. S2CID   13240561.
  4. Nuwer MR (2015). "Measuring outcomes for neurophysiological intraoperative monitoring". Clin Neurophys. 127 (1): 3–4. doi:10.1016/j.clinph.2015.07.005. PMID   26205418. S2CID   44702961.