"If I have seen further it is by standing on the shoulders of giants." - Isaac Newton 1675
Evoked Potential is dedicated to the giants in neuroscience that have helped evoke my potential. Steve Lehman, Marian Diamond, Geoffrey Winer, Charles Yingling & Don Jewett.
Evoked Potential is dedicated to the giants in neuroscience that have helped evoke my potential. Steve Lehman, Marian Diamond, Geoffrey Winer, Charles Yingling & Don Jewett.
Introduction to Intraoperative Neurophysiology
Aage Moller Introduction
Surgery has associated risks and potential to cause further injury to the nervous system. Some changes cannot be detected by visual inspection of the operative field and could occur and progress without the surgeon's knowledge. IOM uses neurophysiological recordings for detecting changes in the function of the nervous system that are caused by surgically induced insults.
Recording of evoked potentials allows assessment of function nearly continuously throughout an operation and are important in making clinical diagnoses. imaging CAT and MRI have made certain tests unnecessary. mostly used in the operating room for stereotaxic surgery and biopsy. imaging detects mainly changes in structures where neurophysiological methods assess changes in function.
Various types of neuro-electric potentials make it possible to asses the function of specific parts of the nervous system continuously during an operation and detect changes in neural function with little delay. Early detection of such functional changes can reduce the risk of post-operative deficits caused by iatrogenic injuries to the nervous system. make it possible to identify which surgical step has caused a problem so that the surgeon can reverse the step that caused the injuries before they become severe enough to result in permanent neurological deficits.
IOM benefits the patient and the surgeon if appropriate neurophysiological methods are applied during operations which neural tissue is at risk. IOM is practiced in many hospitals during such operations and members are now accepted as members of the operating room team. Monitoring the function of the nervous system is still a relatively new addition to the operating room and has a wider range of applications than just the monitoring of function.
IOM protects the integrity of the brain and spinal cord from injury during surgery in real-time. It allows for pre-emptive warning of complications where interventions can be made to correct a problem before it becomes permanent. IOM gives the surgical team comprised of the surgeon, technologist and anesthesiologist, comfort about the patient's neurological safety and gives them the confidence to operate on a patient that may otherwise be deemed too high risk for surgical intervention. Also, the patient and their family can be reassured that the risks of surgical complication are significantly reduced by the presence of an experienced technologist.
IOM is an inexpensive and effective method for reducing the risk of permanent postoperative deficits in many different operations where nervous tissue is being manipulated. provides real-time monitoring of function to an extent that makes it superior to imaging methods that provide information about structure and that are impractical for use in the operating room. Intraoperative neurophysiological monitoring relates to the spirit of the Hippocratic oath: namely "Do no harm" we might not be able to relieve suffering from illness, but we should at least not harm the patient in our attempts to relieve the patient from illness. IOM reduces failures and improves performance.
The greatest benefit is that IOM provides the possibility to reduce the risk of postoperative neurological deficits, it can also be of great value to the surgeon by providing other information about the effects of the surgeon's manipulations that is not otherwise available. IOM can identify specific neural structures, making it possible to determine the location of neural blockage on a nerve. IOM can determine if the therapeutic goal of the operation has succeeded. can often give the surgeon a justified increased feeling of security.
Clearly no sharp border between basic and applied research, Mollers opinion based on many years of experience that the skill of the surgeon together with the good use of electrophysiology in the operating room can benefit the patient who is being operated on and it can benefit many future patients by the progress in treatment that an effective collaboration between surgeons and neurophysiologists promote.
It is not perfect, there can be difficulty of obtaining signals (good technique, anesthesia and anesthetic changes, nervous system compromise, access and injury) there are false positive (false alarms with no negative outcome), potential problems with the techniques themselves and operator error. These are cases where IOM raises an alarm, any available interventions are accomplished, but the patient has neurologic injury anyway. Just because an alarm is raised does not necessarily allow for prompt, complete correction of the problem.
False negative cases are those in which the patient suffers from a neurologic injury that was not predicted by IOM changes. False negative cases are rare, but do occur. Some are due to immediate postoperative deterioration. Other cases are a result of injury in pathways not monitored Occasionally, they are errors by the IOM team, who failed to recognize when they occurred.
Accurate predictions of post-operative deficits also occur where and observed change in the monitoring reflects a real change in the function of a patient's nervous system.
IOM aims to watch over neurologic pathways and to identify any signs of injury. Intraoperative testing aims to identify neurologic structures. Monitoring occurs over many hours, whereas testing is usually done at one or several discrte times. Despite the differences between these two concepts, the two are often lumped together and called IOM.
Monitoring requires sufficient expertise by the team and good communication with the surgon. Details deped on the particular techniques, expecially on whether the aim is testing or monitoring.
Testing to identify a particular neurological structure usually requires persoanl inovlment of a clinical neurophysiioloogyst. or for localization of language or motor cortex. These require professional judgement about what tissue to resect, a level of skill greather than that of a technologist alone. The clinical neurophysiillogist is in the room to make decisions and discuss interpretations and recommendations personally with the surgeon. This is referred to as personal supervision.
In reality, this is ideal but not how it works all of the time and the technologist is responsible for letting a surgeon know when there is trouble
Scoliosis correcionor clippinf of an aneurymsm. technologist often conducts ordinary monitoring in the surgical suite, supervised by a clinical neurophyisiologist who is nearby or online. The degree of involvement is less than that for testing but the availability to intervene remains. This is referred to as direct supervision.
Surgery has associated risks and potential to cause further injury to the nervous system. Some changes cannot be detected by visual inspection of the operative field and could occur and progress without the surgeon's knowledge. IOM uses neurophysiological recordings for detecting changes in the function of the nervous system that are caused by surgically induced insults.
Recording of evoked potentials allows assessment of function nearly continuously throughout an operation and are important in making clinical diagnoses. imaging CAT and MRI have made certain tests unnecessary. mostly used in the operating room for stereotaxic surgery and biopsy. imaging detects mainly changes in structures where neurophysiological methods assess changes in function.
Various types of neuro-electric potentials make it possible to asses the function of specific parts of the nervous system continuously during an operation and detect changes in neural function with little delay. Early detection of such functional changes can reduce the risk of post-operative deficits caused by iatrogenic injuries to the nervous system. make it possible to identify which surgical step has caused a problem so that the surgeon can reverse the step that caused the injuries before they become severe enough to result in permanent neurological deficits.
IOM benefits the patient and the surgeon if appropriate neurophysiological methods are applied during operations which neural tissue is at risk. IOM is practiced in many hospitals during such operations and members are now accepted as members of the operating room team. Monitoring the function of the nervous system is still a relatively new addition to the operating room and has a wider range of applications than just the monitoring of function.
IOM protects the integrity of the brain and spinal cord from injury during surgery in real-time. It allows for pre-emptive warning of complications where interventions can be made to correct a problem before it becomes permanent. IOM gives the surgical team comprised of the surgeon, technologist and anesthesiologist, comfort about the patient's neurological safety and gives them the confidence to operate on a patient that may otherwise be deemed too high risk for surgical intervention. Also, the patient and their family can be reassured that the risks of surgical complication are significantly reduced by the presence of an experienced technologist.
IOM is an inexpensive and effective method for reducing the risk of permanent postoperative deficits in many different operations where nervous tissue is being manipulated. provides real-time monitoring of function to an extent that makes it superior to imaging methods that provide information about structure and that are impractical for use in the operating room. Intraoperative neurophysiological monitoring relates to the spirit of the Hippocratic oath: namely "Do no harm" we might not be able to relieve suffering from illness, but we should at least not harm the patient in our attempts to relieve the patient from illness. IOM reduces failures and improves performance.
The greatest benefit is that IOM provides the possibility to reduce the risk of postoperative neurological deficits, it can also be of great value to the surgeon by providing other information about the effects of the surgeon's manipulations that is not otherwise available. IOM can identify specific neural structures, making it possible to determine the location of neural blockage on a nerve. IOM can determine if the therapeutic goal of the operation has succeeded. can often give the surgeon a justified increased feeling of security.
Clearly no sharp border between basic and applied research, Mollers opinion based on many years of experience that the skill of the surgeon together with the good use of electrophysiology in the operating room can benefit the patient who is being operated on and it can benefit many future patients by the progress in treatment that an effective collaboration between surgeons and neurophysiologists promote.
It is not perfect, there can be difficulty of obtaining signals (good technique, anesthesia and anesthetic changes, nervous system compromise, access and injury) there are false positive (false alarms with no negative outcome), potential problems with the techniques themselves and operator error. These are cases where IOM raises an alarm, any available interventions are accomplished, but the patient has neurologic injury anyway. Just because an alarm is raised does not necessarily allow for prompt, complete correction of the problem.
False negative cases are those in which the patient suffers from a neurologic injury that was not predicted by IOM changes. False negative cases are rare, but do occur. Some are due to immediate postoperative deterioration. Other cases are a result of injury in pathways not monitored Occasionally, they are errors by the IOM team, who failed to recognize when they occurred.
Accurate predictions of post-operative deficits also occur where and observed change in the monitoring reflects a real change in the function of a patient's nervous system.
IOM aims to watch over neurologic pathways and to identify any signs of injury. Intraoperative testing aims to identify neurologic structures. Monitoring occurs over many hours, whereas testing is usually done at one or several discrte times. Despite the differences between these two concepts, the two are often lumped together and called IOM.
Monitoring requires sufficient expertise by the team and good communication with the surgon. Details deped on the particular techniques, expecially on whether the aim is testing or monitoring.
Testing to identify a particular neurological structure usually requires persoanl inovlment of a clinical neurophysiioloogyst. or for localization of language or motor cortex. These require professional judgement about what tissue to resect, a level of skill greather than that of a technologist alone. The clinical neurophysiillogist is in the room to make decisions and discuss interpretations and recommendations personally with the surgeon. This is referred to as personal supervision.
In reality, this is ideal but not how it works all of the time and the technologist is responsible for letting a surgeon know when there is trouble
Scoliosis correcionor clippinf of an aneurymsm. technologist often conducts ordinary monitoring in the surgical suite, supervised by a clinical neurophyisiologist who is nearby or online. The degree of involvement is less than that for testing but the availability to intervene remains. This is referred to as direct supervision.
IOM History
The History - long line of neurophysiologists with Wilder Penfield, George Ojemann, Fred Lenz, Don Jewett and Frank Panza.
Wilder Penfield (1891-1976) founded the Montreal Neurological Institute in 1934. Penfield was a neurosurgeon who had a solid background in neurophysiology, inspired by Sherrington during a Rhodes Scholarship to Oxford. He may be regarded as the founder of intraoperative neurophysiological research and he did ground-breaking work in many areas of neuroscience. His work on the somatosensory system is especially knows. In the 1950's he used electrical stimulation to find epileptic foci and in connection with these operations he did extensive studies of the temporal lobe, especially with regard to memory.
George A. Ojemann contributed much to understanding pathologies related to the temporal lobe as well as to provide basic research regarding memory and in particular regarding the large individual variations of the brain. our knowledge of the human cerebral cortex has expanded. the neural generators of the ABR have benefited from recordings from structures that became exposed during neurosurgical operations.
Fred Lenz mapped the nerve cells in the thalamus. Don Jewett discovered the auditory brainstem response.
Penfield used direct cortical stimulation to define the humunculus of human motor and sensory cortex
ECoG was used to identify regions of epileptic discharges, slowing or lack of fast activity with Jaster Marshall and Walker 1949
initial recording from exposed cortex and later acute depth electrode recordings were added.
Intraoperative neurophysiology began in the laboratory with standard laboratory techniques and transitioned into the operating room. It was found that these techniques, when technologically possible, could reduce the risk of inadvertently injuring neural tissue and thereby reduce the risk of permanent neurological deficits. In the 80's their own society was created, the American Society for Neurophysiological Monitoring; ASNM. Recording of facial nerve, risk of facial paresis or palsy after operation, recordings of somatosensory cortex, orthopedic surgery used monitoring involving the spine in the 70's to reduce the risk of damage to the spinal cord during scoliosis. monitoring of auditory brainstem evoked responses ABR's was also an early application used in microvascular decompression operations for hemi-facial spasm and trigeminal neuralgia in the early 1980's and others thereafter.
routine EEG carried out in cartotid endarterectomy Thompson 1968, Wylie and Ehrenfeld, 1970 Sharbrough, 1973
Many patients were kept awake during carotic clamping because of worries about cortical ischemia during clamping.
Sundt showed how EEG changed at degress of ischemia that could be tolerated for awhile in surgery, leading to widespread acceptance of these monitoring techniques.
EEG developed in the 1970's into a commonly used, although not universally accepted tehcnique to safeguard patiengs during CEA
Spinal cord monitoring grew out of research investigations in the early 1970's, spinal potentials from the epidural space after direct spinal stimulation Shimoji et all 1971 and Imai 1976. Given the neurologic ris of spine surgery, these research techniques were evaluated and validated as a method to mintor spinal cases Tamake 1972, 1981. This school of monitoring used direct spinal epidural stimulation and recording sites
Somatosensory EPs SEPs from the scalp initialll were investigated in the mid 1970's. These were middle and long latency 50 - 200 ms cortical potentials. Nash and colleagues 1974, 1977 Nash and Brodkey 1977 initially applied these SEPs in the operating room but were impeded by variablitiy of signals and sesntivity to anesthesia. Grundy 1982 published a series of reports about anesthegic affects his technique used by others in the earliest staes of SEP cortical potential monitoring used filters at 1-100Hz with middle and long latency potentials
Nuwer and Dawson evaluated the causes of variability and determined that use of short latency SEP techniques resricted filters greatly improved reliability of SEP tracings , SEP became a widely adopted method of spinal cord monitoring. These techniques used angle stimulation with scalp and neck recordings.
in the UK, jones, 1982, used the spinal recordings but moved the stimulator to the posterior tibial nerve which ovaioided any concerns about the safety of repeated spinal cord epidural electrical stimluation. It still required placement of epidural recordings
in the 80's monitoring for large skull based tumors by monitoring cranial motor nerves including CN III, IV and VI especially for tumors involving the cavernous sinus and motor portion of the fifth cranial nerve. IOM of the function of the ear and auditory nerve came into general use and spread to other uses.
1980's refinded for auditory EPs and EMG during surgery around cranial nerves but the auditory brainstem response was discovered by Don Jewett! These were appied to monitor during posterior fossa surgery Moller 1985 such as microvascular decompression and acoustc neuroma resection
commercial equipment available until 1981, first IOM service in UCLA in 1979 offered a variety of techniques to any surgeon in various surgical disciplines. 1980's annual academic meetings of clinical neurophysiollgissts and certain surgical groups included reports about IOM.
IOM textbooks Nuwer and Moller appeared, late 80's wide technicque.
In the 90's certification processes were established by the American Board for Neurophysiological Monitoring, ABNM that certifies diplomats of the American Board for Neurophysiolgical Monitoring DABNM Certification in Neurophysiological Intraoperative Neurophysiological Monitoring CNIM is available through the American Board of Registration of Electroencephalographic and Evoked Potential Technologists (ABRET). Techniques became commercially available by several companies. Methods improved with electrical stimulation of the motor cortex and stimulation of the spinal cord. methods that provided satisfactory anesthesia and also permitted activation of motor system by stimulation of the motor cortex were developed.
Burke subsequently popularized the use of transcranial electrical stimulation as a practical corticospinal technique for use under anesthesia, Hicks 1991 and Burcke 1992. many monitoring teams now use this technique to measure corticospinal pathways in the operating room. measured responses from muslces
Overall the field of intraoperative neurophysiology has developed from disparate difficult techniques in its earlier days three decades ago. Now, it has become a discipline with large number of techniques, applied to a variety of surgical and other procedures. The monitoring teams encompass may types of specialists contributing their own expertise. The goals remain the same as before: to enhance patient care, avoid neurological deficits, allow for more complete preocedures, allow procedures even on some high-risk patients, and provide feedback to the surgeon about actions that could injure the nervous system
Wilder Penfield (1891-1976) founded the Montreal Neurological Institute in 1934. Penfield was a neurosurgeon who had a solid background in neurophysiology, inspired by Sherrington during a Rhodes Scholarship to Oxford. He may be regarded as the founder of intraoperative neurophysiological research and he did ground-breaking work in many areas of neuroscience. His work on the somatosensory system is especially knows. In the 1950's he used electrical stimulation to find epileptic foci and in connection with these operations he did extensive studies of the temporal lobe, especially with regard to memory.
George A. Ojemann contributed much to understanding pathologies related to the temporal lobe as well as to provide basic research regarding memory and in particular regarding the large individual variations of the brain. our knowledge of the human cerebral cortex has expanded. the neural generators of the ABR have benefited from recordings from structures that became exposed during neurosurgical operations.
Fred Lenz mapped the nerve cells in the thalamus. Don Jewett discovered the auditory brainstem response.
Penfield used direct cortical stimulation to define the humunculus of human motor and sensory cortex
ECoG was used to identify regions of epileptic discharges, slowing or lack of fast activity with Jaster Marshall and Walker 1949
initial recording from exposed cortex and later acute depth electrode recordings were added.
Intraoperative neurophysiology began in the laboratory with standard laboratory techniques and transitioned into the operating room. It was found that these techniques, when technologically possible, could reduce the risk of inadvertently injuring neural tissue and thereby reduce the risk of permanent neurological deficits. In the 80's their own society was created, the American Society for Neurophysiological Monitoring; ASNM. Recording of facial nerve, risk of facial paresis or palsy after operation, recordings of somatosensory cortex, orthopedic surgery used monitoring involving the spine in the 70's to reduce the risk of damage to the spinal cord during scoliosis. monitoring of auditory brainstem evoked responses ABR's was also an early application used in microvascular decompression operations for hemi-facial spasm and trigeminal neuralgia in the early 1980's and others thereafter.
routine EEG carried out in cartotid endarterectomy Thompson 1968, Wylie and Ehrenfeld, 1970 Sharbrough, 1973
Many patients were kept awake during carotic clamping because of worries about cortical ischemia during clamping.
Sundt showed how EEG changed at degress of ischemia that could be tolerated for awhile in surgery, leading to widespread acceptance of these monitoring techniques.
EEG developed in the 1970's into a commonly used, although not universally accepted tehcnique to safeguard patiengs during CEA
Spinal cord monitoring grew out of research investigations in the early 1970's, spinal potentials from the epidural space after direct spinal stimulation Shimoji et all 1971 and Imai 1976. Given the neurologic ris of spine surgery, these research techniques were evaluated and validated as a method to mintor spinal cases Tamake 1972, 1981. This school of monitoring used direct spinal epidural stimulation and recording sites
Somatosensory EPs SEPs from the scalp initialll were investigated in the mid 1970's. These were middle and long latency 50 - 200 ms cortical potentials. Nash and colleagues 1974, 1977 Nash and Brodkey 1977 initially applied these SEPs in the operating room but were impeded by variablitiy of signals and sesntivity to anesthesia. Grundy 1982 published a series of reports about anesthegic affects his technique used by others in the earliest staes of SEP cortical potential monitoring used filters at 1-100Hz with middle and long latency potentials
Nuwer and Dawson evaluated the causes of variability and determined that use of short latency SEP techniques resricted filters greatly improved reliability of SEP tracings , SEP became a widely adopted method of spinal cord monitoring. These techniques used angle stimulation with scalp and neck recordings.
in the UK, jones, 1982, used the spinal recordings but moved the stimulator to the posterior tibial nerve which ovaioided any concerns about the safety of repeated spinal cord epidural electrical stimluation. It still required placement of epidural recordings
in the 80's monitoring for large skull based tumors by monitoring cranial motor nerves including CN III, IV and VI especially for tumors involving the cavernous sinus and motor portion of the fifth cranial nerve. IOM of the function of the ear and auditory nerve came into general use and spread to other uses.
1980's refinded for auditory EPs and EMG during surgery around cranial nerves but the auditory brainstem response was discovered by Don Jewett! These were appied to monitor during posterior fossa surgery Moller 1985 such as microvascular decompression and acoustc neuroma resection
commercial equipment available until 1981, first IOM service in UCLA in 1979 offered a variety of techniques to any surgeon in various surgical disciplines. 1980's annual academic meetings of clinical neurophysiollgissts and certain surgical groups included reports about IOM.
IOM textbooks Nuwer and Moller appeared, late 80's wide technicque.
In the 90's certification processes were established by the American Board for Neurophysiological Monitoring, ABNM that certifies diplomats of the American Board for Neurophysiolgical Monitoring DABNM Certification in Neurophysiological Intraoperative Neurophysiological Monitoring CNIM is available through the American Board of Registration of Electroencephalographic and Evoked Potential Technologists (ABRET). Techniques became commercially available by several companies. Methods improved with electrical stimulation of the motor cortex and stimulation of the spinal cord. methods that provided satisfactory anesthesia and also permitted activation of motor system by stimulation of the motor cortex were developed.
Burke subsequently popularized the use of transcranial electrical stimulation as a practical corticospinal technique for use under anesthesia, Hicks 1991 and Burcke 1992. many monitoring teams now use this technique to measure corticospinal pathways in the operating room. measured responses from muslces
Overall the field of intraoperative neurophysiology has developed from disparate difficult techniques in its earlier days three decades ago. Now, it has become a discipline with large number of techniques, applied to a variety of surgical and other procedures. The monitoring teams encompass may types of specialists contributing their own expertise. The goals remain the same as before: to enhance patient care, avoid neurological deficits, allow for more complete preocedures, allow procedures even on some high-risk patients, and provide feedback to the surgeon about actions that could injure the nervous system