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Research paper thumbnail of The Use of Reflex Responses for IOM

Springer eBooks, 2017

There are three goals for intraoperative neurophysiologic monitoring. The first is to reduce the ... more There are three goals for intraoperative neurophysiologic monitoring. The first is to reduce the risk of neurologic complications by detecting insult to neuronal structures. The second is to provide guidance that may affect a surgeon’s approach or actions, such as mapping the location of sensory and motor tracts within the spinal cord. The third is to perform studies detailed enough to help understand normal and pathophysiologic function. Intraoperative reflex techniques are used to help accomplish these three goals. They are used to monitor the function of peripheral nerve, plexus, nerve root, and segmental and suprasegmental function. These reflex techniques will be reviewed in this chapter.

Research paper thumbnail of Current trends in pedicle screw stimulation techniques: lumbosacral, thoracic, and cervical levels

PubMed, Jun 1, 2012

Unequivocally, pedicle screw instrumentation has evolved as a primary construct for the treatment... more Unequivocally, pedicle screw instrumentation has evolved as a primary construct for the treatment of both common and complex spinal disorders. However an inevitable and potentially major complication associated with this type of surgery is misplacement of a pedicle screw(s) which may result in neural and vascular complications, as well as impair the biomechanical stability of the spinal instrumentation resulting in loss of fixation. In light of these potential surgical complications, critical reviews of outcome data for treatment of chronic, low-back pain using pedicle screw instrumentation concluded that "pedicle screw fixation improves radiographically demonstrated fusion rates;" however the expense and complication rates for such constructs are considerable in light of the clinical benefit (Resnick et al. 2005a). Currently, neuromonitoring using free-run and evoked (triggered) electromyography (EMG) is widely used and advocated for safer and more accurate placement of pedicle screws during open instrumentation procedures, and more recently, guiding percutaneous placement (minimally invasive) where the pedicle cannot be easily inspected visually. The latter technique, evoked or triggered EMG when applied to pedicle screw instrumentation surgeries, has been referred to as the pedicle screw stimulation technique. As concluded in the Position Statement by the American Society of Neurophysiological Monitoring (ASNM), multimodality neuromonitoring using free-run EMG and the pedicle screw stimulation technique was considered a practice option and not yet a standard of care (Leppanen 2005). Subsequently, the American Association of Neurological Surgeons/Congress of Neurological Surgeons (AANS/CNS) Joint Section on Disorders of the Spine and Peripheral Nerves published their "Guidelines for the Performance of Fusion Procedures for Degenerative Disease of the Lumbar Spine" (Heary 2005, Resnick et al. 2005a, Resnick et al. 2005b). It was concluded that the "primary justification" of intraoperative neuromonitoring"... is the perception that the safety and efficacy of pedicle screw fixation are enhanced..." (Resnick et al. 2005b). However in summarizing a massive (over 1000 papers taken from the National Library of Medicine), contemporary, literature review spanning nearly a decade (1996 to 2003), this invited panel (Resnick et al. 2005b) recognized that the evidence-based documents contributing to the parts related to pedicle screw fixation and neuromonitoring were "... full of potential sources of error ..." and lacked appropriate, randomized, prospective studies for formulating rigid standards and guidelines. Nevertheless, current trends support the routine use and clinical utility of these neuromonitoring techniques. In particular free-run and triggered EMG have been well recognized in numerous publications for improving both the accuracy and safety of pedicle screw implantation. Currently, treatment with pedicle screw instrumentation routinely involves all levels of the spine - lumbosacral, thoracic, and cervical. Significant historical events, various neuromonitoring modalities, intraoperative alarm criteria, clinical efficacy, current trends, and caveats related to pedicle screw stimulation along the entire vertebral column will be reviewed.

Research paper thumbnail of Monitoring Spinal Nerve Function With H-Reflexes

Journal of Clinical Neurophysiology, Apr 1, 2012

H-reflexes have been used in the clinical neurophysiology laboratory for some time to assess pati... more H-reflexes have been used in the clinical neurophysiology laboratory for some time to assess patients with neuromuscular disorders. There are only a few reports for the application of H-reflexes for intraoperative neurophysiologic monitoring. The goals of this article are to review the intraoperative neurophysiologic monitoring of spinal nerve root function with H-reflexes. The following will be reviewed: (1) Introduction to H-reflexes, (2) pathophysiology of spinal nerve root function, (3) neurophysiologic basis of H-reflexes, (4) gastrocnemius H-reflex, (5) flexor carpi radialis H-reflex, (6) anesthetic technique and research, and (7) intraoperative applications of H-reflexes. H-reflexes are single sweep real-time recordings that provide immediate feedback to the surgeon. They can be used to monitor not only sensory and motor spinal nerve root function but also peripheral sensory and motor nerves, plexus, and postsynaptic spinal cord gray matter function.

Research paper thumbnail of Intraoperative Applications Of The H-Reflex And F-Response: A Tutorial

Journal of Clinical Monitoring and Computing, Jul 1, 2006

Research paper thumbnail of Intraoperative Monitoring of Segmental Spinal Nerve Root Function with Free-Run and Electrically-Triggered Electromyography and Spinal Cord Function with Reflexes and F-Responses

Journal of Clinical Monitoring and Computing, Dec 1, 2005

Research paper thumbnail of From the Electrodiagnostic Lab…

The Spine Journal, May 1, 2006

Research paper thumbnail of From the electrodiagnostics lab…

The Spine Journal, Sep 1, 2003

Research paper thumbnail of Current Trends in Pedicle Screw Stimulation Techniques: Lumbosacral, Thoracic, and Cervical Levels

The Neurodiagnostic Journal, 2012

ABSTRACT. Unequivocally, pedicle screw instrumentation has evolved as a primary construct for the... more ABSTRACT. Unequivocally, pedicle screw instrumentation has evolved as a primary construct for the treatment of both common and complex spinal disorders. However, an inevitable and potentially major complication associated with this type of surgery is misplacement of a pedicle screw(s) which may result in neural and vascular complications, as well as impair the biomechanical stability of the spinal instrumentation resulting in loss of fixation. In light of these potential surgical complications, critical reviews of outcome data for treatment of chronic, low-back pain using pedicle screw instrumentation concluded that “pedicle screw fixation improves radio graphic ally demonstrated fusion rates;” however, the expense and complication rates for such constructs are considerable in light of the clinical benefit (Resnick et al. 2005a). Currently, neuromonitoring using free-run and evoked (triggered) electromyography (EMG) is widely used and advocated for safer and more accurate placement ...

Research paper thumbnail of Monitoring Spinal Nerve Function With H-Reflexes

Journal of Clinical Neurophysiology, 2012

H-reflexes have been used in the clinical neurophysiology laboratory for some time to assess pati... more H-reflexes have been used in the clinical neurophysiology laboratory for some time to assess patients with neuromuscular disorders. There are only a few reports for the application of H-reflexes for intraoperative neurophysiologic monitoring. The goals of this article are to review the intraoperative neurophysiologic monitoring of spinal nerve root function with H-reflexes. The following will be reviewed: (1) Introduction to H-reflexes, (2) pathophysiology of spinal nerve root function, (3) neurophysiologic basis of H-reflexes, (4) gastrocnemius H-reflex, (5) flexor carpi radialis H-reflex, (6) anesthetic technique and research, and (7) intraoperative applications of H-reflexes. H-reflexes are single sweep real-time recordings that provide immediate feedback to the surgeon. They can be used to monitor not only sensory and motor spinal nerve root function but also peripheral sensory and motor nerves, plexus, and postsynaptic spinal cord gray matter function.

Research paper thumbnail of The Use of Spinal Reflex Responses for IOM

Springer eBooks, Dec 1, 2022

Research paper thumbnail of A Temporary Prosthesis for Hip Disarticulation

Research paper thumbnail of The Use of Reflex Responses for IOM

There are three goals for intraoperative neurophysiologic monitoring. The first is to reduce the ... more There are three goals for intraoperative neurophysiologic monitoring. The first is to reduce the risk of neurologic complications by detecting insult to neuronal structures. The second is to provide guidance that may affect a surgeon’s approach or actions, such as mapping the location of sensory and motor tracts within the spinal cord. The third is to perform studies detailed enough to help understand normal and pathophysiologic function. Intraoperative reflex techniques are used to help accomplish these three goals. They are used to monitor the function of peripheral nerve, plexus, nerve root, and segmental and suprasegmental function. These reflex techniques will be reviewed in this chapter.

Research paper thumbnail of Faces of spine care. From the electrodiagnostic lab

Research paper thumbnail of Faces of spine care. From the electrodiagnostic lab

The spine journal : official journal of the North American Spine Society

Research paper thumbnail of Where intraoperative reflexes can be used to monitor nerve root and spinal cord gray matter function

The spine journal : official journal of the North American Spine Society

Research paper thumbnail of From the electrodiagnostics lab... When quantitative sudomotor axon reflex testing helps differentiate central versus peripheral nervous system as the source of sensory symptoms in an extremity

The spine journal : official journal of the North American Spine Society

Research paper thumbnail of Intraoperative long-latency reflex activity in idiopathic scoliosis demonstrates abnormal central processing. A possible cause of idiopathic scoliosis

Spine, Jan 15, 1993

Segmental reflex regulation in 37 patients with idiopathic scoliosis and 8 patients with nonidiop... more Segmental reflex regulation in 37 patients with idiopathic scoliosis and 8 patients with nonidiopathic scoliosis was studied by recording evoked reflex muscle potentials from four muscle groups in each lower extremity during partial neuromuscular blockade. Effects on reflex activity mediated through descending systems arising in the brain stem were investigated by recording from proximal-distal and flexor-extensor muscles. Ipsilateral and contralateral long-latency complex polysynaptic activity was present in all 37 patients with idiopathic scoliosis. This reflex activity was absent in eight nonidiopathic scoliosis patients. Long-latency reflex activity may represent segmental disinhibition. The presence of long-latency reflex activity in patients with idiopathic scoliosis and the absence of this activity in nonidiopathic scoliosis patients with curves of equal magnitude demonstrates that the curve per se is not responsible for the activity. This would imply that abnormal reflex pro...

Research paper thumbnail of From the Electrodiagnostics Lab

Research paper thumbnail of Intraoperative Lower Extremity Reflex Muscle Activity As an Adjunct to Conventional Somatosensory-Evoked Potentials and Descending Neurogenic Monitoring in Idiopathic Scoliosis

Spine, 1995

Lower extremity polysynaptic reflexes and descending neurogenic motor and ascending somatosensory... more Lower extremity polysynaptic reflexes and descending neurogenic motor and ascending somatosensory activity were recorded. Two cases are presented to illustrate the intraoperative use of lower extremity reflex recordings for detecting compromise of spinal cord function. Lower extremity reflex processing can be used to measure integrated spinal cord activity, whereas descending neurogenic and ascending somatosensory potentials measure only long tract function. Eight channels of lower extremity polysynaptic reflex activity were recorded simultaneously after unilateral lower extremity mixed nerve stimulation. Sequential descending neurogenic and ascending somatosensory activity was recorded simultaneously with reflex recordings. In these two patients with idiopathic scoliosis, intraoperative reflexes changed before descending neurogenic and before ascending somatosensory activity changed. High-amplitude synchronous persistent reflex activity correlated with a postoperative neurologic deficit. Low-amplitude asynchronous transient reflex activity was not associated with a postoperative neurologic deficit. Intraoperative lower extremity reflex changes are more sensitive to spinal cord compromise than are changes in long tract function. Lower extremity polysynaptic reflexes monitor the integrated activity of the spinal cord that is responsible for the control of complex motor behavior.

Research paper thumbnail of Evaluation of Intrapedicular Screw Position Using Intraoperative Evoked Electromyography

Spine, 1995

This study analyzed the parameters needed for electrical stimulation of vertebral pedicle drill b... more This study analyzed the parameters needed for electrical stimulation of vertebral pedicle drill bits and screws. The feasibility of using electrically evoked electromyography was studied. Considerable potential for damage of adjacent nerve roots with incorrectly placed bits and screws exists with pedicular fixation of the lumbar spine. Ninety-five drill bits, one hundred forty-four screws, and thirty-four exposed nerve roots were electrically stimulated in thirty-six patients. Simultaneous evoked electromyographic activity was recorded from four muscle groups in each lower extremity during partial neuromuscular blockade. A constant current threshold of 6 mA or less correlated with misplaced drill bits and screws that broached the cortex. Evoked electromyography was 93% sensitive whereas radiography was only 63% sensitive to detecting bits and screws that had broached the cortex. Evoked electromyography is a valuable sensitive adjunct to radiographic examination of pedicle drill bit and screw placement.

Research paper thumbnail of The Use of Reflex Responses for IOM

Springer eBooks, 2017

There are three goals for intraoperative neurophysiologic monitoring. The first is to reduce the ... more There are three goals for intraoperative neurophysiologic monitoring. The first is to reduce the risk of neurologic complications by detecting insult to neuronal structures. The second is to provide guidance that may affect a surgeon’s approach or actions, such as mapping the location of sensory and motor tracts within the spinal cord. The third is to perform studies detailed enough to help understand normal and pathophysiologic function. Intraoperative reflex techniques are used to help accomplish these three goals. They are used to monitor the function of peripheral nerve, plexus, nerve root, and segmental and suprasegmental function. These reflex techniques will be reviewed in this chapter.

Research paper thumbnail of Current trends in pedicle screw stimulation techniques: lumbosacral, thoracic, and cervical levels

PubMed, Jun 1, 2012

Unequivocally, pedicle screw instrumentation has evolved as a primary construct for the treatment... more Unequivocally, pedicle screw instrumentation has evolved as a primary construct for the treatment of both common and complex spinal disorders. However an inevitable and potentially major complication associated with this type of surgery is misplacement of a pedicle screw(s) which may result in neural and vascular complications, as well as impair the biomechanical stability of the spinal instrumentation resulting in loss of fixation. In light of these potential surgical complications, critical reviews of outcome data for treatment of chronic, low-back pain using pedicle screw instrumentation concluded that "pedicle screw fixation improves radiographically demonstrated fusion rates;" however the expense and complication rates for such constructs are considerable in light of the clinical benefit (Resnick et al. 2005a). Currently, neuromonitoring using free-run and evoked (triggered) electromyography (EMG) is widely used and advocated for safer and more accurate placement of pedicle screws during open instrumentation procedures, and more recently, guiding percutaneous placement (minimally invasive) where the pedicle cannot be easily inspected visually. The latter technique, evoked or triggered EMG when applied to pedicle screw instrumentation surgeries, has been referred to as the pedicle screw stimulation technique. As concluded in the Position Statement by the American Society of Neurophysiological Monitoring (ASNM), multimodality neuromonitoring using free-run EMG and the pedicle screw stimulation technique was considered a practice option and not yet a standard of care (Leppanen 2005). Subsequently, the American Association of Neurological Surgeons/Congress of Neurological Surgeons (AANS/CNS) Joint Section on Disorders of the Spine and Peripheral Nerves published their "Guidelines for the Performance of Fusion Procedures for Degenerative Disease of the Lumbar Spine" (Heary 2005, Resnick et al. 2005a, Resnick et al. 2005b). It was concluded that the "primary justification" of intraoperative neuromonitoring"... is the perception that the safety and efficacy of pedicle screw fixation are enhanced..." (Resnick et al. 2005b). However in summarizing a massive (over 1000 papers taken from the National Library of Medicine), contemporary, literature review spanning nearly a decade (1996 to 2003), this invited panel (Resnick et al. 2005b) recognized that the evidence-based documents contributing to the parts related to pedicle screw fixation and neuromonitoring were "... full of potential sources of error ..." and lacked appropriate, randomized, prospective studies for formulating rigid standards and guidelines. Nevertheless, current trends support the routine use and clinical utility of these neuromonitoring techniques. In particular free-run and triggered EMG have been well recognized in numerous publications for improving both the accuracy and safety of pedicle screw implantation. Currently, treatment with pedicle screw instrumentation routinely involves all levels of the spine - lumbosacral, thoracic, and cervical. Significant historical events, various neuromonitoring modalities, intraoperative alarm criteria, clinical efficacy, current trends, and caveats related to pedicle screw stimulation along the entire vertebral column will be reviewed.

Research paper thumbnail of Monitoring Spinal Nerve Function With H-Reflexes

Journal of Clinical Neurophysiology, Apr 1, 2012

H-reflexes have been used in the clinical neurophysiology laboratory for some time to assess pati... more H-reflexes have been used in the clinical neurophysiology laboratory for some time to assess patients with neuromuscular disorders. There are only a few reports for the application of H-reflexes for intraoperative neurophysiologic monitoring. The goals of this article are to review the intraoperative neurophysiologic monitoring of spinal nerve root function with H-reflexes. The following will be reviewed: (1) Introduction to H-reflexes, (2) pathophysiology of spinal nerve root function, (3) neurophysiologic basis of H-reflexes, (4) gastrocnemius H-reflex, (5) flexor carpi radialis H-reflex, (6) anesthetic technique and research, and (7) intraoperative applications of H-reflexes. H-reflexes are single sweep real-time recordings that provide immediate feedback to the surgeon. They can be used to monitor not only sensory and motor spinal nerve root function but also peripheral sensory and motor nerves, plexus, and postsynaptic spinal cord gray matter function.

Research paper thumbnail of Intraoperative Applications Of The H-Reflex And F-Response: A Tutorial

Journal of Clinical Monitoring and Computing, Jul 1, 2006

Research paper thumbnail of Intraoperative Monitoring of Segmental Spinal Nerve Root Function with Free-Run and Electrically-Triggered Electromyography and Spinal Cord Function with Reflexes and F-Responses

Journal of Clinical Monitoring and Computing, Dec 1, 2005

Research paper thumbnail of From the Electrodiagnostic Lab…

The Spine Journal, May 1, 2006

Research paper thumbnail of From the electrodiagnostics lab…

The Spine Journal, Sep 1, 2003

Research paper thumbnail of Current Trends in Pedicle Screw Stimulation Techniques: Lumbosacral, Thoracic, and Cervical Levels

The Neurodiagnostic Journal, 2012

ABSTRACT. Unequivocally, pedicle screw instrumentation has evolved as a primary construct for the... more ABSTRACT. Unequivocally, pedicle screw instrumentation has evolved as a primary construct for the treatment of both common and complex spinal disorders. However, an inevitable and potentially major complication associated with this type of surgery is misplacement of a pedicle screw(s) which may result in neural and vascular complications, as well as impair the biomechanical stability of the spinal instrumentation resulting in loss of fixation. In light of these potential surgical complications, critical reviews of outcome data for treatment of chronic, low-back pain using pedicle screw instrumentation concluded that “pedicle screw fixation improves radio graphic ally demonstrated fusion rates;” however, the expense and complication rates for such constructs are considerable in light of the clinical benefit (Resnick et al. 2005a). Currently, neuromonitoring using free-run and evoked (triggered) electromyography (EMG) is widely used and advocated for safer and more accurate placement ...

Research paper thumbnail of Monitoring Spinal Nerve Function With H-Reflexes

Journal of Clinical Neurophysiology, 2012

H-reflexes have been used in the clinical neurophysiology laboratory for some time to assess pati... more H-reflexes have been used in the clinical neurophysiology laboratory for some time to assess patients with neuromuscular disorders. There are only a few reports for the application of H-reflexes for intraoperative neurophysiologic monitoring. The goals of this article are to review the intraoperative neurophysiologic monitoring of spinal nerve root function with H-reflexes. The following will be reviewed: (1) Introduction to H-reflexes, (2) pathophysiology of spinal nerve root function, (3) neurophysiologic basis of H-reflexes, (4) gastrocnemius H-reflex, (5) flexor carpi radialis H-reflex, (6) anesthetic technique and research, and (7) intraoperative applications of H-reflexes. H-reflexes are single sweep real-time recordings that provide immediate feedback to the surgeon. They can be used to monitor not only sensory and motor spinal nerve root function but also peripheral sensory and motor nerves, plexus, and postsynaptic spinal cord gray matter function.

Research paper thumbnail of The Use of Spinal Reflex Responses for IOM

Springer eBooks, Dec 1, 2022

Research paper thumbnail of A Temporary Prosthesis for Hip Disarticulation

Research paper thumbnail of The Use of Reflex Responses for IOM

There are three goals for intraoperative neurophysiologic monitoring. The first is to reduce the ... more There are three goals for intraoperative neurophysiologic monitoring. The first is to reduce the risk of neurologic complications by detecting insult to neuronal structures. The second is to provide guidance that may affect a surgeon’s approach or actions, such as mapping the location of sensory and motor tracts within the spinal cord. The third is to perform studies detailed enough to help understand normal and pathophysiologic function. Intraoperative reflex techniques are used to help accomplish these three goals. They are used to monitor the function of peripheral nerve, plexus, nerve root, and segmental and suprasegmental function. These reflex techniques will be reviewed in this chapter.

Research paper thumbnail of Faces of spine care. From the electrodiagnostic lab

Research paper thumbnail of Faces of spine care. From the electrodiagnostic lab

The spine journal : official journal of the North American Spine Society

Research paper thumbnail of Where intraoperative reflexes can be used to monitor nerve root and spinal cord gray matter function

The spine journal : official journal of the North American Spine Society

Research paper thumbnail of From the electrodiagnostics lab... When quantitative sudomotor axon reflex testing helps differentiate central versus peripheral nervous system as the source of sensory symptoms in an extremity

The spine journal : official journal of the North American Spine Society

Research paper thumbnail of Intraoperative long-latency reflex activity in idiopathic scoliosis demonstrates abnormal central processing. A possible cause of idiopathic scoliosis

Spine, Jan 15, 1993

Segmental reflex regulation in 37 patients with idiopathic scoliosis and 8 patients with nonidiop... more Segmental reflex regulation in 37 patients with idiopathic scoliosis and 8 patients with nonidiopathic scoliosis was studied by recording evoked reflex muscle potentials from four muscle groups in each lower extremity during partial neuromuscular blockade. Effects on reflex activity mediated through descending systems arising in the brain stem were investigated by recording from proximal-distal and flexor-extensor muscles. Ipsilateral and contralateral long-latency complex polysynaptic activity was present in all 37 patients with idiopathic scoliosis. This reflex activity was absent in eight nonidiopathic scoliosis patients. Long-latency reflex activity may represent segmental disinhibition. The presence of long-latency reflex activity in patients with idiopathic scoliosis and the absence of this activity in nonidiopathic scoliosis patients with curves of equal magnitude demonstrates that the curve per se is not responsible for the activity. This would imply that abnormal reflex pro...

Research paper thumbnail of From the Electrodiagnostics Lab

Research paper thumbnail of Intraoperative Lower Extremity Reflex Muscle Activity As an Adjunct to Conventional Somatosensory-Evoked Potentials and Descending Neurogenic Monitoring in Idiopathic Scoliosis

Spine, 1995

Lower extremity polysynaptic reflexes and descending neurogenic motor and ascending somatosensory... more Lower extremity polysynaptic reflexes and descending neurogenic motor and ascending somatosensory activity were recorded. Two cases are presented to illustrate the intraoperative use of lower extremity reflex recordings for detecting compromise of spinal cord function. Lower extremity reflex processing can be used to measure integrated spinal cord activity, whereas descending neurogenic and ascending somatosensory potentials measure only long tract function. Eight channels of lower extremity polysynaptic reflex activity were recorded simultaneously after unilateral lower extremity mixed nerve stimulation. Sequential descending neurogenic and ascending somatosensory activity was recorded simultaneously with reflex recordings. In these two patients with idiopathic scoliosis, intraoperative reflexes changed before descending neurogenic and before ascending somatosensory activity changed. High-amplitude synchronous persistent reflex activity correlated with a postoperative neurologic deficit. Low-amplitude asynchronous transient reflex activity was not associated with a postoperative neurologic deficit. Intraoperative lower extremity reflex changes are more sensitive to spinal cord compromise than are changes in long tract function. Lower extremity polysynaptic reflexes monitor the integrated activity of the spinal cord that is responsible for the control of complex motor behavior.

Research paper thumbnail of Evaluation of Intrapedicular Screw Position Using Intraoperative Evoked Electromyography

Spine, 1995

This study analyzed the parameters needed for electrical stimulation of vertebral pedicle drill b... more This study analyzed the parameters needed for electrical stimulation of vertebral pedicle drill bits and screws. The feasibility of using electrically evoked electromyography was studied. Considerable potential for damage of adjacent nerve roots with incorrectly placed bits and screws exists with pedicular fixation of the lumbar spine. Ninety-five drill bits, one hundred forty-four screws, and thirty-four exposed nerve roots were electrically stimulated in thirty-six patients. Simultaneous evoked electromyographic activity was recorded from four muscle groups in each lower extremity during partial neuromuscular blockade. A constant current threshold of 6 mA or less correlated with misplaced drill bits and screws that broached the cortex. Evoked electromyography was 93% sensitive whereas radiography was only 63% sensitive to detecting bits and screws that had broached the cortex. Evoked electromyography is a valuable sensitive adjunct to radiographic examination of pedicle drill bit and screw placement.