Paint Management
Intraoperative neuromonitoring has an established role in spine and neurological surgery, but the same principles that make it valuable in the OR apply directly to interventional pain procedures. When the goal is to target a specific nerve structure — for diagnostic, therapeutic, or ablative purposes — the ability to confirm neural identity and monitor surrounding nerve integrity in real time is not just useful; it's a meaningful patient safety measure. IONM provides objective, documented evidence of accurate target localization and protects adjacent neural structures from inadvertent injury throughout the procedure.
Why Monitor Pain Procedures?
Epidural steroid injections carry a small but real risk of direct nerve root injury from needle placement, particularly in cases with limited epidural space or anatomical variation. IONM during ESI provides:
- Nerve identification: Triggered EMG using a monopolar stimulating needle confirms proximity to the target nerve root prior to injection, reducing the risk of intraneural needle placement.
- Nerve root protection: Free-run EMG provides continuous detection of nerve root irritation throughout needle advancement.
- Anesthesia level verification: Train of four monitoring confirms the absence of neuromuscular blockade, lending validity to EMG findings throughout the procedure.
Accurate target localization is critical to both the efficacy and safety of peripheral nerve blocks. Inadvertent intraneural injection or repeated needle redirection in search of paresthesiae are recognized contributors to postoperative neurological sequelae.
Triggered EMG using a nerve stimulator confirms accurate needle positioning relative to the target nerve prior to injection. Free-run EMG monitors surrounding nerve integrity throughout the procedure. Train of four confirms adequate anesthesia depth for valid EMG interpretation.
During kyphoplasty, cement extrusion into the spinal canal or neural foramina represents the primary neurological risk. SSEPs and tcMEPs provide continuous surveillance of spinal cord integrity throughout cement injection, with waveform changes providing an early warning of cord compression from canal extravasation. Free-run EMG monitors for nerve root irritation secondary to foraminal cement leakage.
SCS implant procedures involve two distinct phases where IONM provides value: lead placement through the epidural space and post-placement stimulation mapping prior to battery finalization.
During lead advancement, SSEPs and tcMEPs monitor spinal cord integrity continuously. Free-run EMG detects nerve root irritation from lead contact or mechanical pressure in the epidural space. Once leads are positioned, EMG-guided stimulation mapping — performed before the battery is secured — documents which specific muscle groups are activated by stimulation at each contact configuration. This provides objective, documented verification of therapeutic coverage and becomes part of the permanent implant record.
Effective radiofrequency ablation requires accurate needle placement at the target nerve — typically a medial branch or dorsal ramus — while protecting adjacent motor nerve roots from thermal spread. Triggered EMG confirms target nerve identity prior to ablation. Free-run EMG monitors for unintended activation of motor nerve roots during the procedure, providing immediate feedback if electrode position needs adjustment.
Free running EMG- Useful for identification of nerve and nerve irritation
Triggered EMG- Useful for identification of nerve
SSEP- Provide real time assessment of the ascending pathway of the spinal cord
TcMEP- Provides real time assessment of the descending pathway of the spinal cord
Train of four-
Provides proof of adequate or lack of proof of neuromuscular blockade
Pain Management Procedures and Neuromonitoring
Epidural Steriod Injection
Nerve Blocks
Kyphoplasty
Radio Frequency Ablation (RFA)
Spinal Cord Stimulator Implant Placement
The targeted nerve can be identified using an injectable, mono-polar stimulating needle that sends a small signal to the nerve. The signal is then recorded, utilizing the corresponding muscle group.
Integrity of the surrounding nerves/nerve roots can be monitored utilizing free run EMG.
Train of four can be utilized to quantify the level of neuromuscular blockade or lack there of with purpose of lending validity to EMG
Epidural steroid injections (ESIs) are an acceptable treatment method for discogenic and radicular pain emanating from the cervical, thoracic, and lumbar spine (2, 3, 9, 11, 12, 16, 17, 18,19). ESIs are also utilized in the treatment of spondylosis, nonspecific radiculitis, and spinal stenosis. Other uses reported in the literature and in clinical settings include the treatment of pain from post laminectomy syndrome, post herpetic or post traumatic (including intercostal) neuralgia, muscle contraction headaches, or from a subacute inflammatory spine pain syndrome unresponsive to more conservative treatment (3, 5). Epidurals have also been used to treat pain from malignant syndromes, from viral brachial plexitis or from reflex sympathetic dystrophy. Support for lumbar epidural steroid injections comes mainly from uncontrolled case studies or trials in which 33% to 77% of injected patients reported pain reduction. The success of the injections, as with all therapeutic interventions, depends on patient selection and technique. Unfortunately, even the controlled studies available on epidural steroids are limited methodologically by mixed or nonspecific diagnoses, by lack of functional outcome data, by insufficient patient numbers in control or treatment groups, and by failure to confirm delivery to the epidural space through use of fluoroscopy (4, 8).
Risks associated with needle placement or with the injection of diagnostic/therapeutic substances, including the local anesthetic and steroid suspension, include, infection, bleeding,nerve injury, transient
numbness or weakness, paralysis contrast reaction (allergy), adrenal suppression, and fluid retention with systemic manifestations which may include peripheral swelling. Pneumothorax may occur if undergoing a thoracic procedure. Total spinal blockade is possible with cervical procedures. There is also a potential for minor subcutaneous infection, vasovagal episode, as well as failure to obtain a definitive diagnosis or positive therapeutic injection with persistence of chronic pain. Dural puncture with subsequent spinal (positional) headache has been reported to occur as high as 5% of the time in translaminar injections. However it is
accepted that medical procedures, by their very nature, contain a certain risk to benefit ratio that needs to be taken into consideration when deciding upon a responsible treatment modality, and/or prior to initiating interventional therapies. Procedures that are used primarily as a means of temporary chronic pain control are certainly no exception and currently there are no official safety or procedural guidelines enjoying widespread acceptance in existence, for physicians who routinely perform epidural injection procedures. Such guidelines could potentially be utilized to help reduce or alleviate many of the potential inherent procedural risks. Absolute contraindications to performing epidural injections include known hypersensitivity to agents, local or systemic
infection, local malignancy, bleeding diathesis, congestive heart failure, and uncontrolled diabetes mellitus. Insulin dependent diabetics can
obtain substantial elevations in their blood sugars following epidural steroid injections.
Why Utilize IONM During ESI?
To prevent nerve root/nerve damage by needle insertion
Nerve Identification
Indications
Risks and Contraindications
Nerve Preservation
Assurance of Proper Anesthesia Levels
Indications, Risks, and Contraindications Epidural Corticosteroid Injections
Written by Richard Derby, MD and Michael Kaplan, MD
The targeted nerve can be identified using an injectable, mono-polar stimulating needle that sends a small signal to the nerve. The signal is then recorded, utilizing the corresponding muscle group.
Integrity of the surrounding nerves/nerve roots can be monitored utilizing free run EMG.
Train of four can be utilized to quantify the level of neuromuscular blockade or lack there of with purpose of lending validity to EMG
To identify targeted nerve
Protect surrounding nerves from needle trauma
To evaluate the failure rate, patient acceptance, effective volumes of local anesthetic solution, and incidence of neurologic complications after peripheral nerve block performed using the multiple injection technique with a nerve stimulator, we prospectively studied 3996 patients undergoing combined sciatic-femoral nerve block (n = 2175), axillary blocks (n = 1650), and interscalene blocks (n = 171). The success rate and mean injected volumes of local anesthetic were: 93% with 22.6 +/-4.5 mL in the axillary, 94% with 24.5 +/-5.4 mL in the interscalene, and 93% with 28.1 +/-4.4 mL in the sciatic-femoral nerve blocks. Patients receiving combined sciatic-femoral nerve block showed more discomfort during block placement and worse acceptance of the anesthetic procedure than patients receiving brachial plexus anesthesia. During the first month after surgery, 69 patients (1.7%) developed neurologic dysfunction on the operated limb. Complete recovery required 4-12 wkin all patients but one, who required 25 wk. The only variable showing significant association with the development of postoperative neurologic dysfunction was the tourniquet inflation pressure (<400 mm Hg compared with >400 mm Hg, odds ratio 2.9, 95% confidence intervals 1.6-5.4; P < 0.001). We conclude that using the multiple injections technique with a nerve stimulator results in a success rate of >90% with a volume of <30 mL of local anesthetic solution and an incidence of transient neurologic complication of <2%.
Implications: Based on a prospective evaluation of 3996 consecutive peripheral nerve blocks, the multiple injection technique with nerve stimulator allows for up to 94% successful nerve block with <30 mL of local anesthetic solution. Although the data collection regarding neurologic dysfunction was limited, the withdrawal and redirection of the stimulating needle was not associated with an increased incidence of neurologic complications. Sedation/analgesia should be advocated during block placement to improve patient acceptance.
“Seeking paresthesiae when performing a peripheral nerve block may increase the risk of post- anesthetic neurological sequelae. To test this hypothesis, we prospectively followed two groups of patients who underwent hand surgery with an axillary block. In one group, the axillary plexus was located by actively seeking paresthesiae; in the other, pulsations of the axillary artery indicated an adequate position of the injection needle. Mepivacaine 10 mg/ml, with or without adrenaline, was used. The study included 533 patients, 290 in the paresthesia group and 243 in the artery group. Although unintentional, paresthesiae were elicited in 40% of patients in the artery group. Postanesthetic nerve lesions were seen in ten patients, eight in the paresthesia group and two in the artery group, all of whom had been blocked by mepivacaine with adrenaline. Symptoms varied between light paresthesiae lasting a few weeks, and severe paresthesiae, ache and paresis lasting more than 1 year. The etiology suspected was needle and perhaps injection trauma to the nerves during blocking. We conclude that whenever possible nerve blocks should be performed without searching for paresthesiae.”
Why Utilize IONM for Nerve Block?
Nerve Identification
Nerve Preservation
Assurance of Proper Anesthesia Levels
Nerve Stimulator and Multiple Injection Technique for Upper and Lower Limb Blockade: Failure Rate, Patient Acceptance, and Neurologic Complications
Paresthesiae or No Paresthesiae? Nerve Lesions after Axillary Blocks
Fanelli, G. MD; Casati, A. MD; Garancini, P. MD; Torri, G. MD
FD. Selander*,S. Edshage and T. Wolff
Article first published online: 30 DEC 2008 DOI:10.1111/j.1399-6576.1979.tb01417.x© 1979 Acta
Anaesthesiologica Scandinavica Fonden
Integrity of the surrounding nerves/nerve roots can be monitored utilizing free run EMG.
Train of four can be utilized to quantify the level of neuromuscular blockade or lack there of with purpose of lending validity to EMG
Spinal cord integrity is verified by monitoring for changes caused by bone fragments or leakage of cement into the spinal cord canal
Protect the nerve root and guard for fragment leaks in spinal canal
Kyphoplasty and Intraoperative Neuromonitoring
Nerve Preservation
Assurance of Proper Anesthesia Levels
Spinal Cord Integrity
TcMEPs: Monitors Motor Nerve Function
SSEPs: Monitors Sensory Nerve Function
Free Running EMG: Detects Nerve Irritation. Also after lead placement and before finalizing battery placement and while testing the stim device, EMG assists us by giving us a visual of what muscles the stimulation is targeting, thus enabling the target of specific muscle group with documented verification.
Spinal cord protection and stimulator implant signal verification
