Running head: Neural Mapping Techniques 1 2 3
Case Report: Neural Mapping Techniques for Transpsoas Lateral Interbody Fusion
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Justin Silverstein, DHSc, CNIM1
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Jon Block, DC, CNIM2
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Sushil Basra, MD3
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Hieu Ball, MD4
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Neuro Protective Solutions1
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ION Intraoperative Neurophysiology2
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Long Island Spine Specialists3
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California Comprehensive Spine Institute4
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Correspondence: Justin Silverstein, DHSc, CNIM Neuro Protective Solutions, LLC 140 Adams Ave Ste B-13 Hauppauge, NY 117788 516.902.0057
[email protected]
Running head: Neural Mapping Techniques 1
Abstract
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Background Context: Mapping of the lumbar plexus during lumbar lateral interbody fusions
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(LLIF) using electrical stimulation with concurrent electromyography (EMG) is advocated to
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detect the presence of neural tissue and provide estimates of the proximity of the lumbar plexus
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elements during surgical dilation and retraction of the psoas muscle. Common current techniques
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utilize a myotomal approach when choosing EMG target muscles which may not cover the
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lumbar plexus elements adequately.
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Purpose: To describe a lumbar plexus-based anatomical approach for mapping techniques during
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LLIF procedures.
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Study Design: A case report is presented.
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Methods: Mapping of the lumbar plexus was performed using an electrified sequential dilator
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system and a handheld electrified monopolar stimulating probe with concurrent EMG to record
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responses from muscles innervated by the various elements of the lumbar plexus.
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Results: Stimulus elicited isolated EMG responses from the adductor muscle group during the
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approach to the disc space. After the retractor was deployed and prior to placing the intra-discal
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shim, the surgeon identified what he suspected might be neural tissue within the surgical
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corridor. The surgeon used the electrical probe to stimulate the unidentified structure and a
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threshold muscle response was observed from the adductors utilizing only 0.03mA of stimulation
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intensity, suggesting that the structure was the obturator nerve. The surgeon swept the obturator
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nerve and associated psoas muscle behind the posterior blade so it was no longer within the
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surgical field.
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Conclusion: In this particular case, if our mapping protocol did not include adductor muscle
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recordings it is possible that deployment of the intra-discal shim could have pierced the obturator
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nerve. The authors believe this is an important case study that is worth attention to support the
Running head: Neural Mapping Techniques 1
need for a lumbar plexus - based anatomical approach for mapping the lumbar plexus during
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LLIF procedures as opposed to a myotomal approach which is frequently advocated.
