Methylene Blue to Identify Nerve Pathology and Guide Surgery
The first study to use MB as an operative tool for peripheral nerve surgery, administered using ultrasound guidance, was by Gofeld et al. in 2013. Although that study did show the benefit of using ultrasonography and MB for localizing peripheral nerves, specifically for operations, it did not include a confirmatory test that could be performed prior to administration of MB to validate the intended nerve that was being localized. This study has this added dimension and security for localizing nerves, and that is the use of the ultrasound-guided cannulated needle, which provided nerve stimulation for further confirmation of the intended nerve target. Previously, Thomassen et al. in 2013 described the use of ultrasound guidance and nerve-stimulator guided blocks for neurectomy. In this paper we present a novel technique that provides the peripheral nerve surgeon a helpful tool to plan and execute the surgery. It is a technique that uses readily available, portable, and cost-effective resources that could be easily implemented to the benefit of many patients with a wide range of peripheral nerve problems.
The added benefit of nerve stimulation is unique to this study. It provides a confirmatory motor or sensory response that can be appreciated prior to the administration of MB. This confirmatory variable could potentially prevent incorrectly identifying a target nerve on preoperative ultrasonography. Also, as shown in Fig. 1D and E, the nerve stimulation response that is being monitored by the neurophysiologist provides direct feedback about the distance between the needle and the target nerve.
Furthermore, ultrasonography may have additional roles in the perioperative and intraoperative management of peripheral nerve disease. Ultrasound mapping of nerve pathology may enable delineation of normal structures in relation to nerve pathology, which may assist in planning the optimal surgical approach. As an example, ultrasound may be used to identify the location of normal nerve fascicles in relation to peripheral nerve sheath tumors, thus minimizing the chance of iatrogenic nerve injury. The addition of MB staining of the chosen surgical path may further improve the safety and efficiency of the surgical procedure. Although there have been few publications stating concern for the safety of MB use in patients, this has been easily addressed in this technique by using a dilute concentration of MB at low volumes. Similarly, ultrasound mapping and guidance may enable safe and accurate percutaneous needle biopsies of suspected peripheral nerve sheath tumors.
Intraoperative ultrasonography applied to surgically exposed nerve lesions may provide the surgeon with another tool to evaluate nerve pathology, such as the extent of peripheral nerve injury following trauma. This could be further applied to peripheral nerve sheath tumor resection as a complement to the surgical microscope and intraoperative electrophysiology apparatus, to provide information regarding the internal characteristics of the tumor and its relationship to nerve structures, thereby possibly increasing the potential for normal nerve salvage.
Finally, ultrasound-guided near-nerve neurography may also be useful in the diagnostic workup of peripheral nerve lesions, particularly when evaluating early regeneration after peripheral nerve trauma. Presently, intraoperative compound nerve action potentials are recorded by exposing the nerve and applying electrodes directly to the nerve. Introducing electrodes next to the nerve using ultrasound-guidance techniques is a noninvasive option that may obviate the need for surgical exploration.
Discussion
The first study to use MB as an operative tool for peripheral nerve surgery, administered using ultrasound guidance, was by Gofeld et al. in 2013. Although that study did show the benefit of using ultrasonography and MB for localizing peripheral nerves, specifically for operations, it did not include a confirmatory test that could be performed prior to administration of MB to validate the intended nerve that was being localized. This study has this added dimension and security for localizing nerves, and that is the use of the ultrasound-guided cannulated needle, which provided nerve stimulation for further confirmation of the intended nerve target. Previously, Thomassen et al. in 2013 described the use of ultrasound guidance and nerve-stimulator guided blocks for neurectomy. In this paper we present a novel technique that provides the peripheral nerve surgeon a helpful tool to plan and execute the surgery. It is a technique that uses readily available, portable, and cost-effective resources that could be easily implemented to the benefit of many patients with a wide range of peripheral nerve problems.
The added benefit of nerve stimulation is unique to this study. It provides a confirmatory motor or sensory response that can be appreciated prior to the administration of MB. This confirmatory variable could potentially prevent incorrectly identifying a target nerve on preoperative ultrasonography. Also, as shown in Fig. 1D and E, the nerve stimulation response that is being monitored by the neurophysiologist provides direct feedback about the distance between the needle and the target nerve.
Furthermore, ultrasonography may have additional roles in the perioperative and intraoperative management of peripheral nerve disease. Ultrasound mapping of nerve pathology may enable delineation of normal structures in relation to nerve pathology, which may assist in planning the optimal surgical approach. As an example, ultrasound may be used to identify the location of normal nerve fascicles in relation to peripheral nerve sheath tumors, thus minimizing the chance of iatrogenic nerve injury. The addition of MB staining of the chosen surgical path may further improve the safety and efficiency of the surgical procedure. Although there have been few publications stating concern for the safety of MB use in patients, this has been easily addressed in this technique by using a dilute concentration of MB at low volumes. Similarly, ultrasound mapping and guidance may enable safe and accurate percutaneous needle biopsies of suspected peripheral nerve sheath tumors.
Intraoperative ultrasonography applied to surgically exposed nerve lesions may provide the surgeon with another tool to evaluate nerve pathology, such as the extent of peripheral nerve injury following trauma. This could be further applied to peripheral nerve sheath tumor resection as a complement to the surgical microscope and intraoperative electrophysiology apparatus, to provide information regarding the internal characteristics of the tumor and its relationship to nerve structures, thereby possibly increasing the potential for normal nerve salvage.
Finally, ultrasound-guided near-nerve neurography may also be useful in the diagnostic workup of peripheral nerve lesions, particularly when evaluating early regeneration after peripheral nerve trauma. Presently, intraoperative compound nerve action potentials are recorded by exposing the nerve and applying electrodes directly to the nerve. Introducing electrodes next to the nerve using ultrasound-guidance techniques is a noninvasive option that may obviate the need for surgical exploration.
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