Preoperative ultrasound-guided mapping of peripheral nerves Laboratory investigation

Object . Surgical exposure of a peripheral nerve can be technically challenging, making the operation more extensive and time consuming, particularly in the treatment of small nerves with an anatomically variable position. This study describes the application of ultrasound to facilitate surgical access and localization of targeted peripheral nerves. Methods. A preclinical feasibility study was performed at the University of Washington's Willed Body Program laboratory. Unembalmed cadavers were placed on the dissection table in positions mimicking those typically required for surgical access to specific nerves that can be challenging to localize. A high-frequency portable ultrasound system was used to identify the nerves. An extraneural injection of methylene blue immediately adjacent to the target nerve was performed under ultrasound guidance as the experimental nerve mapping procedure. Surgical dissections through a small skin incision parallel to skin tension lines were guided by the transducer position and angle. Success was determined by the accuracy and rapidity of surgical identification and exposure of the nerve. Results. Using ultrasound-guided mapping, all anticipated peripheral nerves were correctly identified via a direct approach from the skin incision. This was confirmed by performing an anatomical dissection to expose and identify the intended nerve and its relation to the injected methylene blue dye. In no case was intraneural injection of the dye observed. Conclusions. Preoperative ultrasound-guided nerve mapping may be useful in facilitating surgical access to a targeted nerve and thereby minimizing tissue dissection and operating time.