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Date published:
Language: English
PMID: 85702
ISSN: 21646821


Beginning with the first endoscopic parathyroidectomy by Gagner (1996), numerous reports have described the feasibility of endoscopic methods in neck surgery. Some of the difficulties encountered with the early endoscopic methods, namely difficulty manipulating rigid endoscopic instruments in a narrow field, two-dimensional view of the operative field, and presence of a small cervical scar have led to subsequent technological and application of the da Vinci® S Surgical Robot System (Intuitive Surgical, Sunnyvale, CA, USA) to a transaxillary approach to thyroid lobectomy. The transaxillary approach to thyroid lobectomies has provided surgeons and patients with a safe alternative to the traditional open anterior cervical approach while avoiding a palpable cervical scar. Patient positioning for the transaxillary approach and retraction during exposure introduces the potential for a transient or permanent injury to the brachial plexus. We report a case where somatosensory evoked potential monitoring detected an impending brachial plexus injury secondary to patient positioning that was subsequently corrected resulting in a good outcome. We assert that somatosensory evoked potential monitoring should be considered for all patients undergoing a transaxillary approach for thyroid lobectomy.


A 13-year-old female was referred for surgical resection of a significantly enlarged goiter. Her thyromegaly was associated with dysphagia and dyspnea. The patient underwent a robotic assisted transaxillary subtotal thyroidectomy. The reminder of the physical examination was normal including an intact neurological examination.

General anesthesia was induced using sevoflourane 8% in N2O/O2 mixture, 7L and 3L flows respectively. After induction, intravenous (IV) access was obtained. Propofol, fentanyl, and succinylcholine were given in preparation for intubation. Direct larygoscopy was performed without difficulty using a Miller 2 laryngoscopy blade, and the patient was intubated with a size 6.0 cuffed endotracheal tube with externally placed two channel adhesive electrodes (Neurovision Medical, Ventura, CA, USA) at the level of the vocal cords for recurrent laryngeal nerve monitoring. General anesthesia was maintained using a balanced anesthetic technique of 0.5 MAC sevoflourane, propofol infusion, and intermittent fentanyl boluses. No further muscle relaxant was given. The patient's right arm was rotated upwards 180 degrees and pressure points were padded. Her head was turned slightly to the left and her neck was slightly extended (Lewis et al. 2010, Kang et al. 2009).

Stimulation of distal ulnar nerves was performed bilaterally using disposable adhesive disk electrodes (CareFusion Corporation, San Diego, CA, USA). Stimulation pulses were delivered at a rate of 4. 1 Hz with a duration of 300 microseconds. Stimulation intensity was determined by identifying the motor threshold and stimulating at 10% above that value. Stainless steel subdermal needle electrodes were placed at Al, Fpz, Cp4, and Cp3 according to the International 10-20 System. Referential recording montages were as follows: Cp4-Fpz, Cp3-Fpz, and Al -Fpz. The amplifier gain was set at 5,000 and the low and high frequency filters were set at 1 Hz and 3000 Hz respectively. Pre-incision baseline traces were recorded and used for comparison during the procedure. Monitoring was of the N 13 and N20 peaks whose generators are the dorsal column nuclei of the caudal medulla and the primary sensory cortex respectively. Thirty minutes after incision a significant reduction in amplitude of both the N13 and N20 peaks of the right ulnar nerve SSEP was detected. Within a minute after the amplitude reduction was detected, the waveforms flattened out completely (Figure 1). The surgical team was alerted by the neurophysiologist to the change and was advised to reposition the patient's right arm. The arm was repositioned and within one minute the amplitude of both peaks returned to baseline. The waveforms remained unchanged throughout the rest of the procedure. After recovery from anesthesia, a brief neurological assessment was given identical to that given during the preoperative period. Strength, sensation, and proprioception were evaluated in the upper extremities and no deficits were noted.

Normotension and normothermia were maintained throughout the procedure. At the end of the case, the patient was extubated uneventfully in the OR and transported to the pediatric intensive care unit in stable condition. Total operating time was 275 minutes and the patient was discharged later that day.


It has been more than 15 years since Gagner (1996), introduced the first endoscopic neck surgery, and significant advances in both endoscopic equipment and technique have been reported. At least four endoscopic cervical approaches, a chest approach, breast approach, two combined chest/breast approaches, and an axillary approach to the neck have been described (Ganger et al. 1996, Slotema et al. 2008, rkeda et al. 2001, Bellantone et al. 2001, Yoon et al. 2006, Ohgami et al. 2000, Inabnet et al. 2003, Ikeda et al. 2002, Park et al. 2003, Shimizu and Tanaka 2003, Cougard et al. 2005, Henry and Sebag 2006, Palazzo et al. 2006, Sebag et al. 2006). The impetus behind this expanding body of work is the desire to avoid a conspicuous cervical scar. While such a scar is well-tolerated by many patients, local pain, paresthesias, dysesthesias, contractures, hypertrophic scar, or keloid formation have all been described as adverse sequelae of open thyroidectomy. Relocating the surgical scar to a less visible location is the goal of current endoscopic procedures. The transaxillary approach described here leaves incisions that are concealed in the axillary fold. Multiple studies have documented increased patient satisfaction with endoscopic approaches over conventional open approaches, with the transaxillary approach receiving the highest satisfaction scores (Chang et al. 2009).

We report the detection by SSEP monitoring of an impending brachial plexus injury during a transaxillary robotic assisted left thyroid lobectomy. SSEP monitoring has become a critical monitoring device for numerous surgeries and measures the response of the sensory cortex to electrical impulses from peripheral sensory nerve stimulation, including decrease in amplitude, increase in latency, or both (Norris 2009). Patient positioning during this novel approach introduces the potential of a temporary or permanent injury to the brachial plexus. Positional neuropathies are seen in a variety of surgical procedures and are routinely monitored using somatosensory evoked potentials (Anastasian et al. 2009, Schwartz et al. 2006, Kamel et al. 2006, Labrom et al. 2005, Jones et al. 2004, Schwartz et al. 2000, Deinsberger et al. 1998). As the transaxillary approach to thyroidectomies becomes more popular, positional neuropathies are likely to be increasingly reported. A review of the recent literature reveals a robotic transaxillary thyroidectomy case in which ipsilateral arm paralysis was reported. This complication might have resulted increased shoulder retraction (Kang et al. 2009). Three cases of paresis of the brachial plexus have been reported (Passler et al. 2002). Another four patients experienced ulnar nerve paralysis (one definitive case and three transient cases) caused by malpositioning on the operating table (Rosato et al. 2004). These nerve palsy complications can be possibly avoided by somatosensory evoked potential monitoring.

In summary, the use of SSEPs is a convenient and cost-effective way to prevent positional neuropathies during transaxillary thyroidectomies. Therefore, SSEP monitoring should be an extremely useful adjunct modality to prevent possible nerve palsy associated with arm positioning in patients undergoing a transaxillary approach for thyroid and parathyroid surgery. Future, larger scale studies are warranted to validate our experiences.


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Author affiliation:

Scott F. Davis, Ph. D.1,7

Mohamed Abdel Khalek, M.D.2

Jerry Giles, M.D.3

Charles Fox, M.D.4

Lesley Lirette, M.D.5

Emad Kandil, M.D.6

1Clinical Associate Professor

Department of Anesthesiology

2Department of Surgery

3Department of Otolaryngology

4 Associate Professor

Department of Anesthesiology

5 Department of Anesthesiology

6 Assistant Professor

Department of Surgery

Tulane University School of Medicine

New Orleans, Louisiana

7PhyslOM Intraoperative Monitoring

Atlanta, Georgia

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