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Failure to visualise the superior laryngeal nerve using ultrasound imaging.

As a consequence of our interest in this subject, we found the case report by Manikandan et al to be interesting (1). However, to date we have not been able to visualise the superior laryngeal nerve, an experience also reported by other investigators (2,3). In addition, we have not been able to reproduce the images reported by the authors. It would be interesting to hear how reliably Manikandan et al can visualise the superior laryngeal nerve, or if they have any explanation of why others have been unsuccessful. Have they conducted block anatomic dissections to corroborate the superior laryngeal nerve images? We would also be interested in whether other clinicians or investigators have been able or unable to identify the superior laryngeal nerve using ultrasound imaging techniques.

References

(1.) Manikandan S, Neema PK, Rathod RC. Ultrasound-guided bilateral superior laryngeal nerve block to aid awake endotracheal intubation in a patient with cervical spine disease for emergency surgery. Anaesth Intensive Care 2010; 38:946-948.

(2.) Singh M, Chin KJ, Chan VWS, Wong DT, Prasad GA, Yu E. Use of sonography for airway assessment. J Ultrasound Med 2010; 29:79-85.

(3.) Barberey G, Henry Y, Boillot A, Pili-Floury S, Samain E. Ultrasound imaging of the superior laryngeal nerve containing space. From Proceedings of the 2010 Annual Meeting of the American Society Anesthesiologists, October 16, 2010.

H. Vaghadia

R. Lawson

R. Tang

A. Sawka

Vancouver, Canada

Failure to visualise the superior laryngeal nerve using ultrasound imaging--Reply

We appreciate the interest shown by Vaghadia et al on our case report of ultrasound-guided superior laryngeal nerve (SLN) block to aid in awake endotracheal intubation (1). Singh et al had used ultrasound to study the upper airway anatomy. Though they have described in detail the anatomy of the different airway structures and the muscles surrounding the airway, there was no description of the course or relationship of any vascular structures or nerves of the airway (2). We are unable to comment on the results of the study by Barberey et al as the available abstract did not mention the exact technique and landmarks used for SLN identification (3). They have used only the arbitrary SLN-space to study the SLN.

The internal branch of the SLN is accompanied by the superior laryngeal artery, which is a branch of superior thyroid artery, which in turn is the first branch of external carotid artery immediately after bifurcation of the common carotid artery. This relationship is well described in various anatomy books and articles in the literature. The technique described by us primarily involves identification of arterial pulsations and following their relationship to the nerve inferior to the greater horn of hyoid bone. Though we were able to identify the neurovascular structures in our case using the technique described, we agree that there may be initial difficulty in following pulsations of the vessels by the novice. In our experience, the key point in identifying the structures is to place the ultrasound probe gently, because firm placement can compress the structures and distort the anatomy. We have not performed any block anatomical dissections; however, we have used our technique for blocking the SLN bilaterally and performed successfully, awake intubations in a small group of patients. We agree that a clinical study is necessary and we are in the process of studying imaging of different laryngeal nerves using ultrasound in the neck.

References

(1.) Manikandan S, Neema PK, Rathod RC. Ultrasound-guided bilateral superior laryngeal nerve block to aid awake endotracheal intubation in a patient with cervical spine disease for emergency surgery. Anaesth Intensive Care 2010; 38:946-948.

(2.) Singh M, Chin KJ, Chan VWS, Wong DT, Prasad GA, Yu E. Use of sonography for airway assessment. J Ultrasound Med 2010; 29:79-85.

(3.) Barberey G, Henry Y, Boillot A, Pili-Floury S, Samain E. Ultrasound imaging of the superior laryngeal nerve containing space. From Proceedings of the 2010 Annual Meeting of the American Society Anesthesiologists, October 16, 2010.

S. Manikandan

P. K. Neema

R. C. Rathod

Trivandrum, India
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Title Annotation:Correspondence
Author:Vaghadia, H.; Lawson, R.; Tang, R.
Publication:Anaesthesia and Intensive Care
Geographic Code:9INDI
Date:May 1, 2011
Words:665
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