Current thyroid surgery guidelines for voice evaluation can be improved. A response to article: The American Thyroid Association Guidelines on Voice Assessment—Have We Done Enough?
An article in the Journal of the American Medical Association's Otolaryngology journal (The American Thyroid Association Guidelines on Voice Assessment-Have We Done Enough?) suggests that physicians performing thyroid surgery could improve their surgical outcomes if they examined the laryngeal function before and after surgery in the region of the laryngeal nerves. I concur strongly that the lack of assessing laryngeal function before and after surgery near the larynx limits the surgeons understanding of the damage that can be done and limits the patient's ability to know what the true risks of surgery are.
Here is my reasoning for why current thyroid surgery guidelines for voice evaluation can and should be improved.
Letter to the editor of JAMA Otolaryngology Head & Neck Surgery.
There is no reason not to clinically evaluate the voice before and after thyroid surgery for any clinician who aspires to Shonka and Terris’ summary statement1, “For surgeons who are committed to self-improvement, transparency with patients, and quality assessment, implicit in the accurate evaluation of postoperative function and the impact of the thyroid operation is an examination of laryngeal function prior to and following surgery.” Neither the AAO-HNS2 nor the American Thyroid Association3 thyroid surgery clinical guidelines approach what should be assessed when laryngeal nerves are at risk from tumor or surgeon.
Why are the current recommendations insufficient?
The larynx is vocally capable of changing pitch, changing volume and changing clarity of sound. Both superior and recurrent laryngeal nerves control these parameters. A partial injury to even one branch of these bilateral nerves will alter laryngeal vocal function. Saying a surgeon or a patient didn’t complain or didn’t notice a problem is not the same as saying an injury did not occur, yet this is the current standard of assessment. A patient won’t necessarily tell the surgeon about voice impairment. The patient may not even associate a particular impairment with the surgery. The inquisitive surgeon needs to seek if she is to learn how often and when a nerve is injured, that is to go beyond “the patient didn’t complain.”
What are the vocal functions of the larynx?
The general motor function of a superior laryngeal nerve (SLN) is to tension the vocal cord, resulting in high pitch sound and increasing volume when activated. The general function of the anterior branch of the recurrent laryngeal nerve (RLN-ant) is to adduct the vocal cords for phonation. The general function of the posterior branch of the recurrent laryngeal nerve (RLN-post) is to open the glottis to obtain air for phonation (and other needs).
Since there is no easy absolute criteria for the capabilities of these laryngeal functions, the simplest, reasonably complete assessment is to record a set of vocal capabilities and complete functional stroboscopy before and after surgery. The patient acts as her own control.
Why is both an audio and video assessment necessary?
While in theory the superior nerve can be assessed endoscopically, estimating lengthening of the vocal cords visually with a wide-angle endoscope at a non-standard distance is far more difficult than assessing the upper pitch range of an individual. If the highest pitch reachable is lowered after surgery, there has likely been an impairment of the SLN. A subtle unilateral impairment may then be visualized on stroboscopy at high pitch as an asymmetry not present at low pitch. A bilateral impairment may be symmetric, but there is a loss of upper vocal range.
Since compensation for an injury is a natural phenomenon, the examiner who wants to know will unmask compensation. On vocal assessment, an elevation of the lowest pitch after surgery likely represents compensation for an RLN-ant injury. Compensation is derived from hyperadduction provided by opposite RLN-ant, tension provided by the SLN and increased subglottic airflow to entrain a looser cord. Consequently, viewing the stroboscopic examination at the lowest pitch and lowest volume possible removes SLN compensation and excess airflow. Unilateral vocal process rotation past midline becomes more visible. An asymmetric and larger glottic gap and asymmetry in oscillation at low pitch not present prior to surgery will become visible on this low, soft phonation.
An injury to the RLN-post is optimally assessed endoscopically as degree of opening during sniffing (full activation).
It is difficult to find a cheaper, more sensitive and more standard test than a recording of complete vocal capabilities4. Audio recording is nearly free. It is more precise than flexible endoscopy, which occurs at various non-standard distances from the glottis. Changes in vocal capabilities key an examiner where to look and what to look for, improving stroboscopy. Recordings, both audio and video can be examined by other individuals or at a later date, while a written interpretation of function is considerably less accurate.
Consequently, for thyroid, parathyroid and all neck surgeons who are committed to self-improvement, transparency with patients and quality assessment, a voice recording of vocal capabilities before and after surgery along with a stroboscopy recording at low and high pitch and low and high volumes before and after surgery will far more accurately assess neurologic impairment than the present standards proposed by either the AAOHNS or the American Thyroid Association.
1) Shonka DC, Jr., Terris DJ. The American Thyroid Association Guidelines on Voice Assessment-Have We Done Enough? JAMA Otolaryngol Head Neck Surg. 2016;142(2):115-116.
2) Chandrasekhar SS, Randolph GW, Seidman MD, et al. Clinical practice guideline: improving voice outcomes after thyroid surgery. Otolaryngol Head Neck Surg. 2013;148(6 Suppl):S1-37.
3) Haugen BR, Alexander EK, Bible KC, et al. 2015 American Thyroid Association Management Guidelines for Adult Patients with Thyroid Nodules and Differentiated Thyroid Cancer: The American Thyroid Association Guidelines Task Force on Thyroid Nodules and Differentiated Thyroid Cancer. Thyroid. 2016;26(1):1-133.
The letter was declined by the reviewers as they could not see the value in detecting a problem if the patient doesn't tell the surgeon there is a problem. My responses to these reviewers are 1) the patient often realizes they have a problem, but do not relate it to the surgeon causing the injury. 2) If the reviewer is truly interested in improving their surgical skills, they need to look for the problem. Because you don't perceive the problem doesn't mean that it is not there. I could honestly describe this as the Ostrich approach to surgery.