Diagnostic Test for Laryngeal Sensory Neuropathy (Chronic Cough)? SELSAP

Patients who suffer from a persistent chronic cough undergo a tremendous amount of testing, trials of medications, and seeing numerous specialists to try and make the cough go away. Ultimately, the cough may be found due to a rare condition called laryngeal sensory neuropathy which is treated with anti-depressant and even seizure medications. This nerve also may contribute to other chronic throat symptoms including globus, throat-clearing, phlegmy throat, and swallowing issues as well.

Because laryngeal sensory neuropathy (LSN) is a diagnosis of exclusion, an extensive workup is required to rule out all other causes of cough including tests for reflux, reactive airway disease, allergy, etc. Given the time-consuming nature of evaluating a chronic cough, very smart researchers have been trying to develop a test that more directly checks for laryngeal sensory neuropathy (LSN).

Indirect measures of LSN can be determined through laryngeal EMG as well as FEESST testing, but are considered imperfect and/or invasive.

However, one promising test called SELSAP (Surface Evoked Laryngeal Sensory Action Potential) is a non-invasive, surface evoked, sensory nerve function testing of the superior laryngeal nerve. Why the superior laryngeal nerve? It's because that's the nerve that is responsible for causing the sensation/urge to cough in affected patients. It's also the primary nerve that suffers from the neuropathy. [see references below]

The test basically involves placing an electrode to the side of the voicebox and another under the chin. A mild electric stimulus is than performed behind the ear.

Because this test is so new, it is unproven and unclear whether this test will ultimately provide valuable assistance in the evaluation of a patient suffering from chronic cough. Normative values have yet to be rigorously determined.

BUT... it is something that can be considered especially if the history is consistent with LSN and the SELSAP is "clearly" abnormal. In such cases, appropriate treatment can be immediately started without going through the entire chronic cough workup first.

Of course, even though LSN treatment is started, it still behooves to still do the workup to ensure a person does not have more than one cause for persistent cough that would still need to be addressed for true cough resolution. Read more about LSN treatment failures here.

When it comes to swallowing difficulties, if SELSAP does come back abnormal, it may suggest that there is "numbness" of the voicebox region preventing a proper swallow as the body does not "know" where the food is when it passes by leading to aspiration.

Be aware that not all places will offer such testing. Contacting a good neurologist is really one's best bet to see if they are willing to learn and perform SELSAP.

Here is one I know of that performs this test:

Dr. Safwan Jaradeh at Stanford Medical Center
Phone: 650-723-6469


References:
Surface-Evoked Laryngeal Sensory Action Potential Evaluation in Neurogenic Chronic Cough. Journal of Voice, May 28, 2014.

A new noninvasive method for determination of laryngeal sensory function. Laryngoscope. 2011 Jan;121(1):158-63. doi: 10.1002/lary.21182.