Assessment of Laryngopharyngeal Sensation in Adductor Spasmodic Dysphonia

Participant Recruitment Subjects with adductor type LD (AdLD) were identified and recruited by advertisements and by study clinicians at their institution. Advertisements were physically placed in the UCSF Voice and Swallowing Center clinic and were delivered electronically through the website of the National Spasmodic Dysphonia Association and to area LD ("spasmodic dysphonia") support groups.

Adults greater than 18 years old with AdLD were included if they received a diagnosis established by a multi-disciplinary evaluation by a fellowship-trained laryngologist and voice-specialized speech-language pathologist. Subjects diagnosed by a physician outside of the study facility were evaluated in-person by a fellowship-trained laryngologist to confirm their eligibility for this study. All patients were required to have history of favorable response to intra-laryngeal botulinum toxin A (BtxA) treatment, as further demonstration of the correct diagnosis of ADLD. This was especially helpful for patients initially diagnosed outside of our center. Subjects with abductor or mixed type LD were not included in the present study due to their low incidence, but concurrent essential tremor (ET) of the vocal tract was accepted.

Patients were also excluded if they had a history of: concurrent laryngeal diseases or conditions other than AdLD+/-ET; bleeding disorder or current anticoagulation use; head and neck radiation; active tobacco use; or drinking more than two alcoholic beverages per day. If laryngopharyngeal lesions and/or masses, impeding abnormal laryngopharyngeal structure(s), or excessive post-nasal drip were noted on laryngoscopy, then examination ceased, and patients were excluded. Prior to testing, subjects also completed symptom-specific patient reported outcome measures (PROMs), including: Reflux Symptom Index (RSI),18 Voice Handicap Index-10 (VHI-10),19 Dyspnea Index (DI),20 Cough Severity Index (CSI),21 and Eating Assessment Tool-10 (EAT-10).22 These PROMs are standardly collected as part of the routine clinical are for all patients undergoing evaluation at this center and are reported herein for holistic characterization of these subjects but not intended as a reflection or measure of the severity of their AdLD. Lastly, to avoid any potentially confounding physical effects from the injection (e.g., vocal fold edema), no testing was performed in the two weeks immediately following BtxA treatment. For patient convenience and to facilitate maximal enrollment, patients were allowed to undergo testing at any point outside of this post-injection window, although the majority pursued testing immediately prior to a BtxA injection on the same day.

Healthy controls were defined as adults between 18 and 85 years of age without laryngopharyngeal disease and were subject to the same screening and exclusion criteria.23 Additionally, controls were excluded if they had abnormal patient reported outcome measures (i.e. Reflux Symptom Index (RSI) score> 13, Eating Assessment Tool-10 (EAT-10) score>2, or Voice Handicap Index-10 (VHI-10) score> 11).

Aesthesiometer Device As outlined in previous work, modified nylon monofilaments fixed to the end of 5-French open lumen catheters were utilized to deliver tactile stimuli to laryngopharyngeal subsites.12 The Food and Drug Administration (FDA) has previously ruled the aesthesiometer to be a Nonsignificant Risk (NSR) Device Study (Q190371/S001). Three nylon monofilament sizes (6-0, 5-0, 4-0) were cut to a calibrated length of 30 mm to deliver three distinct tactile stimuli of increasing strength, known as buckling-force. The 6-0, 5-0, and 4-0 monofilaments deliver an increasing mean force of 0.03 g, 0.11 g, and 0.30 g, respectively.12 An intermediary strength "4.5-0" monofilament was created by using a 5-0 monofilament of 25mm length, which has been demonstrated to have a mean buckling force of 0.19 g.23 During testing, the monofilaments were passed through the working channel of a flexible ENF-VT2 laryngoscope (Olympus America, Inc., Center Valley, PA) to allow for direct visualization and concurrent stimulation of laryngopharyngeal subsites.