Laryngeal Long Latency Response Conditioning in Abductor Spasmodic Dysphonia

Abstract

Previously, we demonstrated that patients with adductor spasmodic dysphonia (ADSD) have a disinhibition of laryngeal responses to sensory input. In this study, sensorimotor responses to stimulation of the superior laryngeal nerve were compared between 10 subjects with abductor spasmodic dysphonia (ABSD) and 15 normal volunteers. The groups had similar latency and frequency characteristics of their unconditioned adductor responses (p>.05). The conditioned R1 (early) responses of the subjects with ABSD were greater and more variable in amplitude than those of the normal volunteers (p< or =.008). Similar R2 (late) conditioning effects were found in both groups, with a nonsignificant trend toward reduced inhibition of contralateral R2 responses at lower interstimulus intervals (p = .01) in the patient group. Thus, inhibitory mechanisms that modulate the R1 laryngeal sensorimotor pathway in the brain stem may be abnormal in subjects with ABSD. Abnormal modulation of laryngeal sensorimotor responses seems present in both types of spasmodic dysphonia.

Stuttering: a dynamic motor control disorder

“…When paired electrical stimuli are presented at less than 1 s intervals for conditioning the late R2 responses (>60 ms latency) are normally suppressed reflecting central inhibitory processes modulating these responses. Conditioning abnormalities of the R2 response of the laryngeal adductor reflex have been found in both the adductor and abductor types of SD suggesting an abnormality in central suppression of muscle responses to sensory feedback (Deleyiannis, Gillespie, Bielamowicz, Yamashita, & Ludlow, 1999;Ludlow, Schulz, Yamashita, & Deleyiannis, 1995). Decreased or altered afferent feedback reduce spasmodic bursts in some of the dystonias (Kaji, Rothwell, et al, 1995;Yoshida et al, 1998).…”

Exploration on the Underlying Mechanism of Female Predominance in Spasmodic Dysphonia: An Anatomical Study of Nodose Ganglion in Rats

“…In 2006 the prevalence in Iceland was 5.9 cases/100,000 people [3,10]. Around 50,000 people have spasmodic dysphonia in North America, with an estimated number of 1.1-4.26 cases/100,000 people which predominates in female [27].…”

“…It was previously categorized as mental and psychological disorder [13]. Most scholars recently believe that this disease stems from neurodegenerative diseases [10], as classified by the National Institute of Neurological Disorders and Stroke (NINDS). In [24] reported a female predominance of 79 % (134 cases) out of a total population of 168 spasmodic dysphonia patients, which is consistent with previous reports [6].…”

Laryngeal Reflexes

“…Rapid presentations of stimuli to elicit the laryngeal adductor response have been used to examine conditioning effects for the laryngeal adductor response in laryngeal motor control disorders such as spasmodic dysphonia (Deleyiannis, Gillespie, Bielamowicz, et al, 1999; Ludlow, Schulz, Yamashita, et al, 1995). A lack of suppression of the conditioning responses suggests a similar disinhibition to that found using conditioning studies of the blink reflex in spasmodic dysphonia (Cohen, Ludlow, Warden, et al, 1989).…”