Vocal aging and adductor spasmodic dysphonia: response to botulinum toxin injection

Abstract

Aging of the larynx is characterized by involutional changes which alter its biomechanical and neural properties and create a biological environment that is different from younger counterparts. Illustrative anatomical examples are presented. This natural, non-disease process appears to set conditions which may influence the effectiveness of botulinum toxin injection and our expectations for its success. Adductor spasmodic dysphonia, a type of laryngeal dystonia, is typically treated using botulinum toxin injections of the vocal folds in order to suppress adductory muscle spasms which are disruptive to production of speech and voice. A few studies have suggested diminished response to treatment in older patients with adductor spasmodic dysphonia. This retrospective study provides a reanalysis of existing pre-to-post treatment data as function of age. Perceptual judgments of speech produced by 42 patients with ADSD were made by two panels of professional listeners with expertise in voice or fluency of speech. Results demonstrate a markedly reduced positive response to botulinum toxin treatment in the older patients. Perceptual findings are further elucidated by means of acoustic spectrography. Literature on vocal aging is reviewed to provide a specific set of biological mechanisms that best account for the observed interaction of botulinum toxin treatment with advancing age.

Figure 1

Spectrograms of the phrase “… raindrops in the air …” spoken by a 38 year old female: normal control subject is depicted on the top panel, ADSD before BT injection is on the middle, and ADSD after BT injection is on the bottom panel.

Figure 2

Spectrograms of the phrase “When the sunlight …” spoken by a 74 year old female: normal control subject is depicted on the top panel, ADSD before BT injection is on the middle, and ADSD after BT injection is on the bottom panel.

Figure 3

Coronal section of the larynx from 56 year old female illustrating major structural landmarks. Safran-Hematoxylin Stain, 2.5x original magnification. 1 – epiglottis, 2 – unossified thyroid cartilage, 3 – ossified portion of thyroid cartilage, 4 – unossified cricoid cartilage, 5 – ossified portion of cricoid cartilage, 6 – lamina propria of vocal fold, 7 – thyroarytenoid muscle (the major constrictor of vocal fold), 8 – laryngeal ventricle (lined of glandular epithelium), 9 – vestibular fold with G – mucous-serous glands, 10 – conus elasticus, 11 – glottal space.

Figure 4

Coronal sections of the vocal fold from 21years old (A), 63 years old (B) and 72years old (C) females illustrating age related changes in the epithelium and lamina propria. Safran-Hematoxylin Stain, 20x original magnification. E – epithelium, S – superficial layer of the lamina propria, I – intermediate layer of the lamina propria, D – deep laryner of the lamina propria. Portions of the adjacent thyroarytenoid muscle (TA), which form a part of the body of the vocal fold, are also illustrated.

Figure 5

Endoscopic pictures of the vocal folds of a 58 year old woman during phonation, who presents with bowing of the vocal folds, thinning lamina propria and a persistent glottal chink.

Figure 6

Diagrammatic representation of the major structures contributing to the peripheral speech mechanism. Structures of the upper and lower respiratory tracts are functionally interfaced and programmed by the CNS to produce voice and speech.

Figure 7

Age-group plots of the means and standard deviations of visual analog scaling (VAS) scores for the four voice attributes (overall voice quality, roughness, brokenness, breathiness).

Figure 8

Age-group plots of the means and standard deviations of visual analog scaling (VAS) scores for the four fluency attributes (overall fluency, tension struggle, vocal spasms, dysfluent syllables).

Figure 9

Interaction plots of decade by treatment condition for mean composite scores for voice for three groups: non-dysphonic controls, ADSD before BT injection and the same ADSD subjects after BT injection.

Figure 10

Interaction plots of decade by treatment condition for mean fluency composite scores by decade for three groups: non-dysphonic controls, ADSD before BT injection and the same ADSD subjects after BT injection.