Abductor and Adductor Spasmodic Dysphonia Collection

Karen Kost

There are a total of 78 articles in this collection about spasmodic dysphonia (SD), with 47 dedicated to adductor spasmodic dysphonia (ADSD), and only 4 dedicated to abductor spasmodic dysphonia (ABSD). The remaining 27 are ‘unspecified’ because it is not clear whether Adductor or Abductor Spasmodic Dysphonia (SD) is being discussed. This publication profile likely reflects the fact that adductor SD is by far the more common disorder.  It is fascinating to look back at the older publications and review, through time, the approach to this condition in terms of etiology, diagnosis and management.

Several articles address the process of evaluating the voice impairments associated with SD. Despite the description of various acoustic evaluations, there is no widely used tool that characterizes and objectively measures the perceptual symptoms linked to SD. The Unified Spasmodic Dysphonia Rating Scale (USDRS) was suggested as such a measure in the 1990s but has not been adopted widely. The lack of specific diagnostic criteria for SD can make it very difficult to distinguish from other voice disorders such as Muscle Tension Dysphonia (MTD), Vocal Tremor or even the spastic dysarthria noted in Amyotrophic Lateral Sclerosis. To this end, various acoustic analyses have been proposed using Aerodynamic evaluations as well as Acoustic and Motor Speech Parameters.  Electromyography (EMG) also has been discussed as a useful tool in the diagnosis and treatment of patients with movement disorders.

Both Adductor and Abductor Spasmodic Dysphonia have been recognized as neurologically-based focal dystonias for well over 2 decades. Nonetheless, the exact etiology and pathophysiology remains elusive. Recent analysis of brain activity in patients with adductor SD using Functional Magnetic Resonance Imaging suggests that the basal ganglia are involved in the pathophysiology of SD (1).

The treatment of SD has received a great deal of attention in this collection of papers. The number and variety of proposed therapies attests to the fact that there exists no ideal management paradigm at this time. The 2 earliest references to therapy date back to 1993:  in the first, the results of recurrent laryngeal nerve resection for adductor SD are discussed, while in the second, electrical stimulation is suggested as a possible treatment for movement disorders of the larynx, including SD. In the interim, several other management options have been proposed, including voice therapy alone, acupuncture, type II thyroplasty, Botulinim Toxin injections, and in more recent years, denervation/reinnervation. Much of the interest has focused on Botulinum Toxin injection under EMG guidance, because the results, although less than perfect and only temporary, are relatively predictable and consistent. In those very rare instances of resistance to Botulinum Toxin A, administration of Botulinum Toxin B may be effective.  Exactly how Botulinum Toxin should be administered remains somewhat controversial, with treatment protocols advocating unilateral versus bilateral injections at various time intervals. Regardless of the protocol adopted, there is considerable agreement that Botulinum Toxin results in measurable improvement in, amongst others, Voice Handicap Index scores, and Voice Related Quality of Life scores. The coexistence of other vocal pathology such as vocal tremor is generally associated with poorer results.

In summary, the collection provides for thought-provoking reading, allowing the reader to trace changes in the assessment, diagnosis, treatment and evaluation of outcomes in Spasmodic Dysphonia over 25 years.

References

  1. Kiyuna A, Kise N, Hiratsuka M, Kondo S, Uehara T, Maeda H, et al. Brain Activity in Patients With Adductor Spasmodic Dysphonia Detected by Functional Magnetic Resonance Imaging. J Voice. 2017;31(3):379.e1-.e11.
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