Spasmodic Dysphonia Treatment & Management

The symptoms of spasmodic dysphonia often include worsening of voice during periods of stress and relative improvement on sedatives such as alcohol and benzodiazepines. Despite these effects, no clear pharmacological agent provides even marginal relief of spasmodic dysphonia (SD). Typical agents used include benzodiazepines, anticholinergics, and dopamine antagonists. Even when success is noticed with these agents, their use is often precluded due to the well-documented peripheral and CNS side effects. ^[23]

Voice therapy

Clinicians have found that voice therapy in patients with spasmodic dysphonia (SD) generally has limited benefit, although it may help them gain greater insight into their voice production and reduce hyperfunctional compensatory behaviors. ^[1] As such, voice therapy can be useful as an adjunctive treatment.

At present, voice therapy is recommended for the following types of patients with spasmodic dysphonia (SD):

• Patients with mild, intermittent symptoms of adductor spasmodic dysphonia (SD)

• Patients with a psychogenic dysphonia, psychogenic overlay, or symptom exaggeration

• Patients who request assistance with increasing benefit duration following botulinum toxin injection

• Patients with abductor spasmodic dysphonia (SD) who are receiving limited benefit from botulinum toxin injections

• Patients who develop significant muscle tension dysphonia while trying to compensate for muscle spasms

Voice therapy protocol

Voice therapy usually lasts for 6-8 sessions over 8-10 weeks. The key element in this treatment is the reduction of excessive pressure; the maintenance of a nonspasmodic phonation gives patients a sense of control over their treatment.

Focus on reducing the effort associated with voice onset by using gliding phonation with fricatives or vowels.

The program includes replacing short shallow inspirations with slow smooth inspirations, first without phonation and then with phonation. Conscious awareness of lower thoracic breath control and the rhythm of breathing are initiated. Patients are taught to use only the amount of breath needed for a particular phrase. Emphasis is placed on coordinating the lower thoracic exhalation phase of breathing with the onset of phonation.

Phrasing of 3-6 syllables is emphasized. Voiceless phonemes are added to the voiced phonemes to develop awareness in the patient that voicing is now produced more easily than in the past. Exercises to improve resonance are added after treatment for airflow control and breathing is established.

Botulinum toxin therapy

The ideal treatment for spasmodic dysphonia (SD) has not been identified. Currently, the American Academy of Otolaryngology - Head and Neck Surgery endorses the injection of minute quantities of botulinum toxin into laryngeal muscles as the primary treatment modality. Botulinum toxin causes a chemical denervation of muscle fibers by blocking the release of acetylcholine at neuromuscular junctions.

The clinical effect of botulinum toxin is classically thought to result from its peripheral effect, but some research suggests otherwise. The toxin is found to not only affect extrafusal muscle fibers but also the afferent muscle spindle output. Muscle activity is known to be regulated by afferent feedback, so a decrease in muscle spindle output can lead to decreased muscle effectiveness. In addition, because spasmodic dysphonia is by definition a focal dystonia, a deficient level of CNS inhibition is inherent. This lack of inhibition can lead to increased activity of the muscle fibers leading to spasms.

Some suggest that the selective denervation and deafferentation of botulinum toxin may cause an increase in inhibition, causing an improvement in the involuntary muscle spasms. ^[24] For more information, see the Pathophysiology section.

Botulinum toxin injection is accomplished with a monopolar hollow polytetrafluoroethylene (Teflon)–coated EMG needle connected to an EMG recorder.

Typically, the commercially available botulinum toxin is reconstituted with preservative-free 0.9% sodium chloride before injection. Traditionally, this reconstituted solution is injected within 4 hours. A recent study, however, shows no significant difference in efficacy or side effects between this freshly reconstituted BOTOX® and reconstituted BOTOX®, which is stored frozen for 4-8 weeks. This cost-effective measure allows the otolaryngologist a longer period of use without sacrificing quality. ^[25] The patient is placed in either a nearly supine position with a pillow underneath the upper back and with the neck extended or a seated position in an examination chair with the neck extended. The thyroid and cricoid cartilages are palpated, and the midline of the CT membrane is identified.

Dosage

Percutaneous injection of botulinum toxin into the thyroarytenoid (TA) muscle in adductor spasmodic dysphonia (SD) is usually performed with a starting dose of 1.25 U into each TA muscle.

For patients with abductor spasmodic dysphonia (SD), the dose is 5 U for unilateral posterior cricoarytenoid (PCA) injection. The patient returns 2 weeks later for a second contralateral injection if symptoms are not sufficiently abated. Prior to injection, flexible laryngoscopy is performed to confirm that weakened but adequate abduction of the injected vocal fold is present. If abduction is minimal, airway compromise due to contralateral injection is a significant risk. As a result, this injection is postponed. ^[26]

Alternatively, 1.25 U can be administered on one side, while 5-7 U are administered in the other side during the same visit. Botulinum toxin treatment for abductor spasmodic dysphonia (SD) is more difficult than for adductor spasmodic dysphonia (SD) and is associated with greater risk, including mild-to-severe stridor caused by PCA paralysis.

In a case review by Stong et al, patients with abductor spasmodic dysphonia (SD) simultaneously injected with least 2.0-2.5 U in each PCA muscle were found to have no major complications such as intubations, tracheotomies, or admissions for airway observation. Importantly, their review did report a 5% rate of dyspnea on exertion and a 2% rate of dysphagia, which resolved after 2-3 weeks. ^[27]

Procedure

In adductor spasmodic dysphonia (SD), the needle is passed through the skin that lies over the superior edge of the cricoid, just lateral to midline. The needle is then advanced through the CT membrane and superiorly and laterally directed into the right or left vocal fold to reach the TA muscle as seen in the image below.

By entering slightly off the midline, the injection can be accomplished totally submucosally, without entering the airway. The oscilloscope and auditory output of the EMG apparatus are monitored to detect muscle activity. When crisp action potentials are obtained with phonation, needle position in a TA muscle is confirmed. Once the position is confirmed, the toxin is slowly injected.

Injection of botulinum toxin for abductor spasmodic dysphonia (SD) is more technically demanding. The larynx must be grasped and rotated away from the site of the planned injection. The needle is advanced through the inferior constrictor muscle at the posterior border of the thyroid cartilage at the junction of the lower third and upper two thirds of the cartilage. The needle is advanced to the cricoid cartilage and then slightly moved out (under EMG guidance) to the optimal position in the PCA muscle as seen in the image below.

The patient is asked to sniff—an action that yields maximal abduction of vocal folds and activation of the PCA. The EMG signal is observed for correct placement, and the toxin is injected in the area of brisk activity.

Evaluation and rating criteria

Patients are re-evaluated in the second week after injection. Typically, the toxin's effect occurs within the first 48-72 hours. Adductor patients' voices initially become hoarse or breathy. Some patients develop mild aspiration when drinking liquids. Accordingly, advise patients to sip through a straw, to avoid gulping liquids, or to use a supraglottic swallow technique. As noted above, abductor patients may experience stridor or dysphagia.

Patients are given a diary so they can rate themselves before injection, then every day for 2 weeks after injection, and then weekly until the next injection. This rating aids assessment of botulinum toxin treatment effectiveness and indicates the optimal timing and dosage for the next injection.

Treatment regimen

Because of differing sensitivity to botulinum toxin, the injection protocol and dosage must be established for every patient on an individual basis. Each patient is started with a standard dose. This is then increased or decreased based on the patient's side effects, symptom response, and individual needs.

In a study by Holden et al, patients reviewed over a 14-year period were evaluated for changes in dose and interval. Their data showed that over time, doses remained consistent and intervals between injections were found to be relatively stable. ^[28]

Some patients are very sensitive to toxin. They may not have adequate relief with small bilateral doses and too much breathiness at larger doses. For those patients, injections can be initiated with a larger dose unilaterally, with or without a contralateral injection 2 weeks later. A delay allows some recovery before the second dose is administered. Alternatively, patients often do well with only a unilateral injection.

Another approach to prevent breathiness is more frequent administration of bilateral minidose injections (0.1-0.5 U), although the duration of benefit in these patients is only 6-8 weeks.

If results are still suboptimal and the diagnosis of spasmodic dysphonia (SD) is clear, then injection of multiple muscles within the affected group may be helpful. Interarytenoid injections may be helpful in adductor spasmodic dysphonia (SD), while cricothyroid injections maybe be helpful in abductor spasmodic dysphonia (SD). ^{[29, 30]}

A study by Heyes et al indicated that patient age and sex impact the dose of botulinum toxin needed to treat adductor spasmodic dysphonia (SD). The investigators found that in younger patients in the study (aged 60 years or less), the mean dose of botulinum toxin per treatment was 4.4 U, compared with 3.9 U in the older cohort (over age 60 years). The report also found that females received a larger mean per-treatment dose of botulinum toxin than males did (4.2 vs 3.6 U, respectively). ^[31]

In addition to botulinum toxin injections, which have become the standard of care in the treatment of spasmodic dysphonia (SD), several surgical treatments are currently in practice.

Isshiki et al proposed type 2 thyroplasty techniques for adductor spasmodic dysphonia (SD). These techniques were successful in 5 of 6 patients. The concept of these techniques is to change the thyroid cartilage shape to relax and slightly lateralize the vocal folds. The advantages of the surgery include (1) the ability to adjust optimal glottal closure for phonation, (2) unlikely recurrence, (3) no damage to the physiological function of phonation, (4) intraoperative reversibility if ineffective, and (5) the ability to perform readjustments when needed. ^[6]

Conflicting results were presented in a subsequent study by Chan et al, who could not replicate the success of Isshiki and colleagues. ^[32] However, a retrospective study by Sanuki and Isshiki details the success of type 2 thyroplasty with a titanium bridge (to maintain separation of incised thyroid cartilage) in a larger subset of patients. Although limited by length of follow up, significant improvement in comparative perceptual analysis such as degree of strangulation, interruption, and tremor were observed in the patients, who had adductor spasmodic dysphonia (SD), less than a year after surgery. ^[23]

Another study by Sanuki, with Yumoto, indicated that in adductor spasmodic dysphonia (SD), type 2 thyroplasty using implanted titanium bridges can provide long-term symptom relief. At an average follow-up of 41.3 months after surgery, almost all of the 31 patients surveyed reported satisfaction with their postoperative voice, with scores on the Voice Handicap Index-10 (n=17) improving from 26.3 to 9.4. ^[33]

A retrospective study by Nomoto et al indicated that bilateral thyroarytenoid muscle myectomy (TAM) and type 2 thyroplasty are each effective in treating adductor spasmodic dysphonia, with both resulting in comparable improvements on the voice handicap index-10. The study, in which 30 patients underwent TAM and 35 were treated with type 2 thyroplasty, also found that TAM was better than type 2 thyroplasty in improving strangulation, interruption, and tremor but that it tended to worsen breathiness. ^[34]

Recurrent laryngeal nerve denervation and reinnervation was first described in 1999. ^[35] The adductor branch of the recurrent laryngeal nerve (to TA and LCA) is bilaterally denervated and the distal nerve TA is reanastomosed to the ansa cervicalis. In addition, a lateral cricoarytenoid myectomy is performed. The ansa cervicalis reinnervation results in tone of the TA and LCA muscles and prevents reinnervation by the laryngeal nerves affected by spasmodic dysphonia (SD). Most voices improved in the judgment of both professionals and patients, and 83% of patients would recommend or strongly recommend the surgery to others with spasmodic dysphonia (SD). Twenty percent of patients had complications of moderate-to-severe breathiness, with one patient suffering from aspiration.

A follow-up retrospective study by Chhetri et al showed long-term (mean 49 months) improvement in both patient satisfaction and expert perceptual voice evaluation. Again, postoperative breathiness was significant in 30% of patients. ^[8] A Canadian group has been able to reproduce similar results in a small series of patients. Six patients were treated without complication and with favorable results based on subjective evaluation of expert and untrained listeners. One patient required continued botulinum toxin therapy. ^[36]

A final surgical option for adductor spasmodic dysphonia is a bilateral TA and lateral cricoarytenoid myectomy staged a minimum of 6 months apart. This weakens the vocal folds bilaterally to prevent spasms. It is performed under local anesthesia and is titrated to breathiness to eliminate the risk of overresection. Short-term results in 5 patients revealed improved fluency in all patients. ^[9] Long-term studies are needed, especially considering the history of blepharospasm treatment using a similar procedure. Many patients with blepharospasm treated with myectomy had either recurrence of symptoms or dysfunction due to muscular fibrosis or scarring.

These surgical techniques are in their infancy and require wider evaluation and long-term follow-up data before being considered as a standard treatment for spasmodic dysphonia (SD).

For excellent patient education resources, see eMedicineHealth's patient education article BOTOX® Injections.

See the list below:

• Dysphagia is related to the toxin's partial diffusion into the inferior constrictor muscle when the target muscle is the PCA muscle. This adverse effect is transient and usually resolves in 1 week.

• Breathy hypophonia is usually a transient adverse effect of a botulinum toxin injection into the TA muscle and usually resolves within 1-2 weeks.

• Clinically significant aspiration is a very rare complication that is related to the dose of botulinum toxin injected into the TA muscle. Aspiration is transient and resolves in 1-2 weeks.

• Stridor is more serious in patients with abductor spasmodic dysphonia (SD) because of PCA paralysis. Extent of paralysis is related to the botulinum toxin dose.

Most patients experience toxin effect within the first 48-72 hours after injection, with a variable amount of breathy dysphonia and slight aspiration. These adverse effects disappear within the first week, but voice improvement persists for approximately 12 weeks.

Treatment of adductor spasmodic dysphonia (SD) with botulinum toxin achieves good results, with an average benefit of 90% of normal voice function. ^[7]

The aforementioned study by Heyes and colleagues reported that in patients with adductor spasmodic dysphonia (SD), younger individuals (aged 60 years or less) had a significantly shorter mean length of benefit from botulinum toxin treatment than did patients over age 60 years (3.0 vs 3.6 months, respectively). ^[31]

Treatment of abductor spasmodic dysphonia (SD) is more difficult. The abductor muscle (the PCA) is located between the larynx and pharynx and is more difficult to inject. Most patients require bilateral PCA injections. Botulinum toxin treatment achieves an average benefit of 70% of normal voice function. ^[37]

Surgical therapy for spasmodic dysphonia (SD) is still controversial because the side effects can be severe, and wide evaluation with long-term follow-up data is not available.

To date, botulinum toxin injection is the standard therapy for spasmodic dysphonia (SD). Unfortunately, this is just a treatment at the end organ and is not a cure. The key to understanding this disorder is to understand its pathophysiology and that of other spasmodic movement disorders.

Current research, especially gene research, is progressing in the elucidation of the cause of focal dystonia. Advances in the understanding of genetically determined early-onset primary torsion dystonia are offering insight into the pathophysiology of dystonia. An amino acid deletion in the DYT1 gene has been found to be responsible for familial primary torsion dystonia. This defect results in an abnormality in the protein torsinA, which is widely distributed in the CNS. ^[38] Further investigation of the of this gene and its protein products will hopefully spur advances in our understanding of dystonia and improve our treatment of the disorder.