Relationship of Laryngeal Botulinum Toxin Dosage to Patient Age, Vitality, and Socioeconomic Issues

Use of Botulinum Toxin in Spasmodic Dysphonia: A Review of Recent Studies

Spasmodic dysphonia (SD), also known as laryngeal dystonia, is a neurological voice disorder that causes involuntary spasms of the vocal cord muscles. This impacts speech to varying degrees and results in strained and strangled voice quality, as in adductor spasmodic dysphonia, or weak, quiet, and breathy, as in abductor spasmodic dysphonia. While there is currently no cure for SD, voice therapy and chemodenervation with botulinum toxin (btx) injections remain the mainstay of management. Surgery may be performed in some cases; however, btx injections are widely used to treat both adductor and abductor forms of SD. While btx injections may show vocal improvement in both types of SD, results can depend on several factors such as the general health of the patient, onset and severity of the condition, dosage, interval between injections, and expertise of the practitioner. While many studies have documented the efficacy of btx for improving vocal symptoms in individuals with SD, this review aims to discuss some of those studies from the last 10 years.

Patient Experience Contributing to Outcomes of Laryngeal Botulinum Toxin Injection

OBJECTIVES

Laryngeal Botulinum Toxin injection (LBTX) in the adductor musculature is the current therapy for Adductor Spasmodic Dysphonia. This study explores nonbiological factors that can affect the patient experience during this procedure and their association with better or worse self-reported effectiveness.

METHODS

A 14 item survey was used to evaluate the patient experience in patients who had undergone LBTX in Mayo Clinic Jacksonville, Florida, during 2019. Information from the survey, previous medical history, and demographic data were collected, and a descriptive analysis was performed.

RESULTS

Of the 36 patients who participated, the mean age was 65 years and a female predominance was found (66%). The average age at onset of symptoms was 57 years, and voice tremor was associated with 36.1% of patients. Preprocedure education was recognized as a factor affecting outcomes in 87% of patients; 11 patients reported that body position used during the injection could affect the results. Pain or stress experienced at the time of procedure was referred in one-third of patients as an influencing factor too.

CONCLUSION

This study has shown that nonpharmacological factors such as education before the procedure, body position, pain, and stress sensation before LBTX may have a role in the botulinum toxin effect on Adductor Spasmodic Dysphonia patients. This study is the first to describe these variables qualitatively, and further studies may help to improve the patient experience and outcome of LBTX around the world.

The Impact of Socioeconomic Status on Voice Outcomes in Patients With Spasmodic Dysphonia Treated With Botulinum Toxin Injections

OBJECTIVES:

To determine the impact of socioeconomic status (SES) on voice outcomes for spasmodic dysphonia (SD) patients treated with botulinum toxin injections.

METHODS:

This was a prospective cross-sectional study in a tertiary care, academic voice clinic in Canada. Adult SD patients returning to the voice clinic for their botulinum toxin injections were recruited from October 2017 to April 2018. Patients completed a questionnaire on demographic data, the Hollingshead Four-Factor Index for socioeconomic status (validated instrument based on education, occupation, gender, and marital status), and the Voice-Handicap Index 10 (VHI-10) (validated instrument on self-reported vocal handicap). Primary outcome was the association between VHI-10 and Hollingshead Index. Secondary variables were median household income by postal code, duration of disease, gender, age, and professional voice user. Descriptive statistics and multiple linear regression were conducted.

RESULTS:

One hundred and one patients (age = 62.8 ± 13.7 years, 20.8% male) were recruited with VHI-10 of 22.1 ± 8.1 (out of 40) and Hollingshead Index of 46.3 ± 11.7 (range, 8-66). Median household income was $75 875 ± $16 393, which was above the Canadian average of $70 336. About 91.1% were Caucasian, 54.4% had university degree, 86.1% spoke English, and 43.5% were employed. In multiple linear regression, there was mild to moderate negative correlation (r = -.292, P = .004) between VHI-10 and Hollingshead Index when controlling for disease duration, age, gender, and professional voice use.

CONCLUSION:

SD patients treated with botulinum toxin were mostly affluent, Caucasian, well educated, and English speakers. Lower self-perceived vocal handicap was associated with higher socioeconomic status.

OnabotulinumtoxinA for adductor spasmodic dysphonia (ADSD): Functional results and the role of dosage

OBJECTIVE

To report the results of functional outcome, dose trend and relationship between onabotulinumtoxinA (onabotA) dosage and the severity of disease or time between therapy sessions in patients affected by adductor spasmodic dysphonia (ADSD).

PATIENTS AND METHODS

Thirty-two patients underwent 193 EMG-guided intracordal injections of a starting dose of 2 MU of onabotA. At enrollment, each subject was administered the VHI. The response was evaluated using a subjective rating scale (0-100% of normal phonation).

RESULTS

The quality of voice improved significantly after 1 month and stabilized by 3 months. The percentage of normal voice improved 33.34 ± 11.5% (min 26 - max 68). The functional gain was significantly worse in patients presenting with ADSD associated with dystonias in other body regions (31% vs 45% - p < 0.05). The mean dose employed was 3.64 MU (min 1 - max 6) with a trend of increasing dosages up to the 5th treatment after which the doses stabilized over time. The pre-treatment VHI showed a weakly positive correlation with the cumulative dose at the 5th and 10th injections. Benefit duration and the mean between treatment interval were 103 and 136 days respectively. The correlation between dose and inter-injection time is weakly negative (r = -0.22, p < 0.05), however, this is influenced predominantly by the first-to-second injection. After this initial treatment effect, the correlation becomes weakly positive (r = 0.12).

CONCLUSIONS

Our data confirm the efficacy of onabotA to improve the quality of voice in cases of ADSD. The trial period for optimal dosage lasted up to a mean of five injections. The dosage of onabotA impacted the length of response and was influenced by the severity of ADSD. Finally the efficacy of onabotA did not change significantly after repeated administrations.

Review of differential diagnosis and management of spasmodic dysphonia

PURPOSE OF REVIEW

The recent literature on spasmodic dysphonia is reviewed with regard to pathogenesis, differential diagnosis, treatment options, audits, and current methods of management.

RECENT FINDINGS

Advances in technology have enabled clinicians to better understand the connection between brain and laryngeal function and dysfunction. Refinements in imaging and genetic investigation techniques have led to advances in the understanding of the underlying mechanism of this neurolaryngeal disorder. Development of diagnostic assessment tools and measures of quality of life hold the potential to improve treatment and care.

SUMMARY

Fifty articles published between 2014 and 2015 were selected for this review. The sources were drawn from several clinical specialties: 54% come under the scope of laryngology, 32% from neurology, and 14% from other areas. It remains poorly understood, misdiagnosed, and underdiagnosed. Its identification, diagnosis, treatment selection, and coordination of care require an expert specialist multidisciplinary team. More training is required to help people who have this chronic and psychosocially disabling voice disorder, which impinges on all aspects of their lives. Spasmodic dysphonia is now classified as a 'rare' disease in the United States. This designation will assist in international standards of diagnosis, assessment, treatment, and management.