Laryngeal Electromyography in Diagnosis and Treatment of Voice Disorders

Comparison of inhaled versus intravenous anesthesia for laryngoscopy and laryngeal electromyography in a rat model

Background

Propofol and remifentanil intravenous combination is one popular form of total intravenous anesthesia (TIVA) in mainstream clinical practice, but it has rarely been applied to a rat model for laryngoscopy and laryngeal electromyography (LEMG). Our objective was to establish a safe and reproducible general anesthetic protocol for laryngoscopy and endoscopic LEMG in a rat model. Our hypothesis is that TIVA allows a minimally morbid, and feasible laryngoscopy and LEMG.

Methods

Sprague Dawley rats were subjected to either inhalational anesthesia (IA) (isoflurane) or TIVA (propofol and remifentanil) and underwent laryngoscopy and LEMG. The primary outcome was a complete minimally interrupted rigid laryngoscopy and obtaining reproducible motor unit potentials from the posterior cricoarytenoid muscles. The secondary outcome was morbidity and mortality.

Results

Seventeen out of twenty-two rats underwent both TIVA and IA. Only two underwent IA only. All nineteen rats that underwent IA had a successful experiment. Seventeen rats underwent TIVA, however, only nine completed a successful experiment due to difficulty achieving a surgical plane, and respiratory events. Upon comparing the success of the two anaesthetic regimens, IA was superior to TIVA (P = 0.0008). There was no statistical difference between the amplitudes (p = 0.1985) or motor units burst duration (p = 0.82605) of both methods. Three mortalities were encountered, one of which was due to lidocaine toxicity and two were during anesthetic induction. Respiratory related morbidity was encountered in two rats, all seen with TIVA.

Conclusions

TIVA is not an ideal anesthetic regimen for laryngeal endoscopy and LEMG in rat models. Contrary to our hypothesis, IA did not affect the quality of the LEMG and allowed a seamless rigid endoscopy.

Electronic supplementary material

The online version of this article (10.1186/s40463-018-0312-9) contains supplementary material, which is available to authorized users.

Refractory Dysphonia Due to Isolated Cricothyroid Muscle Dystonia

OBJECTIVE

To demonstrate the utility of electromyography (EMG) in the evaluation and management of treatment-resistant dysphonia.

METHOD

We report a case of refractory dysphonia in which EMG was used to identify and treat isolated cricothyroid (CT) dystonia.

RESULTS

The patient, a healthy 43-year-old woman, presented with 9 months of progressive hoarseness. Her symptoms were present across vocal tasks but were particularly bothersome while dictating. On presentation, her voice was rated grade 3, roughness 3, breathiness 1, asthenia 0, and strain 3 (G3R3B1A0S3). Videostroboscopy was remarkable for hyperfunction. Voice therapy was not beneficial despite appropriate effort. Microdirect laryngoscopy revealed no evidence of structural pathology. The patient was referred for EMG because of her normal examination and failure to improve with therapy. The CT muscle demonstrated an increased latency of 750 ms in all vocal tasks. One month after CT injection with 3 units of botulinum toxin (BTX), her voice was improved. Perceptual voice evaluation was rated G1R1B0A0S1. Voice Handicap Index improved from 87 to 35.

CONCLUSIONS

In the absence of structural pathology, EMG can be a useful adjunct in the diagnosis of dysphonia that persists despite adequate trials of voice therapy. To our knowledge, this is the only report of laryngeal dystonia due to isolated CT dysfunction successfully treated with BTX.

The behavioural treatment of muscle tension voice disorders: A systematic review

PURPOSE

A systematic review of behavioural intervention for the treatment of adults with muscle tension voice disorders (MTVD).

METHOD

A search of 12 electronic databases and reference lists for studies published between the years 1990-2014 was conducted using the PRISMA guidelines. Inclusion and exclusion criteria included type of publication, participant characteristics, intervention, outcome measures and report of outcomes. Methodological quality rating scales and confidence in diagnostic scale supported the literature evaluation.

RESULT

Seven papers met the inclusion criteria. Significant improvement on at least one outcome measure was reported for all studies. Effect sizes were small-to-large. Methodological qualities of research were varied. No study explicitly reported treatment fidelity and cumulative intervention intensity could only be calculated for two out of seven studies. Outcome measures were used inconsistently and less than half of the measures had reported reliability values. Confidence in the accuracy of subject diagnosis on average was rated as low. Specific "active ingredients" for therapeutic change were not identified.

CONCLUSION

Voice therapy for the treatment of MTVD is associated with positive treatment outcomes; however, there is an obvious need for systematic and high quality research designs to expand the evidence base for the behavioural treatment of MTVD.