Treatment of spastic dysphonia without nerve section

Neuroprostheses for management of dysphagia resulting from cerebrovascular disorders

Swallowing is a complicated process that involves intricate timing between many different muscles in the mouth and neck. The primary purpose of swallowing is to move food through the mouth and pharynx and into the esophagus for transport to the stomach for digestion. Dysphagia is a general term that refers to a disruption in any part of the process. The consequences of dysphagia include social embarrassment; malnutrition; and aspiration. Of these, aspiration is the most significant as it is associated with a significantly greater risk of pneumonia and death. If patients fail to adequately protect the airways with standard exercise and therapy, they are often disallowed from taking food by mouth and receive nutrition by alternate means. If patients still experience frequent pneumonia, more drastic surgical measures that permanently separate the airway from foodway are required. As an alternative to these surgical procedures, neuroprostheses can dynamically restore airway protection. There are two primary protective mechanisms that neuroprostheses seek to restore. The first is laryngeal elevation and the second is vocal fold closure. The present article is an introductory overview of the swallowing process, the primary muscles and nerves related to swallowing, the effects of dysphagia, the standard treatment options, and the neuroprosthetic options.

The effect of neuromuscular stimulation of the genioglossus on the hypopharyngeal airway

OBJECTIVES

To determine the effects of neuromuscular stimulation (NS) of the genioglossus muscle on hypopharyngeal airway size.

STUDY DESIGN

Fourteen consecutively recruited healthy volunteers underwent percutaneous electrical NS of the genioglossus muscle.

METHODS

Bipolar hooked wires were inserted percutaneously into the genioglossus muscle and used for NS. The anterior--posterior diameter of the hypopharynx was measured at the level of the superior edge of the epiglottis at baseline and during NS from recorded video endoscopic examinations.

RESULTS

NS of the genioglossus muscle resulted in a significant increase in the diameter of the hypopharyngeal airway (P =.002) compared with baseline, ranging from a 33% to 284% increase in airway diameter. Three of the 14 patients demonstrated modest decreases in airway diameter, likely the result of faulty electrode placement in surrounding tongue retrusive muscles.

CONCLUSIONS

NS of the genioglossus muscle was effective in increasing the hypopharyngeal airway and may provide a useful alternative to direct stimulation of the hypoglossal nerve with a nerve cuff electrode in the development of neuroprosthetic treatments for obstructive sleep apnea.

Assessment of posterior cricoarytenoid botulinum toxin injections in patients with abductor spasmodic dysphonia

In this study, we compared 2 techniques for injection of botulinum toxin type A (Botox) into the posterior cricoarytenoid (PCA) muscle for the treatment of abductor spasmodic dysphonia (ABSD). Fifteen patients with ABSD were enrolled in a prospective randomized crossover treatment trial comparing the 2 injection techniques. The PCA muscle was injected with 5 units on each side, with the injections staged 2 weeks apart, via either a percutaneous posterior-lateral approach or a transnasal fiberoptic approach. Eleven patients reported some benefit with the injections; however, the patient-perceived benefits were not related to changes in symptoms on blinded counts by speech pathologists. No significant reductions in the numbers of breathy breaks occurred with either technique, and no differences were found between techniques. Although patients perceived a benefit, blinded symptom counts did not substantiate these benefits. Thus, PCA muscle injections of Botox provided limited benefits to patients with ABSD, demonstrating the need for a more effective therapy for these patients.

Chronic intermittent stimulation of the thyroarytenoid muscle maintains dynamic control of glottal adduction

Patients with laryngeal motor control disorders need improved dynamic glottal closure for speech and swallowing. To evaluate the functional outcome of intermittent chronic thyroarytenoid muscle stimulation in an animal model, 6 canines were implanted with bilateral Medtronic Xtrel systems containing Peterson-type electrodes in the inferior and superior portions of the thyroarytenoid muscle. Stimulation was on one side only at 60 Hz, for 5 s on and 5 s off, over 8 h, 5 days per week, up to 8 months. Monthly videorecordings were done under anesthesia to measure the voltage threshold for detectable movement on each side, and vocal fold displacement and velocity during maximal stimulation of each side. Movement thresholds were lower in the inferior portion of the thyroarytenoid muscle (P </= 0.0005). Movement velocity was greater on the stimulated than on the nonstimulated side after 3 to 8 months (P = 0.039). No differences in the percentage distribution of different myosin heavy chain types were found between the stimulated and nonstimulated muscle samples. Sustained dynamic glottal adduction with no alteration in thyroarytenoid muscle function or fiber type was achieved with intermittent stimulation over 8 months. The results suggest that chronic intermittent thyroarytenoid stimulation has good potential for improving airway protection in dysphagia.

Implantation of a recurrent laryngeal nerve stimulator for the treatment of spastic dysphonia

Spastic dysphonia, a rare speech disorder, is characterized by strained phonation with excessively adducted vocal cords. Recurrent laryngeal nerve section, botulinum toxin injection into the vocalis-thyroarytenoid muscle complex, and other techniques have been used to treat this disorder. We have used percutaneous electrical stimulation of the recurrent laryngeal nerve with good results. Previous dog studies demonstrated the relative safety of an implantable recurrent laryngeal nerve stimulator. In this study, we directly stimulated the recurrent laryngeal nerve and vagus nerve in a dog without change in cardiorespiratory status. A Medtronic peripheral nerve stimulator was implanted in a patient with abductor spastic dysphonia. The cuff electrode was positioned around the recurrent laryngeal nerve and stimulation resulted in improvement in her voice. Extensive cardiopulmonary monitoring did not reveal any adverse response to stimulation and there was no discomfort to the patient. On the basis of the good results of this preliminary study, further study with long-term follow-up is under way.

Adductor laryngeal dystonia (spastic dysphonia): treatment with local injections of botulinum toxin (Botox)

Adductor spastic dysphonia (SD) is a laryngeal dystonia characterized by a choked, constrained voice pattern with breaks in vocal flow. Treatment with a variety of therapies including speech and pharmacotherapy have minimal benefit; only one-third of patients undergoing recurrent laryngeal nerve section have benefitted at 3 years. We have used local injections of botulinum toxin (Botox) bilaterally into vocalis muscles in 42 patients with SD. Injections were through a teflon-coated hollow electromyography (EMG) recording needle. Unilateral small doses (2.5-3.75 U) were of no clinical benefit. Bilateral small doses resulted in sustained improvement lasting 84.4 +/- 9.3 days. The degree of improvement was 61.1 +/- 4.6%. Common side-effects included a brief period of breathy hypophonia (8.5 +/- 2.5 days) and a mild sensation of choking/aspiration of fluids (1.7 +/- 0.6 days); there were no serious adverse effects. Vocal cord paralysis was not necessary for benefit. Follow-up vocalis muscle EMGs revealed denervation. All patients responded to retreatment (longest follow-up 3.5 years). Patients with prior recurrent laryngeal nerve surgery and residual uncomplicated dysphonia had similar results. Our results indicate that local injection of low-dose Botox is the treatment of choice for SD.