Intraoperative laryngeal electromyographic assessment of patients with immobile vocal fold

Diagnostic and therapeutic pitfalls in benign vocal fold diseases

More than half of patients presenting with hoarseness show benign vocal fold changes. The clinician should be familiar with the anatomy, physiology and functional aspects of voice disorders and also the modern diagnostic and therapeutic possibilities in order to ensure an optimal and patient specific management. This review article focuses on the diagnostic and therapeutic limitations and difficulties of treatment of benign vocal fold tumors, the management and prevention of scarred vocal folds and the issue of unilateral vocal fold paresis.

Laryngeal electromyography

Laryngeal electromyography (LEMG) evaluates the integrity of the neuromuscular system in the larynx by recording action potentials generated in the laryngeal muscles during voluntary and involuntary contraction. LEMG is particularly useful for helping to differentiate between disorders involving upper motor neurons, lower motor neurons, peripheral nerves, the neuromuscular junction, muscle fibers, and the laryngeal cartilages and joints. LEMG should be considered to be an extension of the physical examination, not an isolated laboratory procedure. A careful history and laryngeal evaluation determine the indication for LEMG and which muscles or muscle groups, in particular, are to be studied. Abnormalities detected by LEMG are always interpreted within the context of the clinical picture.

Electromyography and the immobile vocal fold

Laryngeal EMG has become a useful tool for the otolaryngologist in the four decades since the pioneering work of Faaborg-Anderson and Buchtal. It is able to distinguish between mechanical limitation and denervation in an immobile vocal fold. In the paralyzed vocal fold, it can guide workup by pointing to the site of the lesion. In the hands of a circumspect clinician, it can provide clinically valuable information regarding prognosis. Useful application of laryngeal EMG must rest on the basic fact that it isa qualitative test. Because of factors like sampling error, interfering signal from neighboring muscles, difficulties in needle placement, and our in-complete understanding of reinnervation physiology, the boundary between sophisticated, subtle interpretation and overreading is particularly difficult to distinguish. EMG diagnosis is based on patterns of abnormalities over time and, like other tests, requires interpretation in a clinical context. As in any such undertaking, there is no substitute for good judgment and experience. The most important benefit of clinical use of laryngeal EMG may be that it has catalyzed and broadened interest in laryngeal neurophysiology in the same way that stroboscopy has focused attention on the structure and function of the vocal fold lamina propria. The continuing refinement of electrodiagnostic approaches to the larynx that has resulted, including quantitative, single-fiber. and vector laryngeal EMG, and evolving methods of nerve conduction testing will continue to yield important insights into mechanisms of neural control that are likely to drive developments in the treatment of vocal fold paralysis in the future.

The evaluation of unilateral vocal fold immobility: is chest X-ray enough?

Unilateral vocal fold immobility (UVFI) is a sign of underlying disease. No consensus exists regarding the appropriate evaluation. This study was performed to determine the ability of a chest radiograph (CXR) to limit further costly testing. The charts of 169 patients with previously undiagnosed UVFI were reviewed. In 113 patients the etiology was identified during the history and physical examination (H&P), or the H&P led to a directed evaluation. There were nine patients in whom the evaluation was incomplete. There were 47 patients in whom the etiology was not identified during the H&P. In 28 patients, the CXR identified the etiology, and in 16 cases the CXR ruled out an intrathoracic cause. There were three patients whose H&P and CXR did not identify their cervical etiology No patients had a thoracic etiology that was not identified by CXR. An algorithm was developed: If H&P fail to determine the etiology or to direct the evaluation, CXR is performed and followed by appropriate evaluation if positive. A negative CXR is followed with computed tomography (CT) of the neck from the skull base to thoracic inlet for right-sided UVFI and to the aortic triangle for left-sided UVFI. Other diagnostic studies are directed by signs and symptoms. A chest CT is not recommended unless there is clinical suspicion of a pulmonary or thoracic process.

Major patterns of laryngeal electromyography and their clinical application

Laryngeal electromyography (LEMG) is clinically valuable in the evaluation of laryngeal dysfunction and vocal fold immobility. To facilitate clinical application of this electrophysiologic test, a detailed description of modified LEMG techniques is presented. The techniques were applied for simultaneous bilateral recordings of the thyroarytenoid, cricothyroid, and posterior cricoarytenoid muscles. The basic patterns of LEMG are classified into three different types: normal, neuropathy, and myopathy. In an attempt to characterize these patterns, we have reported eight LEMG-documented cases: unilateral laryngeal paralysis, bilateral laryngeal paralysis, cricoarytenoid joint dislocation, cricoarytenoid joint ankylosis, laryngeal myopathy, pharyngeal paralysis (soft palate paralysis), spasmodic dysphonia, and unilateral laryngeal paralysis with anastomosis. The significance of the major LEMG patterns is discussed.