Laryngeal epithelial thickness: a comparison between optical coherence tomography and histology.

OBJECTIVES: Optical coherence tomography, an imaging modality using near-infrared light, produces cross-sectional tissue images with a lateral pixel resolution of 10 microm. However, normative data is first needed on epithelial thickness for lesion characterisation, and, to date, little exists. The purpose of our study is to measure normal laryngeal epithelial thickness by in vivo optical coherence tomography, and compare these values to those obtained from fixed ex-vivo laryngectomy specimens. DESIGN AND SETTING: Prospective at a single medical center in California, United States. PARTICIPANTS: A total of 116 patients undergoing operative endoscopy. MAIN OUTCOME MEASURES: Optical coherence tomography images of clinically normal laryngeal subsites were selected. Calibrated measurements of epithelial thickness at various laryngeal subsites were recorded. Measurements of epithelial thickness from corresponding areas were obtained using optical micrometry on histologically normal regions of 15 total laryngectomy specimens. Descriptive statistics were performed. RESULTS: Mean epithelial optical coherence tomography thicknesses were: true vocal cords (81 microm), false vocal cords (78 microm), subglottis (61 microm), aryepiglottic folds (111 microm), laryngeal epiglottis (116 microm) and lingual epiglottis (170 microm). Epithelial thicknesses in fixed tissues were: true vocal cords (103 microm), false vocal cords (79 microm), aryepiglottic folds (205 microm) subglottis (61 microm), laryngeal epiglottis (38 microm) and lingual epiglottis (130 microm). CONCLUSIONS: Optical coherence tomography does not have the artifacts associated with conventional histologic techniques. The inevitable development of office-based optical coherence tomography devices will increase the precision of laryngeal measurements and contribute to the clinical application of this technology in diagnosing laryngeal disease.

New perspectives about human laryngeal muscle: single-fiber analyses and interspecies comparisons.

BACKGROUND: In companion studies on canine and rodent laryngeal muscle, we observed that (1) muscle fibers in both the canine and rodent posterior cricoarytenoid (PCA) muscles have a slower myosin heavy-chain (MyHC) isoform profile than those in the thyroarytenoid (TA) muscle; (2) the muscle fiber composition of PCA and TA muscles in canines and rodents is complex given the presence of so-called hybrid fibers (fibers coexpressing various combinations of MyHC isoforms); (3) the types and proportions of hybrid fibers are both muscle specific and, in some cases, region specific; and (4) the MyHC isoform profile of canine laryngeal muscle appears to be slower than that of rodent laryngeal muscle, suggesting the possibility that larger mammals have a slower MyHC isoform profile. OBJECTIVES: Given the findings of these companion studies and the fact that very little is known about the MyHC isoform composition of laryngeal muscle fibers, the primary objectives of this study were to determine (1) the types of MyHC isoforms found in the human PCA and TA muscles, (2) if there were regional differences in MyHC isoform composition, (3) if hybrid fibers commonly occur in human laryngeal muscle, and (4) if the MyHC isoform profile of human laryngeal muscle is slower than that of canine and rodent laryngeal muscle. RESULTS AND CONCLUSIONS: The findings of this study clearly demonstrate that both the PCA and TA muscles in humans express 3 types of MyHC isoforms (ie, slow type I, fast type IIA, and fast type IIX MyHC isoforms). At the single-fiber level, there were distinct regional differences and hybrid fibers were a common occurrence. Finally, the data demonstrate that the PCA and TA muscles of humans have a slower MyHC profile than that found in either canine or rodent laryngeal muscle.

Are hybrid fibers a common motif of canine laryngeal muscles? Single-fiber analyses of myosin heavy-chain isoform composition.

BACKGROUND: The canine lateral cricoarytenoid muscle contains a large proportion of muscle fibers that coexpress various combinations of myosin heavy-chain isoforms (ie, so-called hybrid fibers). OBJECTIVE: To test the hypothesis that hybrid fibers are a common motif throughout laryngeal muscles. DESIGN: The posterior cricoarytenoid, canine cricothyroid, and thyroarytenoid muscles were removed from 5 beagle dogs. The posterior cricoarytenoid and canine cricothyroid muscles were each dissected into horizontal, oblique, and rectus regions. The thyroarytenoid was separated into medial and lateral regions. Approximately 40 single fibers were microdissected from each region ( approximately 1800 total fibers were sampled) and placed into a denaturing sample buffer. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis was then used to separate the individual myosin heavy-chain isoforms. RESULTS: Each laryngeal muscle contained hybrid fibers; however, the types and proportions of hybrid fibers were clearly muscle specific. Within a given muscle, there were relatively minor regional differences in the types and proportions of hybrid fibers. CONCLUSION: If the myosin heavy-chain isoform composition of a single fiber can be used as a "physiological marker," then the extent of hybridism may reveal the diversity of activity required of a given laryngeal muscle.

Single-fiber myosin heavy-chain isoform composition of rodent laryngeal muscle: modulation by thyroid hormone.

BACKGROUND: Studies have shown that canine laryngeal muscle contains a large number of muscle fibers that coexpress varying combinations of myosin heavy-chain (MyHC) isoforms. Currently, it is not clear whether this phenomenon is unique to canine laryngeal muscle or occurs in all mammals. OBJECTIVES: To examine the single-fiber MyHC isoform composition of rodent laryngeal muscle and to examine the plasticity of single-fiber MyHC isoform composition via manipulation of thyroid state. RESULTS: (1) Findings of single-fiber electrophoretic analyses clearly demonstrate that most fibers in both the posterior cricoarytenoid and thyroarytenoid muscles exhibit MyHC polymorphism. However, the proportions and patterns of polymorphism appear to be muscle specific. (2) Although the fast type IIL isoform was observed in fibers from both muscles, it was always coexpressed in combination with other MyHC isoforms (ie, no pure type IIL fibers were found), and always represented a minor proportion of the total MyHC pool. (3) Altering the thyroid state proved a useful tool for exploring the scope of MyHC isoform expression in these muscles. While the posterior cricoarytenoid muscle seemed more sensitive to the thyroid state, transitions in both muscles were primarily confined to the fast type IIX and IIB MyHC isoforms. CONCLUSION: The findings of this study support the concept that single-fiber MyHC polymorphism occurs commonly in mammalian laryngeal muscle.

Laryngeal synkinesis revisited.

First described in 1982, laryngeal synkinesis continues to play an important diagnostic and therapeutic role following recurrent laryngeal nerve (RLN) injury. Vocal fold motion impairment (formerly called "vocal cord paralysis"), hyperadducted and hyperabducted vocal folds, and certain laryngeal spasmodic and tremor disorders are often best explained by synkinesis. A closer look at these mechanisms confirms that following RLN injury, immobile vocal folds may be nearly normally functional (favorable), or spastic, hyperadducted, or hyperabducted (unfavorable). This has resulted in a functional classification of laryngeal synkinesis as follows: type I laryngeal synkinesis, with satisfactory voice and airway (vocal fold poorly mobile, or immobile); type II synkinesis, with spasmodic vocal folds and an unsatisfactory voice and/or airway; type III synkinesis, with hyperadducted vocal folds and airway compromise; and type IV synkinesis, with hyperabducted vocal folds, poor voice, and possible aspiration. This classification facilitates the understanding of laryngeal pathophysiology following RLN injuries and promotes a more scientific basis for management.

Evaluation and management of bilateral vocal cord immobility.

Bilateral vocal cord immobility can be life threatening for some patients. Others, who have an open glottic chink, may have a breathy dysphonia, intermittent dyspnea, and stridor. These signs and symptoms may also be found in a number of other conditions that cause weakness or paradoxical motion of the vocal cords that mimics paralysis. These other conditions include central nervous system diseases, neuromuscular disorders, laryngospasm, and psychogenic disorders. In addition, patients with cricoarytenoid joint immobility or interarytenoid scar can also have similar symptoms at presentation. It is critical to consider the differential diagnosis of an assumed bilateral vocal cord paralysis and understand the management of paradoxical movement, weakness, joint fixation, interarytenoid scar, laryngospasm, and psychogenic disorders. The treatment for bilateral immobility should proceed only after a thorough evaluation, which might include electromyography and/or examination during general anesthesia under dense anesthetic paralysis. Reconstructive procedures are the treatments of choice, and destructive procedures should be chosen only as a last resort.

Facial trauma and ocular/orbital injury.

BACKGROUND AND OBJECTIVES: Ocular injuries occur commonly in patients with facial trauma. Patients with significant eye injuries may present with grossly normal eyes and good visual acuity; however, subsequent ocular disorders may become apparent. The estimates of incidence vary considerably. Trauma is the second leading cause of blindness, and a review is, therefore, warranted. METHODS AND MATERIALS: Several extensive studies are reviewed. Blunt and penetrating trauma are examined by their respective subdivisions. The initial assessment and ophthalmologic examination of patients with facial trauma are discussed, and the type of injury that may occur secondary to trauma is delineated. Management is reviewed and discussed, including a recently developed diagnostic scoring system. Three clinical cases illustrate the procedure. RESULTS AND/OR CONCLUSIONS: The diagnosis of ocular injuries resulting from trauma is difficult. The recently introduced scoring system was found to improve the procedure. Based on this system, the authors have devised an algorithm to assist the clinician, with emphasis on visual acuity and the importance of visual examination.

Motor versus sensory neuron regeneration through collagen tubules.

Differences in regeneration of sensory and motor nerves were studied in rats to determine the effects of entubulation with collagen conduits. The rat sciatic nerve was repaired either with a 10-mm saline-filled gap or with a no-gap end-to-end repair cuffed within collagen tubules. These repairs were compared with the standard epineurial repairs. The populations of regenerated motor and sensory neurons in the peroneal nerves of all repairs were compared against the populations of normal peroneal neurons using horseradish peroxidase retrograde labeling. The epineurial repair resulted in regeneration of 65 percent (409 +/- 150) of motor neurons and 79 percent (2127 +/- 516) of sensory neurons (n = 6). The no-gap end-to-end repair in a collagen tubule resulted in regeneration of 53 percent (338 +/- 203) of motor and 70 percent (1893 +/- 794) of sensory neurons (n = 7). In the 10-mm gap repair, only 6.2 percent (39 +/- 18) of motor neurons but 63 percent (1710 +/- 557) of sensory neurons regenerated (n = 5). These results show that collagen entubulation supports nerve regeneration in end-to-end nerve repairs comparably to standard epineurial suture repairs. With the 10-mm gap repairs in collagen tubules, sensory neurons regenerated consistently better than motor neurons in the same environment. Therefore, intrinsic differences exist between motor and sensory neuron regeneration in the same nerve.

The use of 3-dimensional models in auricular reconstruction.

Reconstruction of the microtic auricle is a difficult process requiring considerable experience and dedication to detail. It is a multistage proposition requiring the talents of both the reconstructive surgeon and the otologic surgeon. Reconstruction of the external ear usually precedes the reconstruction of the middle ear. Often, a template is used by the reconstructive surgeon to aid in this complicated process. Traditionally, templates used by the reconstructive surgeon have been 2 dimensional (usually x-ray paper) and made from the opposite normal ear or another normal ear in cases of bilateral microtia. Use of a 2-dimensional model only provides a rough estimate of the cartilage framework needed. Considerable experience is therefore needed to get this cartilage framework "just right." We have developed a number of 3-dimensional synthetic templates to aid in the creation of an accurate cartilage framework implant. These templates serve as a more accurate guide in the complex cartilage carving and assembly process. The use of 3-dimensional templates has improved our technical reconstructive results in a small number of patients. We present these results and propose future application of these ideas.

A new concept in laryngeal muscle: multiple myosin isoform types in single muscle fibers of the lateral cricoarytenoid.

This report describes the first known investigation of canine laryngeal muscle in which single fibers were dissected and their myosin heavy chain (MHC) isoform content was analyzed. Both SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and western blot techniques were used. The data from single fiber SDS-PAGE indicate that the lateral cricoarytenoid (LCA) is predominantly a fast muscle composed of the following MHC isoforms: Type I, 16.3%; Type IIA, 71.3%; Type IIX, 10.4%; and Type IIB, 2.0%. The results reveal a phenomenon that, to our knowledge, has not been previously described for laryngeal muscle: the presence of two or more MHC isoforms in a single canine LCA muscle fiber. A large number (41%) of muscle fibers coexpressed two or more MHC isoforms. The three most common patterns of coexpression were Type IIA/IIX (72%), Type IIA/I (16%), and Type IIA/IIX/I (8%). Interestingly, the fast Type IIX MHC isoform was typically present with other isoforms and rarely found by itself in individual fibers. Additional experiments are underway to determine whether other laryngeal muscles exhibit such an unusually high ratio of MHC isoform polymorphism.

Complications of thyroid surgery.

The current study reports complications from thyroidectomy in 253 consecutive patients from 1988 to 1992. There were 10 temporary cases of hypoparathyroidism. After total thyroidectomy, one of 34 patients (3.2%) developed permanent hypoparathyroidism. Complications of recurrent laryngeal nerve (RLN) injury or hypoparathyroidism were no more common following completion thyroidectomy than total thyroidectomy. Unplanned RLN injury was seen in 13 patients of which 7 were permanent (2.1% of 334 nerves at risk). All 13 patients with RLN injury experienced a reduction in speech "loudness", but only 3 reported "hoarseness". The RLN may be injured without serious vocal disability. Eleven of 171 right RLN's at risk were injured as compared to 2 of 163 left RLN's. The volume of thyroid tissue resected was positively associated with RLN injury (p < 0.05) and not hypoparathyroidism. These findings are discussed. Hypoparathyroidism, not "symptomatic" RLN injury, is the most problematic complication impacting on the decision whether or not to perform total or completion thyroidectomy.

Nerve wound healing. An overview.

This article describes the mechanisms of peripheral nerve healing and the efforts to achieve an optimal healing outcome. The mainstay of treatment has been adherence to good surgical technique and the use of microsurgical equipment. Despite advances in microsurgery, complete structural and functional recovery is uncommon. Research focused on adjunctive methods for nerve repair is also reviewed in this article.

Evaluation and treatment of the unilateral paralyzed vocal fold.

The evaluation and treatment of patients with unilateral vocal fold paralysis have evolved as improvements in objective measurements of phonatory function and new modalities for treatment have developed. A thorough history, physical examination, subjective voice evaluation, objective voice analysis, and electromyography are used to make a diagnosis, determine the cause, and plan treatment. The goal of treatment of the patient with a unilateral vocal fold paralysis is to restore normal phonatory function without aspiration. Multiple modalities have developed to allow for restoration of nearly normal phonatory function, and these include voice therapy alone or in combination with injection medialization, laryngoplastic phonosurgery, or laryngeal reinnervation. Otolaryngologists should be familiar with the incidence, cause, evaluation, and state-of-the-art treatment of unilateral vocal fold paralysis of optimize patient care and avoid suboptimal results often seen with antiquated or inappropriate treatment.

Survey of postgraduate fellows in otolaryngology-head and neck surgery.

A survey of fellowship-trained otolaryngologists was undertaken. Seven hundred forty-four questionnaires were mailed, and 344 were returned. The survey respondents were asked questions regarding their fellowship training, location of practice, attitudes regarding certification, relevancy of fellowship to practice, and quality of fellowship training, among others. Results of this survey provide some information regarding the ongoing proliferation of fellowships in Otolaryngology--Head and Neck Surgery and the philosophies of those having taken fellowships. Generally, this survey indicates that fellowship-trained specialists feel that there are enough fellowships currently, and suggestions are made to improve the quality of fellowship training. Almost 70% of this survey's respondents prefer a Certificate of Added Qualifications from the American Board of Otolaryngology for credentialing and validation of their fellowship training.

Aerodynamic and temporal disruptions of speech in laryngeal insufficiency.

OBJECTIVES: To describe the effects of laryngeal insufficiency on aerodynamic and temporal aspects of speech breathing and speech production. DESIGN: A survey study with statistical comparisons of patient and normal subject groups. SETTING: Private and institutional practice. PATIENTS: A convenience sample of 23 subjects with laryngeal insufficiency was compared with a volunteer sample of 20 normal-speaking subjects. Patients had frank unilateral recurrent nerve paralysis-paresis or idiopathic laryngeal insufficiency as verified by videostrobolaryngoscopy. MAIN MEASURES: Mean airflows, air volumes, and durations for speech inspirations, speech phrases, and non-inspiratory pauses during samples of monologue speech. RESULTS: In comparison with the normal group, the patient group had significantly (P < .01) higher expiratory airflows and volumes during speech and reduced speech phrase durations. In addition, breaths per minute, inspiratory minute volume, and inspiratory airflow were significantly (P < .01) higher for the patient group. An experimental measure of aerodynamic yield for speech increased the statistical separation of the patient and normal groups compared with analyses using simple expiratory airflow measures alone. CONCLUSIONS: Insufficient contact of the true vocal folds during speech can affect more than just voice quality. Likely effects include (1) reduced speech phrase duration, (2) increased breaths per minute, (3) increased inspiratory minute volume, and (4) increased inspiratory airflow rate.

Unilateral recurrent laryngeal nerve paralysis.

Recurrent laryngeal nerve (RLN) injury [without injury to the superior laryngeal nerve (SLN)] is the most common traumatic neurolaryngological lesion. The acute effects are immediate flaccidity of the ipsilateral vocal fold, loss of abduction and adduction, severe dysphonia to complete paralytic aphonia, and, frequently, aspiration of food and drink into the trachea. This article reviews the function of the four intrinsic laryngeal muscles innervated by the RLN and the individual effects of RLN transection on these muscles. Following acute denervation, the subsequent progression is either chronic denervation or nerve regeneration with laryngeal muscle reinnervation. Four possible scenarios are discussed here: complete reinnervation with synkinesis, partial reinnervation with synkinesis, mixed RLN injuries, and no reinnervation (complete paralysis). Electromyography may eventually assist the laryngologist in establishing these diagnoses, but currently not enough normative data exist for confirming laryngeal synkinesis unequivocally in every case. Treatment is generally by Teflon injection, medialization thyroplasty, arytenoid adduction procedures, or reinnervation by nerve transfer. The author's preference is nerve transfer, insofar as the quality of resultant phonatory voice, in his hands, has been superior to the other techniques.

Facial paralysis in a benign osseous parotid tumor: a case report.

This unique lesion has not been described in the literature so far. It appears to have originated from the base of the skull (i.e., styloid process of the temporal bone). Its pathology was extensively reviewed and it appeared to be a benign proliferative mass, but had produced a total facial nerve paralysis with invasion and destruction of the nerve. Although not palpable clinically, it had invaded the deep lobe of the parotid gland, thus reinforcing the importance of a work-up with CT scans and MR imaging to work-up a facial paralysis of unknown cause lasting more than 6 months.

Endoscopic laser medial arytenoidectomy for airway management in bilateral laryngeal paralysis.

A review of our recent experience in patients with bilateral laryngeal paralysis is described. While we continue to use phrenic nerve transfers in patients with mobile arytenoids, patients with fixed arytenoids generally require some sort of vocal cord lateralization, either by arytenoidectomy and arytenoidopexy or by partial vocal cord resection. The endoscopic laser medial arytenoidectomy is a convenient and effective method for opening the posterior glottic airway. One arytenoid is reduced medially with the carbon dioxide laser. After about 3 months the opposite arytenoid can be treated similarly, if necessary. The procedure does not appear to affect arytenoid mobility, as the posterior commissure mucosa and underlying interarytenoid muscle are protected and hence unaffected by the procedure. Those patients with at least one mobile arytenoid cartilage are candidates for posterior cricoarytenoid muscle reinnervation. Although ansa cervicalis and phrenic nerve techniques have been described, the author has concentrated efforts on the phrenic nerve. This report describes the endoscopic laser medial arytenoidectomy procedure, while the phrenic nerve patients will be reported in a subsequent manuscript.