Laryngoscopy

Visualization of the larynx is critical in any assessment of a patient with dysphonia. Laryngoscopy uses optics and light to allow the clinician to visualize the laryngeal structures. Traditionally, the larynx has been visualized in the awake clinic patient indirectly using a laryngeal mirror. Although the view may be adequate with a laryngeal mirror, functional examination can be limited, and full visualization may be limited. With the development of optics and associated technologies, laryngoscopy can be performed with a variety of endoscopes: rigid angled laryngoscopes, flexible fiberoptic laryngoscopes, and flexible distal chip laryngoscopes. Video cameras can also be added for further magnification and recording.

More than 20 years ago, a prospective, nonrandomized trial performed by Barker and Dort evaluated the ability to complete either a mirror or rigid endoscopic examination. In the patients who went on to have direct laryngoscopy, Barker and Dort evaluated the accuracy of findings between the 2 techniques. Among the 100 patients they tested, nearly half of patients could not tolerate mirror evaluation. More than 80% tolerated a rigid endoscopic examination. Fewer than 30% underwent direct laryngoscopy, and among them, both examination techniques proved largely accurate, with rigid endoscopic techniques having zero false-negative evaluations. With the significant advances made in endoscopic technology since that report, a 2009 study of 43 patients similarly compared rigid laryngoscopy using a 30° endoscope to mirror examination and showed statistically significant improvements in patient comfort with less gagging (80% preferred rigid endoscopy), improved visualization of laryngeal structures by physicians, and the ability to display results of endoscopic evaluation for patients to see simultaneously. By comparison, a single study has suggested that flexible fiberoptic visualization offers decreased patient discomfort relative to rigid endoscopy (evidenced by cardiovascular response to direct vs fiberoptic laryngoscopy in patients emerging from anesthesia following thyroidectomy) and improved visualization.

Uncontrolled, observational studies, and anecdotal and expert opinion suggest that the use of fiberoptic visualization often affords the ability to palpate the glottis and supraglottis for assessment of sensory function, allows for improved dynamic assessments, and may provide some improved visualization of the subglottic region. This must be weighed against good evidence that suggests image quality is improved with the use of rigid endoscopes, however. A randomized case-controlled direct comparison among the 3 most frequently used methods (flexible fiberoptic endoscopes, distal chip flexible endoscopes, and rigid angled endoscopes) in 2008 showed that although flexible fiberoptic endoscopes provide the most cost-effective option for visualizing the larynx, they provided less information than rigid visualization in nearly one-quarter of patients, most notably during stroboscopy.

Although both rigid and flexible endoscopes have specific strengths and weakness, one of the chief advantages of either method over mirror laryngoscopy is the simultaneous use of magnification, video recording, and stroboscopy.

Laryngostroboscopy

Although laryngoscopy alone can visualize anatomic abnormalities, such as masses and impaired mobility of the vocal folds, it cannot provide visualization of the mucosal vibration (the source of the voice). Under constant illumination, the vocal folds vibrate at a much higher frequency than the human eye can discern. Addition of a stroboscopic light source allows the viewer to discriminate the motion of the vibratory edge of the vocal folds in “slow motion.”

In comparison with laryngoscopy alone, stroboscopy improves diagnostic yield, as demonstrated in several observational studies over the past 30 years. In 1991, Sataloff and colleagues reported the largest of these studies, assessing nearly 1900 patients over a 4-year period. Additional diagnoses were discovered in 29% of patients, and the prestrobe diagnoses were found to be inaccurate in 18% of patients. Subsequent publication of 292 prospectively identified patients who underwent a similar protocol involving initial laryngoscopy followed by stroboscopy showed similar results, with stroboscopy altering the diagnosis and treatment outcome in 14% of the patients. A small (40 patients) retrospective review of stroboscopy use in the setting of laryngeal trauma found that even after computed tomography (CT) and laryngoscopy, stroboscopic evaluation replaced the need for direct laryngoscopy to evaluate mucosal integrity and vocal fold function in several patients. Avoidance of secondary trauma of operative direct laryngoscopy led to earlier discharge for matched grades of laryngeal injury.

A 2010 retrospective review of pediatric patients with unresolved dysphonia after prior endoscopy and treatment found the addition of stroboscopy (both rigid and flexible) identified a new diagnosis that resulted in additional therapy in nearly all patients.

Direct laryngoscopy

Operative direct laryngoscopy (with or without magnification) as a diagnostic tool may assist in establishing a diagnosis for dysphonia in patients with certain laryngoscopic findings (eg, a mass lesion). It may also be indicated in patients in whom awake visualization of the larynx cannot be achieved. Operative direct laryngoscopy offers the additional benefit of palpation of the cricoarytenoid joint and the mucosa of the vocal folds, as well as the opportunity for diagnostic biopsy. Phonomicrosurgical intervention can also be done concurrently with diagnosis in selected circumstances.

Although dynamic evaluation in the sedated patient is limited, multiple retrospective reviews suggest that the improved visualization provided by operative positioning, palpation, magnification, and improved depth perception of binocular microscopy results in alternate or additional diagnoses. Poels and colleagues found that, despite preoperative stroboscopy, alternate diagnoses were made in 36% of the 221 patients who underwent direct laryngoscopy. An additional 31% of patients had additional lesions (largely intracordal) discovered at the time of surgery. A more recent review of 100 patients at another tertiary care center identified additional lesions (often bilateral) in 9% of patients. Nearly half of these patients had a change in treatment plans after the altered diagnosis.

Laryngeal electromyography

Laryngeal electromyography (LEMG) assesses the electrical activity and the functional status of the innervation to the targeted laryngeal muscles (typically cricothyroid, thyroarytenoid, and often posterior cricoarytenoid muscles).

A 2005 study of the practices of laryngologists who belong to the American Broncho-Esphogological Association indicated that among respondents, 75% used LEMG to confirm or diagnose unilateral vocal fold immobility. Evidence to support its use in a purely diagnostic capacity is largely of a nonrandomized, retrospective nature, however. To address this issue specifically, the Neurolaryngology Study Group convened a multidisciplinary panel to examine the evidence for LEMG in diagnosis and prognosis. The diagnostic accuracy was based on multiple small studies and one large unblinded retrospective study, which confirmed the neurologic basis of vocal fold paresis or paralysis in 83% to 92% of cases and was able to contrast neurologic impairment with cricoarytenoid motion disorders in the remaining patients (2%–12%). One of the larger studies reviewed reported that LEMG led to a change in the type of imaging performed in 11% of patients and altered the timing or type of surgical intervention in another 40% of patients.

Meyer and Hillel published an updated review of the literature in 2009 of primarily level IV evidence. They identified a blinded study from Philadelphia that reported increased sensitivity for identification of a paretic nerve from 64% to 86%. Another reviewed study reported that LEMG altered the timing or choice of therapy in nearly 50% of patients. More recent studies (level III evidence) compared the efficacy of LEMG to laryngoscopy for diagnosis of neurologic impairment. Sataloff and colleagues reported that LEMG results corroborated laryngoscopic diagnosis in 95% of patients (661 of 689), and identified neurologic abnormality in 22% (14 of 62) without a prior diagnosis. Importantly, Gavazzoni and colleagues caution that no single electrophysiologic parameter alone confers a high sensitivity (although nearly all carried greater than 90% specificity) and adds that duration since onset of impairment decreases the diagnostic certainty.

Hydman and colleagues studied LEMG as a prognostic indicator in recurrent laryngeal nerve injury in 15 patients with vocal fold paresis 2 to 3 weeks after iatrogenic injury but anatomically intact recurrent laryngeal nerves. Patients with axonal injury based on LEMG findings had 50% significantly worsened functional and videostroboscopic outcomes.

Radiographic imaging

Although most patients with dysphonia do not require imaging, abnormalities in structure of the larynx or mobility of the vocal folds may prompt additional investigation with radiographic imaging. Imaging may be useful in assessing the extent of mass lesions. In malignancy, imaging allows assessment of regional lymphatic involvement, as well as defining the extent of the mass. CT or magnetic resonance imaging (MRI) can be used to assess for invasion of the laryngeal cartilage, which offers prognostic information for staging of laryngeal and hypopharyngeal cancer. MRI is highly sensitive for identifying cartilage invasion, but it is less specific than CT owing to increased signal patterns often caused by inflammation.

Imaging is also indicated if initial workup of dysphonia reveals a paralyzed vocal fold without a known cause. Historically, a chest radiograph and/or a neck CT with contrast was used to identify vascular anomalies or mass lesions. In recent years, radiographs have become extraneous, as both positive and negative results lead to CT imaging. In a recent prospective study by El Badawey and colleagues of 86 patients presenting with vocal cord palsy, 36% had positive CT findings, which correlated with the cause for immobility. Most of these were suspicious for malignancy in the lungs or mediastinum.

Skull-base imaging with MRI is indicated in vocal fold paresis with other cranial nerve palsies. Principally, expert opinion supports its use in diagnosing skull base or jugular foramen neoplasm (glomus tumors, schwannomas, and so forth) or metastatic disease responsible for multiple lower cranial nerve palsies. Two studies of skull base invasion in nasopharyngeal carcinoma found MRI to be more sensitive than CT for identifying bony invasion. Several investigators have found that MRI does not add additional sensitivity to CT in terms of identifying the presence of malignancy.

Dysphonia, and specifically vocal fold paresis, can result from intracranial processes as well. MRI and CT may be warranted if signs or symptoms concerning for stroke warrant intracranial imaging to evaluate for ischemic or hemorrhagic sources. Clearly, for patients with pacemakers or metallic implants, MRI may be contraindicated. In children with vocal fold palsy, one must balance the risk of radiation exposure with CT to the possible need for sedation with MRI. The actual dose of radiation received by the thyroid and its long-term effect are still uncertain. The risk of MRI is an approximately 5% chance of an episode of hypoxia during the required sedation. In patients with intravenous contrast allergies, gadolinium-enhanced MRI is likely the safer study.

Self-rated assessments

Several commonly used perceptual rating systems are intended to better characterize dysphonia and to assess the negative impact of voice disturbance on a patient’s quality of life. The more widely known among them are the 30-question Voice Handicap Index (VHI), with its revised, streamlined 10-question version (VHI-10), and the Voice-Related Quality of Life survey (V-RQOL). In severe voice disorders, patient ratings of severity and quality of life impact were highly correlated on each of the 3 instruments. Recent studies suggest this correlation persists even in mild to moderately severe dysphonia.

Although scores may be sensitive to change within each individual subject, the scores may be poorly correlated with the morbidity of the underlying disease process or objective measures of voice disorder. Studies validating use in other languages find that spasmodic dysphonia and functional disorders tend to produce worse ratings than nonbenign pathologies. A cross-sectional case-controlled survey of patients who underwent total laryngectomy showed a distribution of scores generally equivalent to or better than Chinese patients with benign voice disorders (39–48 vs 38–70). Additionally, a recent study of almost 500 public school teachers in Brazil using the VHI-10 showed little correlation between teacher ratings of impairment and quality of life and objectively identified voice disorders.

Clinician-rated measures

Two clinician-rated scales are commonly used to assess the acoustic quality and severity of voice disorders. The GRBAS (overall grade [G], roughness [R], breathiness [B], asthenia-weakness [A], and strain [S]) is a clinician-based 0-point to 3-point graded assessment of quality and severity of voice disorder. Although seemingly valid, some concerns exist about the use of this measure.

The Consensus Auditory-Perceptual Evaluation of Voice (CAPE-V) is another provider-rated system developed by the American Speech-Language-Hearing Association. It is a standardized measure of roughness, breathiness, strain, pitch, and loudness. Although it may have slightly better interrater reliability than the GRBAS, it is still subject to the experience of the rater and may be biased by lack of blinding of the assessor.

Although these tools allow for an objective quantification of the severity of voice disorders, no evidence has demonstrated that they influence the diagnosis or treatment of patients who present with dysphonia. Without data to suggest additional diagnostic or treatment benefit, these tools may be useful for research purposes and communication among clinicians, but use in clinical practice is at the discretion of the treating clinician.

Laryngoscopy

Visualization of the larynx is critical in any assessment of a patient with dysphonia. Laryngoscopy uses optics and light to allow the clinician to visualize the laryngeal structures. Traditionally, the larynx has been visualized in the awake clinic patient indirectly using a laryngeal mirror. Although the view may be adequate with a laryngeal mirror, functional examination can be limited, and full visualization may be limited. With the development of optics and associated technologies, laryngoscopy can be performed with a variety of endoscopes: rigid angled laryngoscopes, flexible fiberoptic laryngoscopes, and flexible distal chip laryngoscopes. Video cameras can also be added for further magnification and recording.

More than 20 years ago, a prospective, nonrandomized trial performed by Barker and Dort evaluated the ability to complete either a mirror or rigid endoscopic examination. In the patients who went on to have direct laryngoscopy, Barker and Dort evaluated the accuracy of findings between the 2 techniques. Among the 100 patients they tested, nearly half of patients could not tolerate mirror evaluation. More than 80% tolerated a rigid endoscopic examination. Fewer than 30% underwent direct laryngoscopy, and among them, both examination techniques proved largely accurate, with rigid endoscopic techniques having zero false-negative evaluations. With the significant advances made in endoscopic technology since that report, a 2009 study of 43 patients similarly compared rigid laryngoscopy using a 30° endoscope to mirror examination and showed statistically significant improvements in patient comfort with less gagging (80% preferred rigid endoscopy), improved visualization of laryngeal structures by physicians, and the ability to display results of endoscopic evaluation for patients to see simultaneously. By comparison, a single study has suggested that flexible fiberoptic visualization offers decreased patient discomfort relative to rigid endoscopy (evidenced by cardiovascular response to direct vs fiberoptic laryngoscopy in patients emerging from anesthesia following thyroidectomy) and improved visualization.

Uncontrolled, observational studies, and anecdotal and expert opinion suggest that the use of fiberoptic visualization often affords the ability to palpate the glottis and supraglottis for assessment of sensory function, allows for improved dynamic assessments, and may provide some improved visualization of the subglottic region. This must be weighed against good evidence that suggests image quality is improved with the use of rigid endoscopes, however. A randomized case-controlled direct comparison among the 3 most frequently used methods (flexible fiberoptic endoscopes, distal chip flexible endoscopes, and rigid angled endoscopes) in 2008 showed that although flexible fiberoptic endoscopes provide the most cost-effective option for visualizing the larynx, they provided less information than rigid visualization in nearly one-quarter of patients, most notably during stroboscopy.

Although both rigid and flexible endoscopes have specific strengths and weakness, one of the chief advantages of either method over mirror laryngoscopy is the simultaneous use of magnification, video recording, and stroboscopy.

Laryngostroboscopy

Although laryngoscopy alone can visualize anatomic abnormalities, such as masses and impaired mobility of the vocal folds, it cannot provide visualization of the mucosal vibration (the source of the voice). Under constant illumination, the vocal folds vibrate at a much higher frequency than the human eye can discern. Addition of a stroboscopic light source allows the viewer to discriminate the motion of the vibratory edge of the vocal folds in “slow motion.”

In comparison with laryngoscopy alone, stroboscopy improves diagnostic yield, as demonstrated in several observational studies over the past 30 years. In 1991, Sataloff and colleagues reported the largest of these studies, assessing nearly 1900 patients over a 4-year period. Additional diagnoses were discovered in 29% of patients, and the prestrobe diagnoses were found to be inaccurate in 18% of patients. Subsequent publication of 292 prospectively identified patients who underwent a similar protocol involving initial laryngoscopy followed by stroboscopy showed similar results, with stroboscopy altering the diagnosis and treatment outcome in 14% of the patients. A small (40 patients) retrospective review of stroboscopy use in the setting of laryngeal trauma found that even after computed tomography (CT) and laryngoscopy, stroboscopic evaluation replaced the need for direct laryngoscopy to evaluate mucosal integrity and vocal fold function in several patients. Avoidance of secondary trauma of operative direct laryngoscopy led to earlier discharge for matched grades of laryngeal injury.

A 2010 retrospective review of pediatric patients with unresolved dysphonia after prior endoscopy and treatment found the addition of stroboscopy (both rigid and flexible) identified a new diagnosis that resulted in additional therapy in nearly all patients.

Direct laryngoscopy

Operative direct laryngoscopy (with or without magnification) as a diagnostic tool may assist in establishing a diagnosis for dysphonia in patients with certain laryngoscopic findings (eg, a mass lesion). It may also be indicated in patients in whom awake visualization of the larynx cannot be achieved. Operative direct laryngoscopy offers the additional benefit of palpation of the cricoarytenoid joint and the mucosa of the vocal folds, as well as the opportunity for diagnostic biopsy. Phonomicrosurgical intervention can also be done concurrently with diagnosis in selected circumstances.

Although dynamic evaluation in the sedated patient is limited, multiple retrospective reviews suggest that the improved visualization provided by operative positioning, palpation, magnification, and improved depth perception of binocular microscopy results in alternate or additional diagnoses. Poels and colleagues found that, despite preoperative stroboscopy, alternate diagnoses were made in 36% of the 221 patients who underwent direct laryngoscopy. An additional 31% of patients had additional lesions (largely intracordal) discovered at the time of surgery. A more recent review of 100 patients at another tertiary care center identified additional lesions (often bilateral) in 9% of patients. Nearly half of these patients had a change in treatment plans after the altered diagnosis.

Laryngeal electromyography

Laryngeal electromyography (LEMG) assesses the electrical activity and the functional status of the innervation to the targeted laryngeal muscles (typically cricothyroid, thyroarytenoid, and often posterior cricoarytenoid muscles).

A 2005 study of the practices of laryngologists who belong to the American Broncho-Esphogological Association indicated that among respondents, 75% used LEMG to confirm or diagnose unilateral vocal fold immobility. Evidence to support its use in a purely diagnostic capacity is largely of a nonrandomized, retrospective nature, however. To address this issue specifically, the Neurolaryngology Study Group convened a multidisciplinary panel to examine the evidence for LEMG in diagnosis and prognosis. The diagnostic accuracy was based on multiple small studies and one large unblinded retrospective study, which confirmed the neurologic basis of vocal fold paresis or paralysis in 83% to 92% of cases and was able to contrast neurologic impairment with cricoarytenoid motion disorders in the remaining patients (2%–12%). One of the larger studies reviewed reported that LEMG led to a change in the type of imaging performed in 11% of patients and altered the timing or type of surgical intervention in another 40% of patients.

Meyer and Hillel published an updated review of the literature in 2009 of primarily level IV evidence. They identified a blinded study from Philadelphia that reported increased sensitivity for identification of a paretic nerve from 64% to 86%. Another reviewed study reported that LEMG altered the timing or choice of therapy in nearly 50% of patients. More recent studies (level III evidence) compared the efficacy of LEMG to laryngoscopy for diagnosis of neurologic impairment. Sataloff and colleagues reported that LEMG results corroborated laryngoscopic diagnosis in 95% of patients (661 of 689), and identified neurologic abnormality in 22% (14 of 62) without a prior diagnosis. Importantly, Gavazzoni and colleagues caution that no single electrophysiologic parameter alone confers a high sensitivity (although nearly all carried greater than 90% specificity) and adds that duration since onset of impairment decreases the diagnostic certainty.

Hydman and colleagues studied LEMG as a prognostic indicator in recurrent laryngeal nerve injury in 15 patients with vocal fold paresis 2 to 3 weeks after iatrogenic injury but anatomically intact recurrent laryngeal nerves. Patients with axonal injury based on LEMG findings had 50% significantly worsened functional and videostroboscopic outcomes.

Radiographic imaging

Although most patients with dysphonia do not require imaging, abnormalities in structure of the larynx or mobility of the vocal folds may prompt additional investigation with radiographic imaging. Imaging may be useful in assessing the extent of mass lesions. In malignancy, imaging allows assessment of regional lymphatic involvement, as well as defining the extent of the mass. CT or magnetic resonance imaging (MRI) can be used to assess for invasion of the laryngeal cartilage, which offers prognostic information for staging of laryngeal and hypopharyngeal cancer. MRI is highly sensitive for identifying cartilage invasion, but it is less specific than CT owing to increased signal patterns often caused by inflammation.

Imaging is also indicated if initial workup of dysphonia reveals a paralyzed vocal fold without a known cause. Historically, a chest radiograph and/or a neck CT with contrast was used to identify vascular anomalies or mass lesions. In recent years, radiographs have become extraneous, as both positive and negative results lead to CT imaging. In a recent prospective study by El Badawey and colleagues of 86 patients presenting with vocal cord palsy, 36% had positive CT findings, which correlated with the cause for immobility. Most of these were suspicious for malignancy in the lungs or mediastinum.

Skull-base imaging with MRI is indicated in vocal fold paresis with other cranial nerve palsies. Principally, expert opinion supports its use in diagnosing skull base or jugular foramen neoplasm (glomus tumors, schwannomas, and so forth) or metastatic disease responsible for multiple lower cranial nerve palsies. Two studies of skull base invasion in nasopharyngeal carcinoma found MRI to be more sensitive than CT for identifying bony invasion. Several investigators have found that MRI does not add additional sensitivity to CT in terms of identifying the presence of malignancy.

Dysphonia, and specifically vocal fold paresis, can result from intracranial processes as well. MRI and CT may be warranted if signs or symptoms concerning for stroke warrant intracranial imaging to evaluate for ischemic or hemorrhagic sources. Clearly, for patients with pacemakers or metallic implants, MRI may be contraindicated. In children with vocal fold palsy, one must balance the risk of radiation exposure with CT to the possible need for sedation with MRI. The actual dose of radiation received by the thyroid and its long-term effect are still uncertain. The risk of MRI is an approximately 5% chance of an episode of hypoxia during the required sedation. In patients with intravenous contrast allergies, gadolinium-enhanced MRI is likely the safer study.

Self-rated assessments

Several commonly used perceptual rating systems are intended to better characterize dysphonia and to assess the negative impact of voice disturbance on a patient’s quality of life. The more widely known among them are the 30-question Voice Handicap Index (VHI), with its revised, streamlined 10-question version (VHI-10), and the Voice-Related Quality of Life survey (V-RQOL). In severe voice disorders, patient ratings of severity and quality of life impact were highly correlated on each of the 3 instruments. Recent studies suggest this correlation persists even in mild to moderately severe dysphonia.

Although scores may be sensitive to change within each individual subject, the scores may be poorly correlated with the morbidity of the underlying disease process or objective measures of voice disorder. Studies validating use in other languages find that spasmodic dysphonia and functional disorders tend to produce worse ratings than nonbenign pathologies. A cross-sectional case-controlled survey of patients who underwent total laryngectomy showed a distribution of scores generally equivalent to or better than Chinese patients with benign voice disorders (39–48 vs 38–70). Additionally, a recent study of almost 500 public school teachers in Brazil using the VHI-10 showed little correlation between teacher ratings of impairment and quality of life and objectively identified voice disorders.

Clinician-rated measures

Two clinician-rated scales are commonly used to assess the acoustic quality and severity of voice disorders. The GRBAS (overall grade [G], roughness [R], breathiness [B], asthenia-weakness [A], and strain [S]) is a clinician-based 0-point to 3-point graded assessment of quality and severity of voice disorder. Although seemingly valid, some concerns exist about the use of this measure.

The Consensus Auditory-Perceptual Evaluation of Voice (CAPE-V) is another provider-rated system developed by the American Speech-Language-Hearing Association. It is a standardized measure of roughness, breathiness, strain, pitch, and loudness. Although it may have slightly better interrater reliability than the GRBAS, it is still subject to the experience of the rater and may be biased by lack of blinding of the assessor.

Although these tools allow for an objective quantification of the severity of voice disorders, no evidence has demonstrated that they influence the diagnosis or treatment of patients who present with dysphonia. Without data to suggest additional diagnostic or treatment benefit, these tools may be useful for research purposes and communication among clinicians, but use in clinical practice is at the discretion of the treating clinician.