Glottic insufficiency is characterized by incomplete closure of the vocal folds when phonating, which causes inappropriate leakage of air through the glottis on attempting to phonate and there is an increased risk of aspiration. A wide range of laryngeal symptoms including dysphonia, dysphagia, and aspiration with recurrent chest infections may result.
There are a variety of causes of glottic insufficiency. These include unilateral vocal fold paralysis or vocal fold paresis (unilateral or bilateral). Vocal fold immobility is a physical finding rather than a diagnosis. Therefore, it is essential to investigate the underlying cause as a priority. The largest case series to date cites the most common cause of unilateral vocal cord paralysis as surgical injury. This finding represents a shift in etiology as historically non-laryngeal malignancy was thought of as the leading cause of unilateral vocal fold paralysis.
Other causes of glottic insufficiency are presbylaryngitis, sulcus vocalis, scarring or deformation of the vocal fold. The latter may be congenital, idiopathic or secondary to iatrogenic causes such as prolonged intubation and laryngeal tumor excision.
A literature search does not reveal any comprehensive epidemiological data on glottic insufficiency; this may be due in part to the varying causes and complexity of causes of glottic insufficiency as well as likely under-diagnosis and the need to directly visualize the vocal folds to make the diagnosis.
One of the functions of the vocal folds is to protect the airway through their sphincteric action. This protection is particularly crucial during swallowing. The vocal folds also function to control airflow and pressure and to generate voice through vibration. A vocal note production is through the repeated contact vibratory movements of the vocal folds. Glottic insufficiency hampers these functions due to the incomplete contact between the two vocal folds.
Glottic insufficiency produces a variety of symptoms. From the start of the consultation, the clinician should begin to assess the patient’s voice informally; The patient may sound, and complain of, a weak voice, of effortful or painful phonation (odynophonia), and may have shortness of breath while talking and have a weak cough. There may be a history of dysphagia and recurrent chest infections due to aspiration. It is important to seek out “red-flag” symptoms such as unilateral throat pain, dysphagia, weight loss, which may suggest a neoplastic etiology.
Further history taking from the patient should ascertain whether there has been any recent surgery, in particular, cervical, thyroid or thoracic surgery. The patient’s vocal needs, whether socially or professionally, e.g., a professional singer, should be established as this may help determine the most suitable intervention.
The GRBAS (grade, roughness, breathiness, asthenia, and strain) scale is a widely used metric for evaluating vocal health and can be used in the clinic setting to rate the patient’s voice. Though it relies on perceptual evaluation, it may be useful as a comparative tool pre- and post-intervention.
Prior to a focussed examination of the phonatory apparatus, a general ear, nose and throat examination is in order. This may reveal causes of dysphonia extrinsic to the phonatory apparatus such as neck masses, nasal polyps, enlarged tonsils which can contribute to changes in voice quality. Palatal paralysis associated with an ipsilateral vocal fold paralysis is suggestive of a high vagal lesion. A full cranial nerve examination should also be performed to assess the involvement of other cranial nerves to rule out a high lesion.
Palpation of the larynx to assess for tenderness, suppleness or excessive tension may help in ruling out muscle tension dysphonia as a cause of the patient’s dysphonia. The patient can be asked to carry out the “ee-sniff” maneuver while the examiner slips their fingers behind the thyroid alar to directly palpate the cricoarytenoid joint. Vocal fold paralysis will result in no movement on the ipsilateral side, and a gentle tap felt on the examiner’s finger on the contralateral side.
Directly visualizing the glottis is the most sensitive and specific method for assessing vocal fold movement abnormalities.
Visualization can start with flexible laryngoscopy in the clinic. Vocal fold asymmetry and bowing may be visualized, as well as lesions such as vocal fold scarring and sulcus vocalis which may be causing a closure deficiency of the vocal folds. The exact vocal cord positioning should be noted and may indicate the level of injury; e.g., a paramedian positioning of the cords is suggestive of injury at the level of the recurrent laryngeal nerve compared with lateral positioning of the cords suggesting both recurrent laryngeal and superior laryngeal nerve injury.
Video stroboscopy allows assessment of the dynamic functioning of the vocal folds. Subtle abnormalities of mucosal motion can be detected, and functional deficits that accompany symptoms such as breathy phonation can undergo assessment.
Serology tests tend to add little value when evaluating glottic insufficiency, however, should the patient’s symptoms be suggestive of systemic disease as a cause of their glottic insufficiency, particularly if there is suspicion of rheumatoid arthritis or other autoimmune conditions, the relevant serology tests should be obtained.
Vocal fold immobility is a physical finding rather than a diagnosis per se. It is necessary to determine the underlying cause. Commonly there is no identifiable cause found during the initial consultation. A contrast CT or MRI from the level of the skull base down to the diaphragm may need to be done to assess for any lesions along the full course of the recurrent laryngeal nerve and the vagus nerve in the neck.
Laryngeal electromyography should be a consideration if there is a suspicion of the etiology of the vocal cord immobility. It aids in differentiating between motion impairment due to structural issues such as mechanical fixation, dislocation, and ankylosis of the cricoarytenoid joint which may cause a closure defect, versus motion impairment caused by denervation of the vocal fold.
Due to its poor sensitivity, acoustic voice recording is less useful as a tool for screening phonatory apparatus pathology. However, it helps aid the objective analysis of voice outcomes. The clinician can compare results based on computer-based analysis of acoustic signals rather than relying on patient or examiner subjective reporting.
Restoration of glottic competence may improve voice quality, dysphagia and reduce the risk of aspiration. Addressing these symptoms may improve the patient’s overall quality of life. The patient’s characteristics such as age, occupation, social circumstances as well as their preferences will help dictate management.
Whatever the specific etiology of the glottic insufficiency, voice therapy usually plays a significant role. For unilateral vocal fold paralysis, voice therapy is the initial management choice since up to 60% of cases will resolve spontaneously. For glottic scarring and sulcus vocalis, surgical results tend to be unpredictable and conservative measures of anti-reflux medications, steroids and voice therapy can serve as initial trial therapy. Voice therapy may be effective alone but can also be usefuld as an adjunct to surgical management.
Surgical options for glottic insufficiency aim to medialize the affected vocal fold such that glottic closure is achievable during phonation and the lower airway is better protected. The techniques employed are Injection augmentation, medialization thyroplasty (type 1 thyroplasty), laryngeal reinnervation and arytenoid adduction.
Injection augmentation utilizes a variety of materials injected into the vocal fold that provide bulk to restore the normal form and function of the vocal folds. It confers the advantage of producing immediate results and is a more minimally invasive option compared with laryngeal framework surgery. Materials currently used include absorable hemostatic powder, bovine and human-derived collagen, fat, dermal filler (calcium hydroxylapatite), hyaluronic acid gels, and micro-ionized acellular dermis. Teflon has previously had use as an injectable agent, however, it correlated with foreign body giant cell granulomas, and has associations with significant vocal deficits which have persisted even with corrective procedures.
In medialization thyroplasty, the position of the vocal cord is medialized by an external approach in which a permanent implant getis placed through a thyroid cartilage window. Medialization thyroplasty using various implants, commonly expanded polytetrafluoroethylene (E-PTFE) and silastic, is deemed the gold standard treatment for large glottic gaps and is the mainstay surgical intervention for unilateral vocal cord palsy.
Arytenoid adduction involves recreating the pull of the lateral cricoarytenoid muscle thus repositioning the vocal process medially. It tends not to be used as the sole procedure but is useful as an adjunct where there is impaired vocal process contact.
Non-selective laryngeal reinnervation involves anastomosing the ANCA cervicalis to the recurrent laryngeal nerve maintaining thyroarytenoid muscle bulk and tone. It has the potential for excellent vocal functioning as the vocal cords remain pliable compared with other techniques.
For sulcus vocalis and vocal fold scars, along with injection augmentation and medialization laryngoplasty which address the glottic gap, epithelium freeing techniques are commonly employed in combination with injection augmentation or implantation to help improve the vibratory function of the vocal fold.
Omori et al. performed a case series of patients with glottic insufficiency dysphonia that studied the influence of glottal gap size and etiology on vocal functioning. They found vocal fold palsy to be associated with the largest glottal gaps and significantly worse vocal function when compared with vocal fold atrophy and sulcus vocalis. However irrespective of the etiology, similar glottal gap sizes were associated with similar vocal functioning, suggesting glottal gap size is the primary influence of vocal function rather than the etiology of the glottic insufficiency.
The vocal function has been shown to improve with both medialization thyroplasty and injection augmentation techniques. [. Injection augmentation is safe and clinically effective and is performable with similar outcomes either under general anesthesia or, if the patient is an appropriate candidate, in a clinic setting.
Success with vocal fold fat injections tends to be variable due to the unpredictability of reabsorption of the fat in the first few weeks. Over-injection by 30% is required to allow for this implant loss, and patients should understand they will be dysphonic for approximately 3 weeks. As to whether any injectable agents are particularly superior to others, a Cochrane systematic review looking at patients with unilateral vocal fold palsy concluded that there is a current lack of evidence to suggest this.
Medialization thyroplasty has shown good outcomes while short-term vocal function results of augmentation may be good, for larger glottic gaps, medialization thyroplasty may provide superior longer-term results. There is a scarcity of data available as to the long-term effectiveness of injection augmentation. Dominguez et al. ran a case series of eighty-three patients, and they found that although initial voice outcomes were similar in both fat-injection and medialization thyroplasty groups, the effects of the fat injections wore off with time as evidenced by worse voice-handicap index and glottal index scores.
As well as glottic insufficiency affecting voice quality, glottis insufficiency may also cause dysphagia and aspiration with potential for recurrent lower respiratory tract infections. Medialization thyroplasty is predominantly considered a phonosurgical procedure. However, it has the potential to play a role in improving swallow function and preventing potential life-threatening consequences of aspiration. In their case series of 84 patients with unilateral vocal fold motion impairment, all had dysphonia, and 61% experienced swallowing difficulties).
Voice therapy may be effective alone but is also useful as an adjunct to surgery. The voice therapist can educate the patients as to how to efficiently optimize voice production as well as discourage counterproductive compensations that the patient may have developed such as extraneous neck muscle movements on attempting to phonate.
A systematic review of the current literature shows that a significant portion of unilateral vocal fold paralysis patients have dysphagia. In the context of glottic insufficiency, the focus is often on phonosurgery for voice improvement. However, symptoms of dyspnoea, dysphagia, and aspiration may be present in addition to vocal issues and may also be able to be equally addressed with the surgical interventions mentioned herein.
Management options for patients will need to be highly individualized based on a number of factors; the cause of the glottic insufficiency; whether the patient’s glottic insufficiency is likely to improve with time (for example unilateral vocal cord paralysis will improve in many cases which may negate the need for surgical intervention); the patient’s social and occupational factors. For example, a vocal cord palsy patient may be trialed on voice therapy, or have temporizing vocal cord injection augmentation as a first intervention while a professional voice user with a large glottic gap may require the more permanent option of laryngeal framework surgery. These factors are complex, and management of patients with glottic insufficiency is challenging. As such it requires an inter-professional and holistic approach to optimize patient management. As well as the involvement of specialist laryngologist and voice therapist in the patient’s care, other health professionals whose expert knowledge may be necessary for the patient’s care include neurologists, dieticians, nutritionist, nursing staff, psychologists and pharmacists.
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