Etiology
Comment
Paralytic etiology
Traumatic
Lesion of the recurrent laryngeal nerve or of the vagal nerve on both sides
Iatrogenic
Mainly during thyroid surgery
Neurologic
Myasthenia gravis, stroke, and amyotrophic lateral sclerosis are typical examples
Idiopathic
Reason remains unclear after complete diagnostic work-up
Non-paralytic etiology
Neoplastic
Tumorous infiltration of the vocal folds on both sides
Traumatic
Actually, posttraumatic, when an endolaryngeal lesion or endolaryngeal surgery has led to scar tissue formation hindering the vocal fold movements on both sides
Inflammatory
Seldom, for instance, by inflammatory reaction of the arytenoid cartilages due to rheumatoid arthritis
Overall, thyroidectomy still is the most frequent cause of BVFI, mostly by bilateral lesion of the recurrent laryngeal nerve. A steady decline in the proportion of BVFI attributed to thyroidectomy is seen in the last decades with a concurrent rise in trauma and malignancy. The proportion for BVFI due to thyroidectomy, malignancy, traumatic reason, neurologic disease, idiopathic reason, and nonclassified reasons is about 60%, 8%, 13%, 10%, 5%, and 6% [1]. BVFI due to a malignancy is more frequent in recurrent and metastatic than in primary disease. Most important malignancies beyond thyroid cancer are laryngeal cancer, esophageal cancer, and mediastinal lymph node metastasis. Traumatic lesions include blunt and open neck trauma but also other iatrogenic lesions than post-thyroidectomy (carotid endarterectomy, anterior cervical fusion, esophageal surgery). Bilateral trauma due to prolonged endotracheal tube intubation is very rare. When a BVFI occurs due to intubation, then it is mainly delayed due to subglottic or interarytenoid fibrosis and cricoarytenoid ankylosis. If BVFI occurs immediately after extubation, three reasons are discussed: cricoarytenoid joint inflammation, cricoarytenoid joint dislocation, and recurrent laryngeal nerve neurapraxia. It may occur when the endotracheal tube cuff lies immediately inferior to the true vocal folds. It is meant that the cuff can compress recurrent nerve fibers as they enter through the thyroid cartilage lamina [1].
BVFP is less frequent than unilateral paralysis. The ratio is about 1:5 [3]. The annual incidence of post-thyroidectomy BVFP for benign disease is estimated with <0.1–2.3% calculated on hospital-based data [4, 5]. The annual incidence of BVFP after total thyroidectomy for thyroid cancer is about 1.3% [4]. The true incidence of BVFI or BVFP based on population-based data is unknown. The annual surgical rate for BVFI calculated from population-based data is given with about 2.8/100,000 population [3].
Congenital BVFP in the neonate is very rare. Never the less, vocal fold paralysis is the second most common congenital laryngeal anomaly in newborns (30–60% of all laryngeal anomalies) [2]. The estimated incidence of congenital BVFP is 0.75 cases per million births per year [6].
5.3 Symptoms and Diagnostics
5.3.1 Symptoms
The classical presentation of patients with peripheral BVFI is the inability to abduct the vocal folds resulting in a narrow glottic chink. The presentation of a patient with BVFI varies. Initially a patient may have a breathy voice without respiratory complaints. Over time the voice can improve as airway symptoms worsen. Such patients may be in a precarious position with respect to the airway. Depending on the width of the remaining glottic chink, their body mass, the presence of comorbidity, and their usual physical activity, the patients may develop severe dyspnea. About 4–14% of these patients tolerates this condition and does not require any surgical treatment, though some of them may decompensate after years and surgery becomes inevitable [7]. In the worst case, BVFI, especially in cases of BVFP, after acute damage of the recurrent laryngeal nerve on both side or if on side was damaged already chronically and the other side is damaged during revision surgery, the free space left between the immobile vocal folds can be very small. Then, BVFP can even become life-threatening.
If no reinnervation occurs, BVFP results in progressive atrophization of the denervated laryngeal muscles, a process starting after nerve injury and causing the consequent gradual reduction of the muscle mass. Usually it is assumed that some spontaneous reinnervation due to axonal regeneration takes place within a year since the occurrence of BVFP. Hence, permanent surgical solutions are often applied only after six upon the occurrence of recurrent laryngeal nerve injury. Reinnervation after severe nerve lesion with muscle fiber degeneration is expected to require between 6 and 12 months to be completed but leads to misdirected reinnervation due to nerve sprouting. This results clinically in increase of muscle mass, i.e., less atrophy of the vocal folds and better resting tone, but still and permanently no movement is regained. Hence, permanent surgical solutions are often applied only after 6–12 months upon the occurrence of recurrent nerve injury.
Most patients with BVFI presenting for surgery are patients with BVFP. When these patients with BVFI present for surgical management, they often have dyspnea or stridor with an apparently normal voice. Voice quality is often better in patients with BVFI than in patients with unilateral immobility. Congenital BVFP causes stridor and respiratory distress in the neonate and infant.
5.3.2 Diagnostics
Diagnostics for BVFI have several important aims: clarifying the reason and type of BVFI, determining the need for surgery, as well as assessing the outcome. Investigations comprise review of patient’s history, physical examination with endoscopy, phoniatric examinations including stroboscopy, voice and speech tests, and electrophysiological tests. Testing the airway function includes imaging, pulmonary function testing, sleep studies, and validated quality of life questionnaires. Imaging is not described in more detail in this chapter as imaging is related to the underlying etiology or assumed cause. A sleep study might be indicated if sleep disturbances occur in a patient with BVFI as the disease might be compensated in the daytime but decompensated during the night. Table 5.2 gives an overview about the most important diagnostic investigations.
Table 5.2
Overview about the most important diagnostic investigations for patients with bilateral vocal fold immobility (BVFI)
Diagnostic investigation | Comment |
|---|---|
History | Comorbidity and for instance smoking habits can have influence on the functional severity of BVFI |
Physical examination | Physical resilience is important in the early postoperative phase, because due to laryngeal swelling, the symptoms can be transiently even more severe after surgery |
Laryngoscopy | Important to detect residual movement, tension of the vocal folds, and position of the arytenoid cartilages |
Stroboscopy | To confirm the immobility |
Voice and speech tests | Voice pathology has to be quantified at best before treatment and during follow-up after treatment |
Pulmonary function tests | At least a peak flow meter should be used, or, at best, spirometry should be performed together with a pulmonologist |
Sleep studies | Indicated in patients with breathing problems especially during the night |
Swallowing tests | Important when the patients has also swallowing complaints as some type of surgery might impair swallowing function |
Electrophysiological tests | Means mainly laryngeal electromyography, important to differentiate between paralytic and non-paralytic etiologies of BVFI. Import prognostic tool in patients with paralytic etiology |
Patient-related outcome measures (PROM) and quality of life assessments | Important instruments to evaluate the outcome of treatment |
Miscellaneous | Six-minute walk test gives a good impression about the functional impairment of the patient |
Imaging studies: necessary to clarify the etiology of BVFI |
5.3.3 Medical History and Demographic Data
The following symptoms, if present, should be addressed: breathing problems, snoring problems, voice quality, swallowing problems, problems while performing indoor activities, problems while performing outdoor activities, issues at workplace, and issues during leisure time. All comorbidities and long-term medication should be recorded. Severe illnesses and surgeries related to or which may be related to the BVFI should be reported. Not only standard demographic data can be relevant for treatment decision-making, but also data on smoking and drinking habits, body weight, and body mass index are relevant.
5.3.4 Physical Examination and Standard Otolaryngology Examination
Physical examination to assess the subject’s physical status is very important to estimate the physical resilience of the patients. Especially after transoral surgery, there might be a transient critical phase due to local postoperative swelling with even poorer respiratory function than before surgery. The most important step of the otolaryngological examination is the transnasal or transoral (rigid and/or flexible) endoscopic evaluation of the larynx. Endoscopy is needed to document the bilateral vocal fold immobility, the tension, flaccidity or atrophy of the vocal fold, and, where appropriate, endolaryngeal lesions or scar tissue. The position of both arytenoid cartilages is described (normal position, signs of fixation, medial tilting). At best, laryngoscopy is performed as videolaryngoscopy. Videolaryngocopy allows recording the natural status of the vocal folds and the configuration of the glottic gap during phonation and sniffing.
5.3.5 Phoniatric Examinations
Videostroboscopy should be part of the videolaryngoscopy. The videostrip should include, if possible, a short stroboscopy sequence during phonation vocal [ee:] at the normal speech frequency level with and without pitch (Fig. 5.1). Evaluation of the videostroboscopy is descriptive (impression of the examiner concerning, e.g., laryngeal tissue abnormalities, tissue appearance, vocal fold edge, ample laryngeal movement, arytenoid movement, supraglottic compression, vibratory characteristics, glottic closure, vibratory amplitude, vibratory symmetry, mucosal wave, appearance of laryngeal anatomy, and physiology description of vocal use).
Fig. 5.1
The videolaryngoscopy should include a short stroboscopy sequence during phonation vocal [ee:] at the normal speech frequency level with and without pitch. (a) The larynx at rest; (b) during phonation. Evaluation of the videostroboscopy is descriptive (impression of the examiner concerning, e.g., laryngeal tissue abnormalities, tissue appearance, vocal fold edge, ample laryngeal movement, arytenoid movement, supraglottic compression, vibratory characteristics, glottic closure, vibratory amplitude, vibratory symmetry, mucosal wave, appearance of laryngeal anatomy, and physiology description of vocal use)
There are manifold test procedures but no international standard for the evaluation of voice pathologies. Some of the procedures presented here are described in more detail in the guideline of the European Laryngological Society [8]. The following diagnostic procedure allows a comprehensive and detailed picture of the functional deficits of a patient with BVFI.
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