Example case - PABRLN Paralysis of the anterior branch of the recurrent laryngeal nerve
Etiology
This syndrome results from an injury to the recurrent laryngeal nerve. It may affect all, one or several of the intrinsic laryngeal muscles (thyroarytenoid, lateral cricoarytenoid, posterior cricoarytenoid, interarytenoid) except the cricothyroid. There may be varying degrees of paresis since the injury may be incomplete, reinnervation may occur or reinnervation with synkinesis may occur. This disordered reinnervation may cause isotonic contraction rather than functional contraction and movement.
Diagnosis
History
Typical complaints
onset
abrupt laryngitis if problem started after surgery or viral illness
thyroid surgery
carotid artery or vascular
Anterior cervical fusion or other neck surgery approached from the front.
chest or heart surgery may in particular injure the left side
gradual laryngitis if problem starts from tumor involving the path of the recurrent laryngeal nerve
skull base
neck
thyroid
lung
weak voice
Endurance is diminished (the patient may report a voice that functions for them for two to eight hours rather than a full day. They are using the cricothyroids to provide a some tension on the paralysed fold such that it will vibrate at a speaking pitch and this causes fatigue.)
cannot compete with background noise
trouble swallowing or choking on liquids
unable to sing
speaking pitch too high
Subtleties
This tends to be a disorder that is often just subclinical in its symptoms. The injured person gets along, but certain things suddenly tip the scale. The paralyzed cord is just barely compensating and a respiratory infection (cold) results in weeks of laryngitis instead of days. Loud talking makes the voice give out so the person habitually avoids background noise and talking loudly and never has trouble, then one day overuses the voice and is hoarse for a prolonged period afterwards. The thin or weak cord has been nursed along by the patient's vocal behaviour and then a straw “breaks the camels back”.
Occasionally after a surgery, the intubation or the surgery may injury the nerve to the vocal cords and I suspect that many times patients are told, “Just wait, it will get better.” which in some sense is the truth. The voice improves, but then... the problem hovers along in a subclinical fashion, appearing at some later time as a seemingly mysterious vocal weakness.
And because the vocal cord may be moving normally (in terms of abduction and adduction) or nearly normally, the patient will even give the history that they have seen an ENT doctor (otolaryngologist) and were told that the vocal cords were functioning normally.
Character of a patient with Unilateral Recurrent Laryngeal Nerve Injury
at times the patient will rate their current ability to talk rather than their innate degree of talkativeness and give a low rating
Vocal capabilities
Speaking voice
air wasting
Yelling voice
soft edged shout
luffing sound (asynchronous vibration like a sail flapping in the wind) on loud phonation at low pitch
Maximum phonation time
markedly reduced at anchor pitch (often less than 10 seconds)
Pitch range
obligate falsetto (physical inability to phonate in other than falsetto register) This is the opposite of a superior laryngeal nerve injury where the TA and LCA provide tension at low pitch but the cricothyroid is unable to provide additional tension to raise the pitch
diplophonia - less noticeable at higher pitch as cricothyroids begin to tense the atrophic vocal fold.
Gelfoam - indicated for about 1 months of relief when the possibility of spontaneous neurologic recovery exists but off market because of a recall on the product 4/2001.
Teflon
permanent
has long term risk of granuloma formation
Reinnervation
This procedure typically supplies bulk but not mobility to the intrinsic larynx of the larynx
It effectively provides the same benefit as a medialization procedure.
It takes 6 to 12 months to have an effect.
It does avoid the use of an implant.
Some other nerve may have to be used and sacrificed if a stump from the original nerve is unavailable.
Cranial nerve XII - Would you give up the use of a portion of your tongue (which is used for articulation) to have a stonger voice when an artifical implant would do the same thing?
Ansa cervicalis - I have not heard of any significant morbidity to sacrificing this nerve
