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Normal recovery:

–Occurs after a minor injury

–Restoration of complete range of motion

–Restoration of appropriate intentional motion

Synkinetic recovery:

–Occurs after a moderate injury

–PCA neurons split reinnervation to anterior adductor muscles and posterior abductor muscles

–On many occasions the vocal cords on endoscopy appear immobile, resting in or lateral to the midline, or move slightly and movement may be appropriate in direction

–Tension is maintained during phonation, rather than flutter

–Many times, the reinnervated vocal cord is tighter than the “normal” cord during phonation in the vocal underdoer or aged person with bowing of the “normal” cord

–Perhaps this represents a nearly 50: 50 arrangement when abductor and adductor neurons reinnervating LCA and TA

–There may also be a mix of abductor and adductor neurons reinnervating the PCA

–If normal recovery does not occur, this is the next best “ideal” spontaneous recovery. That is, it does not require intervention by surgery.

Dyskinetic recovery:

–More severe injury

–Overgrowth of PCA (abductor) neurons to LCA muscle

Vocal process may cross the midline

Vocal process may be highly angled toward midline

Vocal process may move in the opposite direction of intention

medial during inspiration

lateral during phonation

lateral during expiration

–Dyspnea or stridor

May be light to very strong

Not due to weakness, it is hyper reinnervation

May occur 10−20 years after injury

Often misdiagnosed as unresponsive asthma because of remote interval from injury

–Dyskinetic activity may increase with vocal use

–High rate of spontaneous laryngospasm

Responds to botulinum toxin injection into “paretic” cord

Responds to reinnervation of anterior branch with ansa cervicalis with improved stability and steady tension during phonation

Main issues in bilateral RLN injury:

–Initial symptoms after bilateral injury

Weak voice

Partially out of breath

Choking on water

–Symptoms after several months

PCA (abductor) neurons activate LCA movement toward midline

Louder voice, more dyspnea

More stridor

Increase frequency and intensity of laryngospasm

–Patients often learn to relax TA muscle and/or CTA muscle during inspiration

Shortens vocal cord

Allows central membranous cord to bow laterally

– Botulinum toxin injection

If placed into LCA muscle, tends to improve airway

If placed in TA muscle, may precipitate functional airway obstruction via Bernoulli effect moving membranous cord toward midline during inspiration.