Hoarseness After Thyroidectomy: Recurrent Laryngeal Nerve Injury, Prevention and Treatment

The recurrent laryngeal nerve (RLN) leaves the vagus (CN X) and reaches the larynx. The left RLN loops around the aortic arch (long course); the right RLN loops around the subclavian artery (short course). The left RLN is therefore longer and more vulnerable; the right has a non-recurrent variant in 0.5%.

The RLN runs behind the thyroid lobe between trachea and oesophagus. Identifying and preserving the nerve during thyroidectomy is the golden rule. It enters near the lower pole, ascends to the cricoid, and enters the larynx near Berry's ligament — injury is most common around this point.

RLN innervation: posterior cricoarytenoid (PCA — the only vocal fold abductor), interarytenoid, lateral cricoarytenoid, vocalis and thyroarytenoid muscles (closure and tensioning). Unilateral RLN injury: vocal fold paralysis (usually paramedian position), hoarseness, breathy voice, aspiration risk during swallowing. Bilateral injury: stridor + respiratory distress + emergent tracheostomy.

External branch of the superior laryngeal nerve (SLN-EB): innervates the cricothyroid muscle, which tenses and elongates the vocal fold. Injury: loss of high frequencies, perceived "thinness" and reduced projection. Singers feel this distinctly. SLN-EB injury frequency 5-15% but mostly subclinical.

Anatomical variants: non-recurrent right RLN (0.5% — emerges directly from the vagus at neck level), variants of Berry's ligament, tubercle and tracheoesophageal groove positions. IONM in every case helps manage these. We expand on the clinical framework in our thyroid surgery programme.

RLN injury (most critical): roughly 5-8% transient, 1-2% permanent in experienced hands. Mechanisms: traction (intraoperative pulling — the most common), compression (forceps/retractor pressure), thermal injury (cautery or harmonic scalpel heat), transection (rarest but most severe), ischaemia (devascularisation), suture entrapment (nerve inadvertently ligated).

Clinical consequence depends on injury degree: neuropraxia (transient, recovers in 3-6 months), axonotmesis (axon cut but sheath intact — partial recovery in 6-12 months), neurotmesis (full transection — no spontaneous recovery, needs reconstruction).

Superior laryngeal nerve (SLN-EB) injury: SLN-EB runs near the upper thyroid pole. Injury: loss of high frequencies, voice "thinning". Typically noticed by singers and high-pitched voice users.

Other causes:

Intubation irritation: endotracheal tube pressure on the vocal folds; oedema and mild localised damage. Usually resolves in 3-7 days.

Postoperative oedema: tissue oedema affects vocal fold function transiently. May last 1-2 weeks.

Postoperative haematoma: blood collection in the surgical bed compressing the RLN. Emergency drainage required — hoarseness + neck swelling + dyspnoea is an urgent picture.

Laryngospasm / reflex oedema: rare; transient hoarseness without vocal fold injury.

Pre-existing voice issue: subclinical preoperative vocal fold pathology (polyp, haemorrhage) noticed after surgery. Hence preoperative flexible laryngoscopy is recommended, especially in professional voice users.

IONM is the gold standard in modern thyroid surgery. How it works: a special endotracheal tube with electrodes at vocal fold level + a hand-held stimulator probe used by the surgeon. The surgeon stimulates the nerve and receives an EMG response — real-time sound and waveform.

Advantages: safer anatomical nerve identification (especially with variants), early detection of nerve traction and thermal injury, confirmation of nerve integrity at end of surgery, decision-making for proceeding to contralateral side in staged thyroidectomy.

IONM types: intermittent IONM (non-continuous, probe-driven stimulation — most common), continuous IONM (vagal continuous electrode — used in advanced cases or substernal goitre).

What IONM does not do: it does not eliminate nerve injury (surgeon experience remains critical), does not locate the nerve visually, does not change the oncologic extent of surgery.

When the nerve signal is lost: the surgeon immediately changes manoeuvres — reducing traction, removing thermal sources, lowering cautery settings. If the signal returns surgery continues; if not, contralateral surgery is postponed (to avoid the bilateral RLN injury nightmare).

IONM impact: meta-analyses show RLN injury rate reduced by about 50% (especially in high-risk cases). Modern endocrine surgery without IONM is controversial. For the related clinical reference, see thyroidectomy page.

Routine day-1 assessment: ask the patient about voice quality, get them to say "aaa", check simple speech. Significant hoarseness triggers flexible laryngoscopy.

Flexible laryngoscopy: a 5-minute office procedure assessing vocal fold mobility. Findings: full mobility — nerve preserved; full paralysis (paramedian position) — RLN injury; partial paresis (reduced motion) — neuropraxia or partial injury; bilateral immobility — bilateral injury (EMERGENCY — respiratory distress, may need tracheostomy).

Laryngeal electromyography (LEMG): for advanced cases or prognostic evaluation. Gives true prognosis on innervation. Performed 4-6 months postop (acute phase difficult to interpret).

Imaging: neck US/CT in suspected haematoma. Visualising RLN path is rarely needed.

Voice quality measures: Voice Handicap Index (VHI), GRBAS scale, acoustic analysis (jitter, shimmer, harmonics). Important for voice therapy follow-up.

Aspiration risk: swallowing assessment (FEES — fibre-optic endoscopic evaluation of swallowing). RLN paralysis patients have a 20-30% aspiration risk. Early intervention (diet, posture, injection medialisation if needed) prevents aspiration pneumonia.

Transient paresis / mild cases: voice rest (1-2 weeks), voice therapy (SLP), gentle voice exercises. Most resolve in 3-6 months.

Early (3-6 month) intervention: if voice quality is poor or aspiration risk exists, early injection medialisation is considered. Materials: gelfoam (temporary, 4-6 weeks), hyaluronic acid (3-6 months), calcium hydroxylapatite (1-2 years), autologous fat (long-term but absorbable).

Injection medialisation: local anaesthesia, office or short-stay procedure. The paralysed vocal fold is brought toward the midline, allowing the healthy fold to close better. Rapid result (days-weeks), reversible.

Long-term treatment (beyond 6 months — if nerve does not recover spontaneously):

Type 1 thyroplasty (medialisation laryngoplasty): a window in the thyroid cartilage is opened and the vocal fold pushed medially with a silastic block or Gore-Tex implant. Under local anaesthesia, real-time voice tuning. A durable solution with excellent voice improvement.

Arytenoid adduction: combined with thyroplasty to close the posterior glottic defect. Added in advanced cases.

Laryngeal reinnervation: ansa cervicalis to RLN anastomosis. Effective but results appear in 6-12 months. Often preferred in younger patients (regeneration capacity).

Bilateral RLN paralysis: the hardest situation. Acute: tracheostomy (permanent or temporary). Late: glottic widening (posterior cordotomy, arytenoidectomy) — voice slightly worse but airway opens. Reinnervation attempts also done.

Voice therapy: foundational in all cases — preop evaluation, early postop start, adaptation. Weekly SLP sessions for 12-16 weeks. We share patient experiences on our Istanbul thyroid surgery page.