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AN38.1-3 | Larynx — Part 3
SELF-CHECK
A. Permanent loss of singing voice
B. Development of aspiration pneumonia
C. Acute respiratory obstruction requiring tracheostomy
D. Hypocalcaemia from parathyroid removal
Reveal Answer
Answer: .
With bilateral RLN injury, both posterior cricoarytenoid muscles (the only abductors of the vocal cords) are paralysed. Both vocal cords lie in the paramedian position → the rima glottidis is severely narrowed → acute inspiratory stridor → respiratory failure. Emergency tracheostomy (or endoscopic cordotomy/arytenoidectomy) is required. Hypocalcaemia is also a concern after total thyroidectomy, but it is not the immediately life-threatening problem here.
SELF-CHECK
A. Glottic tumours are more radiosensitive
B. The true vocal cord has almost no lymphatic drainage → late nodal metastasis → T1 glottic cancer is typically N0 at presentation
C. Glottic tumours are histologically more differentiated
D. The glottis is more accessible to endoscopic laser surgery
Reveal Answer
Answer: .
The true vocal cords (glottis) have a paucity of lymphatics — there is almost no lymphatic drainage of the vocal cord itself. Therefore, T1 glottic tumours (confined to the cord) rarely spread to lymph nodes at presentation. In contrast, the supraglottis has rich lymphatics that drain bilaterally to deep cervical nodes → T1 supraglottic tumours are frequently N1/N2 at diagnosis. This anatomical difference explains the markedly different prognosis.
SELF-CHECK
A. Space between the thyroid cartilage and the hyoid bone (thyrohyoid membrane)
B. Space between the thyroid cartilage and the cricoid cartilage (cricothyroid membrane)
C. Space between the cricoid cartilage and the first tracheal ring (cricotracheal membrane)
D. Space between the 2nd and 3rd tracheal rings (standard tracheostomy site)
Reveal Answer
Answer: .
The cricothyroid membrane (conus elasticus) between the inferior border of the thyroid cartilage and the superior border of the cricoid cartilage is the correct site for cricothyrotomy. It is the most accessible avascular midline structure for emergency airway access, accessed inferior to the vocal cords (the upper airway obstruction). Tracheostomy is the elective procedure performed lower down (between the 2nd and 3rd tracheal rings). The thyrohyoid membrane is above the laryngeal inlet and would not bypass the obstruction.
CLINICAL PEARL
Right non-recurrent laryngeal nerve — a surgical trap: In approximately 0.5–1% of patients, the right RLN does not loop under the subclavian artery but instead takes a direct transverse course from the right vagus to the larynx, passing at the level of the inferior thyroid artery. This is ALWAYS associated with an aberrant right subclavian artery (arteria lusoria) arising from the descending aorta and passing posterior to the oesophagus. A surgeon who is unaware of this variant may mistake the non-recurrent RLN for the inferior thyroid artery and ligate it — causing permanent right vocal cord paralysis. Pre-operative CT angiogram identifies the vascular anomaly. Key rule: if you cannot find the right RLN in the tracheo-oesophageal groove, consider a non-recurrent variant and carefully trace the vagus for a direct transverse branch before applying any ligature near the inferior thyroid artery.