Differential Diagnosis for Hoarseness of Voice after Surgery

Single most likely diagnosis

• A. Unilateral partial RLN injury: This is the most likely cause because the patient has undergone surgery for a large multinodular goitre, which is a procedure known to risk damaging the recurrent laryngeal nerve (RLN). The RLN is closely associated with the thyroid gland and can be injured during thyroid surgery, leading to vocal cord dysfunction and hoarseness. The fact that indirect laryngoscopy did not show visible pathology of vocal cord movement suggests a partial injury, which could still cause significant symptoms.

Other Likely diagnoses

• D. External laryngeal nerve injury: Injury to the external laryngeal nerve, which controls the cricothyroid muscle, can also occur during thyroid surgery. This could lead to changes in voice pitch and quality, contributing to hoarseness.
• B. Bilateral partial RLN injury: Although less common than unilateral injury, bilateral partial injury to the RLN could occur, especially in surgeries involving large goitres. This would likely result in more severe respiratory and voice symptoms.

Do Not Miss diagnoses

• Tracheomalacia: While less likely, tracheomalacia (softening of the tracheal cartilages) could be a complication of long-standing large multinodular goitre or the surgical procedure itself. It's a critical diagnosis not to miss because it can lead to significant respiratory distress.

Rare diagnoses

• Other rare nerve injuries or conditions: Other rare conditions, such as injury to other nerves in the vicinity or pre-existing conditions affecting the larynx, could potentially cause hoarseness. However, these are less likely given the context of recent thyroid surgery.