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 underwent surgery for a large multinodular goiter, which increases the risk of injury to the recurrent laryngeal nerve (RLN). The RLN is closely associated with the thyroid gland and can be easily damaged during thyroid surgery, leading to hoarseness of voice. The fact that indirect laryngoscopy did not show visible pathology of vocal cord movement suggests a partial injury, which can still cause significant symptoms.

Other Likely diagnoses

• D. External laryngeal nerve injury: The external laryngeal nerve (ELN) is also at risk during thyroid surgery. Injury to the ELN can cause weakness of the cricothyroid muscle, leading to changes in voice pitch and hoarseness. This diagnosis is less likely than RLN injury but still a possibility given the surgical context.
• B. Bilateral partial RLN injury: While less common than unilateral injury, bilateral partial RLN injury can occur, especially in surgeries involving large goiters. This would lead to more severe voice changes and potentially respiratory difficulties, but the fact that only hoarseness is mentioned makes this less likely.

Do Not Miss diagnoses

• C. Tracheomalacia: Although rare, tracheomalacia (softening of the tracheal cartilages) can be a complication of thyroid surgery, especially if there was significant manipulation or injury to the trachea. This condition can lead to respiratory distress and is critical to identify early. While the primary symptom is hoarseness, the potential for airway compromise makes this a "do not miss" diagnosis.

Rare diagnoses

• Other rare causes of hoarseness after thyroid surgery might include injury to other nerves or structures in the neck, but these are less likely and would typically be associated with additional symptoms or findings not mentioned in the scenario.