This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Larynx, Subject name: ENT
A patient with Pancoast's tumour develops loss of voice after radiation. It is due to 
Select and explain. 
A. Vocal cord infiltration with secondary, B. Involvement of recurrent laryngeal nerve, C. Irradiation to vocal cords, D. Radiation stenosis of larynx
B: Involvement of recurrent laryngeal nerve
Answer: B: Involvement of recurrent laryngeal nerve 
Explanation: The recurrent laryngeal nerve is involved in Pancoast's tumour. Pancoast's tumour is a tumour of the pulmonary apex. Right recurrent laryngeal nerve arises from the vagus at the level of the subclan aery, hooks around it and then ascends between the trachea and oesophagus. The left recurrent laryngeal nerve arises from the vagus in the mediastinum at the level of the arch of the aoa, loops around it and then ascends into the neck in the tracheo-oesophageal groove. Ref: PL Dhingra; Textbook of EAR, NOSE and THROAT; edition 6