Most common cause of vocal cord palsy is
Neuritis or surgical trauma (thyroidectomy) is the most impoant cause. Thyroid surgery is the most common cause when both recurrent and external laryngeal nerves of one side may be involved. Ref: PL Dhingra Textbook of Ear, Nose and Throat, Edition 6, page - 300
Surgical
Inflammatory
Trauma
Malignancy
Larynx