True statement about the paralysis of the recurrent laryngeal nerve is: (A) Common on left side, (B) 50% idiopathic, (C) Cord will lie laterally, (D) Speech therapy given
Answer is A. Paralysis of recurrent laryngeal nerve common on the left side.
The common causes are

Bronchogenic cancer
Accidental trauma
Thyroid surgery
Thyroid disease (benign or malignant)
Cervical lymphadenopathy
Carcinoma cervical oesophagus
Carcinoma thoracic oesophagus
Aortic aneurysm
Mediastinal lymphadenopathy