<prompt> In a patient with head injury, unexplained hypotension warrants evaluation of:Upper cervical spineLower cervical spineThoracic spineLumbar spine  <response>: High thoracic or cervical cord transection causes hypotension and bradycardia due to functional sympathectomy sometimes with Horner syndrome. Ref: Harrisons Principles of Internal Medicine, 15th Edition, Page 2441; Surgery: Basic Science and Clinical Evidence By Jeffrey A. Noon, Philip S. Barie, Randall Bollinger, 2008, Page 314 