In a patient with head injury, unexplained hypotension warrants evaluation of:
High thoracic or cervical cord transection causes hypotension and bradycardia due to functional sympathectomy (sometimes with Horner syndrome). Ref: Harrison's 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
Upper cervical spine
Lower cervical spine
Thoracic spine
Lumbar spine