Autonomic dysreflexia is suspected when patients with spinal cord injury report headaches and hypertension. A 52-year-old man was diagnosed with C5-C6-C7 cervical spinal cord injury, traumatic subdural hemorrhage, intracerebral hemorrhage, and skull fracture. The patient underwent surgery at another hospital. The patient was hospitalized for comprehensive rehabilitation after 7 months. The assessment revealed an American Spinal Cord Injury Association Impairment Scale grade A at the C7 level due to complete spinal cord damage. Evaluation of muscle weakness that occurred after experiencing severe headache and hypertension revealed an intracerebral hemorrhage caused by cerebral venous sinus thrombosis. The patient showed improvement in muscle strength over time and was monitored for warfarin administration. Furthermore, cerebral venous sinus thrombosis should be considered as a differential diagnosis when patients with spinal cord injury who have experienced polytrauma complain of headache and hypertension, as they share clinical symptoms with autonomic dysreflexia. Additional evaluations, such as imaging examinations, should be conducted, as necessary.