A 39-year-old man is brought to the emergency department (ED) after his car struck a tree. He experienced a transient loss of consciousness with a 3-minute episode of retrograde amnesia at the scene of the accident, despite wearing a seat belt and shoulder harness. He was disoriented to date and place.
Now, in the ED, his pulse rate is 98 beats per minute; respiration rate, 20 breaths per minute; and blood pressure, 140/90 mm Hg. Temperature is not recorded. He complains of occipital headache and numbness and tingling in his left arm. He has a 3-cm tender area in the occipital scalp; there is no swelling or bony depression. Grip in the left hand and flexion and extension of the left forearm are weak. His left arm demonstrates a mild pronator drift; sensory testing reveals diminished sensation in the arm. His speech is slow, and he is unable to relate the history of the crash. Heart, lungs, and abdomen are normal.
He began having problems with his left arm 2 weeks earlier. He also had difficulty in walking and seemed confused. He was examined in the ED and told he might have had a stroke; however, a head CT scan was normal.
He has a history of coronary artery disease and hypercholesterolemia and takes atenolol(Drug information on atenolol), 25 mg/d, and lisinopril(Drug information on lisinopril), 10 mg/d, for hypertension. He smokes 1 pack of cigarettes daily and was a heavy drinker in the past. No history of seizures or neurologic disease.
A noncontrast head CT scan and cervical spine x-ray series are ordered.
What clues to the cause of this patient's symptoms are evident in the scan?