USMLE Step 1 Question 376

Question:

A 50-year-old man is brought to the emergency room complaining of a severe headache. The headache began 15 minutes earlier and has not subsided. There is no recent history of head trauma and his vision is normal. His blood pressure is 110/60. His heart rate is 85 bpm. Upon lumbar puncture, his sampled CSF appears bloody. Which of the following is most likely underlying cause of this man’s distress?

Correct Answer: C.  Subarachnoid hemmorrhage

A subarachnoid hemorrhage (C) results from the rupture of an aneurysm (usually berry) or an ateriovenous malformation (AVM).

Spinal tap reveals a bloody or xanthochromatic CSF specimen.

Epidural (A) or subdural (D) hematomas most likely result from blunt trauma to the head. While epidural hematomas are often immediate and secondary to fracture of the temporal bone, the subdural variety are insidious and a delayed consequence of bridging vein rupture.

Parenchymal hematomas (B) are caused by hypertension, amyloid angiopathy, diabetes mellitus and tumors. There is no such history here to support this diagnoses.

Temporal arteritis (E) is the most common vasculitis and affects arteries from large to small size. Symptoms are not as rapid in onset as described here and include jaw claudication and impaired vision.