A 55-year-old man presents with a severe and unremitting left-sided headache for two days. There is no history of photophobia, nausea or vomiting, numbness or weakness, visual disturbances, altered mentation, loss of consciousness, or recent cranial trauma.
He also reports an intermittent fever of up to 39 °C (102.2 °F) for two weeks, associated with a 3 kg weight loss. No other symptoms were present.
His medical history is significant for ankylosing spondylitis for 30 years, which was complicated by aortic regurgitation 20 years ago. He defaulted on his treatment almost 15 years ago and has not been followed up since.
His surgical and family histories are unremarkable. He drinks socially and does not smoke. There is no history of recent travel, or contact with animals or sick individuals.
Close questioning reveals a visit to a dentist three weeks ago, for scaling. He did not inform the dentist about his comorbidities and had not received pre-procedural antibiotic prophylaxis.
A complete blood count is significant for a leukocyte count of 21,000/mm3 (normal: 4,500-11,000), with 85% neutrophils. His ESR is 102 mm/hour (normal: 0-22). Liver and renal functions are normal, as is a urinalysis. Chest x-rays show cardiomegaly.
A noncontrast CT brain shows no obvious mass lesions or features suggestive of focal or subarachnoid hemorrhage.