• It most commonly occurs in patients with preexisting pituitary adenomas, but 3 out of 4 patients with pituitary adenomas are unaware of their diagnosis.
• Patients may acutely present with thunderclap headache, with or without visual field deficits or cranial nerve dysfunction. They may also have meningeal symptoms due to extravasation of blood into the subarachnoid space.
• Endocrine dysfunction is common but not readily diagnosed in the ED.
• Symptoms may be triggered by some hormonal treatments (e.g. GnRH agonists for prostate CA), head trauma, angiographic procedures, or anticoagulation therapy.
• CT is diagnostic in only one-third of cases, but can reveal the intrasellar mass in 80% of cases, and therefore should be the initial test. Blood may be missed in subacute cases.
• MRI is the test of choice, with a sensitivity of over 90%.  

Bottomline: Keep pituitary apoplexy in your differential when considering SAH or meningitis, especially in the presence of risk factors, and have a low threshold to order an MRI. 

References