====== Subarachnoid hemorrhage headache ======

[[Headache]] accounts for approximately 2% of Emergency Department (ED) visits, with [[subarachnoid hemorrhage]] (SAH) occurring in 0.5% to 6%
((Bellolio MF, Hess EP, Gilani WI, VanDyck TJ, Ostby SA, Schwarz JA, Lohse CM,
Rabinstein AA. External validation of the Ottawa subarachnoid hemorrhage clinical
decision rule in patients with acute headache. Am J Emerg Med. 2015
Feb;33(2):244-9. doi: 10.1016/j.ajem.2014.11.049. Epub 2014 Dec 3. PubMed PMID:
25511365.
)).

Most patients with SAH experience abrupt headache, often [[thunderclap]] in nature, that reaches maximal intensity within one minute
((Ducros A, Bousser MG. Thunderclap headache. BMJ. 2013 Jan 8;346:e8557. doi:
10.1136/bmj.e8557. Review. PubMed PMID: 23303883.
)).

The patients without headache have no specific clinical characteristics over patients with common SAH
((Naganuma M, Fujioka S, Inatomi Y, Yonehara T, Hashimoto Y, Hirano T, Uchino M.
Clinical characteristics of subarachnoid hemorrhage with or without headache. J
Stroke Cerebrovasc Dis. 2008 Nov-Dec;17(6):334-9. doi:
10.1016/j.jstrokecerebrovasdis.2008.04.009. PubMed PMID: 18984423.
)).

Usually severe (classic description: “the worst headache of my life”) and sudden in onset
((Long B, Koyfman A, Runyon MS. Subarachnoid Hemorrhage: Updates in Diagnosis
and Management. Emerg Med Clin North Am. 2017 Nov;35(4):803-824. doi:
10.1016/j.emc.2017.07.001. Epub 2017 Aug 24. Review. PubMed PMID: 28987430.
)). 

[[Sentinel headache]]s are similar to SAH headaches, which may occur days to weeks prior to aneurysm rupture. The incidence appears in 10%-43% of patients with subsequent aneurysmal SAH
((Polmear A. Sentinel headaches in aneurysmal subarachnoid haemorrhage: what is 
the true incidence? A systematic review. Cephalalgia. 2003 Dec;23(10):935-41.
Review. PubMed PMID: 14984225.
))

If severe or accompanied by reduced level of [[consciousness]], most patients‘ present for medical evaluation. Patients with H/A due to minor hemorrhages will have blood on [[CT]] or [[LP]].
However, warning. headaches may also occur without SAH and maybe due to aneurysmal enlargement or to hemorrhage confined within the aneurysmal wall.

Warning H/A are usually sudden in onset, severe, and clear within 1 day.
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[[Headache]] developed almost instantaneously in only half the patients with [[aneurysm rupture]] and in two thirds of patients with benign [[thunderclap headache]] (BTH). In patients with acute severe headache, female sex, the presence of seizures, a history of loss of consciousness or focal symptoms, vomiting, or exertion increases the probability of [[aneurysmal subarachnoid hemorrhage]] aSAH, but these characteristics are of limited value in distinguishing aSAH from BTH. [[Aneurysm rupture]] should be considered even if focal signs are absent and the [[headache]] starts within minutes
((Linn FH, Rinkel GJ, Algra A, van Gijn J. Headache characteristics in
subarachnoid haemorrhage and benign thunderclap headache. J Neurol Neurosurg
Psychiatry. 1998 Nov;65(5):791-3. PubMed PMID: 9810961; PubMed Central PMCID:
PMC2170334.
)).
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The diagnosis of aSAH itself may not be a challenge as the classical presentation is sudden severe headache described as “worst headache ever experienced in life.” Other manifestations such as brief loss of consciousness, sentinel headache, nausea and vomiting, photophobia, neck stiffness, seizures and focal deficits may however cause diagnostic confusion
((Kassell NF, Torner JC, Haley EC, Jr, Jane JA, Adams HP, Kongable GL. The international cooperative study on the timing of aneurysm surgery. Part 1: Overall management results. J Neurosurg. 1990;73:18–36.)).