Sentinel headache in intracranial aneurysms: this stranger

Key point:

    • To understand the relationship between sentinel headache and subarachnoid hemorrhage (SAH);

    • To understand clinical significance that SH has in unruptured intracranial aneurysms (IUAs).

The presence of a severe, sudden headache, often referred to as a warning leak, minor leak, or sentinel headache (SH), during the days or weeks before subarachnoid hemorrhage (SAH) has been reported in 15% to 60% of all patients admitted with an SAH. The clinical significance and pathophysiology of SH have been a matter of debate. In their studies, Linn et al.[1] defined SH not as a less serious variant of subarachnoid hemorrhage, and Jakobbson et al.[2] stated that an active diagnostic attitude toward patients experiencing a sudden and severe headache is warranted, as it offers a means of improving overall outcome in patients with SAH. However since it is most often retrospectively diagnosed, some researchers have even questioned the existence of SH and they attributed its high incidence to a "retrospective bias".

In 2006, starting from the hypothesis that there is a link between the aneurysmal SAH and the clinical sign of SH,  Beck et al.[3] investigated the relation between SH and aneurysm re-bleeding, comparing the re-bleeding rate of patients who presented with SH before the index SAH and those without SH.

Sentinel Headache definition

1 Severe headache of unknown character and intensity lasting at least 1 hour in the last 4 weeks before the index SAH
2 Improvement before the index SAH or another deterioration that led to a diagnosis of SAH
3 Previous condition with a lack of a proven diagnosis of SAH.

Authors included 237 consecutive patients with SAH proven by computed tomography (CT) or lumbar puncture. They recorded all cases of SH and pre-operative re-bleeding; all patients underwent an early surgery (24 to 48 hours).

Association SH and Re-bleeding

OR (SH – rebleeding /SH- no rebleeding) 13.6 (95% CI, 5.2 to 35.1; P0.0001)
RR (SH – rebleeding /SH- no rebleeding)

9.0 (95% CI, 4.1 to 19.7)

This study demonstrated that aneurysm re-bleeding strongly correlate with SH, since patients with SH have a risk of an early re-bleeding 10-fold higher than those without SH.

However, there have not been identified specific clinical features to distinguish SH from other types of headache. Indeed, the diagnosis of SH is based on the definition of symptoms and exclusion of hemorrhagic manifestations. But, in patients with UIAs whether the headache  comes from the aneurysm is not clear. Recently, some researchers[4-5-6] tried to answer this question, analyzing SH from the neuroradiological point of view; they showed an association between SH and susceptibility changes (SWI sequences) around the aneurysm. In particular, Wan et al.[6] in his study divided 36 patients with UIAs in two groups: SH group, those with sudden and severe headache with no clear reason occurring within 4 weeks before admission, and non-SH group, all other patients. All patients were studied with DSA and SWI. For all patients were calculated PHASES score, size ratio, aspect ratio and inflow angle.

What did they found?


They found that abnormal signals on SWI sequence were independently associated with sentinel headache (P=0.001).

SH (N=15) vs. non-SH (N=20)
Size larger in SH group
Irregular shape more irregular in SH group
Size ratio greater in SH group
Aspect ratio greater in SH group
Inflow angle greater in SH group


SH (N=15) non-SH (N=20)
PHASES score 7.47±2.97 5.52±3.79


Authors concluded that SH could be identified with neuroradiological imaging and that patients with SH had significantly higher PHASES scores than those without SH. UIAs in the SH group had more “dangerous” characteristics.


In conclusion:

  • Despite some researchers questioned the existence of SH and attributed its high incidence to retrospective bias, the correlation between SH and aSAH found in many studies elucidates about its existence and importance.
  • Identification of SH in a detailed medical history is mandatory in patients with aSAH, since patients with SH have a risk of re-bleeding 10 times higher than those without SH.
  • Treatment of UIAs should be taken into consideration for patients with SH, since in these cases the PHASES score is higher than that in those without SH.
  • SH could be a potential manifestation of aneurysmal changing potentially identifiable in the MR imaging.



1.F H Linn, E F Wijdicks, Y van der Graaf, F A Weerdesteyn-van Vliet, A I Bartelds, J van Gijn. Prospective study of sentinel headache in aneurysmal subarachnoid haemorrhage. Lancet. 1994 Aug 27;344(8922):590-3. doi: 10.1016/s0140-6736(94)91970-4.

2.K E Jakobsson, H Säveland, J Hillman, G Edner, S Zygmunt, L Brandt, L Pellettieri. Warning leak and management outcome in aneurysmal subarachnoid hemorrhage. J Neurosurg. 1996 Dec;85(6):995-9. doi: 10.3171/jns.1996.85.6.0995.

3.Jürgen Beck, Andreas Raabe, Andrea Szelenyi, Joachim Berkefeld, Rüdiger Gerlach, Matthias Setzer, Volker Seifert. Sentinel headache and the risk of rebleeding after aneurysmal subarachnoid hemorrhage. Stroke. 2006 Nov;37(11):2733-7. doi: 10.1161/01.STR.0000244762.51326.e7. Epub 2006 Sep 28.

4.Wycliffe ND, Choe J, Holshouser B, et al. Reliability in detection of hemorrhage in acute stroke by a new threedimensional gradient recalled echo susceptibility weighted imaging technique compared to computed tomography: a retrospective study. J Magn Reson Imaging 2004; 20: 372–377.

5.Haacke EM, Xu Y, Cheng YN, et al. Susceptibility weighted imaging (SWI). Magn Reson Med 2004; 52: 612–618.

6.Zheng Wan, Hao Meng, Ning Xu, Tianyi Liu, Zhongping Chen, Yang Sun, Honglei Wang. Clinical characteristics associated with sentinel headache in patients with unruptured intracranial aneurysms. Interv Neuroradiol. 2020 Nov 4;1591019920971977. doi: 10.1177/1591019920971977. Online ahead of print.

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