Sentinel Headache: A Warning Sign Preceding Every Fourth Aneurysmal Subarachnoid Hemorrhage
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* H. Joswig
* J.Y. Fournier
* G. Hildebrandt
* M.N. Stienen

With great interest, we read the recent retrospective study of Oda et al1 in the *American Journal of Neuroradiology* reporting a 33.9% incidence of minor leaks preceding aneurysmal subarachnoid hemorrhage (aSAH) confirmed by neuroradiologic methods, in which the authors found a much lower incidence of sentinel headache (SH) of 11% by patient interview. Our data from an ongoing Swiss prospective observational study (ClinicalTrials.gov identifier: [NCT02129010](http://www.ajnr.org/lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT02129010&atom=%2Fajnr%2F36%2F9%2FE62.atom)) confirms that SH preceding aSAH is not by any means a rare phenomenon. In 8 (24.2%) of 33 patients, SH was confirmed by either the patient or next of kin. Contrary to those of Oda et al,1 the data from our study (Table) do not indicate any difference in radiologic bleeding characteristics, such as the presence of intracerebral hemorrhage and a higher rebleeding rate, or worse outcome in patients with SH. Nonetheless, mortality in our SH group was considerably high (37.5%), which once again renders distinguishing dangerous headache from innocuous headache on clinical grounds of paramount importance. In the absence of nuchal rigidity, a diminished level of consciousness, or focal neurologic deficits, any sudden onset of atypical headache should raise the suspicion of SH and should be followed by further investigations. It is therefore important to appreciate the sensitivity and specificity and the limitations of CT and lumbar puncture.2

View this table:
[Table1](http://www.ajnr.org/content/36/9/E62/T1)

Characteristics of patients with aneurysmal subarachnoid hemorrhage with and without sentinel headachea

Education on a primary care level is key to correctly identifying SH and preventing major aSAH with its subsequent morbidity and mortality. For example, a Swedish educational program for local physicians proved to be effective in reducing diagnostic errors by 77%.3 Whether any of our 8 patients confirmed positive for SH previously sought medical attention was not explicitly investigated by the study protocol. To consolidate awareness among primary care physicians, this short report of prospectively collected data complementing the retrospective study of Oda et al1 is meant to highlight the importance of SH preceding aSAH: About every fourth patient with aSAH has preceding symptoms.

## Acknowledgments

CSF protein INNOTEST ELISA test kits were provided by Innogenetics N.V. (Ghent, Belgium); this funding source has no role in the acquisition of the data stated in the current report.

The current study was approved by the ethics committee, St. Gallen, Switzerland (EKSG 13/011/1B). All study participants or substitute decision makers gave informed consent before taking part. Study protocol can be found at ClinicalTrials.gov (Identifier: [NCT02129010](http://www.ajnr.org/lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT02129010&atom=%2Fajnr%2F36%2F9%2FE62.atom)).

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*   © 2015 by American Journal of Neuroradiology