H. Joswig, J.Y. Fournier, G. Hildebrandt
Department of Neurosurgery
Cantonal Hospital St. Gallen
St. Gallen, Switzerland

M.N. Stienen
Department of Neurosurgery
Cantonal Hospital St. Gallen
St. Gallen, Switzerland

Department of Neurosurgery
Hôpitaux Universitaires de Genève
Geneva, Switzerland

With great interest, we read the recent retrospective study of Oda et al¹ in theAmerican 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) 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

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).

References

1. Oda S, Shimoda M, Hirayama A, et al. Neuroradiologic diagnosis of minor leak prior to major SAH: diagnosis by T1-FLAIR mismatch. AJNR Am J Neuroradiol 2015 May 14. [Epub ahead of print] » Abstract/FREE Full Text
2. Edlow JA, Caplan LR. Avoiding pitfalls in the diagnosis of subarachnoid hemorrhage. N Engl J Med 2000;342:29–36 » CrossRef » Medline
3. Fridriksson S, Hillman J, Landtblom AM, et al. Education of referring doctors about sudden onset headache in subarachnoid hemorrhage: a prospective study. Acta Neurol Scand 2001;103:238–42 » CrossRef » Medline

Reply

S. Oda, M. Shimoda, A. Hirayama, M. Imai, F. Komatsu, H. Shigematsu, J. Nishiyama
Department of Neurosurgery
Tokai University Hachioji Hospital
Tokyo, Japan

M. Matsumae
Department of Neurosurgery
Tokai University School of Medicine
Kanagawa, Japan

We appreciate the comments from Joswig et al. In our article, we reported that the true incidence of warning headache is challenging to establish because it is difficult to obtain complete information from patients in poor clinical condition.^1,2 Therefore, the diagnosis of a minor leak by interview has poor accuracy, and it is difficult to grasp the clinical implications of an interview-diagnosed minor leak. Thus, we investigated the clinical features of patients with minor leak diagnosed by T1-FLAIR mismatch at the time of admission.²

In our report, the incidence of patients whose history of warning headache was unknown by interview was high (46.5%, 59 of 127 cases). If we excluded these 59 patients whose history of warning headache was unknown by interview, warning headache determined by interview was 20.6% (14/68 patients). This is statistically similar to the percentage in the data of the letter by Joswig et al (24.2%) by the Fisher exact test (P = .424). Furthermore, the patients with warning headache diagnosed by interview had the same clinical features (elderly age, higher rate of rebleeding, intracerebral hemorrhage, and poor outcome) as patients diagnosed with minor leak by T1-FLAIR mismatch. The reasons for this discrepancy in clinical features between patients with warning headache diagnosed by interview in our data and patients with sentinel headache (SH) diagnosed by interview in the Joswig et al data are unknown. One reason may be the extremely low incidence of World Federation of Neurosurgical Societies (WFNS) grade I in patients with warning headache diagnosed by interview (43% [6 of 14] versus 81% [44 of 54] in patients without warning headache diagnosed by interview) in our data.

The overall percentage of WFNS grade I in patients who were able to confirm the presence or absence of a warning headache in an interview was high (74%, 50 of 68 patients), in contrast to that in patients whose history of warning headache was unknown by interview (36%, 21 of 59 patients). Thus, patients who could confirm the presence or absence of a warning headache in an interview had good status at admission, with patients presenting without a warning headache having the best prognosis. We think that the difference in clinical features of patients with warning headache between the 2 studies results from the low number of cases with poor clinical condition and the low number of the patients whose history of warning headache was unknown by interview in the data of Joswig et al. Furthermore, we think that there are too few cases in their data to examine the clinical features of patients with a warning headache. However, these opinions are speculative.

We agree with Joswig et al that SH preceding aneurysmal subarachnoid hemorrhage is not a rare phenomenon. We understand the importance of diagnosis at the time of SH preceding major attack. We expect further investigation by Joswig et al.

References

1. Jakobsson KE, Säveland H, Hillman J, et al. Warning leak and management outcome in aneurysmal subarachnoid hemorrhage. J Neurosurg 1996;85:995–99 » CrossRef » Medline
2. Oda S, Shimoda M, Hirayama A, et al. Neuroradiologic diagnosis of minor leak prior to major SAH: diagnosis by T1-FLAIR mismatch. AJNR Am J Neuroradiol 2015 May 14. [Epub ahead of print] » Abstract/FREE Full Text