To find a specified diagnosis for every patient investigated in the hospital emergency room for acute headache suspicious of subarachnoid haemorrhage (SAH), and to describe similarities and differences between the diagnostic groups.
We used a standardized set of questionnaires and supplementary tests, including cerebral computed tomography (CT) and if needed lumbar puncture, in the investigation of the patients. Two neurologists diagnosed the same cases independently.
We found 30 different diagnoses as the cause of acute headache. Sixteen per cent had a SAH, and 57% had a primary headache. Patient characteristics, conditions at headache onset and accompanying symptoms were surprisingly similar in the diagnostic groups. For three SAH patients, it took 30 min to reach maximum pain intensity. In all diagnostic groups, a large proportion of the patients reached maximum pain within 60 s.
To distinguish between benign and malignant causes of acute headache is difficult based on clinical features. The consistent use of CT and lumbar puncture is valuable when investigating sudden onset 'first or worst headache ever'. This can reduce the risk of missing a SAH diagnosis, and make it possible to give more exact diagnoses to patients suffering from both primary and secondary headaches.