Table 1 Search criteria to identify articles on sudden and severe headache (performed September 2009)

1. headache/di, ep, et, co, mo, cf, ra

1. exp primary headache/

2. headache disorders, primary/

2. exp cough headache/

3. vascular headaches/

3. exp exertional headache/

4. intracranial hypertension/

4. exp hypnic headache/

5. intracranial hypotension/

5. exp postural headache/

6. pseudotumor cerebri/

6. exp secondary headache/

7. intracranial vasospasm/

7. exp thunderclap headache/

8. (acute disease/ or catastrophic illness.mp. or critical illlness/ or emergencies/) and (headache/ or headache disorder/) [mp=title, original title, abstract, name of substance word, subject heading word]

8. exp vascular headache/

9. 7 and (headache/ or headache disorder/)

9. (coitus/ or orgasm/) and exp "headache and facial pain"/

10. thunderclap headache?.mp.

10. exp acute disease/ and exp "headache and facial pain"/

11. coit*.mp. and (headache/ or headache disorder/)

11. exp intracranial hypotension/

12. call fleming.mp.

12. exp brain pseudotumor/ and exp "headache and facial pain"/

13. worst headache?.mp.

13. exp brain vasospasm/ and exp "headache and facial pain"/

14. sentinel headache?.mp.

14. thunderclap headache?.mp.

15. explosive headache?.mp.

15. coit*.mp. and exp "headache and facial pain"/

16. reversible cerebral vaso*.mp.

16. call fleming.mp.

17. postpartum angio*.mp.

17. worst headache?.mp.

18. postpartum vasc*.mp.

18. sentinel headache?.mp.

19. 1 or 2 or 3 or 4 or 5 or 6 or 7 or 8 or 9 or 10 or 11 or 12 or 13 or 14 or 15 or 16 or 17 or 18

19. explosive headache?.mp.

20. reversible cerebral vaso*.mp.

21. postpartum angiopathy.mp.

Gross total references

Gross total references

Duplicates

Duplicate references

Net total references from MEDLINE

Net total references

All references Identified