A systematic review of causes of sudden and severe headache (Thunderclap Headache): should lists be evidence based?

Table 2 Estimated efficiency of systematic search for causes of sudden and severe headache

		In academic review
		Yes	No
In systematic review	Yes	69**	46
	No	4	*Estimated 3 articles unobserved

*Where the number of unobserved cases is equal to (46 × 4) / 69 (see reference[16, 26].
**If we count all vasoconstriction syndromes as one single cause, then the value of this cell in 45, but the number of unobserved cases would still be close to 3.

ISSN: 1129-2377