Overall , complete headache relief was observed in only 1 participant ; 16 of 45 ( 35.6 % ; 95 % CI 21.8 to 51.2 ) had a reduction in headache of 33 % or more and 8 of 45 ( 17.8 % ; 95 % CI 6.1 to 29.4 % ) had a minimum clinical significant difference of 30mm or more on VAS with 4 in each group .