( MaassenVanDenBrink ( ( says ( ( migraine headaches ) ( probably ( are ( ( ( caused ( by ( dilation ( of ( ( blood vessels ) ( in ( the head ) ) ) ) ) ) ) but ) ( located ( outside ( ( ( the brain ) , ) ( ( resulting ( in ( inflammation ( of tissue ) ) ) ) ( surrounding ( the vessels ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP MaassenVanDenBrink)) (VP (VBZ says) (SBAR (S (NP (JJ migraine) (NNS headaches)) (ADVP (RB probably)) (VP (VBP are) (VP (VP (VBN caused) (PP (IN by) (NP (NP (NN dilation)) (PP (IN of) (NP (NP (NN blood) (NNS vessels)) (PP (IN in) (NP (DT the) (NN head)))))))) (CC but) (VP (VBN located) (PP (IN outside) (NP (NP (DT the) (NN brain)) (, ,) (VP (VBG resulting) (PP (IN in) (NP (NP (NN inflammation)) (PP (IN of) (NP (NN tissue))))) (S (VP (VBG surrounding) (NP (DT the) (NNS vessels))))))))))))) (. .)))
MaassenVanDenBrink says migraine headaches probably are caused by dilation of blood vessels in the head but located outside the brain, resulting in inflammation of tissue surrounding the vessels.
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (NP (NN blood) (NNS vessels)) (PP (IN in) (NP (DT the) (NN head)))) (VP (VBP dilate)))) (, ,) (NP (NP (DT a) (NN migraine)) (, ,) (NP (DT a) (JJ severe) (NN headache)) (, ,)) (VP (MD can) (VP (VB occur))) (. .)))