( ( Migraine headaches ) ( ( are ( ( associated ( with ( ( intense ( ( constriction and ) dilation ) ) ( of ( the ( blood vessels ) ) ) ) ) ) ( in ( ( a region ) ( of ( the brain ) ) ) ) ) ) . ) )
(ROOT (S (NP (JJ Migraine) (NNS headaches)) (VP (VBP are) (VP (VBN associated) (PP (IN with) (NP (NP (JJ intense) (NN constriction) (CC and) (NN dilation)) (PP (IN of) (NP (DT the) (NN blood) (NNS vessels))))) (PP (IN in) (NP (NP (DT a) (NN region)) (PP (IN of) (NP (DT the) (NN brain))))))) (. .)))
Migraine headaches are associated with intense constriction and dilation of the blood vessels in a region of the brain.
(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))) (. .)))