( ( Migraine headaches ) ( ( are ( ( vascular headaches ) ( ( in which ) ( ( some event ) ( ( triggers ( the ( blood vessels ) ) ) ( to ( the ( brain ( to ( ( ( ( ( constrict and ) then ) dilate ) , ) ( leading ( to ( ( ( ( ( ( ( ( ( ( a ( severe headache ) ) , ) nausea ) , ) vomiting ) , ) ( eye pain ) ) , ) and ) ( other symptoms ) ) ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (JJ Migraine) (NNS headaches)) (VP (VBP are) (NP (NP (NN vascular) (NNS headaches)) (SBAR (WHPP (IN in) (WHNP (WDT which))) (S (NP (DT some) (NN event)) (VP (VBZ triggers) (NP (DT the) (NN blood) (NNS vessels)) (PP (TO to) (NP (DT the) (NN brain) (S (VP (TO to) (VP (VB constrict) (CC and) (RB then) (VB dilate) (, ,) (S (VP (VBG leading) (PP (TO to) (NP (NP (DT a) (JJ severe) (NN headache)) (, ,) (NP (NN nausea)) (, ,) (NP (NN vomiting)) (, ,) (NP (NN eye) (NN pain)) (, ,) (CC and) (NP (JJ other) (NNS symptoms)))))))))))))))) (. .)))
Migraine headaches are vascular headaches in which some event triggers the blood vessels to the brain to constrict and then dilate, leading to a severe headache, nausea, vomiting, eye pain, and other symptoms.
(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))) (. .)))