(S (S (BASENP (NNS Migraines)) (VP (VBP are) (VP (VP (VBN described) (PP (IN by) (BASENP (DT the) (NNP World) (NNP Health) (NNP Organisation)))) (PP (IN as) (NP (BASENP (DT a) (JJ major) (JJ worldwide) (NN cause)) (PP (IN of) (BASENP (NN disability)))))))) (PERIOD .))