She was not able to speak, but appeared to comprehend well.
 Patient suffered a stroke
(ROOT (S (S (NP (PRP She)) (VP (VBD was) (RB not) (ADJP (JJ able) (S (VP (TO to) (VP (VB speak))))))) (, ,) (CC but) (S (VP (VBD appeared) (S (VP (TO to) (VP (VB comprehend) (ADVP (RB well))))))) (. .)))
(ROOT (S (NP (NN Patient)) (VP (VBD suffered) (NP (DT a) (NN stroke)))))
( ( ( ( ( She ( ( was not ) ( able ( to speak ) ) ) ) , ) but ) ( appeared ( to ( comprehend well ) ) ) ) . )
( Patient ( suffered ( a stroke ) ) )