(S (S (S (BASENP (NN DCA)) (VP (VBZ is) (VP (VBN known) (S (VP (TO to) (VP (VB be) (ADJP (RB relatively) (JJ safe)))))))) (COMMA ,) (SBAR (IN although) (S (NP (NP (BASENP (NN pain)) (COMMA ,) (BASENP (NN numbness))) (CC and) (BASENP (NN gait) (NNS disturbances))) (VP (MD may) (VP (VB occur)))))) (PERIOD .))