Doctors worried that , because of her cerebral palsy , Lucy would never be able to speak or use sign language to communicate with her deaf sister , but after the first volume was made , Lucy started to sign , and later , to speak . Doctors worried that , due to her cerebral palsy , Lucy would never be able to speak or use sign language to communicate with her deaf sister , but after production of the first volume , Lucy began to sign , and later , to speak .