It is later revealed that Spike's hearing loss is the result of a chromosomal abnormality, not the car accident, when Spike goes to have Cochlear implant surgery.
After taking Spike to get Cochlear implant surgery to restore his hearing, Kendall is horrified and guilt-ridden when Dr. Joe Martin reveals to her and Ryan that Spike's hearing loss was in fact caused by a chromosomal abnormality and that it was purely coincidental that the abnormality manifested itself at the time of the car accident.