Your body has an unpredictable relationship with cybernetics. Unlike Cyber Rejection, an implant can give you no trouble at all for years, and then suddenly be rejected for no apparent reason, resulting in severe complications, or death.

If medical care fails a Very Difficult check, or does not have appropriate neurological facilities (unlikely if a licensed practicioner does the implantation), -2 to any attribute or -1D for any appropriate disadvantage (usually mental, sometimes physical) PER LEVEL check is missed.

Rejection is determined by GM fiat, or by rolling 2D each by the character and GM. The GM's roll is modified by the amount the implantation roll fails or succeeds by. If the GM rolls higher, the implant is rejected. The timing of the rejection is up to the GM--it may be years before ACCRS manifests, though one episode means subsequent episodes will display more rapid onset.