Extrusion–based additive manufacturing appreciates rising attention in the medical area due to its material flexibility, ability to fabricate complex, patient–specific parts and investment costs in the low to medium range. Thus, amongst other medical deployments, the application of the technology to fabricate permanent cranial implants is investigated for several years now. This mini–review gives an overview on the status quo of cranial implants by extrusion–based additive manufacturing with focus on the polymer polyetheretherketone (PEEK) and elucidates general requirements for an adequate implementation. Intra–operative AM to minimize the number of operations and/or operation time is revealed as important goal in the literature. However, this target is yet not satisfyingly accomplished by clinic–internal extrusion–based AM because of insufficient print qualities, the lack of clinical studies and undefined risk sharing. Further investigations should include a systematic evaluation of the complete benefit chain from data generating to clinical study including quality documentation and risk management. Consecutively, a successful result of such investigations would be a vital step towards clinical acceptance of extrusion–based AM for cranial implants made of PEEK.