New-onset seizures after cranioplasty—a different view on a putatively frequently observed phenomenon

Background New-onset seizures after cranioplasty (NOSAC) are reported to be a frequent complication of cranioplasty (CP) after decompressive hemicraniectomy (DHC). There are considerable differences in the incidence of NOSAC and contradictory data about presumed risk factors in the literature. We suggest NOSAC to be a consequence of patients’ initial condition which led to DHC, rather than a complication of subsequent CP. We conducted a retrospective analysis to verify our hypothesis. Methods The medical records of all patients ≥ 18 years who underwent CP between 2002 and 2017 at our institution were evaluated including incidence of seizures, time of seizure onset, and presumed risk factors. Indication for DHC, type of implant used, timing of CP, patient age, presence of a ventriculoperitoneal shunt (VP shunt), and postoperative complications were compared between patients with and without NOSAC. Results A total of 302 patients underwent CP between 2002 and 2017, 276 of whom were included in the outcome analysis and the incidence of NOSAC was 23.2%. Although time between DHC and CP differed significantly between DHC indication groups, time between DHC and seizure onset did not differ, suggesting the occurrence of seizures to be independent of the procedure of CP. Time of follow-up was the only factor associated with the occurrence of NOSAC. Conclusion New-onset seizures may be a consequence of the initial condition leading to DHC rather than of CP itself. Time of follow-up seems to play a major role in detection of new-onset seizures.