Incidence and Characteristics of Cranial Nerve Injuries: A Nationwide Observational Study in Japan.

Background: Large-scale data on cranial nerve injuries are scarce. Methods: This study enrolled 361,706 patients registered in the Japanese Trauma Data Bank from 2004 to 2018. We selected patients with cranial nerve injury using the corresponding Abbreviated Injury Scale codes and examined the incidence and characteristics. Results: In total, 347,101 patients were eligible for inclusion in our analysis. By mechanism of trauma, all cranial nerve injuries occurred in <1% of registered cases. The highest incidence was 0.2190% (55/25,117) for facial nerve injury in bicycle crash. By cause of trauma, all cranial nerve injuries occurred in <1% of registered cases. The highest incidence was 0.1943% (37/19,044) for facial nerve injury in occupational injury. No patients with spinal accessory nerve injury were observed. The most common cranial nerve injury was to the facial nerve (n = 278). Most cranial nerve injury patients are in the 30s to 50s age range, and there was a male predominance. Multiple cranial nerve injuries were observed in 81 patients. Many cranial nerve injury cases are complicated by skull base fractures. Conclusions: We revealed the incidence and characteristics of cranial nerve injury. Our findings may help physicians detect these injuries at an early stage in patients at risk.