The immediate and permanent frequency of injury to the marginal mandibular branch of the facial nerve (MMN) after
neck dissection has only scarcely been addressed in the medical literature. We investigated the risk of injury in 159 consecutive patients after
neck dissection for various reasons in level I B and level II A, respectively. In 95 patients with
oral cancer 13 (14%) of the cases had malfunction of the lower lip domain 2 weeks after
neck dissection in level I B indicating
paresis to the MMN. Follow-up analyses 1-2 years after the operation showed permanent
paralysis in 4 to 7% of the cases in whom two of them had the nerve sacrificed for oncologic reasons during the operation. In 18 patients with parotic
cancer the corresponding permanent frequency of MMN
paralysis was 11.1%. In 46 patients with
neck dissection in level II A but not in level I B, no
paresis of the MMN was registered. Recognition of the MMN during the operation, pre- or postoperative
radiation therapy, re-operation for deep
hemorrhage, age, gender or postoperative
infection did not have any statistically significant influence on the frequency of MMN injury. In conclusion we found a moderate risk of injury to the MMN after
neck dissection in level I B whereas the corresponding risk after level II A dissection was negligible.