Using the Masseteric Artery to Navigate the Masseteric Nerve in Facial Reanimation Surgery

Background and Objectives: The masseteric artery (Ma) enters the masseter muscle (Mm) together with the masseteric nerve (Mn) via the mandibular notch. Morphological detail on the intramuscular course of the Ma and its relationship to the Mn remains scarce to date. When utilizing the Mn in facial reanimation surgery, a constant relationship between the Ma and Mn could be used for intramuscular orientation when preparing the Mn and for an indirect localization via ultrasound. This study examines the intramuscular course of the Ma and its relationship to the Mn. Materials and Methods: Sixty hemicrania obtained from thirty postmortem individuals aged between 54 and 99 years and embalmed using the Thiel methods were examined. Results: Four types of Ma were identified according to their endpoint in the Mm. In 5% of cases, no Ma could be identified (Type 0), 48.3% (Type 1) terminated within the upper third, 41.7% (Type 2) in the middle third, and 5% (Type 3) in the lower third. The Ma consistently entered the Mm inferior and in 85% of cases additionally slightly posterior to the Mn. The main trunk of the Ma crossed the Mn in the upper third of the Mm in 31.7% of cases, in the middle third in 23.3%, and in the lower third in 1.7% of cases. Of these, 13.3% had the Ma crossing the Mn. Smaller branches crossed the Mn in 45% of cases. Conclusions: If an Ma is present, it may be used for intramuscular orientation and indirect location of the Mn via the mandibular notch. Since the Ma reaches the lower third of the muscle in only a few cases, it is unsuitable for intramuscular orientation to locate the Mn via a distal approach.