A cadaveric study of surgical landmarks for retrograde parotidectomy

Retrograde parotidectomy is employed in situations where tumors or scar tissue obscure the facial nerve trunk, making anterograde parotidectomy hazardous. Hence, the reliability of anatomical landmarks in retrograde parotidectomy is of equal practical importance.

Distances from soft tissue and osseous landmarks to the corresponding peripheral branches of the facial nerve were measured in 41 half-head specimens. The distances were from: i) the zygomatic arch (Z) to the buccal branch (B); ii) the retromandibular vein (RMV) to the marginal mandibular branch (MM); and iii) the angle of the mandible (A) to MM. These distances were compared in left vs, right sides, male vs. female groups, occlusal vs. nonocclusal sides.

No statistically significant differences were found in any of the three distances between all groups compared, amongst which, the mean distances from A to MM were the shortest and least variable (Male = 8.9 ± 3.0 mm vs. Female = 6.8 ± 3.5 mm; Left = 7.3 ± 2.8 mm vs. Right = 8.8 ± 3.9 mm; Occlusal = 8.6 ± 3.5 mm vs. Nonocclusal = 7.8 ± 3.4 mm).

The findings indicate that all three landmarks are useful for surgeons to locate the facial nerve branches during retrograde parotidectomy. Since all three landmarks were consistent indicators for the corresponding facial nerve branches, the surgeon has more than one option should one landmark be obscured by tumors. The optimal landmark is the distance from A to MM because it is shortest and most reliable, followed by RMV to MM, and Z to B.