Morphometry of stylomastoid foramen and its clinical application in facial nerve block

Stylomastoid foramen is an important site for Nadbath facial nerve block. Exact localization of foramen holds the key to success, thus decreasing the complications. Wide racial variation exists in position of stylomastoid foramen in different population groups.

The aim was to study the morphometry of stylomastoid foramen and its location with respect to nearby anatomical landmarks.

A total of 100 dry skulls (60 male and 40 female) were studied to locate the position of center of stylomastoid foramen (CSMF) with respect to tip and anterior border of the mastoid process and jugular foramen (JF). Along with this angle between antero-posterior line passing through the tip of the mastoid process and line joining the tip with stylomastoid foramen was also measured.

In 83.51% sides of skulls, the most common position of foramen was found to be anterior to the line passing through anterior border of the mastoid process. The mean distance of center of foramen from the tip of the mastoid process was 15.26 ± 1.4 mm on right and 14.32 ± 1.8 on the left side (P < 0.001) and from JF was 12.28 ± 1.9 mm and 12.96 ± 2.1 mm on the right and left sides, respectively (P < 0.01). The position of CSMF was found at an angle of 66.57° ± 2.6° and 65.96° ± 1.8° on the right and left sides, respectively from the tip of the mastoid process.

This study makes possible the identification of the exact position of stylomastoid foramen and its application in facial nerve block.