Background: Estimating the exact position of the stylomastoid foramen is crucial for several
procedures of skull base surgery, and it may imply the recognition of some external
key landmarks. This could prevent some complications with knowing the relation and
the exact osseous anatomy. Here, we described some nuances and compared some differences
with the current literature. In dorsolateral approaches is important to recognize
the location of the stylomastoid foramen. Here, we found in our analysis some external
topographic projections as key landmarks to estimate the exact point of the stylomastoid
foramen.
Methods: Specimens were obtained from the anthropology department of the Faculty of Medicine
of the National Autonomous University of Mexico, and the Surgical Neuroanatomy Laboratory
of the University La Salle, Mexican Faculty of Medicine. Craniums were used to analyze
and measure the juxtaposition of the stylomastoid foramen from the groove point of
the digastric groove, emissary mastoid foramen, posteroinferior tympano-mastoid suture,
and the jugular process of the occipital bone. Measures from the groove point and
the distal emissary mastoid foramen were obtained using a caliper for the longitudinal
distance, and a metric cord for curvilinear distance.
Results: Nineteen dry skulls, corresponding to 37 sides were analyzed to visualize the proximity
of the extracranial orifice of the stylomastoid foramen with some osseous key landmarks.
The variants and the morphometric differences of the estimated distances were compared
with the current descriptions, in addition to some technical nuances from the key
landmarks were described.
Conclusion: The extracranial key osseous landmarks as de groove point and the inferior border
of the tympanomastoid suture represent a viable reference for estimating the stylomastoid
foramen exit point. The variability of emissary mastoid foramen could be discerned
in relation to the anatomical pattern of exit. These key landmarks could be used at
the moment of the drilling of the mastoid, or during the removal of the posterior
belly of the digastric muscle during the rectosigmoid, or far lateral approach.
