Suboccipital retrosigmoid surgical approach for internal auditory canal--a morphometric anatomical study on dry human temporal bones.

Suboccipital retrosigmoid craniotomy with removal of posterior wall of internal auditory canal is preferred by many surgeons operating on acoustic neuromas, as it is a simple and safe approach. To study the topographic landmarks of the posterior surface of the temporal bone. We studied the surgical anatomy of 224 dry adult human temporal bones, measured the various distances on posterior wall of petrous bone relevant for suboccipital surgical approach to internal auditory canal. The internal auditory canal (IAC) lies within 32-44 mm from posterior wall of sigmoid sulcus and within 3-8 mm from the superior border of petrous bone. The point corresponding to highest point of jugular bulb was found between 4 and 9 mm away from the inferior border of IAC. The maximum distance found between bony orifice of vestibular aqueduct and IAC was 14 mm and the minimum distance was 6 mm.The vertical diameter of IAC ranged between 3 and 7 mm. These parameters may help the surgeons for better exposure of internal auditory canal and for avoiding damage to vital surrounding structures.