Facial Nerve Rerouting during Skull Base Surgery

The facial nerve seen in its normal anatomic position within the temporal bone seen after completion of a canal wall down mastoidectomy (subtotal petrosectomy). Note than the descending portion of the nerve in the mastoid overlies the jugular foramen. (1G, first genu; 2G, second genu; SMF, stylomastoid foramen; JB, jugular bulb; CA, carotid artery.)
Anterior re-routing of the facial nerve with the ear canal in place gains relatively little additional exposure of the jugular foramen region.
With the ear canal removed the facial nerve can be displaced forward with the hinge point either at the first or second genu (as depicted here).
Full mobilization of the facial nerve from the first genu to the stylomastoid foramen substantially enhances surgical exposure of the jugular foramen and carotid genu. Leaving intact the fascial envelope at the stylomastoid foramen helps to preserve the blood supply to the nerve. Anteriorly re-routing of the nerve can usually be accomplished with either no functional deficit or with transient weakness which recovers well over time. (For use of this technique, see Chapter 8.)
Posterior rerouting of the facial nerve is carried out in the exposure of difficult clival or pre-pontine lesions such as mid-basilar aneurysms. The entire facial nerve from the brainstem to the stylomastoid foramen is mobilized and the nerve is reflected posteriorly onto the cerebellar surface. In the process of the mobilization, the greater superficial petrosal nerve is severed. Total facial nerve rerouting typically results in a transient complete facial paralysis which recovers incompletely and with synkinesis. (For its, use see section 2.2 in Chapter 2.)

From ATLAS OF SKULL BASE SURGERY & NEUROTOLOGY. Thieme. ©2009

All images are copyright by RK Jackler. Permission granted for non-profit educational use of images, with attribution to their source.

Created by: Robert Jackler (surgeon) and Christine Gralapp (artist).

With contributions by:
Nikolas Blevins, Griffith Harsh, Michael Kaplan, Lawrence Pitts, Charles Yingling, and Corey Mass.

For legend references, please see the print book.