Conquering the Castle

Abstract

Objective To describe 2 subapproaches of the middle fossa approach: the transillumination method and transection of lines using the foramen spinosum, greater superficial petrosal nerve, and trigeminal impression to locate the malleus head for safe identification and decompression of the geniculate ganglion and facial nerve. Study Design Cadaver study. Setting A tertiary university hospital anatomy laboratory. Subjects and Methods The present study was conducted using 7 formalin-fixed cadaver heads (14 sides). A 0° endoscope was introduced into the external ear canal toward the posterosuperior quadrant of the tympanic membrane, after which transillumination was used to locate the malleus head. The brightest point indicated the convergence of the greater superficial petrosal nerve and a line drawn along the superior semicircular canal. An additional line was drawn parallel to the petrous ridge from the foramen spinosum and along the pathway of the greater superficial petrosal nerve. A third line connected the trigeminal impression to the zygomatic root. The area posterior to the intersection of these 2 lines separately with the third line was considered the zone of location of the malleus head. Among 17 patients undergoing surgery for facial paralysis between 1993 and 2011, transillumination was used in 6 patients to identify the malleus head to locate the geniculate ganglion. Results These techniques were proven to be reliable in locating the malleus head to find the geniculate ganglion in 14 dissected cadaveric temporal bones. Conclusion Two methods of locating the malleus head for facial decompression were defined.