Decompression of the tympanic and labyrinthine segments of the facial nerve by middle cranial fossa approach: an anatomic study

Abstract

Background: Peripheral facial palsy is characterized by the permanent or temporary interruption of facial muscle function. The middle cranial fossa (MCF) approach has been used to decompress the facial nerve (FN) when hearing needs to be preserved. In this work, we describe a technique for decompressing the FN through the MCF approach, which allows the direct exposure of the labyrinthine and entire tympanic segment of the FN, with preservation of inner ear function.

Methods: Twenty cadavers heads were used in this study. The reference landmarks used were the middle meningeal artery, greater superficial petrosal nerve, arcuate eminence, inferior petrosal sinus and meatal plane following the petrous apex from its most anterior and medial portion.

Results: The tympanic segment of the FN presented, on average, a total length of 11 ± 0.67 mm to the right and 11.5 ± 0.60 mm to the left. The longitudinal lengths of the bone window in the tegmen tympani were 16.8 ± 1.67 mm to the right and 16.8 ± 1.20 mm to the left. The cross-sectional lengths of the bone window in the tegmen tympani were 5.5 ± 1.20 mm and 5.0 ± 1.75 mm to the right and left sides, respectively. The average value of the elliptical area formed by the longitudinal and transversal lengths of the bone window made in the tegmen tympani was 72.5 ± 22.5 mm(2) to the right and 65.9 ± 30.3 mm(2) to the left.

Conclusion: The proposed technique can be used for the surgical decompression of the tympanic, labyrinthine and meatal segments of the FN through the MCF in addition to reducing the surgical time and the risk to patients.

Keywords: Anatomy; Facial nerve; Facial palsy; Middle cranial fossa.