A modified retrosigmoid approach for direct exposure of the fundus of the internal auditory canal for hearing preservation in acoustic neuroma surgery.

Abstract

This is a clinical report on a modified retrosigmoid approach with direct exposure of the fundus of the internal auditory canal for hearing preservation in acoustic neuroma surgery. Retrospective case review. Tertiary referral center of an ear, nose, and throat department in a public hospital. One hundred fifty consecutive procedures were reviewed, including 61 males and 89 females with an age range of 13 to 69 years and a mean age of 47 years. There were 15 patients with tumor occupying solely the internal auditory canal and 135 patients with extension into the cerebellopontine angle with an extrameatal diameter of up to 52 mm and a mean of 11.5 mm. The retrosigmoid approach included a wide craniotomy, a perimeatal petrous bone removal up to the blue line of the labyrinth, and a direct exposure of the fundus at the orifices of the facial and cochlear nerves. The quadrant of the superior vestibular nerve remained unexposed. Hearing was measured according to the American Academy of Otolaryngology-Head and Neck Surgery criteria for reporting results of hearing preservation and by comparison with the preoperative level. Facial nerve function was measured using the House-Brackmann grading. The radicality of tumor removal was investigated with mid- to long-term magnetic resonance imaging (MRI). Measurable hearing was preserved in 45.3%, and in 32.4% of these cases, it was within 15 dB/15% discrimination. Grade 1 or 2 facial function was preserved in 85.3%. MRI follow-up revealed a 3.3% tumor residual or regrowth in the complete series. No residual tumor was found at the 3-year MRI in the last series of patients operated on with direct control of the fundus. This modified retrosigmoid approach permits the direct exposure of the facial and cochlear quadrants of the fundus. This allows tumor dissection under direct visual control. Removing the tumor from the vestibular quadrant of the fundus is done blindly in a minority of cases and carries a minimal risk of residual tumor. This technique requires only conventional equipment and skills of neurotology.