Advantages and Complications of Fisch Partial Mastoido-Tympanectomy for Tumors of the Retromandibular Fossa and Post-Styloid Space

Background: Fisch partial mastoido-tympanectomy (FPMT) is a rarely described surgical technique that provides access to tumors of the retromandibular fossa and post-styloid space that abut the inferior mastoid and tympanic bone without invasion into the temporal bone. The hearing-preserving technique provides additional anterior exposure compared with mastoidectomy with facial nerve decompression, and allows unique access to the deep lobe of the parotid gland as well as the jugular bulb and carotid artery as needed. Although initially described in 1986, little information regarding the clinical experience with FPMT exists in the literature.

Objective: To characterize a single surgeon’s experience with the FPMT technique of partial temporal bone resection.

Design: Retrospective review of medical records from 2009 to 2016.

Setting: Academic medical center.

Participants: Seven patients who underwent tumor resection with FPMT.

Surgical Technique: Following postauricular incision and exposure of mastoid cortex and tympanic bone, the posterior and inferior external auditory canal (EAC) soft tissue is elevated to the annulus without violation of canal lumen. Intact canal wall mastoidectomy with skeletonization of facial nerve is performed, and mastoid tip is amputated. Tympanic bone is drilled immediately inferior to tympanic ring into styloid base up to the jugular bulb anterior to facial nerve. When indicated, the procedure is combined with neck dissection, parotidectomy, or facial nerve cable grafting.

Main Outcome Measures: Complications.

Results: Six males and one female underwent FPMT. The average age was 63 years, with a range of 44 to 79 years. No patients underwent radiation therapy prior to surgery. Facial nerve was intentionally sacrificed in six cases, no cases were converted to more extensive temporal bone resection procedures, and no postoperative hearing loss occurred. No incidents of positive surgical margins were encountered. The only intraoperative complication experienced was violation of the external auditory canal in four cases, which resulted in postoperative wound healing issues in two cases. A fistula between the EAC and mastoid occurred in one of these cases secondary to anterolateral free flap breakdown with subsequent infection, and the second case was complicated by EAC wound breakdown into the margin of the pectoralis major rotational flap resulting in a condylectomy defect and fistula communicating with the EAC. All cases with EAC violation were corrected with temporalis fascia support grafts, but the two cases without postoperative complications also consisted of additional supporting free muscle graft inferior to the fascia graft to eliminate the adjacent dead space caused by the tympanic bone drilling defect.

Conclusion: FPMT allows for release of tumors of the post-styloid space and retromandibular fossa without compromise of hearing status. Preservation of external auditory canal soft tissues is challenging and violation is experienced relatively frequently due to shearing forces during soft tissue retraction. Due to the risk of wound healing complications inherent to FPMT it is important for the surgeon to determine whether or not the additional anterior exposure provided when compared with mastoidectomy with facial nerve decompression is worth the potential added risk. When encountered, robust repair of defects is encouraged to prevent further wound healing complications.

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