Surgical Parameters for Minimally Invasive Trans–Eustachian Tube CSF Leak Repair: A Cadaveric Study and Literature Review

Abstract

BACKGROUND:Cerebrospinal fluid rhinorrhea from a lateral skull base defect refractory to spontaneous healing and/or conservative management is most commonly managed via open surgery. Approach for repair is dictated by location of the defect, which may require surgical exploration. The final common pathway is the eustachian tube (ET). Endoscopic ET obliteration via endonasal and lateral approaches is under development. Whereas ET anatomy has been studied, surgical landmarks have not been previously described or quantified. We aimed to define surgical parameters of specific utility to endoscopic ET obliteration. METHODS:A literature review was performed of known ET anatomic parameters. Next, using a combination of endoscopic and open techniques in cadavers, we cannulated the intact ET and dissected its posterior component to define the major curvature position of the ET, defined as the genu, and quantified the relative distances through the ET lumen. The genu was targeted as a major obstacle encountered when cannulating the ET from the nasopharynx. RESULTS: Among 10 ETs, we found an average distance of 23 ± 5 mm from the nasopharynx to the ET genu, distance of 24 ± 3 mm from the genu to the anterior aspect of the tympanic membrane and total ET length of 47 ± 4 mm. CONCLUSIONS:Although membranous and petrous components of the ET are important to its function, the genu may be a more useful surgical landmark. Basic surgical parameters for endoscopic ET obliteration are defined.

Morphological Observations of the Bony Canal Structure of the Eustachian Tube in Elderly Human Cadavers With Cone-Beam Computed Tomography and Principal Component Analysis

“…To cannulate the ET successfully and minimize the risk of harm, an understanding of ET anatomical structure is the most important factor. 24 In our macroscopic observation, the border between the bony zone and cartilage zone was unclear, and there was a very narrow border between the ET cartilage zone and the carotid artery. Attention must be paid to the carotid artery during cannulation and surgical treatments with an endonasal approach.…”

“… 23 The ET is composed of bone, cartilage, and connective tissue. Based on data from 10 cadavers, Brown et al 24 reported the mean distance from the nasopharynx to the ET genu was 23 mm (SD 5 mm), the mean distance from the ET genu to the anterior aspect of the tympanic membrane was 24 mm (SD 3 mm), and the mean total ET length was 47 mm (SD 4 mm). To cannulate the ET successfully and minimize the risk of harm, an understanding of ET anatomical structure is the most important factor.…”

Surgical Anatomy of the Temporal Bone

“…The bony part attaches to the ET sulcus or sulcus tuba, which is contiguous to the FL medially. The FL is located in the incomplete confluence of the union of the body and the lingular process of the greater sphenoid wing anteriorly, the clivus of the occipital bone medially and the petrous apex posteriorly and covered with the fibrocartilaginous tissue that separates the ET from the ICA [23].…”

“…Vascular compression and arachnoid adherence of the TN branches result in trigeminal neuralgia. During endoscopic vascular decompression and Meckel's cave approaches, the VC, the bone between V2 and the VC and the pneumatization of the sphenoid sinus form a safe route to access and to decompress Gasser's ganglion with branches, the cranial nerves (III, IV, VI), and the petrous ICA [13,23].…”

Commentary: Endoscopic Endonasal Eustachian Tube Obliteration for Cerebrospinal Fluid Rhinorrhea: Case Series and Scoping Review

“…CSF leak after lateral skull base surgery occurs in >10% of cases. 3 As such, a less invasive approach with low morbidity is the preferred method of CSFR correction, as opposed to reoperation and its associated risks, such as complications of the facial nerve. 4 The authors note that the anatomic constraints of the nasal cavity, nasopharynx, and ET make EEETO particularly technically challenging, with knot tying through the transnasal corridor commonly regarded as the most difficult part of the procedure.…”