Subcochlear Approach for Cholesterol Granulomas of the Inferior Petrous Apex

Abstract

Cholesterol granulomas of the petrous apex are drained through two major extralabyrinthine routes: one, along the posterosuperior chain of air cells, and two, along the anteroinferior chain. Procedures that use the posterosuperior chain approach the apex from the sinodural angle, the base of the zygomatic arch, the attic, or through the arch of the superior semicircular canal. Operations that use the anteroinferior chain reach the apex along the internal carotid canal (Ramadier's operation) or by a posterior infralabyrinthine approach between the descending facial nerve and jugular bulb. Inferior petrous apex cholesterol granulomas may be unreachable by any of these routes, and hence the subcochlear route is proposed as an alternative. The subcochlear approach starts in a triangle bounded superiorly by the cochlea, anteriorly by the internal carotid canal and posteriorly by the deep jugular vein. This operation requires lowering the inferior bony canal wall to the level of the "crutch." It provides access to an inferiorly situated cholesterol granuloma, yet preserves hearing. It allows enough room for the placement of a tube drain from the petrous apex to the mastoid. It is particularly useful when a high jugular bulb precludes the use of the posterior infralabyrinthine route.

Double‐barrel stenting in infracochlear approach for drainage of petroux apex cholesterol granulomas

“…The infracochlear approach is in essence a combination of the transcanal approach described by Farrior for a small glomus tympanicum,10 and the subcochlear and infracochlear approaches described by Ghorayeb and Jahrsdoerfer11 and by Giddings et al,12 respectively.…”

Endonasal endoscopic approach to the petrous apex: an image‐guided quantitative anatomical study1

“…Traditional surgical methods employed in excising petrous apex lesions have included infralabyrinthine, 2 translabyrinthine, 4 transcochlear, 3 subcochlear, 5 suboccipital and middle fossa approaches 6 . However, these approaches are often associated with considerable morbidity, with complete extirpation rendered difficult or impractical in some cases due to their location deep in the middle cranial fossa and their proximity to important anatomical structures, including the facial nerve, carotid artery, jugular bulb and otic capsule.…”

“…Lesions of the petrous apex encompass a wide range of varied pathologies including cholesterol granulomas, cholesteatomas, vascular neoplasms and rarely squamous cell carcinomas 1 . Numerous skull base and neurosurgical procedures have been described for their removal 2–6 although problems with morbidity have in part been responsible for the trend towards the use of minimally invasive surgical approaches. Endoscopic assisted transsphenoidal techniques have been sporadically reported in case reports, 7–11 but this has not yet gained universal acceptance.…”

Cholesterol Granuloma of the Petrous Apex

“…Primary lesions account for approximately 40% of petrous apex lesions. [1][2][3][4][5][6] PATHOPHYSIOLOGY OF CHOLESTEROL GRANULOMA Cholesterol granuloma of the petrous apex forms as a result of foreign-body giant-cell reaction to cholesterol crystals. The poor ventilation, interference with drainage, and hemorrhage in a usually pneumatized space are predisposing factors leading to the formation of the cyst.…”

“…Primary petrous apex lesions are those that arise from the central petrous apex or the anatomic boundaries of the region, and account for approximately 40% of petrous apex lesions. [1][2][3][4][5][6] Secondary lesions impinge on the petrous apex from an outside source, which may derive from invasion from a bordering region or from a metastatic lesion; secondary lesions account for the remaining 60% of petrous apex lesions.…”