Petrous bone cholesteatomas (PBCs) are slow-growing expansile epidermoid lesions arising in the petrous portion of the temporal bone with an incidence of 4 to 9% of all petrous pyramid lesions. These could be congenital, acquired, or iatrogenic. Congenital PBCs are most plausibly explained by the persistence of fetal epidermoid formation in the petrous bone or the middle ear from which it expands to the petrous bone. In such cases, the first symptoms are facial nerve paralysis, vertigo, and deaf ear due to invasion of the facial nerve and labyrinth. The acquired variety is due to the migration of squamous epithelium into the petrous bone secondary to a perforation in the tympanic membrane. The iatrogenic variety is due to the implantation of cholesteatoma after an otologic surgery. Fetid otorrhea, progressive facial palsy, vertigo, and hearing loss of any type (conductive, sensorineural, mixed) are usually encountered in these patients. Otoscopy may be irrelevant or only demonstrates pars flaccida perforation or an open mastoid cavity with evidence of suppurative discharge. A computed tomography (CT) scan and magnetic resonance imaging (MRI) are fundamental to evaluate the extension of the lesion and to determine the surgical management. The rarity of these lesions, slow and silent growth pattern, their complex location in the skull base, proximity to vital neurovascular structures (facial nerve, internal carotid artery, sigmoid sinus, jugular bulb, lower cranial nerves, dura), and tendency to recur make PBCs very challenging to diagnose and treat. PBCs have shown to be locally aggressive by involving the petrous bone and the areas surrounding it, such as the clivus, nasopharynx, sphenoid sinus, and the infratemporal fossa, and even extending intradurally. Also, the close proximity of the disease to the labyrinth and the facial nerve puts to risk both hearing and facial nerve function, which is reflected in the high incidence of facial nerve palsy (34.6–100%) seen in the important series reported in literature. Surgery remains the mainstay of treatment of PBCs. The choice of surgical approach has evolved from radical petromastoid exenteration with marsupialization of the cavity to closed and obliterative techniques following complete eradication Advancements in neuroradiology and microscopic lateral skull base surgery have made it possible today to completely extirpate these lesions safely with minimal recurrences and perioperative morbidity. The primary objective in surgical approaches for PBCs is to ensure total disease eradication along with complete control and safety of the surrounding important neurovascular structures. The development of the transotic and transcochlear approaches, combined with various other skull base approaches, has helped achieve both these objectives and is considered the mainstay of surgery for PBCs. The classification proposed by Sanna divides PBCs into five groups based on the relationship of the disease to the labyrinthine block. This radiological classification allows standardization in reporting and a clear planning of the surgical approach ( ▶ Table 10.1, ▶ Table 10.2). Also see ▶ Fig. 10.1, ▶ Fig. 10.2, ▶ Fig. 10.3, ▶ Fig. 10.4, ▶ Fig. 10.5, ▶ Fig. 10.6, ▶ Fig. 10.7, ▶ Fig. 10.8, ▶ Fig. 10.9, ▶ Fig. 10.10, ▶ Fig. 10.11, ▶ Fig. 10.12, ▶ Fig. 10.13, ▶ Fig. 10.14, ▶ Fig. 10.15, ▶ Fig. 10.16, ▶ Fig. 10.17, ▶ Fig. 10.18, ▶ Fig. 10.19, ▶ Fig. 10.20, ▶ Fig. 10.21, ▶ Fig. 10.22, ▶ Fig. 10.23, ▶ Fig. 10.24, ▶ Fig. 10.25, ▶ Fig. 10.26, ▶ Fig. 10.27, ▶ Fig. 10.28, ▶ Fig. 10.29, ▶ Fig. 10.30, ▶ Fig. 10.31, ▶ Fig. 10.32, ▶ Fig. 10.33, ▶ Fig. 10.34, ▶ Fig. 10.35, ▶ Fig. 10.36, ▶ Fig. 10.37, ▶ Fig. 10.38, ▶ Fig. 10.39, ▶ Fig. 10.40, ▶ Fig. 10.41, ▶ Fig. 10.42, ▶ Fig. 10.43, ▶ Fig. 10.44. Fig. 10.1 Left acquired or iatrogenic supralabyrinthine petrous bone cholesteatoma in a radical cavity. A whitish retrotympanic mass is seen at the level of the second portion of the facial nerve. The patient presented with progressive facial nerve paralysis and total hearing loss. A correct diagnosis depends not only on otoscopy but also on the symptomatology (facial paralysis, anacusis) and a high-resolution CT scan. Fig. 10.2 CT scan of the case presented in ▶ Fig. 10.1, axial section. Involvement of the lateral semicircular canal and the vestibule (arrows) is well visualized. The cholesteatoma invades the cochlea anteriorly, while medially it reaches the fundus of the internal auditory canal. The posterior semicircular canal is not invaded. Fig. 10.3 CT scan of the case presented in ▶ Fig. 10.1, coronal section. The medial extension of the cholesteatoma can be appreciated (arrow). Fig. 10.4 Postoperative CT scan. A transcochlear approach was performed and the operative cavity was obliterated with abdominal fat (arrows). Fig. 10.5 Right acquired supralabyrinthine petrous bone cholesteatoma. A whitish mass is present in the mastoid cavity of an open tympanoplasty. The mass occupies the whole epitympanum and extends interiorly behind the tympanic membrane. The patient presented with ipsilateral facial paralysis and conductive hearing loss. Fig. 10.6 CT scan of the case presented in ▶ Fig. 10.5. The cholesteatoma invades the cochlea (arrow). Total removal of the pathology was accomplished using a transcochlear approach with obliteration of the operative defect using abdominal fat. The external auditory canal was closed as cul de sac. The facial nerve was infiltrated at the level of the geniculate ganglion and was repaired using a sural nerve graft. Fig. 10.7 Another example of right acquired supralabyrinthine petrous bone cholesteatoma. The patient presented with right facial nerve paralysis. Otoscopy reveals a right epitympanic erosion. Fig. 10.8 CT scan of the case presented in ▶ Fig. 10.7, coronal view. Typical location and erosion of acquired small supralabyrinthine petrous bone cholesteatoma (arrow). Fig. 10.9 Left congenital supralabyrinthine petrous bone cholesteatoma with extension toward the apex.Otoscopy is negative. The patient complained of progressive facial nerve paralysis of 5 years’ duration as well as conductive hearing loss ( ▶ Fig. 10.10, ▶ Fig. 10.11). Fig. 10.10 CT scan of the case presented in ▶ Fig. 10.9. Coronal view showing extension of the cholesteatoma into the internal auditory canal (arrows). Fig. 10.11 Right congenital infralabyrinthine apical petrous bone cholesteatoma in a 30-year-old female patient. In the posterosuperior quadrant, a white retrotympanic view is observed. The patient had complained of right anacusis since childhood and instability of 1-year duration. The facial nerve was normal. Fig. 10.12 CT scan of the case presented in ▶ Fig. 10.11. Coronal view demonstrating the involvement of the infralabyrinthine apical compartment by the cholesteatoma (arrow). Fig. 10.13 CT scan of the case presented in ▶ Fig. 10.11. A more anterior coronal view at the level of the cochlea. Fig. 10.14 Postoperative CT scan showing total removal of the cholesteatoma through the transcochlear approach and obliteration of the operative cavity using abdominal fat.
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