Key points
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Middle ear paraganglioma is a benign neoplasm that typically presents with vascular tinnitus and progressive hearing loss depending on the size and location of the tumor.
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Petrous apex cholesterol granuloma is a cystic, inflammatory lesion typically resulting from hemorrhage into a mucosalized space; they can managed with marsupialization into the middle ear or mastoid in symptomatic patients.
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Middle ear adenoma is a benign but locally aggressive lesion that has a high incidence of recurrence without complete surgical excision.
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Transcanal endoscopic ear surgery is a means of managing temporal bone neoplasms given the unparalleled visualization of the tumor’s relationship to the critical anatomic structures within the lateral skull base.
| CT | Computed tomography |
| MEA | Middle ear adenoma |
| MEP | Middle ear paraganglioma |
| PACG | Petrous apex cholesterol granuloma |
| TEES | Transcanal endoscopic ear surgery |
Introduction
Lesions involving the temporal bone, although rare, are often a challenge to manage given the adjacent critical structures that are localized within the skull base. Fortunately, most lesions involving the middle ear and mastoid are benign, thus obviating the need to obtain the wide tissue margins that would typically result in significant morbidity. The microscopic transcanal or postauricular approaches are the traditional means to excise lesions of the middle ear and mastoid. Transcanal endoscopic ear surgery (TEES) is a relatively new option that can be used to address pathology of the middle ear and mastoid. TEES uses the ear canal as the access point to address pathology of the temporal bone. The endoscope, unlike the microscope, is not limited by line of site issues and allows for improved illumination of the surgical field. The endoscope provides a wide field view that allows the surgeon to examine areas not typically visible with the microscope without removal of bone lateral to the area of interest. The endoscope also does not require a postauricular incision, which results in less postoperative pain and allows for a faster recovery. Disadvantages of TEES include moving from 2-handed to 1-handed tissue dissection, and the lack of depth perception. This article describes the usefulness of TEES for the management of temporal bone lesions including middle ear paragangliomas (MEPs), adenoma, petrous apex cholesterol granuloma (PACG), and other lesions.
Introduction
Lesions involving the temporal bone, although rare, are often a challenge to manage given the adjacent critical structures that are localized within the skull base. Fortunately, most lesions involving the middle ear and mastoid are benign, thus obviating the need to obtain the wide tissue margins that would typically result in significant morbidity. The microscopic transcanal or postauricular approaches are the traditional means to excise lesions of the middle ear and mastoid. Transcanal endoscopic ear surgery (TEES) is a relatively new option that can be used to address pathology of the middle ear and mastoid. TEES uses the ear canal as the access point to address pathology of the temporal bone. The endoscope, unlike the microscope, is not limited by line of site issues and allows for improved illumination of the surgical field. The endoscope provides a wide field view that allows the surgeon to examine areas not typically visible with the microscope without removal of bone lateral to the area of interest. The endoscope also does not require a postauricular incision, which results in less postoperative pain and allows for a faster recovery. Disadvantages of TEES include moving from 2-handed to 1-handed tissue dissection, and the lack of depth perception. This article describes the usefulness of TEES for the management of temporal bone lesions including middle ear paragangliomas (MEPs), adenoma, petrous apex cholesterol granuloma (PACG), and other lesions.
Technique
The patient is positioned 90° to 180° away from anesthesia after induction and intubation. Total intravenous anesthesia is the technique of choice because it reduces the chance of patent movement, does not require muscle relaxants, and is reported to reduce intraoperative bleeding. A 3-mm diameter 14-cm length endoscope with varying degrees of angulation (0°, 30°, 45°, 70°) and a high-definition 3-chip camera are the ideal equipment for TEES. Local anesthesia with lidocaine or bupivacaine with epinephrine is infiltrated into the membranous canal skin, tragus, and postauricular area, which can be done with the microscope and a speculum or with the endoscope without a speculum. Excess hair in the membranous canal is trimmed to prevent smearing of blood and irrigation on the tip of the endoscope. Topical 1:1000 epinephrine on cotton or 0.025- by 0.25-inch cottonoids can be placed on the medial canal skin and tympanic membrane, which helps to reduce bleeding. The extent and location of middle ear pathology dictates the type of canal incisions that are made.
A standard tympanomeatal flap is elevated for pathology located posterior to the annulus, which typically entails incisions that are just anterior to the level of the lateral process of the malleus superiorly and at the 6 o’clock position inferiorly. The inferior and posterior osseous annulus can be removed with a drill or curette to provide additional exposure of the hypotympanum and retrotympanum. Angled endoscopes permit visualization of anterior, superior, posterior, or inferior extensions of disease that often obviates the need for additional bone removal. Bone removal may be required in some cases to allow for instrument and suction access to the pathology.
Three TEES approach options are available for lesions localized anterior to the malleus, or within the petrous apex. Malleus degloving necessitates a wider tympanomeatal flap with elevation of the tympanic membrane off the malleus lateral process, handle, and umbo. Malleus degloving provides excellent exposure to the anterior and posterior mesotympanum, but limited exposure of the protympanum if there is a prominent anterior canal wall bulge. This approach can also be used for the infracochlear approach to the petrous apex. Disadvantages of this approach are that a myringoplasty may be required, because a tear in the tympanic membrane may be difficult to avoid when elevating the drum off the umbo.
A superiorly based tympanomeatal flap provides access to the entire hypotympanum, retrotympanum, and anterior mesotympanum. The canal incisions for the superiorly based tympanomeatal flap approach start at the level of the lateral process of the malleus and extends around the posterior canal wall along the inferior canal and up the anterior canal wall. The canal incision is typically made at least 7 mm lateral to the anterior, posterior, and inferior annulus to account for any additional removal of the inferior and posterior medial canal. The canal skin is then elevated down to the tympanic annulus and the fibrous annulus is elevated out of the annular sulcus. The tympanic membrane is left pedicled to the superior canal skin and the malleus. This approach provides wide access for the infracochlear approach to the petrous apex, and allows for excision of most middle ear tumors, which do not extend superior into the epitympanum. At the completion of tumor removal, the tympanomeatal flap is easily restored to its normal anatomic position, often without the need for a tissue graft.
Ear canal and tympanic membrane degloving can be used for almost any lesion within the middle ear or medial temporal bone. In this approach, the osseous ear canal skin along with the entire tympanic membrane is removed after separating the drum from the malleus and the osseous annulus. A canaloplasty can then be performed to further enhance exposure to the entire middle ear and to more deep-seated lesions. Removal of the lateral chain with primary or delayed reconstruction can further enhance exposure. The canal skin and tympanic membrane can be replaced at the end of the procedure in addition to the use of a tissue graft if necessary. Patients with nonserviceable hearing can undergo blind sac closure with middle ear and Eustachian tube obliteration, which may be preferred in cases where entry into the subarachnoid space is required.
Middle ear paraganglioma
MEP, also known as glomus tympanicum, is a benign, slow-growing, vascular neoplasm that typically originates from the tympanic plexus of Arnold’s and Jacobson’s nerve along the cochlear promontory. MEP is also the most common neoplasm that originate within the middle ear. Histologically these tumors are composed of balls of chief cells (Zellballen formation) intermixed with sustentactular cells. MEPs have an identical appearance to their counterparts in other head and neck locations, including those lesions that arise from the carotid artery, jugular bulb, and vagus nerve. Malignant and catecholamine-producing head and neck paragangliomas are rare and this is no exception for those that arise in the temporal bone.
Paragangliomas are rare, and represent 1% of all tumors of the head and neck with the carotid body being the most common location. A recent series of 115 patients confirmed that the vast majority of MEPs occur in females (90%). The mean age at time of diagnosis for MEPs was 55.2 years with a bimodal distribution in the late 30 s and the early 60 s.
MEPs most commonly present with symptoms of hearing loss, pulsatile tinnitus, and ear fullness, although approximately 12% are incidentally identified on physical examination. These tumors rarely present with bloody otorrhea or cranial neuropathies.
Surgical excision is the preferred management strategy for MEPs, although observation or radiation are also options in selected cases. Several staging systems (Fisch–Mattox, Sanna, Glasscock–Jackson; Tables 1–3 ), exist for describing the extent of MEPs, which uses both physical examination and imaging with either computed tomography or MRI ( Fig. 1 ).
| Grade | Definition |
|---|---|
| A | Tumor entirely within the middle ear space |
| B | Tumor only within the middle ear or mastoid portion of the temporal bone |
| C | Tumor within the infralabyrinthine temporal bone or petrous apex |
| D1 | Tumors with <2 cm of intracranial extension |
| D2 | Tumors with ≥2 cm of intracranial extension |
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