History

The first scholarly treatise on mastoid surgery for suppurative disease was by Schwartze in 1873.^1,2 The procedure he described was a cortical mastoidectomy with limited exenteration of mastoid air cells. For acute and coalescent mastoiditis, which were prevalent in the preantibiotic era, this procedure proved remarkably efficacious. As one might expect, however, the simple mastoidectomy rarely cured chronic otitis media or cholesteatoma. During the next 20 years, it became evident that creating an open cavity was necessary for these diseases, and in 1890, Zaufal described removing the superior and posterior canal wall, tympanic membrane, and lateral ossicular chain, a procedure now known as the radical mastoidectomy.³ This procedure was modified by Bondy, who recognized that disease limited to the pars flaccida could simply be exteriorized, leaving the uninvolved middle ear alone. His description of the “modified radical mastoidectomy” or “Bondy procedure” in 1910 represented one of the first reports addressing hearing function.¹

Interest in hearing preservation and restoration gained further attention after Lempert introduced the fenestration operation in 1938, and Zollner and Wullstein described tympanoplasty techniques in the early 1950s.^4–6 During the next decade, Jansen, Sheehy, and others extended these principles of restoring function and maintaining normal anatomy with the introduction of the intact canal wall mastoidectomy with facial recess approach.^7,8

Anatomy

The temporal bone consists of four parts: squamous, tympanic, mastoid, and petrous (Figs. 142-1 and 142-2). The smallest part is the tympanic portion, which forms the external auditory canal. This chapter focuses primarily on the mastoid portion, which articulates with the parietal and occipital bones and houses the mastoid air cell system, which is in continuity with the air cells of the petrous pyramid. Transmastoid procedures provide access to the facial nerve, internal carotid artery, jugular bulb, labyrinth, internal auditory canal, and petrous apex.

Figure 142-1. Right temporal bone. Lateral view.

(From Donaldson JA, Duckert LG, Lambert PR, Rubel EW, eds. Surgical Anatomy of the Temporal Bone. 4th ed. New York: Raven Press; 1992.)

Figure 142-2. Left temporal bone. Posterolateral view.

(From Donaldson JA, Duckert LG, Lambert PR, Rubel EW, eds. Surgical Anatomy of the Temporal Bone. 4th ed. New York: Raven Press; 1992.)

Important surface landmarks on the mastoid include the temporal line, which extends posteriorly from the zygomatic root and is the insertion site for the temporalis muscle. There is considerable variability in the prominence of this structure among individuals. The suprameatal spine or spine of Henle is a small bony protuberance extending superficially from the posterior and superior bony external auditory canal. It is located just inferior to the temporal line, and shows variability in size among individuals. Just posterior to this spine is a cribriform area, which approximates the location of the underlying mastoid antrum.

All major components of the temporal bone are present in infants, but there is one notable difference that has surgical implications. In infants, the mastoid tip has yet to develop, and the stylomastoid foramen is located more superficially, making the facial nerve vulnerable to surgical trauma.

Nomenclature

The otologic surgeon has various mastoid procedures from which to choose, depending on extent of disease. In addition, variations on these standard approaches are often discussed in the literature. The nomenclature for mastoid surgery can seem confusing at first. Concomitant surgery involving the middle ear requires additional terminology, such as tympanoplasty or ossiculoplasty. Box 142-1 lists the standard mastoid procedures for addressing chronic ear disease.

Operative Procedure (see Key Indicator Video on website)

The surgical site is prepared by shaving 1 to 2 cm of hair around the ear and injecting 5 to 10 mL of local anesthetic with a vasoconstrictor (e.g., 1% lidocaine with 1 : 100,000 epinephrine) postauricularly and within the external ear canal. To facilitate closure, the C-shaped incision is placed about 1 cm behind the postauricular crease, rather than within it (Fig. 142-3). If extensive saucerization of the mastoid cavity is planned (e.g., translabyrinthine or retrolabyrinthine approach to the cerebellopontine angle, skull base tumor resection), the incision is placed more posteriorly.

Figure 142-3. Postauricular incision is placed about 1 cm behind the postauricular crease, facilitating skin closure.

(From Sheehy JL. Surgery of chronic otitis media. In: English GE, ed. Otolaryngology. Philadelphia: Lippincott; 1986:1.)

Superiorly, the incision is carried down to the temporalis fascia. Inserting a small Weitlaner retractor and lifting it laterally facilitates this dissection. The subcutaneous tissues are elevated off the fascia and easily incised. Inferiorly, the incision is extended to the anterior lateral surface of the mastoid tip. An incision placed more posteriorly on the mastoid involves the insertion of the sternocleidomastoid muscle and results in more bleeding and postoperative discomfort. Making two periosteal incisions—one along the temporal line and the second perpendicular to this and extending to the mastoid tip—exposes the mastoid bone itself. The periosteum is elevated and retracted forward with the auricle.

With the mastoid cortex fully exposed, the first bur cut is made along the temporal line, which approximates the level of the middle cranial fossa dural plate. It is important to recognize, however, the variability of the position of the tegmen, depending on the degree of mastoid pneumatization. The second bur cut is made perpendicular to this and tangential to the external bony canal; it should be carried inferiorly to the mastoid tip (Fig. 142-4).

Figure 142-4. Initial bur cuts are along the temporal line and tangential to the bony canal.

(From Sheehy JL. Mastoidectomy: the intact canal wall procedure. In: Brackmann DE, Shelton C, Arriaga MA, eds. Otologic Surgery. Philadelphia: Saunders; 1994.)

Although various drill systems are available, several common principles relate to bur selection and fluid irrigation. When possible, larger rather than smaller burs are preferable for bone dissection. This facilitates saucerization and exposure, and it avoids creating small openings in the bone that can more easily damage underlying structures. It is important, however, to choose a bur that is not so large that it obstructs the field of dissection. It is also critical to note the backside of the bur while drilling, to prevent injuring structures opposite the point of dissection.

A variety of burs exist, ranging from burs that aggressively remove bone to those that are used more for bone polishing. A bur with a cutting or fluted surface is selected for removing cortical bone, whereas a fine diamond grain surface is required when removing the last layer of bone over the facial nerve or sigmoid sinus. When drilling over an irregular surface, a fluted bur has a tendency to “skip” in the direction of the bur rotation.

Appropriate irrigation is necessary to clear bone dust from the field of dissection, to prevent excessive heat transfer to underlying structures (especially the facial nerve), and to maintain a clean cutting surface on the bur. Whether a self-irrigating drill or a suction irrigation system is being used, appropriate adjustment of the level of irrigation facilitates accurate and safe bony dissection.

A key landmark in performing mastoid surgery is the antrum with the dome of the horizontal semicircular canal (HSCC) along its floor. The ease of locating the antrum depends largely on the degree of mastoid pneumatization. Three key principles assist this part of the dissection: saucerization, identification of the tegmen plate, and thinning the posterior canal wall. The deepest dissection is at the point where the initial cortical bone cuts intersect, but widely saucerizing toward the tegmen and especially posteriorly (from the sinodural angle to the mastoid tip) as the antrum is approached is essential. Posteriorly, one must consider the sigmoid sinus, which could be far forward in a poorly pneumatized mastoid. Appropriate saucerization helps identify its lateral surface and prevent injury. The importance of identifying the tegmen plate cannot be overemphasized. All mastoid air cells should be removed superiorly, effectively skeletonizing this structure. The tegmen is followed medially, anticipating that the plane of the tegmen will vary, usually bulging slightly into the cavity midway between the cortex and the floor of the antrum. Failure to identify the superior limit of the mastoid dissection could result in opening the antrum too inferiorly, injuring the HSCC or the genu of the facial nerve, or both.

All air cells should be removed from the back of the bony external auditory canal. A mastoid cavity may appear small simply because insufficient attention was directed toward this area of dissection. In addition, a thin posterior canal wall assists localization of the facial nerve, as described later.

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