31.1 Introduction

While many surgical approaches to the internal auditory canal (IAC) and cerebellopontine angle (CPA) have been described, the translabyrinthine (TL), middle cranial fossa (MF), and retrosigmoid (RS) approaches remain the most commonly employed today (Fig. 31‑1 , Fig. 31‑2 , Fig. 31‑3 , Fig. 31‑4 ). The decision to utilize one approach over another is influenced by tumor characteristics, anatomic factors, patient factors, and surgical team experience.s. Literatur

The advantages and disadvantages of each surgical approach are not universally agreed upon. In fact, there are very dogmatic and opposing opinions among many highly skilled surgeons regarding the merits of each approach. This suggests there is more than one acceptable approach and that a surgeon’s personal experience should play an important role in the selection. Similar to the choice between observation, surgery, and radiosurgery, it is not possible to follow a standard decision tree to arrive at a “best” surgical approach. Rather, it is important to fully understand the pros and cons of each approach in the surgeon’s own hands based on personal experience. An honest assessment of one’s own results with the different strategies is critical to achieving the best possible outcome for each individual patient.

Detailed descriptions of each surgical approach are presented in separate chapters and will not be repeated here: the TL approach is presented in Chapters 33 and 34, the RS approach in Chapters 35 and 36, the MF approach in Chapter 37, and the endoscopic transcanal transpromontorial approach in Chapter 39. Instead, this chapter will review thought processes and nuances regarding approach selection and highlight how various factors impact decision making. Our view of the suitability of the various approaches in different clinical situations has evolved over time as a result of critical analysis of our results.

Specific tumor characteristics, anatomic factors, and patient factors will exclude or favor a particular approach. Typically, there are competing factors and the weighted importance of each need to be estimated. For example, a hearing preservation approach may slightly increase the likelihood of tumor recurrence. If that is true, then we must consider how likely we are to preserve hearing in a specific case. In the following sections, we highlight the factors that ultimately drive us to a particular surgical approach. In many cases, there are equally valid options, in our opinion. A list of commonly referenced advantages and limitations of the three approaches is outlined in Table 31‑1 .

31.2 Tumor Characteristics

31.2.2 Tumor Location

Tumor location is another important factor to consider when selecting a surgical approach. For a hearing preservation case, an IAC tumor located at the fundus would be approached by the MF approach but that same tumor at the porus would most often be removed through the RS approach. A tumor that deeply impacts the fundus and modiolus may be very challenging to save functional hearing regardless of approach (Fig. 31‑5 ). For a large tumor that has its greatest dimension parallel to the petrous bone and anterior to the axis of the IAC, we would favor an RS approach (Fig. 31‑6 ). In contrast, the same sized tumor that is deeply indenting the brainstem is more favorably approached through the TL corridor. If there is evidence of tumor extension into the labyrinth, the TL or transotic approach provides the best access (Fig. 31‑7 ). Also, if there is the potential for needing to place an interposition graft, perform a hypoglossal-facial anastomosis, or insert a cochlear implant, the TL approach provides all the needed flexibility.

31.3 Anatomic Factors

Specific patient anatomy should influence the choice of surgical approach. The venous drainage system should always be inspected on preoperative magnetic resonance imaging (MRI) scans. There is a higher risk of injuring the sigmoid sinus and jugular bulb with the TL approach. If the patient has a highly dominant or solitary transverse sigmoid sinus system, then we are more likely to consider the RS approach (Fig. 31‑8 , Fig. 31‑9 ).

A “high” jugular bulb is often cited as a reason to choose the RS approach but this decision is more nuanced. We have seen the jugular bulb extend superior to the IAC, making exposure of the IAC tumor impossible without decompressing this part of the venous system and compressing the bulb inferiorly (Fig. 31‑10 )—a very difficult task working through the RS craniotomy. In these cases of unusual venous anatomy, it is easier and safer to work through the mastoid (Fig. 31‑11 ).

A very sclerotic mastoid with an anteriorly displaced sigmoid sinus makes the TL approach more difficult and thus the RS relatively more favored (Fig. 31‑12 , Fig. 31‑13 ). Patients with chronic ear disease, tympanic membrane perforation, or potential to develop cholesteatoma are usually best approached by avoiding the potentially infected or diseased mastoid and middle ear. Thus, in these cases we favor the RS or MF approach. In the unusual case were the TL is still preferred, subtotal petrosectomy with ear canal closure may be used to first address any concomitant ear disease.

Prior surgical history may be a significant factor in selecting surgical approach. For recurrent tumors, we tend to favor utilizing a different approach from the original surgery.s. Literatur This allows the initial dissection to proceed through previously untouched surgical planes, thereby avoiding scar tissue or inadvertent injury of decompressed structures. Hearing preservation is rarely a consideration when approaching a recurrent tumor; therefore, we typically use the RS or TL approach. A patient with an open mastoid cavity may be better approached through an RS craniotomy to decrease risk of infection and simplify the surgery. There are many other surgeries or procedures patients may have undergone that could impact the general advantages and disadvantages of each approach and must therefore be factored in to the final selection.

While not commonly discussed, body habitus may influence decision making regarding approach selection. A morbidly obese patient with a short neck can make the RS approach highly unpleasant. We perform most RS cases with the patient in a lateral decubitus position, which is less safe than a supine position for very large individuals. The TL approach may also be difficult but the shoulder can more easily be accommodated and in the worst cases the ear canal can be oversewn for more access. The MF approach, with the surgeon at the head of the bed, also reduces the impact of body habitus, assuming neck mobility is adequate for head rotation.

31.4 Patient Factors

Hearing status and one’s desire to preserve it is the most obvious and initial patient factor to consider. If hearing preservation is considered feasible, then the TL approach is not used. As mentioned previously, the specific tumor location in the IAC will lead us to either the MF or RS approach when attempting to preserve hearing. However, there is a higher risk of temporary and permanent facial nerve weakness with the MF approach as expanded upon later in the chapter. Depending on the patient’s wishes and their priority placed on facial nerve function, we may use the RS approach in the setting of a tumor at the fundus that we would typically prefer to remove through the MF approach. It may even be reasonable to sacrifice excellent hearing to maximize the chances of having normal facial nerve function in select cases. For example, some patients have felt that their careers depend on an attractive aesthetic appearance and normal facial nerve function—trial lawyers and TV personalities have been a few that we have encountered. Based on past experience, we are confident that we will achieve normal facial nerve function in over 95% of cases when the tumor is restricted to the IAC and removed through the TL approach. For us, the MF approach is less predictable (Fig. 31‑14 ).

For a patient with a history of chronic headaches or migraines, we commonly prefer the TL approach when hearing preservation is not a major consideration. Although the risk of long-term headaches appears to be similar regardless of treatment approach, in our experience, patients with a headache history have more trouble in the first 3 to 6 months following RS surgery.s. Literatur

Preoperative dizziness or the concern for postoperative dizziness is commonly cited as a reason to perform the TL approach. However, the notion that one particular approach is better than another is not strongly supported by the literature, and thus is not a factor we consider.s. Literatur ^,​ s. Literatur

The MF approach requires extradural retraction of the temporal lobe. While patients generally tolerate this quite well, we commonly avoid this approach in patients older than 65 years or in patients with a known seizure disorder. While many cite retraction of the cerebellum as a disadvantage of the RS, this does not appear to have a long-term influence on patient outcome regardless of age.s. Literatur

There is no question that every patient wants to spend as little time as possible in the hospital and the recovery process, but this may be even more important for some. As a whole, patients undergoing TL tumor removal recover faster than the RS cohort. They tend to have less headache, neck pain, and fatigue. If there is a low likelihood of preserving hearing, it may be reasonable to forgo trying and use the TL approach with the primary goal being a quicker recovery.s. Literatur

Related posts:

28 Intraoperative Eighth Nerve Monitoring During Vestibular Schwannoma Microsurgery 32 Management of the Facial Nerve During Vestibular Schwannoma Microsurgery 33 Translabyrinthine Approach for Vestibular Schwannoma Resection 38 Transotic Approach for Vestibular Schwannoma Resection 44 Salvage Microsurgery After Radiation Treatment of Vestibular Schwannoma 48 Postoperative Counseling, Restrictions, and Care

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