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The most common indications for this approach are repair of superior semicircular canal dehiscence and approach to the IAC for acoustic neuroma resections. Usually small, intracanalicular tumors with good hearing are approached via this route. Vestibular nerve section and total facial nerve decompression, CSF leak, and meningocele repair are other less common indications for this approach. There is significant temporal lobe retraction during this approach, so this makes it less suitable for older patients.

The skull base is a very complex anatomical region with an irregular bony architecture, which is classically divided into anterior, middle, and posterior compartments called fossae. The presence of dural folds, blood vessels, and cranial nerves provides a surgical challenge for even the most experienced neurosurgeon. Several approaches have been described to reach different parts of the middle fossa. These skull base approaches usually require bony drilling for exposure, to control the tumor blood supply, and to minimize brain retraction. Knowledge of anatomy acquired in the laboratory, as well as learning to handle relevant microinstrumentation, including microdrills, is of paramount importance for the young neurosurgeon who is interested in the difficult field of skull base surgery.

The middle cranial base can be divided into a medial portion, the sellar and the parasellar region, where the pituitary gland and cavernous sinus are located and a lateral portion, containing the middle cranial fossa and the upper surface of the temporal bone (Fig. 1). The focus of this paper is the cavernous sinus and adjacent parts of the middle cranial fossa [22, 23].

The middle fossa transpetrosal approach was originally developed by King in 1970, and so-called “extended middle fossa approach”, which was combined with middle fossa craniotomy and translabyrinthine approach [6]. The method was mainly applied to acoustic tumors, but it was indicated to clival lesions by Hakuba et al. [2].

A critical component of many skull base approaches is the safe removal of the petrous bone (Brackmann et al. 1994, Baldwin et al. 1994, Spetzler et al. 1992, Sekhar et al. 1994, Al-Mefty et al. 1988, Hitselberger and House 1966, House 1979, Morrison and King 1973). Petrosectomy opens a corridor of exposure to the center of the skull base. The transpetrosal approaches include the retrolabyrinthine (Spetzler et al. 1994), translabyrinthine (Brackmann et al. 1992, House 1979, Morrison and King 1973), transcochlear (House and Hitselberger 1976), and middle fossa approaches (House and Shelton 1992, Brackmann et al. 1994). Still, exposure gained from these approaches can be limited medially at the region of interest or inadequate for larger lesions. Therefore, transpetrosal approaches have been used in combination with other approaches to gain even more exposure. For example, the combined supra- and infratentorial approach joins the sub temporal and transpetrosal exposures (Daspit et al. 1991, Spetzler et al. 1992, Spetzler et al. 1991, Hitselberger and House 1966) and the far-lateral combined supra- and infratentorial approach adds to them the far lateral exposure (Baldwin et al. 1994, Heros 1986, Sen and Sekhar 1990, Sen and Sekhar 1991, Spetzler and Grahm 1990b, Baldwin et al. 1995). We have continued to experiment with combination approaches, and one that has proven useful is the orbitozygomatic-combined supra- and infratentorial approach. This chapter reviews the surgical anatomy and techniques involved with the transpetrosal approaches, discusses the various combination approaches that use petrosectomy as their foundation, and identifies the current indications for these techniques.

Basilar anterior-inferior cerebellar artery (AICA) aneurysms are rare lesions: detection and treatment of one single aneurysm has been reported only in recent years. In 1989, Kamii described 1 personal case and collected 33 cases in the literature. One year later with another personal, Russegger was able to find 26 cases in the literature. The first case done in our series in 1963 was described in detail (Case 10, G.Mc., cf. Chapter 9, p. 119).

The basilar bifurcation is the most common aneurysm site (50.7%) in the posterior circulation, comprising about 5–6% of all solitary intracranial aneurysms. The majority are saccular, but a few (< 1%) are fusiform in origin. This aneurysm has proved to be the most difficult of all intracranial aneurysms, surgeons having taken a decade longer to reduce its surgical morbidity to near that of any on the anterior circulation.

The meningioma, being a benign tumor, has been intimately involved in the evolution of neurosurgical technique. Since an operative cure is at least theoretically possible with complete tumor removals, attempts at improvement in intra- and perioperative management have usually resulted in significant advances in neurosurgery.

The first case of primary tumor of nerve V was reported by R. W. Smith in 1838 (cited in [43]). Trigeminal neurinomas are not frequent, as they only represent 0.2% of all intracranial tumors [43]. They constitute a special type of cavernous sinus (CS) tumors explained by the anatomical situation of the nerve V, both in Meckel’s cave and the adjacent cerebellopontine angle (CPA) (Fig. 1).

An association between arachnoid cysts of the middle fossa (ACMF) and complicating subdural haematoma (SDH) has been previously noted. More recently it has been hypothesized that ACMF may predispose to SDH formation.

The parasellar space known since Winslow (1732) as the cavernous sinus, although an important vascular and nervous crossroads, has for long been a matter of controversy. The fact that its description still differs from one book to another and that the same term is used to designate the space itself and one of its components, is confusing, particularly for the medical student.