Skull Base Surgery of the Posterior Fossa

71

protrusion of the jugular tubercle may limit ante-
rior exposure, and in the manner that removal of
the occipital condyle prominence provides an
opening to the pre-medullary region, so removal
of the jugular tubercle prominence gains access
to the pre-pontomedullary space (Fig. 5.6b). As
the glossopharyngeal, vagus, and accessory
nerves cross the posterior surface of the jugular
tubercle intradurally, performing the transtuber-
cular approach requires the removal of the tuber-
cle without causing cranial nerve injury by
traction or heat. The drilling is most safely done
through an intradural approach, with direct visu-
alization of the lower cranial nerves. Caution
must be also be exercised when drilling the lat-
eral aspect of the jugular tubercle, which abuts
the medial edge of the jugular bulb.
The transtubercular approach can be appreci-
ated by drawing parallels with the familiar
cranio- orbital approach (Table 5.1); each involves
stepwise removal of bone to gain exposure of a
deep target while preserving critical adjacent
neural and vascular structures.

Paracondylar Variants

Further lateral exposure, or access to the poste-

rior aspect of the jugular foramen, can be obtained

with the transjugular variant. Lateral to the poste-

rior part of the occipital condyle is a quadrilateral

prominence extending toward the squamous

occipital bone, the jugular process. The rectus

capitis lateralis extends upward from the trans-

verse process of C1 to insert on the jugular pro-

cess, and detaching this muscle reveals the

extracranial aspect of the jugular foramen imme-

diately anterior. Removal of the jugular process

exposes the transition between the sigmoid sinus

and jugular bulb (Fig. 5.7a). Further lateral expo-

sure of the jugular bulb can be better achieved

using a lateral technique, such as a transtemporal

approach.

Lateral to the jugular foramen, at the anteroin-

ferior end of the digastric groove, is the stylomas-

toid foramen bearing the facial nerve. To gain

access to the mastoid segment of the facial nerve

and the presigmoid dura in the transmastoid vari-

ant, the posterior mastoid is removed up to the

facial canal (Fig. 5.7b). The sigmoid sinus can

then be retracted laterally.

Fig. 5.6 The supracondylar variants. (a) The supracon-
dylar variant increases rostral exposure while preserving
the articular surface of the condyle. The shaded region
denotes exposed cancellous bone below the hypoglossal
canal. (b) Removal of the jugular tubercle in the transtu-

bercular variant provides access to the pre-

pontomedullary region. The edge of bone that is removed

is depicted by the dotted line, and the intradural course

of the cranial nerves exiting the jugular foramen is

shown in yellow

5 Far Lateral Approach and Its Variants