Skull Base Surgery of the Posterior Fossa

20

injure it with posterior retraction of the sterno-
cleidomastoid muscle. The facial nerve should be
identified as it exits the stylomastoid foramen and
passes lateral to the styloid process before enter-
ing the parotid gland anteriorly. The facial nerve
may be transposed anteriorly to increase access
to the petrosal portion of the jugular foramen, but
this typically causes weakness. The styloid pro-
cess can be removed if access to the high internal
carotid and anterior aspect of the jugular foramen

is desired. Removal of the rectus capitis lateralis

muscle opens the posterior edge of the jugular

foramen (Fig. 1.2d).

Lateral

The simplest lateral trajectory to the posterior

fossa is a subtemporal approach, which is limited

inferiorly by the tentorium, but can expose the

Fig. 1.10 Transtemporal postauricular approach to jugu-
lar foramen. (a) Left mastoid and cervical exposure.
Lateral exposure of the jugular foramen involves a mas-
toidectomy approach combined with an upper neck dis-
section. It is important to recognize the different muscular
layers and the diverging trajectories of the lower cranial
nerves as they exit the cranium. (b) Mastoidectomy and
internal jugular vein exposure. The transverse process of
the atlas and its muscular relationships with the skull base
is a crucial surgical landmark. The accessory nerve
courses posteriorly toward the sternocleidomastoid mus-
cle near the transverse process and may pass anterior or

posterior to the jugular vein. The internal jugular vein

passes immediately anterior to the transverse process. (c)

Full exposure of left jugular bulb and infralabyrinthine

area. Mobilization of the facial nerve anteriorly increases

the exposure at a risk of irreversible weakness. Detachment

of the rectus capitis lateralis muscle and removal of the

jugular process of the occipital bone further exposes the

posterior part of the jugular foramen. (d) The jugular vein

is resected, and the medial wall of the jugular bulb is pre-

served to avoid damaging the medially located lower cra-

nial nerves. The inferior petrosal sinus empties into the

jugular foramen

J. Basma and J. Sorenson