Skull Base Surgery of the Posterior Fossa

69

dylar fossa (Fig. 5.3e). Exposure of the emis-
sary vein denotes the lateral limit of the basic far
lateral approach (Figs. 5.3f and 5.4).

Transcondylar Variants

Increased anterior exposure of the lower clivus,
basilar artery, and anterior medulla may be gained
with removal of the occipital condyle in part or
whole. The condyles lie in a posterolateral to
anteromedial orientation at the anterolateral
aspect of the foramen magnum. Their articular
surfaces are convex and are oriented inferolater-
ally toward the superior facets of C1, which are
oriented superomedially. The intracranial open-
ing of the hypoglossal canal is situated approxi-
mately 5 mm superior to the condyle, one-third
of the distance from its posterior edge, typically
6–10 mm [ 2 ]. The canal courses anterolaterally,
exiting one-third of the distance behind the
anterior edge of the condyle, medial to the jugu-
lar foramen. As it carries the hypoglossal nerve
within a channel fully surrounded by cortical
bone, removal of the condyle is guided by the

changes from condylar cortex, to cancellous bone

within the condyle, to the posterior cortex of the

canal.

Fig. 5.3 Bone removal of the far lateral approach. (a) The
teardrop-shaped suboccipital craniotomy extends across
the rim of foramen magnum. (b) Soft tissue attachments
are stripped from the ventral surface of the C1 lamina
prior to its removal. (c) The dura is stripped from the rim
of foramen magnum to allow for further lateral bone
removal. (d) A high-speed diamond burr is used to remove
bone of the foramen magnum toward the occipital con-

dyle. (e) Exposure of the posterior condylar emissary vein

(particularly large in this specimen) within the condylar

canal denotes the lateral limit of the far lateral approach.

(f) Removal of the foramen magnum rim to the base of the

condyle and of C1 to the lateral mass completes the far

lateral approach. The dura previously underlying the C1

arch ( 1 ) and suboccipital bone ( 2 ) is fully exposed

Fig. 5.4 Schematic diagram of the basic far lateral expo-

sure. The suboccipital craniotomy and bone removal of

foramen magnum extends from midline to occipital con-

dyle. The laminectomy of C1 extends from midline to the

lateral mass. Occipital condyle ( 1 ), lateral mass of C1 ( 2 ),

transverse foramen of C1 ( 3 ), mastoid tip ( 4 )

5 Far Lateral Approach and Its Variants