Skull Base Surgery of the Posterior Fossa

72

Intradural Exposure

The dura is opened as an inverted-U with the
medial limb extending inferiorly across the fora-
men magnum opening, and retracted laterally
(Fig. 5.8a). Variations such as a low or medial
sigmoid sinus or transdural PICA must be recog-
nized. Brisk bleeding may arise from a prominent
marginal sinus. If the vertebral artery has been
mobilized medially, the dura is opened while
maintaining a circumferential cuff at its penetra-
tion; the posterior spinal artery may be incorpo-

rated into this fibrous ring and must be preserved.

The dentate ligament and bands of arachnoid

membrane are divided to create windows for

visualization and access to the target pathology

(Fig. 5.8b).

Conclusions

The modifications of the far lateral technique that

are incorporated into any procedure are deter-

mined by the location and extent of pathology

and the specific anatomy of each patient

Table 5.1 Comparison of the cranio-orbital and transtubercular approaches

Cranio-orbital Transtubercular

Craniotomy Frontotemporal Far lateral

Blood supply Superficial temporal artery Occipital artery

Muscle Temporalis Suboccipital muscle group

Bony obstacle (outer) Greater sphenoid wing Foramen magnum

Bony obstacle (middle) Lesser sphenoid wing Occipital condyle

Bony obstacle (inner) Anterior clinoid process Jugular tubercle

“Buried” nerve Optic nerve Hypoglossal nerve

Nerves at risk Superior orbital fissure contents Jugular foramen contents

Nearby artery ICA (clinoidal and supraclinoid

segments)

VA (V3 and V4 segments)

Nearby venous lake Cavernous sinus Jugular bulb

Connecting venous channel Clinoidal space Condylar emissary vein

Fig. 5.7 The paracondylar variants. (a) Removal of the
jugular process lateral to the occipital condyle in the tran-
sjugular variant exposes the posterior aspect of the jugular

bulb. (b) The mastoid segment of the facial nerve is

exposed with removal of posterior mastoid bone in the

transmastoid variant

K. Au et al.