Skull Base Surgery of the Posterior Fossa

207

centeromedian mesencephalon [ 85 , 86 , 112 ]. The

addition of an anterior petrosectomy [ 113 ] allows

the surgeon to expose the basilar trunk down to

the level of the sixth cranial nerve. This additional

exposure can be used to treat aneurysms of the

BA or the AICA, as well as cavernous malforma-

tions located at the mesencephalic-pontine junc-

tion on the ventral surface of the brainstem.

Approaches to the Lateral Midbrain

The lateral midbrain surface can be approached

using a posterior petrosal approach [ 114 ], a retro-

sigmoid approach, or a lateral (or extreme lateral)

supracerebellar infratentorial (SCIT) [ 115 ]

approach. These approaches afford the surgeon

exposure of the lateral PCA and SCA that may be

used for the surgical treatment of aneurysms or

AVMs that involve these vessels. They also allow

the surgeon to visualize the lateral midbrain sur-

face, thereby facilitating removal of intrinsic

lesions, such as cavernous malformations. The

lateral brainstem contains the lateral mesence-

phalic sulcus safe-entry zone, which is readily

exposed using a lateral or extreme lateral SCIT

approach to resect lateral mesencephalic lesions

[ 85 , 86 ]. At our institution, we have moved away

from the use of the posterior petrosal approaches

due to the added morbidity associated with their

use. In lieu of the posterior petrosal approaches,

we prefer to approach lesions in the lateral mid-

brain using the retrosigmoid approach or the

SCIT approach (and its variants).

Fig. 14.7 Skull base approaches to the posterior fossa (Used with permission from Barrow Neurological Institute,
Phoenix, Arizona)

14 Microsurgical Management of Posterior Fossa Vascular Lesions