Skull Base Surgery of the Posterior Fossa

210

Approaches to the Lateral Medulla

The lateral medulla can be exposed using a low
retrosigmoid or a far lateral approach [ 85 , 86 ,
123 ]. These approaches allow for visualization of
the lower BA, the vertebrobasilar junction, the
VA, the PICA, and the lateral medullary surface.
Aneurysms involving these arteries can be surgi-
cally treated using these approaches with excel-
lent proximal control and exposure for treatment.
Additionally, AVMs of the lateral cerebellar
hemisphere and lateral medulla can be resected
using these approaches. These approaches also

expose the anterior medullary sulcus, the olive,

and the lateral medullary zone (or the inferior

cerebellar peduncle), all of which can be used as

safe-entry zones to resect intrinsic medullary

lesions.

Approaches to the Dorsal Medulla

and Cervicomedullary Junction

The posterior medulla and the cervicomedullary

junction can be exposed using a suboccipital cra-

niotomy. In addition to pontine lesions, the suboc-

Fig. 14.9 Retrosigmoid approach to an anterior inferior
cerebellar artery (AICA) aneurysm. A 68-year-old woman
presented who had a history of aneurysmal subarachnoid
hemorrhage 4 years previously caused by rupture of an
AICA aneurysm, which was treated by a flow-diverting
device. Upon presentation to our institute, the aneurysm
exhibited (a) continued growth on computed tomography
angiography. (b) Anteroposterior and (c) lateral vertebral
artery angiography better delineates the anatomy of the

recurrent right AICA aneurysm. The aneurysm was

approached using a right retrosigmoid craniotomy. The

aneurysm was occluded using a stacking clipping strategy.

Postoperative (d) anteroposterior and (e) lateral vertebral

artery angiography demonstrates complete occlusion of

the aneurysm with preservation of the parent artery (Used

with permission from Barrow Neurological Institute,

Phoenix, Arizona)

M.Y.S. Kalani and R.F. Spetzler