212
ized controlled trials, the International
Subarachnoid Aneurysm Trial (ISAT) [ 124 ] and
the Barrow Ruptured Aneurysm Trial (BRAT)
[ 17 ]. A shortcoming of ISAT, in particular, is the
relatively small number of posterior circulation
aneurysms that were treated in this trial, 3%, yet
the results of the trial were widely applied to all
posterior circulation aneurysms. In the BRAT
study, endovascular coil embolization did seem
to confer an improved outcome, with results that
were sustained at both 3- and 6-year follow-ups
[ 125 , 126 ]. Based on this data, and many smaller
case series, the current treatment recommenda-
tion for most posterior circulation aneurysms is
an endovascular first approach. This recommen-
dation does not preclude scenarios in which sur-
gical treatment can be an alternative and, at times,
a better alternative to endovascular therapy.
With regard to surgical outcomes of posterior
circulation aneurysms for each specific vascular
territory, several studies warrant discussion and
are described below.Basilar and Vertebral Artery Aneurysms
Peerless et al. [ 127 ] reviewed their extensive
experience with microsurgical clipping of BA
aneurysms and reported a morbidity of 25%
and mortality rate of 8% for all basilar aneu-
rysms treated. In their series, the rate of mor-
bidity was related to the size of the aneurysm.
The morbidity and mortality was 13% for small
aneurysms and increased to 42% for giant aneu-
rysms. Samson et al. [ 128 ] reviewed their
results with surgical treatment of basilar apex
aneurysms and noted a rate of morbidity of
17% and a rate of mortality of 7% at the time ofFig. 14.11 Retrosigmoid, trans-middle cerebellar pedun-
cle approach to a pontine cavernous malformation. A
38-year-old woman with a pontine cavernous malforma-
tion presents for evaluation. (a) Preoperative axial
T2-weighted and (b) sagittal T1-weighted magnetic reso-
nance imaging scans demonstrate the lesion. The middle
cerebellar peduncle (MCP) safe-entry zone was used to
approach this pontine lesion. (c) Postoperative axial
T2-weighted and (d) sagittal T1-weighted magnetic reso-
nance imaging scans demonstrate the complete removal
of the lesion. (e) Intraoperative neuronavigation trajecto-
ries in axial and (f) coronal views demonstrate the trajec-
tory of surgical approach without (vertical dashed line at
right) and with (vertical dashed line at left) the dissection
of the petrosal fissure. Dissection of the petrosal fissure is
an important step for dissection and exposure of the MCP
during a transpeduncular approach to the pons (Used with
permission from Barrow Neurological Institute, Phoenix,
Arizona)M.Y.S. Kalani and R.F. Spetzler