204
hemorrhage and may allow a patient to recover
more readily from the bleed by removing blood
and toxic blood products from the eloquent struc-
tures of the brainstem.
Preoperative Evaluation
Patient History and General
Considerations
The preoperative evaluation of patients with poste-
rior circulation vascular lesions should begin with
a thorough history and physical examination [ 87 ].
The history should consist of family history of
aneurysms or vascular malformation, personal his-
tory of prior hemorrhage, predisposing factors
such as hypertension, fibromuscular, and collagen
vascular disorders, and disorders such as Osler-
Weber-Rendu syndrome. The patient’s social his-
tory, specifically smoking and illicit drug use,
should be obtained. History of recent infection,
trauma, cancer, or immunosuppression should also
be obtained, as these can predispose patients to the
risk of rare aneurysm types, such as infectious or
traumatic aneurysm formation. The patient should
be asked to describe symptoms and durations
because some patients may have experienced a
sentinel bleed, a forbearer of a larger eventual
hemorrhage from an aneurysm or vascular malfor-
mation. The patient should also be questioned
regarding nausea, vomiting, or a history of tran-
sient weakness, which may be indicative of com-
pressive or ischemic etiology. A review of patient
medications often reveals much about other under-
lying conditions that could predispose the patient
to the formation of aneurysms or ischemic lesions
in the posterior circulation. Additionally, medica-
tions such as antiplatelet and antithrombotic medi-
cations should be noted. Allergies to medications
can also reveal much about patient physiology.
Specifically, any allergy to common antiplatelet
medications should be noted.
A detailed physical examination, including a
thorough neurological examination, should be per-
formed to evaluate for alterations in mood, cogni-
tion, new onset or progressive weakness, gait
instability, evidence of cerebellar dysfunction,
brainstem symptoms, and cranial nerve deficits.
Patients undergoing microsurgical treatment
of vascular pathologies should undergo routine
laboratory testing including a basic metabolic
panel, a complete blood count, coagulation sta-
tus, and a chest x-ray. Patients with a history of
cardiac disease should be evaluated and cleared
by a cardiologist for surgery. An additional group
of patients who require close medical workup are
those who will undergo surgery in a sitting posi-
tion because the presence of a patent foramen
ovale in this position can result in preventable
complications.Diagnostic ImagingIn patients who present with sudden onset neuro-
logical alterations, the initial evaluation should
include computed tomography (CT). CT has a
sensitivity of nearly 100% for detecting SAH
immediately after ictus [ 88 ]. When hemorrhage
is not shown on CT but the patient has a history
concerning for hemorrhage, a lumbar puncture
should be performed to evaluate the presence of
any blood cells. All patients who are suspected of
having vascular lesions in the posterior circula-
tion should undergo a CT angiography (CTA)
study. CTA with three-dimensional reconstruc-
tion protocols can evaluate the vascular tree,
including collateral circulation and can identify
aneurysms, dissections, vascular malformations,
and vascular malignancies. CTA has a sensitivity
of 96% for aneurysms as small as 3 mm, but may
underestimate the size of partially thrombosed
aneurysms [ 89 , 90 ]. For cases of suspected vas-
cular lesions, we favor obtaining imaging of the
vasculature of the head and neck.
An alternative to CT is magnetic resonance
imaging (MRI) and magnetic resonance angiog-
raphy (MRA). These modalities permit improved
visualization of soft tissues and better assessment
of aneurysm size compared to CT. MRI can help
delineate the proximity of the vascular malfor-
mations to eloquent brain regions. Because blood
of various ages has different signal intensities,
MRI can help identify the age of any hemorrhage
from cavernous malformations. Fluid-attenuated
inversion recovery (FLAIR) MRI sequences
have a sensitivity approaching that of CT forM.Y.S. Kalani and R.F. Spetzler