Intracranial Aneurysms and MR Angiography: Questions and Answers
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Intracranial Aneurysms
Institution
Intracranial Aneurysms
Intracranial Aneurysms and MR Angiography:
Questions and Answers
H. Richard Winn, Department of 1'/eurological Surgery, Uniuersity of Washington School of Medicine, Seattle
Many patients with unruptured aneurysms
come to medical attention because their lesions
are discovered by magnetic r...
Intracranial Aneurysms and MR Angiography:
Questions and Answers
H. Richard Winn , Department of 1'/eu rologica l Surgery , Uni uersity of Was hington School of Medicin e, Sea ttle
Many patients with unruptured aneurysms by MR . If location influences sensitivity of de-
come to medical attention because their lesions tection, the anterior communicating artery lo -
are discovered by magnetic resonance (MR). cation may emerge as the most frequently over-
Recent studies suggest a low ( 1) mortality and looked site. In the Huston et al series , only one
morbidity with surgical obliteration of these un- patient had an aneurysm at this location. In
ruptured aneurysms. This contrasts with signif- regard to the influence of hemorrhage on detec -
icantly higher overall rates once the aneurysm tion rate, the presence of subarachnoid or in-
is ruptured. Thus, a highly reliable and accurate tracerebral hemorrhage , by its appearance ,
detection technique to discover unruptured could increase the rate of detection. However,
aneurysms is desirable and , if available , could as illustrated by the patient in their Figure 3 , the
significantly lower the likelihood of a lethal false -positive rate also may increase.
outcome of aneurysmal subarachnoid A neurosurgeon faced with a patient who may
hemorrhage.
have a cerebral aneurysm needs to know the
The article by Huston et al (2) in this issue of
the AJNR assesses the rate of detection of an- answers to the following questions: Does an
eurysms by MR angiography (MRA). These au- aneurysm exist? Has it ruptured? What is its
thors note that the size of the aneurysm and location and configuration? Are there coexisting
type of MR sequencing influence the sensitivity and perhaps confounding conditions such as
of detection. Thus, 87% of aneurysms greater multiple aneurysms , an arteriovenous malfor-
than 5 mm were detected by time-of-flight mation , or associated athrosclerotic disease in
MRA, but smaller aneurysms were discovered the proximal or cervical vessels? Today , plain
Jess often. MR appears similar in sensitivity to computed tomography and angiography pro -
less costly infusion computed tomography vide answers to these questions , but MR is help-
scanning (3) . The latter technique was capable ful at a secondary level. In the future , further
of detecting 96% and 69% of aneurysms 6 to 9 advances in technology may allow these que s-
mm and 3 to 5 mm, respectively. Among the tions to be addressed by MR technology alone.
relevant questions that remain to be addressed
are the influence of hemorrhage and location on
References
the detection rate (ie , What is the rate of detec-
tion of ruptured versus unruptured aneu- 1. Solo m on RA , F ink M E , Pile-Spell man J, Spellman. J Neurosurg
1993;80:440 - 446
rysms?).
2. Huston J Ill , Nichols DA, Leutm er PH, et al. Blinded p rospective
In our experience, anterior communicating eva lu ation of sensitivity of MR angiography to known intra c ran ial
artery aneurysms are underrepresented in our ane urys m s: im portance of ane urysm size. AJNR Am J f'leurora -
unruptured series compared with patients pre- dio/1994;15 :1607-1614
senting with subarachnoid hemorrhage. Many 3. Newe ll DW , LeRoux PD , Dacey RG , Stimac GK, Winn HR . J
of these unruptured aneurysms are diagnosed Neurosurg 1989;71: 175- 179
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