Introduction: Current rupture risk models are based largely on aneurysm size and location. These models are imperfect as reflected in the aneurysm paradox– the observation that most ruptured aneurysms are small, but that small, incidentally discovered, unruptured aneurysms harbor the lowest rupture risk. It is difficult to determine which incidentally found aneurysms warrant elective treatment to prevent future rupture. Newer imaging strategies, including high-resolution magnetic resonance vessel wall imaging (MR-VWI) for the first time give us an indirect view of the vessel wall in our aneurysm patients. MR-VWI has already proven to be a potent biomarker of aneurysm rupture, and may also be useful in subcategorizing unruptured aneurysms for further risk stratification (1-6).
Methods: A prospectively maintained database of unruptured aneurysms imaged with MR-VWI was retrospectively reviewed (Chart1). Demographic information, medical comorbidities, and aneurysm properties were obtained (Table1). Two expert, blinded reviewers scored aneurysms for degree of wall enhancement (none or thin vs thick) (Fig1). A multivariate logistic regression model was built to assess factors that predicted aneurysm wall enhancement.
Results: Of the 94 unruptured aneurysms included in the final analysis, 64% had none or thin enhancement, and 36% had thick enhancement (inter-rater kappa 0.86, 95% CI=0.76-0.96). Symptomatic presentation (both suspicious headache and cranial nerve palsy) was strongly associated with thick aneurysm wall enhancement (suspicious headache OR=8.6, 95% CI=1.9-45.7; cranial nerve palsy OR=219, 95% CI=13.6-13764). Larger aneurysm size was also independently associated with aneurysm wall enhancement (OR=1.26/mm, 95% CI=1.1-1.5) (Table2).
Conclusions: Symptomatic presentation (suspicious headache, or cranial nerve palsy) and larger aneurysm size were independent predictors for thick aneurysm wall enhancement. This is the first study to determine a relationship between suspicious headache without evidence of overt SAH and aneurysm wall enhancement. This finding provides further evidence that aneurysm wall enhancement may be a useful biomarker to further risk stratify unruptured saccular intracranial aneurysms.
Patient Care: Vessel wall imaging of unruptured intracranial aneurysms represents a new strategy to subcategorize aneurysms for rupture risk assessment. The current work demonstrates that symptomatic presentation (both cranial palsy and suspicious headache) strongly increases the chances that intracranial aneurysms have thick wall enhancement. This suggests that aneurysm wall enhancement may be useful as a predictive factor in assessing unruptured intracranial aneurysms, and high-resolution MR-VWI may become part of the standard assessment protocol for unruptured aneurysms. Future prospective clinical studies designed to address this are warranted.
Learning Objectives: By the conclusion of this session, participants should be able to:
1) Recognize vessel wall enhancement of intracranial aneurysms
2) Describe the potential implications of enhancing intracranial aneurysms
3) Understand the limitations of vessel wall imaging in evaluating intracranial aneurysms
References: 1. Matouk et al., Vessel wall magnetic resonance imaging identifies the site of rupture in patients with multiple intracranial aneurysms: proof of principle. Neurosurgery 2013, Mar 72(3):492-6.
2. Edjlali et al., Does aneurysmal wall enhancement on vessel wall MRI help to distinguish stable from unstable intracranial aneurysms? Stroke 2014, Dec 45(12):3704-6.
3. Omadaka et al., Quantitative assessment of circumferential enhancement along the wall of cerebral aneurysms using MR imaging. AJNR 2016, Jul 37(7):1262-6.
4. Nagahata et al., Wall enhancement of the intracranial aneurysms revealed by magnetic resonance vessel wall imaging using three-dimensional turbo spin-echo sequence with motion-sensitized driven-equilibrium: a sign of ruptured aneurysm? Clin Neuroradiol 2016, Sep 26(3):277-83.
5. Liu et al., Relationship between aneurysmal wall enhancement and conventional risk factors in patients with unruptured intracranial aneurysms: a black-blood MRI study. Interv Neuroradiol 2016, Oct 22(5):501-5.
6. Matouk et al., High-resolution vessel wall magnetic resonance imaging in intracranial aneurysms and brain arteriovenous malformations. Top Magn Reson Imaging 2016, Apr 25(2):49-55.