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Updated: Jul 23, 2026

Microsurgical Clip Obliteration of Middle Cerebral Aneurysm Using Intraoperative Flow Assessment
Published on: September 25, 2009
Small cerebral aneurysms presenting with symptoms other than rupture
J A Friedman1, D G Piepgras, M A Pichelmann
1Department of Neurological Surgery, Mayo Clinic, Rochester, MN 55905, USA. friedman.jonathan@mayo.edu
Small unruptured intracranial aneurysms (<1 cm) can cause symptoms like nerve deficits or stroke. These symptomatic aneurysms may be underrepresented in natural history studies due to preferential treatment.
Area of Science:
- Neurosurgery
- Neurology
Background:
- Natural history studies suggest small unruptured intracranial aneurysms (<1 cm) have a low rupture risk.
- Symptomatic aneurysms may be underrepresented in studies due to preferential treatment.
Purpose of the Study:
- Compare surgically treated symptomatic aneurysms (<1 cm) at Mayo Clinic with ISUIA data.
- Investigate the presentation of small unruptured intracranial aneurysms.
Main Methods:
- Reviewed 97 patients with 117 aneurysms (<1 cm) treated surgically at Mayo Clinic (1980-1991).
- Excluded aneurysms with rupture history or >1 cm on cross-sectional imaging.
- Compared findings with Mayo Clinic patients in the ISUIA retrospective cohort.
Main Results:
- 15.5% of patients (15/97) presented with symptoms other than rupture.
- Symptoms included third nerve deficit, cerebral ischemia, and visual loss.
- No symptomatic aneurysms (<1 cm) were found in the ISUIA retrospective cohort from Mayo Clinic.
Conclusions:
- Small unruptured intracranial aneurysms can cause neurologic symptoms via mass effect or emboli.
- Symptomatic small aneurysms are preferentially treated, potentially underrepresenting them in natural history studies.
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