Introduction Pure arterial malformations (PAM) are rare vascular lesions characterized by dilated, tortuous arterial loops without venous shunting. The natural history of these lesions remains unclear. We report the long-term clinical and radiological outcomes in the largest series of patients with PAM.

Methods Retrospective review at a tertiary academic referral center for patients with a PAM. Follow-up clinical and radiological data were collected and analyzed for clinical symptoms and radiographic changes.

Results Twenty-five patients met the inclusion criteria. The mean age at presentation was 30.9 ± 14 years. Nineteen (76%) patients were female and six (23.1%) were male. Eleven (44%) patients had ≥1 symptom at presentation, of which, only 3 (12%) could be linked to PAM. The most common symptom was headache (n=8). PAMs involved a single vessel in 16 (64%) cases and ≥2 vessels in 9 cases (36%). Fifteen (60%) lesions were isolated to the anterior circulation compared to 6 (24%) in the posterior circulation. The most frequently involved vessel was the supraclinoid internal cerebral artery (36%). An associated saccular aneurysm was present in 32% of patients. Ten lesions were partially calcified. The mean radiographic and clinical follow-up was 21.4 ± 26.6 months and 44.5 ± 34.8 months, respectively. None of the patients developed new symptoms related to their lesion or radiographic progression over the duration of follow-up.

Conclusion PAMs are rare incidental vascular lesions found most frequently in young, asymptomatic females. PAMs have a benign clinical and radiographic natural history and are best managed conservatively with serial imaging.

Disclosures S. Oushy: None. W. Brinjikji: None. H. Cloft: None. R. Vine: None. G. Lanzino: None.