Radiologic Surveillance of Untreated Unruptured Intracranial Aneurysms: A Single Surgeon's Experience

The management of untreated unruptured intracranial aneurysms remains controversial. The natural history is still not well understood and many patients are not routinely followed up. We present a single surgeon's data on radiologic surveillance of these lesions.

A total of 94 patients with 152 unruptured intracranial aneurysms, with a mean follow-up time of 3.4 years from the time of diagnosis, underwent surveillance using computer tomogram angiography, magnetic resonance angiography, or digital subtraction angiography. Aneurysm growth was defined as an increase in ≥1 dimensions above the measurement error. Statistical analysis was performed.

Of 152 aneurysms, 126 (83%) were <7 mm, 25 (16%) were 7-12 mm, and 1 aneurysm was 13-24 mm. Eighteen of 152 (12%) cerebral aneurysms in 17 patients grew larger; 7% (9/126) of the aneurysms were <7 mm and 36% (9/25) of the aneurysms were 7-12 mm enlarged. Spontaneous aneurysmal rupture occurred in 4 of 152 aneurysms (2.6%) (i.e., 4/94 patients [4%]), with an average initial aneurysm size of 5.7 mm. The risk of aneurysm rupture per patient-year was 5% with growth, 0.2% without growth, and there was a 24-fold increase in aneurysmal rupture risk for growing aneurysm (P = 0.005). Of aneurysms in group 1 patients (no previous subarachnoid hemorrhage [SAH]) 15% (16/109) compared with 5% (2/43) of group 2 (previous SAH) aneurysms showed evidence of growth during the study period (P = 0.0424).

These results support imaging follow-up of patients with untreated unruptured intracranial aneurysms, including those with aneurysms smaller than the current treatment threshold of 7 mm. Apart from the initial size, aneurysm growth is associated with an increased risk of SAH and therefore growing aneurysms warrant treatment. The data also demonstrated that incidental aneurysms, in patients without previous SAH, do not behave less aggressively, contrary to current opinion.