Recurrence pattern predicts aneurysm rupture after coil embolization

Introduction Hemorrhage from a recurrent aneurysm is a major concern after coiling for intracranial aneurysms. We aimed to identify aneurysm recurrence patterns associated with hemorrhage. Material and methods We investigated radiological data of patients who underwent coiling for intracranial aneurysms in 2008–2016 and were followed-up for at least 6 months. Aneurysm recurrence patterns were classified as: type Ⅰ, enlargement of aneurysm neck; type Ⅱ, recurrent cavity within the coil mass; type Ⅲ, recurrent cavity along the aneurysm wall; and type Ⅳ, formation of a daughter sac. We evaluated the incidence of various recurrence patterns with or without hemorrhage. Results Of the 173 aneurysms included in the study (mean follow-up period, 32 months; range, 6–99 months), 22 (13%) recurred and required re-treatment. The recurrence patterns included type Ⅰ, Ⅱ, Ⅲ, and Ⅳ in 7 (4%), 4 (2%), 9 (5%), and 2 (1%) cases, respectively. Most of the type Ⅰ, Ⅱ, and Ⅲ recurrences occurred within 1 year, and type Ⅳ occurred at 7 years after coiling. Three aneurysms exhibited hemorrhage, one with type Ⅲ and two with type Ⅳ pattern. The two aneurysms with type Ⅳ recurrence initially occurred as type Ⅰ; however, the recurrent neck enlarged gradually, resulting in new sac formation. Conclusions We recommend prompt re-treatment for aneurysms recurring with type Ⅲ or Ⅳ patterns, as such patterns were associated with hemorrhage. Furthermore, we need a special care to type Ⅰ recurrence with enlargement of recurrent neck because this specific pattern may develop to type Ⅳ.