Aneurysmal remnants after microsurgical clipping: Classification and results from a prospective angiographic study (in a consecutive series of 305 operated intracranial aneurysms)

The aim of this prospective study, carried out in a consecutive series of 3 05 microsurgically clipped aneurysms, was to check the absence of an aneury smal remnant on post-operative angiography, and if a remnant was found to q uantify its size in order to consider additional cliping to avoid the risk of rebleeding. Out of the 305 aneurysms, 292 (96%) were located in the anterior and 13 (4% ) in the posterior circulation. Post-operative angiography was performed on average two weeks after surgery. Determination of the presence or not of a n aneurysmal remnant and its quantification was done by an independent obse rver (JCA). Aneurysmal remnants were classified into 5 grades: grade I: les s than 50% of neck size, grade II: more than 50% of neck size, grade III: r esidual lobe of a multilobulated sac, grade IV: residual sac of less than 7 5% of aneurysmal size and grade V: residual sac of more that 75% of aneurys mal size. Correlations between presence land size) of the remnant and anato mical-surgical data obtained from the operative report were studied. Clipping was considered incomplete in 18 of the 305 aneurysms (5.9%). The g roup with residual neck only (grade I = 8 cases, Grade II = 4 cases) amount ed to 4% of the whole series, whereas the group with residual neck + sac (g rade III = 4, grade IV = 1, Grade V = 1) to 1.9%. Only this latter group wa s amenable to re-operation for complementary clipping without creating a st enosis of the parent artery. Our results are in the range of those of other published series. Anatomical -surgical factors for predisposition to incomplete clipping are discussed. The rates of sac obliteration using microsurgical clipping are to be compar ed with those recently achieved by electrically detachable coiling. The cla ssification which we have developed is proposed for future comparison with endovascular results.