Object: The investigation of surgical cases of a ruptured middle cerebral artery (MCA) aneurysm to identify the risk factors of an intraoperative premature rupture.
Methods: Based on an 8-year period and among 927 patients with a ruptured intracranial aneurysm, the medical records of 182 consecutive patients with a ruptured MCA aneurysm were examined for cases of a premature rupture, and the risk factors were then investigated. The considered risk factors included: the patient age, gender, WFNS clinical grade, modified Fisher grade, presence of an ICH, frontal ICH, temporal ICH, volume of the ICH, maximum diameter of the ruptured MCA aneurysm, length of the pre-aneurysmal M1 segment between the carotid bifurcation and the MCA aneurysm, and the presence of a sphenoid ridge proximation sign. The use of axial source images and a three-dimensional reconstruction of the brain CTA revealed a sphenoid ridge proximation sign based on the spatial proximation between a potential rupture point of the MCA aneurysm and the cortical arachnoid of the sphenoidal sylvian fissure, adjacent superficial sylvian veins, and the sphenoid ridge.
Results: A total of 11 patients (6.0%) suffered a premature rupture of the MCA aneurysm during surgery. The premature rupture occurrences were classified according to the stage of the surgery as follows: 1) craniotomy and dural opening (n = 1), 2) aspiration or removal of the ICH (n = 1), 3) retraction of the frontal lobe (n = 1), 4) dissection of the sphenoid segment of the sylvian fissure to access the proximal vessel (n = 4), and 5) peri-aneurysmal dissection (n = 4). Univariate and multivariate analyses revealed that the presence of a sphenoid ridge proximation sign, a frontal ICH associated with the ruptured MCA aneurysm, and the length of the pre-aneurysmal M1 segment were all statistically significant risk factors for a premature rupture of a MCA aneurysm.
Conclusions: Patients exhibiting a sphenoid ridge proximation sign, the presence of a frontal ICH, and/or a short pre-aneurysmal M1 segment are high-risk patients for an intraoperative premature rupture of a MCA aneurysm. Such high-risk MCA aneurysms have a superficial location close to the arachnoid in the sphenoidal compartment of the sylvian fissure and have a rupture point directing anteriorly.