Among them, those located at its so-called M1 segment (from its origin up to the bifurcation) range between 2% and 7% of all the aneurysms.
Most MCA aneurysms have been found at the division of the M1-M2 junction due to hemodynamic stress or congenital factors 2).
The majority of distal MCA aneurysms are located at the M2 or M3 segments 6).
Eighteen intracranial aneurysms, including 13 unruptured and 5 ruptured aneurysms, were treated with LVIS Jr stent-assisted coil embolization.
A total of 18 stents were successfully delivered to the target aneurysms, and the technical success rate was 100%. There was complete occlusion in 8 (44.4%) of 18 cases, neck remnants in 7 (38.9%) cases, and partial occlusion in 3 (16.7%) cases. In-stent thrombosis occurred in 1 case, and the symptoms disappeared after transvenous tirofiban injection. The modified Rankin Scale score at discharge was 0 in 14 patients, 1 in 3 patients, and 2 in 1 patient.
The LVIS Jr stent provided excellent trackability and deliverability and is safe and effective for the treatment of wide-necked MCA aneurysms with tortuous and smaller parent vessels 8).
Lyon et al. report the presentation and successful endovascular treatment of a large, ruptured, middle cerebral artery bifurcation aneurysm in a 5-week-old girl, one of only a few reported in the literature. Clinical and radiological findings at follow-up are also presented. The authors then review the literature on aneurysmal subarachnoid hemorrhage in infants, with particular regard to outcome after either endovascular or open surgical management. They also provide recommendations for follow-up in pediatric patients whose intracranial aneurysms have been treated with coil embolization 9).
Sejkorová et al., analyzed a case of a ruptured middle cerebral artery (MCA) aneurysm for which they acquired imaging data at three time points, including at rupture. A patient with an observed MCA aneurysm was admitted to the emergency department with clinical symptoms of a subarachnoid hemorrhage. During three-dimensional (3D) digital subtraction angiography (DSA), the aneurysm ruptured again. Imaging data from two visits before rupture and this 3D DSA images at the moment of rupture were acquired, and computational fluid dynamics (CFD) simulations were performed. Results were used to describe the time-dependent changes of the hemodynamic variables associated with rupture. Time-dependent hemodynamic changes at the rupture location were characterized by decreased WSS and flow velocity magnitude. The impingement jet in the dome changed its position in time and the impingement area at follow-up moved near the rupture location. The results suggest that the increased WSS on the dome and increased low wall shear stress area (LSA) and decreased WSS on the daughter bleb with slower flow and slow vortex may be associated with rupture. CFD performed during the follow-up period may be part of diagnostic tools used to determine the risk of aneurysm rupture 10).
Ravindra et al., report the case of a previously healthy 6-month-old girl who presented with right arm and leg stiffening consistent with seizure activity. An initial CT scan of the head demonstrated acute subarachnoid hemorrhage in the basal cisterns extending into the left sylvian fissure. Computed tomography angiography demonstrated a 7 × 6 × 5-mm saccular aneurysm of the inferior M2 division of the left middle cerebral artery. The patient underwent left craniotomy and microsurgical clip ligation with wrapping of the aneurysm neck because the vessel appeared circumferentially dysplastic in the region of the aneurysm. Postoperative angiography demonstrated a small remnant, sluggish distal flow, but no significant cerebral vasospasm. Fifty-five days after the initial aneurysm rupture, the patient presented again with an acute intraparenchymal hemorrhage of the left anterior temporal lobe. Angiogram revealed a circumferentially dysplastic superior division of the M2 branch, with a new 5 × 4-mm saccular aneurysm distinct from the first, with 2 smaller aneurysms distal to the new ruptured aneurysm. Endovascular parent vessel occlusion with Onyx was performed. Genetic testing revealed a mutation of the MYH11. To the authors' knowledge, this is the first report of rapid de novo aneurysm formation in an infant with an MYH11 mutation. The authors review the patient's clinical presentation and management and comprehensively review the literature on this topic 11).
A 56-year-old woman with an unruptured, multi-lobulated MCA aneurysm, whom primarily refused surgery; therefore, she was scheduled for stent-assisted coiling. After successful deployment of the stent, it unfortunately then became snagged by the microcatheter and was pulled backwards. The subsequent surgical procedure (i.e. clipping of the MCA aneurysm) was challenging, due to the position of the dislodged stent. Such as misplacement of the stent is rarely documented: It resulted in the difficult handling of a MCA aneurysm. Aneurysms of the MCA should primarily be considered for surgical clipping. In conclusion, an increased risk for eventual surgery should be considered, in cases where endovascular treatments with stents are performed. 12).
A case of a huge intramural hematoma in a thrombosed middle cerebral artery aneurysm. A 47-year-old female patient with liver cirrhosis and thrombocytopenia presented to the neurosurgical unit with a 5-day history of headache and cognitive dysfunction. Magnetic resonance imaging and computed tomography of the brain showed a thrombosed aneurysm located in the right middle cerebral artery with a posteriorly located huge intramural hematoma mimicking an intracerebral hematoma. Imaging studies and cerebrospinal fluid analysis showed no evidence of subarachnoid hemorrhage. Angiography showed a partially thrombosed aneurysm at the origin of the right anterior temporal artery and an incidental aneurysm at the bifurcation of the right middle cerebral artery. Both aneurysms were embolized by coiling. After embolization, the thrombosed aneurysmal sac and intramural hematoma had decreased in size 4 days later and almost completely disappeared 8 months later. This is the first reported case of a nondissecting, nonfusiform aneurysm with a huge intramural hematoma, unlike that of a dissecting aneurysm 13).