Introduction The endovascular treatment of middle cerebral artery (MCA) aneurysms has been controversial due to the frequency of complex anatomy and relative ease of surgical clipping in this location. We present the largest reported single-centre experience in the endovascular treatment of MCA aneurysms.

Methods The neurointerventional database at our institution was reviewed for all endovascular treatments of MCA aneurysms through August 2012. Patient demographics, aneurysm characteristics, treatment modality, intraprocedural haemorrhagic and thromboembolic events (any occurrence of intraprocedural thrombus or embolus), 30-day periprocedural neurological events and follow-up angiographic studies were recorded.

Results From December 1996 to August 2012, 281 patients underwent 331 attempted endovascular procedures for treatment of an MCA aneurysm. Of these, 326 procedures were completed (5 attempted and failed). 217 procedures used balloon assistance. 85 were primary coilings. 4 were with the Pipeline device. 25 were with stent assistance. 17 were retreatments. 92 were for ruptured aneurysms. Mean aneurysm size was 6.6 mm.

The rate of intraprocedural aneurysm rupture or vessel perforation was 2.7% (9 of 331). 2 resulted in disabling strokes (mRS>2 at discharge) in patients with unruptured aneurysms, comprising the only patients with new disabling strokes with unruptured aneurysms in the entire cohort (0.6%, 2 of 331).

The rate of intraprocedural thromboembolic events was 13.9% (46 of 331), mostly in patients with acute subarachnoid haemorrhage (SAH, p<0.0001). Of these, 10 were symptomatic (3.0%); 9 of the 10 had SAH. Of the 10, 3 were transient ischaemic attacks (TIA) and 7 were strokes in the setting of SAH with confounding factors, either severe vasospasm (n = 4) or a large Sylvian clot with surrounding oedema (n = 3). 6 of the 7 went on to have mRS>2 at discharge.

In patients without intraprocedural thromboembolic events, there were no disabling strokes in patients with unruptured aneurysms. There were an additional 3 TIA’s (1 with SAH) and 6 non-disabling strokes (1 with SAH) within 30 days. There was one non-disabling delayed parenchymal haemorrhage (IPH) in a patient who underwent stent-assisted coiling of an unruptured aneurysm. There were 3 strokes in the setting of SAH with confounding severe vasospasm; 2 of these were disabling.

The rate of angiographic occlusion or near occlusion at 6 months or greater follow-up was 76.2% (214 out of 281).

Conclusion Endovascular treatment of MCA aneurysms is associated with a high intraprocedural thromboembolic event rate, though mostly asymptomatic and in the setting of acute SAH. Almost all periprocedural strokes were confounded by severe vasospasm or a large Sylvian clot with surrounding oedema. In the absence of these factors, endovascular treatment of MCA aneurysms is safe and effective with current technology, and indications for endovascular treatment of this subgroup will likely continue to expand as newer devices become available.

Disclosures Y. Kadkhodayan: None. J. Delgado Almandoz: 2; C; Covidien. J. Fease: None. J. Scholz: None. R. Anderson: None. B. Crandall: 2; C; Covidien. D. Tubman: 2; C; Covidien, Microvention.