The supraorbital keyhole approach offers a limited access for aneurysms located at the middle cerebral artery (MCA) bifurcation with long M1 segments or proximal M2 aneurysms. Alternative minimally invasive routes centered on the pterion have been developed to address these aneurysms. Appropriate dissection and reconstruction of the temporal muscle are important for optimal exposure and best cosmetic results with the pterional keyhole craniotomy. The authors describe the technical nuances of temporal muscle dissection and reconstruction adapted to the pterional keyhole craniotomy.
After incising the scalp in a curvilinear fashion behind the hairline, an interfascial dissection is performed, allowing anterior reflection of the superficial temporal fat pat and superficial temporal fascia. The temporal muscle is incised 7–10 mm below its insertion at the superior temporal line. The deep temporal fascia and temporal muscle are incised vertically, completing a T-shaped incision. Subperiosteal dissection of both muscle flaps preserves the deep temporal arteries and nerves. A craniotomy measuring 2.5–3 cm in diameter, based anteriorly at the pterion, is made over the sylvian fissure. Dissection of the sylvian fissure and of MCA aneurysms can proceed without the use of retractors. The bone flap and associated hardware is entirely covered by the temporal muscle, which is reconstructed in 2 layers: the temporal muscle/deep temporal fascia and the superficial temporal fascia.
This dissection technique prevents damage to branches of the facial nerve and minimizes temporal muscle damage. Dividing the temporal muscle vertically and reflecting both parts anteriorly and posteriorly prevents suboptimal illumination and visualization under the microscope. Covering the bone flap and related hardware with a multilayer anatomical reconstruction optimizes cosmetic results.