Far lateral approach with intraoperative ultrasound Doppler identification of the vertebral artery.

A 69-year-old woman presented with right hemiparesis and magnetic resonance imaging revealed a meningioma at the ventral aspect of the foramen magnum. We used a retromastoid curvilinear incision down the lateral aspect of the neck to expose the semispinalis and other muscles. Guided by ultrasound to avoid damage to the vertebral artery beneath the semispinalis, we incised the semispinalis muscle in a U-shape that hinged at the retromastoid curvilinear incision with its one limb along the border of the foramen magnum and the other limb along the posterior arch of the atlas. The other muscles were divided in line with the curvilinear incision and retracted posteriorly with the bulk of semispinalis to expose the bones, not disturbing the U-shaped piece of semispinalis that covered the vertebral artery. Similarly guided by ultrasound, we performed far lateral suboccipital craniectomy and laminectomy, exposed the dura above and below the dural entry of the vertebral artery, opened the dura cephalad and caudal to the dural entry of the vertebral artery, and excised the tumor. This method provided adequate exposure to the lateral aspect of the cranio-vertebral junction and minimized the risks of dissecting the whole extradural segment of vertebral artery. It requires more cases to determine whether the results of this patient can be generalized.