The "no-drill" technique of anterior clinoidectomy: a cranial base approach to the paraclinoid and parasellar region.

INTRODUCTION: A high-speed power-drilling technique of anterior clinoidectomy has been advocated in all publications on paraclinoid region surgery. The entire shaft of the power drill is exposed in the operative field; thus, all neurovascular structures in proximity to any portion of the full length of the rotating drill bit are at risk for direct mechanical and/or thermal injury. Ultrasonic bone removal has recently been developed to mitigate the potential complications of the traditional power-drilling technique of anterior clinoidectomy. However, ultrasound-related cranial neuropathies are recognized complications of its use, as well as the increased cost of device acquisition and maintenance.

METHODS: A retrospective review of a cerebrovascular/cranial base fellowship-trained neurosurgeon's 45 consecutive cases of anterior clinoidectomy using the "no-drill" technique is presented. Clinical indications have been primarily small to giant aneurysms of the proximal internal carotid artery; however, in addition to ophthalmic segment aneurysms, selected internal carotid artery-posterior communicating artery aneurysms and internal carotid artery bifurcation aneurysms, and other large/giant/complex anterior circulation aneurysms, this surgical series of "no-drill" anterior clinoidectomy includes tuberculum sellae meningiomas, clinoidal meningiomas, cavernous sinus lesions, pituitary macroadenomas with significant suprasellar extension, other perichiasmal lesions (sarcoid), and fibrous dysplasia. A bony opening is made in the mid-to posterior orbital roof after the initial pterional craniotomy. Periorbita is dissected off the bone from inside the orbital compartment. Subsequent piecemeal resection of the medial sphenoid wing, anterior clinoid process, optic canal roof, and optic strut is performed with bone rongeurs of various sizes via the bony window made in the orbital roof.

RESULTS: No power drilling was used in this surgical series of anterior clinoidectomies. Optimal microsurgical exposure was obtained in all cases to facilitate complete aneurysm clippings and lesionectomies. There were no cases of direct injury to surrounding neurovascular structures from the use of the "no-drill" technique. The surgical technique is presented with illustrative clinical cases and intraoperative photographs, demonstrating the range of applications in anterior and central cranial base neurosurgery.

CONCLUSION: Power drilling is generally not necessary for removal of the anterior clinoid process, optic canal roof, and optic strut. Rigorous study of preoperative computed tomographic scans/computed tomographic angiography scans, magnetic resonance imaging scans, and angiograms is essential to identify important anatomic relationships between the anterior clinoid process, optic strut, optic canal roof, and neighboring neurovascular structures. The "no-drill" technique eliminates the risks of direct power-drilling mechanical/ thermal injury and the risks of ultrasound-associated cranial neuropathies. The "no-drill" technique provides a direct, time-efficient, and efficacious approach to the paraclinoid/ parasellar/pericavernous area, using a simplified mechanical route. This technique is applicable to any neurosurgical diagnosis and approach in which anterior clinoidectomy is necessary. It is arguably the gentlest and most efficient method for exposing the paraclinoid/parasellar/pericavernous region.