The No-Drill Technique of Anterior Clinoidectomy—A Skull Base Approach Tailored to Pathology

Introduction: Published articles describe a power drilling technique of anterior clinoidectomy. The entire “shaft” of the power drill is exposed in the operative field; thus all neurovascular structures in proximity to the full length of the rotating drill bit are at risk of direct mechanical and thermal injury. Ultrasonic bone removal has been recently developed. However, ultrasound-related cranial neuropathies are recognized complications of its use, in addition to its increased cost.

Methods: A retrospective review of the author's 40 consecutive cases of anterior clinoidectomy utilizing the no-drill technique is presented. Clinical indications include: ophthalmic segment aneurysms, tuberculum sellae meningiomas, clinoidal meningiomas, selected ICA-PComm and ICA bifurcation aneurysms, other large/giant/complex anterior circulation aneurysms, basilar bifurcation aneurysms, cavernous sinus lesions, pituitary macroadenomas, other perichiasmal lesions (sarcoid), and fibrous dysplasia.

Results: A bony opening is made in the mid-to-posterior orbital roof during the process of the initial pterional craniotomy. Periorbita is dissected from inside the orbital compartment. Subsequent piecemeal resection of the medial sphenoid wing, anterior clinoid process, and optic canal roof is performed with various bone-biting instruments. No power drilling was employed in this series. Optimal microsurgical exposure was obtained in all cases. There were no cases of direct injury to surrounding neurovascular structures. Illustrative cases demonstrating intraoperative surgical technique are presented.

Conclusions: Power drilling is generally not necessary for anterior clinoidectomy. Rigorous study of preoperative CT (and CTA), MRI, and angiogram is essential to identify important anatomic relationships between the anterior clinoid and neighboring neurovascular structures. The no-drill technique eliminates the risks of direct power-drilling mechanical/thermal injury and the risk of ultra-associated cranial neuropathies.