The Combined COZ-Extended Middle Fossa (COZEM) Approach: Anatomical Basis and Case Example

Objective: To describe the advantages and limitations of the combined cranio-orbitozygomatic (COZ) and extended middle fossa (anterior petrosal) approach for resection of skull base tumors.

Introduction: Skull base approaches are intended to maximize exposure of intracranial pathology and limit the need for brain retraction. Occasionally, a single skull base approach will not suffice to expose the entire lesion. In these cases, a staged resection may be planned, but the extra anesthesia and hospitalization may be undesirable. We describe the combined COZ-extended middle fossa approach (COZEM) as a useful method to pathology that extends from floor of the third ventricle to the internal acoustic meatus (IAM). We illustrate the approach with cadaveric dissection and a case example.

Methods: Cadaver heads were prepared with standard fixation and silicone injection. A standard COZ approach was performed followed by extradural removal of Kawase's triangle (anterior petrous ridge). The dura was opened and the tentorium was divided. Wide exposure from the floor of the third ventricle to the IAM was obtained in addition to exposure across the midline.

Case Illustration: A 38-year-old woman presented with headaches and progressive left hemiparesis. On MRI, she was found to have a large epidermoid tumor extending from the floor of the third ventricle to the IAM, with mass effect on the right cerebral peduncle. A gross total resection was performed via a COZEM approach. Postoperatively, the patient developed a transient facial palsy, which completely recovered by 3 months, but was otherwise neurologically intact.

Conclusion: The combined cranio-orbitozygomatic and extended middle fossa (COZEM) approach provides a wide surgical corridor for the resection of skull base lesions. COZEM can be used for single-stage resections of large tumors.