Pushing the Boundaries of the Lateral Orbitotomy through a Lateral Canthotomy Approach: Successful Resection of Two Middle Cranial Fossa Pathologies with Extension into the Posterior Cranial Fossa—An Anatomical and Technical Note

Introduction: A lateral orbitotomy through a lateral canthotomy approach has been reported to provide excellent exposure for both lateral orbital pathology and middle cranial fossa lesions. Possible advantages include decreased tissue trauma, decreased blood loss, shorter hospitalizations, and a better aesthetic outcome compared with conventional craniotomies. Extension of the pathology to the posterior fossa has been thought to be a relative limitation of this approach.

Methods: We present two cases of middle fossa pathology with extension into the posterior fossa that were successfully treated with this approach. The clinical, radiographic, and anatomical data are presented and analyzed. Furthermore, five formalin-fixed, colored silicone-injected cadaveric specimen were microscopically dissected to demonstrate the crucial surgical steps, and illustrate the relevant anatomy.

Results: The first case involves a 38-year-old woman with right-sided trigeminal neuropathy refractory to medical management secondary to a trigeminal schwannoma. The tumor was centered in Meckel’s cave, but extended to the posterior cranial fossa through the porus trigeminus. The patient refused blood transfusion based on religious belief and this approach was chosen partly to minimize blood loss. The second patient was a 73-year-old man with gradual worsening of left-sided vision, ipsilateral refractory trigeminal neuralgia, and partial CN III, IV, V, and VI impairment. Imaging showed a caverno-petro-sphenoidal likely meningioma. The patient had multiple medical comorbidities, which increased the risk of a larger approach. A lateral orbitotomy with lateral canthotomy was thought to be appropriate to minimize the surgical trauma, with the primary goal of surgery being decompression of the neural elements for symptomatic relief. In both cases and all cadaveric dissection, the lateral orbitotomy approach (LOA) provided adequate access to the medial middle cranial fossa and the lateral cavernous sinus wall to accomplish the goals of surgery. Our cadaveric anatomic dissection illustrated the relevant anatomy, e.g., frontalis nerve, canthal ligaments and lateral wall of the cavernous sinus, and clarified the key surgical nuances of this approach, including the steps more unfamiliar to the neurosurgeon e.g., cantholysis, zygomatic osteotomies, and reconstruction. The deep surgical corridor was defined by the anterior clinoid and the anterior petroclinoidal fold superomedially, the tentorial edge and the porus trigeminus in the depth and the maxillary division laterally. With moderate retraction the trigeminal ganglion could be exposed in its entirety. Access to the posterior fossa and visualization of the prepontine and cerebellopontine cisterns was feasible only in live patients when the porus trigeminus was dilated by tumor. A complete resection was achieved in the first case, and a subtotal in the second. Both patients experienced significant improvement in their symptoms after the surgery, had excellent cosmesis and no visual complications.

Conclusion: In selected patients with tumor dilatation of the porus trigeminus, a lateral orbitotomy approach through a lateral canthotomy can be safe and effective for treating middle fossa pathology with extension in the posterior fossa. Possible advantages include decreased blood loss, shorter hospitalization, and a better aesthetic outcome.