Optic Apparatus Compression between a Pendulous a1 and a Sprawling Skull Base Meningioma Stable for >10 Years: Rationale for Surgery, Approach, and Outcome

Introduction: Expansive skull base meningiomas are not amenable to complete resection; however, limited decompression of a compromised vascular or neural element for functional preservation can be attempted. The indications, timing, and approach for such a “targeted” surgery require much discernment.

Methods: A 68-year-old female with multiple previous contralateral surgeries for a sprawling skull base meningioma presented with poor right eye vision, right eye being her functional eye. Baseline deficits were near-total blindness in left eye, left CN III weakness and Left face numbness. Additionally, she had undergone a left EC-IC bypass with the right hemisphere completely perfused via the Acomm and PComm arteries (ipsilateral stenosed ICA).

MRI over a xxx-year period showed no change in size. The optic chiasm and right optic nerve and tract were compressed by tumor from below ([Fig. 1]). A large pendulous right A1 was also pushing down over this optic pathway ([Fig. 1]). It was unclear as to duration of visual deficit. Visual fields are shown in [Fig. 2]. The patient had been driving and working through this period and was the role provider of her family. Having been under observation with serial imaging and with unknown duration of visual compromise the patient was counseled for selective optic nerve decompression. After initially declining, she later consented to surgery.

Results: A modified right sided cranio-orbito-zygomatic approach was undertaken to debulk the tumor from underneath the optic apparatus in the opticocarotid triangle and between the ICA and CN III. The optic canal was deroofed and falciform ligament was divided to release the optic nerve completely. Intraoperatively a large ipsilateral pendulous A1 artery was noted to be compressing the optic nerve from above ([Fig. 3]) producing an indentation groove on the nerve. The A1 was dissected and elevated from the nerve akin to a “microvascular decompression.” The optic nerve was found to be compressed at three points—at falciform ligament (large supra clinoid ICA pushing the nerve upwards); tumor from below; and A1 from above. At the end of the surgery the nerve was well decompressed at all these pressure points.

At one month postoperative visit, she reported subjective improvement in vision (awaiting formal visual field tests).

Conclusion: In a vast sprawling skull base meningiomas that has shown long-term stability on MR imaging and with unknown duration of visual loss; the timing, indications and goal of surgery must be arduously dwelled upon to intervene with targeted surgery. The patients need for driving for a livelihood was of immense consideration.

This case also represents a “microvascular decompression” of the optic nerve due to compression from A1 vessel above and tumor from below.

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No conflict of interest has been declared by the author(s).