Background: Fenestrations, such as those of the vertebral artery (VA), are generally regarded as arterial slits. To the authors' knowledge, large fenestrations of the VA were reported twice previously, those morphological patterns being different. We hereby report a third pattern of such large fenestration of the VA. Methods: It was found serendipitously on the computed tomography angiograms of a 63 year-old male which were documented retrospectively. Results: The findings were as follows:1.the right VA entered the posterior fossa, crossed to the left side and joined the opposite VA to form the basilar artery;2.the right posterior inferior cerebellar artery was absent;3.the left VA entered the posterior fossa then it had a huge fenestration with 2 limbs: an anterior one, appearing as the main trunk of the VA coursing to form the BA, and a posterior, coiled one, inserted at both ends into the VA;4.that posterior limb of the left VA fenestration sent off 2 posterior inferior cerebellar branches;5.a slit-like fenestration of the basilar artery was also found. Conclusions: Large fenestrations of the VA could result if, during embryogenesis, the proximal segment of the lateral basivertebral anastomosis and the distal segment of the proatlantal artery persist. Large fenestrations of the VA bring into a narrow neurosurgical field an additional arterial trunk that should be carefully documented preoperatively in order to avoid hemorrhagic events.

Hyrtl [Wien Med Wochenschr. 1862;19:291-292] reported firstly the ophtalmopetrosal sinus (OPS) running from the superior orbital fissure and emptying either in the transverse sinus, or in its junction with the superior petrosal sinus. Since then, this anatomic variant was mostly referred and poorly studied. Neither Hyrtl, nor other authors brought any evidence of such OPS. It is hereby reported and proofed such an OPT which was found at dissection. It drained ophthalmic veins and coursed posteriorly, first on the greater wing (alar segment), then on the temporal bone (temporal segment, on the petrosquamous fissure), emptying in the transverse sinus. A lateral type of the superior petrosal sinus connected the OPS and the transverse sinus. The OPS courses on the middle fossa floor, lateral to the Meckel's cavum, foramen ovale, foramen spinosum, and fallopian hiatus. It is a rare thus unexpected finding during specific approaches of the middle fossa floor.

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