Severe Intraoperative Orbital Venous Congestion during Resection of a Frontal Meningioma Presenting with Post-operative Vision Loss and Ophthalmoplegia: A Case Report.

We describe a unique case of a middle-aged man who noticed complete vision loss in the right eye after awaking from resection of a large right-sided frontal meningioma. Visual acuity was hand motions, and there were multiple signs of right orbital venous congestion. Magnetic resonance imaging and venography (MRI/V) of the brain and orbits demonstrated expected post-operative findings with no evidence of cavernous sinus thrombosis or fistula. Empiric treatment with intravenous antibiotics and intravenous methylprednisolone were ineffective. Immediate post-operative computerised tomography (CT) images were re-reviewed and revealed right restricted diffusion of the entire intraorbital right optic nerve. Discussion with the neurosurgical team revealed that during craniotomy, a prominent diploic venous plexus in the frontal bone adjacent to the meningioma was identified and coagulated with bone wax. Review of pre-operative imaging revealed large diploid flow voids in the right frontal bone, corresponding to the intraoperative findings. This prominent venous plexus appeared to drain from the meningioma posteriorly into the vein of Labbe. A second pathway drained anteriorly through the right angular vein into the orbit. We hypothesise that the posterior outflow pathway was coagulated intraoperatively, causing redirection of all venous outflow from the meningioma into the right orbit through the anterior pathway. This resulted in significant orbital hypertension with manifest signs and symptoms. Furthermore, sudden rise in intraorbital pressure led to infarction of the optic nerve, leaving the patient with hand motions vision. We suggest that pre-operative vascular imaging should be performed in patients with large meningiomas, as pre-operative embolisation of venous outflow channels may prevent severe post-operative complications.