Intraoperative Continuous Flash Visual Evoked Potentials Monitoring During Endoscopic Skull Base Surgery

Intraoperative Continuous Flash Visual Evoked Potentials Monitoring During Minimally Invasive Endoscopic Skull Base Surgery, a Novel Approach to Improve Patient Outcome

Skull base surgeries performed in areas involving the visual pathway are associated with varying levels of postoperative visual dysfunction. The goal of intraoperative FVEP monitoring is to detect and prevent intraoperative visual pathway injury.

Skull base surgeries performed in areas involving the visual pathway are associated with varying levels of postoperative visual dysfunction. For instance, surgical resection of suprasellar meningiomas has been shown to worsen visual function in 14 - 28% of patients and surgical resection of craniopharyngiomas worsen visual function in 3 - 11.5% of patients. Manipulation of the optic nerve and interference with the microvasculature during surgical dissection is thought to be responsible for the visual loss.

Through intraoperative monitoring and prompt identification of flash visual evoked potentials (FVEPs) deterioration, corrective surgical measures could be undertaken to improve or stabilize postoperative visual dysfunction. Furthermore, intraoperative FVEPs monitoring may influence surgical decision-making thus contributing to predict and prevent postoperative visual dysfunction as well as allowing more total resection of a tumour when the monitoring is stable.

This study's aim is to determine if intraoperative continuous FVEPs monitoring can predict and prevent or minimize possible visual pathway injury that may appear during minimally invasive endoscopic skull base surgery.

Inclusion Criteria:

• Adult population (18 years and older), admitted to The Ottawa Hospital (TOH)-Civic Campus for a chiasmal or pre-chiasmal lesion, undergoing first time minimally invasive endoscopic skull base surgery

• Patient able to personally sign and date the informed consent document

• Patients will be selected based on the surgeon's determination that:

  1. The visual system will be at risk of iatrogenic injury
  2. The intraoperative FVEPs monitoring could rapidly detect this injury AND
  3. Corrective measures could be taken during surgery to reverse it.

Exclusion Criteria:

• patients having a pre-existent retinal disease, cardiac pacemaker
• contraindication for total intravenous anaesthesia (TIVA)
• unable to complete required pre and post-operative visual assessment or unable to complete their post-operative follow-up visits at TOH-Civic Campus
• anticipated goggle movement related to reflection of the frontal skin flap
• preoperative visual deficits (e.g., profound deficits in visual acuity or dense visual field loss)