Preventing visual field deficits from neurosurgery

OBJECTIVE: We assessed whether display of optic radiation tractography during anterior temporal lobe resection (ATLR) for refractory temporal lobe epilepsy (TLE) can reduce the severity of postoperative visual field deficits (VFD) and increase the proportion of patients who can drive and whether correction for brain shift using intraoperative MRI (iMRI) is beneficial. METHODS: A cohort of 21 patients underwent ATLR in an iMRI suite. Preoperative tractography of the optic radiation was displayed on the navigation and operating microscope displays either without (9 patients) or with (12 patients) correction for brain shift. VFD were quantified using Goldmann perimetry and eligibility to drive was assessed by binocular Esterman perimetry 3 months after surgery. Secondary outcomes included seizure freedom and extent of hippocampal resection. The comparator was a cohort of 44 patients who underwent ATLR without iMRI. RESULTS: The VFD in the contralateral superior quadrant were significantly less (p = 0.043) with iMRI guidance (0%–49.2%, median 14.5%) than without (0%–90.9%, median 24.0%). No patient in the iMRI cohort developed a VFD that precluded driving whereas 13% of the non-iMRI cohort failed to meet UK driving criteria. Outcome did not differ between iMRI guidance with and without brain shift correction. Seizure outcome and degree of hippocampal resection were unchanged. CONCLUSIONS: Display of the optic radiation with image guidance reduces the severity of VFD and did not affect seizure outcome or hippocampal resection. Correction for brain shift is possible but did not further improve outcome. Future work to incorporate tractography into conventional neuronavigation systems will make the work more widely applicable.