3D digital exoscope is safe tool in the surgery of olfactory groove meningiomas

Digital 3D exoscopes have been introduced as alternatives for operating microscopes in microneurosurgery. It has been hypothesized that exoscope may provide benefits especially at the most anterior skull base, where surgical trajectories often require heavy tilting of the magnification device. We evaluated the safety and practicality of the digital 3D exoscopes in surgery of olfactory groove meningiomas (OGM) during the transition from using a microscope to an exoscope.

In this retrospective cohort study, we included all consecutive adult patients who underwent surgery for OGM (n = 22) by a single senior neurosurgeon between 2016 and 2024 either with a microscope (n = 13) or an exoscope (n = 9). We reviewed the pre- and postoperative MRIs, patient records (including Modified Rankin Scale (mRS)), and surgical videos of all the patients. The surgical approach was unilateral fronto-temporal in all the cases.

The patients in the exoscope group had larger tumors (median 61cm³ (IQR 49) vs. 17cm³ (IQR 32)), more clinical symptoms and required more help in their daily activities preoperatively (mRS ≥ 3: n = 3 (33%) vs n = 1 (8%)). Gross-total or near total resection was achieved in all the patients. The exoscopic surgeries took longer (165 min (IQR 106) vs. 121 min (IQR 27)), probably due to the larger tumor sizes. Two severe complications occurred, one in each group (post-op hematoma and blindness of ipsilateral eye). Clinical outcomes were nearly the same in both groups. At the 3-month follow-up, eight (89%, exoscope) and 12 (92%, microscope) patients were independent (mRS 0-2). Horizontal adjustments were more common when operating with the microscope (median 251 (range 148-359) vs. 103 (range 19-187)) while tilting movements were more frequent with the exoscope (median 122 (range 74-182) vs. 76 (range 44-133)).

The surgical outcomes for OGMs remained consistent during the transition from using a microscope to an exoscope. The exoscope is a safe tool in the surgery of OGMs, even when operating on large tumors. The wider range of angular movement of the camera head is particularly advantageous when accessing the anterior skull base. In line with this, exoscope-assisted surgeries relied more on tilting movements, whereas microscope-assisted surgeries required more horizontal adjustment.