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EM-guided neuronavigation in the semi-sitting position was safe and technically feasible. It enabled fast and accurate referencing without loss of navigation accuracy despite repositioning of the patient. In contrast to conventional opto-electric neuronavigation there were no line of sight problems.

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The surgical treatment of distal anterior cerebral artery (DACA) aneurysms still presents a challenge for neurosurgeons because of their small size and their location in the depth of the narrow frontal interhemispheric fissure. This study aimed to investigate feasibility, safety, accuracy, and usefulness of electromagnetic (EM) navigation to aid clipping of DACA aneurysms. Eight patients (age between 2 and 68 years, mean age 49.8 years) with a DACA aneurysm underwent EM-guided neuronavigated microsurgery for clipping of the aneurysm. All patients underwent craniocervical 3D-CT angiography preoperatively. After planning the optimal approach and surgical trajectory avoiding opening of the frontal sinus, the head was fixed. Intraoperative screenshots were correlated with the microscopical view of the DACA aneurysms before clipping. EM-guided neuronavigation using CT angiography for DACA aneurysms enabled fast and accurate referencing of the patient and planning of a tailored craniotomy without opening of the frontal sinus. Intraoperative accuracy was highly reliable except in one instance due to dislocation of the dynamic reference frame (DRF). There was a good correlation between the 3D-CT angiography-based navigation data sets and the intraoperative vascular anatomy. In all patients, bridging veins were spared. The aid of EM neuronavigation was considered useful in all instances. EM-guided neuronavigation using CT angiography for surgery of DACA aneurysms is a useful tool optimizing the surgical approach directly to the aneurysm minimizing additional damage to the surrounding tissue during preparation of the aneurysm and the parent vessel.

BACKGROUND Microsurgical clipping with extradural anterior clinoidectomy (EDAC) for paraclinoid aneurysm is an established technique with good angiographic outcomes, although postoperative worsening of visual acuity remains a concern. Multiple reports show visual acuity deteriorating after clipping, yet the cause remains unclear. OBJECTIVE To analyze results of asymptomatic paraclinoid aneurysm surgeries treated with EDACs, specifically focusing on the microanatomy of paraclinoid structure dissection. This determined the causes of delayed visual impairment and microsurgical indications. METHODS Results of the treatment with EDAC of 94 patients with cerebral aneurysm and normal preoperative visual acuity but also full visual fields were retrospectively analyzed. RESULTS The mean aneurysm size was 6.2 (±3.3) mm. Clipping was performed in 87 cases and trapping in 7 cases. Complete angiographic occlusion was observed in 91 patients. In 26 cases, a postoperative visual deficit occurred. A total of 20 cases exhibited partial visual field deficits, including 5 who were asymptomatic. Visual deficits were only detectable by postoperative ophthalmologic testing. Six showed light perception impairment or blinding. Of the 15 patients with symptomatic partial visual field deficits, 5 showed improvement at follow-up. Visual deficits persisted in 22 patients at the last follow-up. Multivariate logistic regression analysis revealed that medial projecting aneurysm (adjusted odds ratio [OR]: 10.43) and the opening of the carotidoculomotor membrane (adjusted OR: 5.19) were significantly related to visual impairment. CONCLUSION Excess dissection of carotidoculomotor membranes causes postoperative delayed visual worsening. For treating small, asymptomatic paraclinoid aneurysms, carotidoculomotor membranes should not be opened, and microsurgical clipping should not be performed for preoperative asymptomatic medial projecting aneurysms.