Parasellar region meningiomas with optic canal (OC) invasion: Correlation between the degree of decompression of the OC and the improvement of visual acuity

Purpose: To evaluate the correlation between the degrees of circumferential decompression of the optic canal (OC) and the improvement of visual acuity in patients with parasellar meningiomas (PMs) with optic canal invasion. Methods: This is a monocentric retrospective study conducted at author’s institution. The visual acuity was evaluated preoperative and at 3-months after surgery with Snellen acuity test. The degree of decompression of the OC was calculated through postoperative multiplanar CT-scan reconstructions in coronal plane at intraorbital opening (IOO), intracranial opening (ICO) and middle point between them (MP). OC was then divided in two segments (anterior and posterior). Results: 29 consecutive patients were identified. Improvement of visual acuity was observed in 18 patients (62 %). Mean decompression achieved at ICO, MP and IOO was 226.2◦± 43.6◦ (range: 68.7◦-297.1◦), 217.5◦± 37.2◦ (range: 75.3◦-268.7◦) and 204.6◦± 41.2◦ (range: 67.3◦-252.6◦) respectively. A decompression > 90◦ of the anterior segment of the OC, a decompression > 180◦ of the posterior segment and a full-length decompression > 90◦ were associated visual acuity improvement at univariate analysis (p = 0.010, p = 0.002 and p < 0.001, respectively). A decompression > 180◦ of the posterior segment and a full-length decompression > 90◦ of the OC maintained statistical significance at multivariate analysis (p = 0.030 and p = 0.035, respectively). Conclusion: Anterior segment decompression > 90◦ and posterior segment decompression > 180◦ were associated with improvement of visual acuity at 3 months after surgery. A full-length decompression of the optic canal > 90◦ showed better visual outcome, while a full-length decompression > 180◦ did not seem to be related to significative improvements in visual acuity.