Abstract
Optic nerve sheath meningioma (ONSM) is a rare benign tumor of the central nervous system. Although lesions in this region typically grow slowly, their proximity to the optic nerve directly impacts the frontal visual pathway and may lead to severe vision problems. The mainstream treatment for ONSM has shifted from traditional surgery to stereotactic radiosurgery (SRS). Among these, ZAP-X (ZAP Surgical Systems, Inc., San Carlos, California), the latest generation of SRS systems, offers a novel approach to clinical treatment of ONSM with its noncoplanar rotational focus technology, six-dimensional dynamic tracking, and submillimeter (<0.4 mm) treatment precision. This system avoids traditional head-pin injuries and reduces radiation trauma to surrounding healthy tissues, while providing short-duration, high-efficiency treatment with integrated intelligence, real-time imaging verification, and adaptive planning features. We report the case of a 61-year-old male patient who had worn glasses for over 20 years and presented with progressive vision deterioration in the right eye for more than two years. Conventional vision correction was ineffective, prompting him to seek medical attention. Cranial and orbital magnetic resonance imaging (MRI) revealed a localized lesion in the intraorbital segment of the right optic nerve, showing the "tram-track sign." Demyelination tests indicated negative results for serum autoantibodies against aquaporin-4 and myelin oligodendrocyte glycoprotein (MOG). Pretreatment examinations revealed corrected visual acuity: 0.5 (left eye), 0.1 (right eye); normal appearance of the left eyeball, while the right eyeball was externally deviated by 45°; both pupils were round and equal in diameter (0.3 mm), with a slightly sluggish light reflex in the right eye and positive relative afferent pupillary defect sign (+). Intraocular pressure was 15 mmHg (left) and 14 mmHg (right). Fundus examination showed a white optic disc in the right eye, with significantly tortuous and dilated retinal veins forming a "spiral" pattern, while the contralateral fundus was unremarkable. Based on these findings, the patient was ultimately diagnosed with primary ONSM in the right eye. Due to the patient's high expectations for vision preservation, ZAP-X SRS was chosen as the treatment modality. Postoperative follow-up over 1.5 years showed good visual recovery, with stable clinical and imaging findings. As a globally advanced radiotherapy modality, this case suggests that the ZAP-X system may provide a safe and effective treatment option for ONSM. The patient experienced significant visual field recovery immediately after the initial fractionated treatment, with long-term stability in visual acuity, prompting us to report this case.