Optic Nerve Edema in Pediatric Middle Cranial Fossa Arachnoid Cysts: Report of 51 Cases from a Single Institution

Background Middle fossa arachnoid cysts (MFACs) are rare, congenital lesions that may rupture and cause symptoms of elevated intracranial pressure (ICP). Thus, we sought to describe the presence and factors associated with optic nerve edema in MFACs, focusing on the utility of ophthalmologic evaluations for guiding cyst management. Methods We reviewed clinical and radiographic information for all MFAC patients with ophthalmologic evaluations at our institution. Headache, cranial nerve palsy, emesis, altered mental status, fatigue, and seizures were considered MFAC-related symptoms. Univariate and multivariable analyses evaluated factors associated with optic edema. Results Fifty-one patients between 2003-2022 met inclusion. Most patients were symptomatic with a single arachnoid cyst. Cysts were a median volume of 169.9 cm3 (IQR: 70.5, 647.7). Evidence of rupture with subdural hematoma/hygroma occurred in 19 (37.3%) cases. Eighteen (35.3%) patients underwent surgery for their cyst and/or rupture-associated intracranial bleed.Eleven (21.6%) patients had optic edema; all were symptomatic and experienced cyst rupture. Ten of these patients received surgery. Postoperatively, optic edema resolved in 80% of cases. Cyst volume and symptoms were not associated with optic edema, however, patients with ruptured cysts, particularly those with traumatic rupture, were more likely to have optic edema and receive surgery (p<0.001). Conclusions We found optic edema in 21.6% of evaluated MFACs, this comprised of 57.9% of ruptured cases. Optic edemawas not found in unruptured cysts. Cyst fenestration improved optic edema and patient symptoms. In conjunction with clinical history and neuroimaging, optic edema may help guide MFAC management, particularly in patients with cyst rupture.