Neurosurg Focus 40 (4):E9, 2016S port-related concussion (SRC) has emerged as a public health problem, affecting athletes of all ages and participation levels. 11,35,43 While SRC by definition includes normal imaging results, a minority of sportrelated head injuries result in structural brain injury. 3,18,19,84,85 These cases are often neurosurgical emergencies and can result in permanent neurological deficit and/or death. Recent literature has postulated that athletes with arachnoid cysts (ACs) demonstrate a higher rate of structural brain injury after trauma, specifically subdural hematoma (SDH) or hygroma. 37,44,79 ACs are congenital lesions bordered by an arachnoid AbbreviAtioNs AC = arachnoid cyst; ICP = intracranial pressure; IPH = intraparenchymal hemorrhage; IQR = interquartile range; PCS = postconcussion syndrome; SDH = subdural hematoma; SRC = sport-related concussion. objeCtive Arachnoid cysts (ACs) are congenital lesions bordered by an arachnoid membrane. Researchers have postulated that individuals with an AC demonstrate a higher rate of structural brain injury after trauma. Given the potential neurological consequences of a structural brain injury requiring neurosurgical intervention, the authors sought to perform a systematic review of sport-related structural-brain injury associated with ACs with a corresponding quantitative analysis. MethoDs Titles and abstracts were searched systematically across the following databases: PubMed, Embase, CINAHL, and PsycINFO. The review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. Peer-reviewed case reports, case series, or observational studies that reported a structural brain injury due to a sport or recreational activity (hereafter referred to as sport-related) with an associated AC were included. Patients were excluded if they did not have an AC, suffered a concussion without structural brain injury, or sustained the injury during a non-sport-related activity (e.g., fall, motor vehicle collision). Descriptive statistical analysis and time to presentation data were summarized. Univariate logistic regression models to assess predictors of neurological deficit, open craniotomy, and cystoperitoneal shunt were completed. resUlts After an initial search of 994 original articles, 52 studies were found that reported 65 cases of sport-related structural brain injury associated with an AC. The median age at presentation was 16 years (range 4-75 years). Headache was the most common presenting symptom (98%), followed by nausea and vomiting in 49%. Thirteen patients (21%) presented with a neurological deficit, most commonly hemiparesis. Open craniotomy was the most common form of treatment (49%). Bur holes and cyst fenestration were performed in 29 (45%) and 31 (48%) patients, respectively. Seven patients (11%) received a cystoperitoneal shunt. Four cases reported medical management only without any surgical intervention. No significant predictors were found for neurological deficit or open cr...