Nontraumatic symptomatic de novo arachnoid cyst in an adolescent patient treated with cystoperitoneal shunting: illustrative case.

backgroundArachnoid cysts are often congenital, asymptomatic lesions detected in the pediatric population. When seen in adults, they usually occur following trauma. De novo formation of arachnoid cysts is uncommon, with only a few instances cited in the literature and most of which occurred in the pediatric population. Treatment options for these lesions include observation, craniotomy for cyst resection, microsurgical/endoscopic fenestration, or shunting. OBSERVATIONS: In this report, the authors describe a female patient with a de novo, symptomatic, enlarging middle cranial fossa arachnoid cyst detected at age 16 years. She was treated with the placement of a cystoperitoneal shunt. After surgery, she experienced clinical and radiological improvement. LESSONS: We illustrate successful shunting of a de novo arachnoid cyst in a symptomatic teen patient. Although arachnoid cysts in certain intracranial locations are more likely to produce symptoms, those in the middle cranial fossa tend to be asymptomatic. To our knowledge, this is the first reported case of a symptomatic de novo arachnoid cyst located in the middle cranial fossa in a postpubertal patient. Although the current presentation is rare, the authors demonstrate an effective surgical treatment of a symptomatic, large, de novo arachnoid cyst in a postpubertal pediatric patient.