Tectal gliomas as a rare finding in presumed idiopathic congenital aqueductal stenosis: patient series.

backgroundSmall tectal gliomas (TGs) may be unrecognized at initial diagnosis of noncommunicating hydrocephalus, with the etiology typically attributed to idiopathic congenital aqueductal stenosis (CAS). There are 2 published cases of TGs found on follow-up imaging after treatment with endoscopic third ventriculostomy (ETV). The authors investigated for this phenomenon in a large cohort of patients with TG or CAS treated with ETV or CSF shunting. OBSERVATIONS: The authors reviewed records at their institution from 1999 to 2024, identifying 10 patients initially diagnosed with presumed idiopathic CAS and later found to have underlying TG. Of these, 7 were younger than 1 year of age at hydrocephalus presentation. The median time from CAS to glioma diagnosis was 13 months. Reasons for repeat imaging that identified glioma included postoperative surveillance and recurrent hydrocephalus. Five (50%) lesions grew over follow-up, and 2 required chemotherapy. LESSONS: The authors describe the eventual emergence of TG as a probable cause of hydrocephalus in a cohort of patients initially diagnosed with CAS. As most of these cases were identified incidentally on interval imaging to evaluate adequate function of CSF diversion procedures, follow-up imaging to evaluate for tectal expansion should be considered in children, particularly infants, with a new diagnosis of idiopathic CAS. https://thejns.org/doi/10.3171/CASE24695.