Hydrocephalus in neurofibromatosis type 1 (NF1) is most commonly associated with tectal gliomas or aqueductal narrowing. Intraventricular hamartomatous lesions causing mechanical obstruction are rarely reported, particularly with histopathological confirmation. A 35-year-old female with genetically confirmed NF1 presented with progressive headache, vomiting, gait imbalance, seizures, and altered sensorium. Magnetic resonance imaging using high-resolution constructive interference in steady state (CISS) sequences demonstrated a well-defined cerebrospinal fluid (CSF)-intensity lesion measuring 2.6 × 2.4 × 1.6 cm in the posterior third ventricle extending into the aqueduct of Sylvius, resulting in obstructive hydrocephalus. Contrast-enhanced MRI could not be performed due to the patient's altered sensorium and lack of cooperation during imaging. The radiological impression favored an intraventricular arachnoid cyst. The patient underwent endoscopic third ventriculostomy with concurrent biopsy. Intraoperative findings confirmed aqueductal compression. Histopathological examination demonstrated a benign glial hamartoma with strong glial fibrillary acidic protein positivity and a low proliferative index. The patient showed significant clinical improvement following surgery and remained neurologically stable at 6-month follow-up. Third ventricular glial hamartoma should be considered in the differential diagnosis of obstructive hydrocephalus in patients with NF1. Imaging findings may mimic cystic or low-grade neoplastic lesions, and histological confirmation may be necessary in symptomatic cases. Endoscopic third ventriculostomy combined with biopsy provides effective CSF diversion and definitive diagnosis.

Institutional ethics committee approval was obtained. Written informed consent was obtained from the patient for publication.

K.S.D.P. conceptualized and drafted the manuscript and did surgical assistance. V.V.R.C did the surgery and reviewed the manuscript. B.V.D. analyzed radiologically and interpreted and reviewed the manuscript. S.P.M. provided surgical assistance and reviewed the manuscript. P.K. collected the data and reviewed the manuscript. B.C.M.P. provided surgical assistance and reviewed manuscript.

Article published online:
08 May 2026

© 2026. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution License, permitting unrestricted use, distribution, and reproduction so long as the original work is properly cited. (https://creativecommons.org/licenses/by/4.0/)

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