Operative Neurosurgery 30:468–471, 2026
This surgical case instruction contrasts suprasellar arachnoid cysts (SACs) and third ventricular cysts (3VCs), emphasizing their distinct imaging features, clinical presentations, and risks of obstructive hydrocephalus. It summarizes patient examples, MRI findings, and outcomes after endoscopic cyst fenestration, demonstrating restoration of cerebrospinal fluid flow and symptom resolution.
The article details stepwise endoscopic techniques—cyst plane development, wall reduction, excision, and membrane management—highlighting anatomical cues that guide whether endoscopic third ventriculostomy is necessary. Practical tips on preserving hypothalamic structures, restoring aqueduct patency, and minimizing reaccumulation are provided for neurosurgical practice.
Prevalence Intracranial arachnoid cysts occur in ~2.6% of children and ~1.4% of adults; suprasellar arachnoid cysts (SACs) comprise ~9%–21% of pediatric arachnoid cysts and can be confused with rarer third ventricular cysts (3VCs).
Presentation SACs and 3VCs often enlarge and cause obstructive hydrocephalus with symptoms of increased intracranial pressure, prompting urgent treatment to restore CSF circulation.
Imaging differences (SAC) SACs elevate the third ventricular floor, displace mammillary bodies superiorly/posteriorly, and elongate/stretch the midbrain and aqueduct, with aqueduct occlusion from distortion and the posterior cyst wall.
Imaging differences (3VC) 3VCs displace the third ventricular floor and mammillary bodies inferiorly with midbrain compaction; the aqueduct is obstructed by midbrain distortion and the inferoposterior cyst wall.
Treatment rationale A shunt without cyst fenestration can lead to asymmetric hydrocephalus and/or continued cyst enlargement due to cyst-related occlusion of the foramina of Monro; neuroendoscopy enables cyst fenestration with low morbidity risk at experienced centers.
Endoscopic steps A stepwise intraventricular endoscopic approach includes: developing the cyst/ventricle plane; reducing cyst wall size (coagulation); excising roof/lateral/medial walls (with caution laterally in SACs due to hypothalamic fusion); removing/reducing floating membranes (especially posteriorly) to open access to the aqueduct.
Inferior wall strategy In SACs, inferior membrane fenestration may be unnecessary because the prepontine cistern is already exposed/communicates with the third ventricle; in 3VCs, the inferior aspect is the third ventricular floor, and endoscopic third ventriculostomy (ETV) is an option.
ETV decision point If posterior membrane resection fully restores aqueduct patency, ETV may not be necessary; reducing expansile membranes is pursued to lower risk of reaccumulation from scarring.
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