Late-onset aqueductal membranous occlusion treated neuroendoscopic procedure and consideration of its pathological findings: A case report

Background: Aqueduct of Sylvius stenosis/obstruction interferes with cerebrospinal fluid (CSF) flow and leads to the non-communicating hydrocephalus. Acquired non-neoplastic causes of aqueduct of Sylvius stenosis/ obstruction include simple stenosis, gliosis, slit-like stenosis, and septal formation, but the detailed mechanisms are not clear. In the present study, we experienced a case of late-onset aqueductal membranous occlusion (LAMO) successfully treated by neuroendoscopic procedure, which allowed us to examine the pathology of the membranous structures of the aqueduct of Sylvius occlusion. Case Description: A 66-year-old woman presented with gradually progressive gait disturbance, cognitive dysfunction, and urinary incontinenc. Brain magnetic resonance imaging (MRI) showed enlargement of the bilateral lateral ventricles and the third ventricle without dilatation of fourth ventricle, and heavily T2-weighted images showed an enlarged aqueduct of Sylvius and a membranous structure at its caudal end. Gadolinium contrast-enhanced T1-weighted images showed no neoplastic lesions. We diagnosed this case that the hydrocephalus due to late-onset idiopathic aqueductal stenosis or LAMO and the patient underwent endoscopic third ventriculostomy and endoscopic aqueduct oplasty. Membranous tissue specimens were obtained from the occluded aqueduct of Sylvius at the time of treatment. Histopathological examination revealed gliosis, and inside the gliosis, there were cell clusters that appeared to be ependymal cells and were corpora amylacea. We confirmed CSF flow at the site of obstruction of the aqueduct of Sylvius and the stoma of the third ventricle floor by MRI images. Her symptoms were improved immediately. Conclusion: We experienced a case of LAMO successfully treated by neuroendoscopic procedure, which allowed us to examine the pathology of the membranous structure of the aqueduct of Sylvius. The pathological study of LAMO is rare, and we report it, including a review of the literature.