In recent years, neuroendoscopy has added further knowledge about the anatomy of the cerebral aqueduct in vivo. Longatti et al. (70) well described the endoscopic anatomy of the sylvian aqueduct as it appears when approaching it with a flexible fiberscope through the third ventricle (70).
Stenosis of the the inlet of the aqueduct
Stenosis of the proximal third of the aqueduct
Stenosis of the distal third of the aqueduct
The aqueduct may become stenotic because of compression from mass lesions or as consequence of intrinsic pathology (“non-tumoral aqueductal stenosis”). Intrinsic aqueductal stenosis may be congenital or acquired, idiopathic or secondary to a known etiology. Different etiological factors can be identified in approximately only 25% of cases (51).
According to Russell (91), non-tumoral aqueductal stenosis can be classified histopathologically into four types: