Normal variations in the caliber of the human cerebral aqueduct

The formation of cerebrospinal fluid: Nearly a hundred years of interpretations and misinterpretations

“…Since the aqueduct of Sylvius can be considered a CSF vessel, about 15 mm in length and 1-2 mm in width, that connects the third and the fourth brain ventricles (Brinkmann et al, 2000;Flyger and Hjelmquist, 1957;Longatti et al, 2007;Mascalchi et al, 1988), this technique has also been applied to aqueductal CSF flow Brinkmann et al, 2000;Mark and Feinberg, 1986;Mascalchi et al, 1988). The aqueduct is a suitable location for the characterization of CSF flow since it is a narrow structure, which results in a higher velocity (several cm/s) than, for example, in the third ventricle.…”

“…However, in articles on the subject of hydrodynamics in the aqueduct of Sylvius, the expression for CSF flow is used in many situations without an explanation and/or in the where r = d/2 and the diameter of the aqueduct is assumed to be 2.0 mm (Brinkmann et al, 2000;Flyger and Hjelmquist, 1957;Longatti et al, 2007), and thus the calculated results are shown in Table 1.…”

Endoscopic anatomy of the fourth ventricle

“…After the aditus has been crossed, 2 strictures with a lumen enlargement between them, the so-called ampulla aqueducti, are noted. The first stricture is caused by the intraluminal protrusion of the superior colliculi 2,5,20,21 whereas the second one (narrower accord- ing to some authors) is due to the inferior colliculi. Ventrally, a trace of a sulcus is visible continuing in the fourth ventricle.…”

The Aqueduct

“…Turkewitsch and Bickers recognized five portions, namely the aditus ad aquaeductum or aditus aquaeducti, the anterior part with a first constriction, ampulla, genu (second constriction), and the posterior part [9,10]. The quadrigeminal plate appears to be relevant in aqueduct geometry; due to its protrusion into the aqueductal lumen, the superior colliculus is responsible for the first constriction (the narrowest), while the second constriction is caused by the protruding inferior colliculus.…”