PMC3815032_01
(a) PreoperariveT2-weighted on the axial section revealed a marked dilatation of the lateral and third ventricles. (b) Sagittal section of MRI showed that the cyst was iso-intense to the CSF, indicating that the arachnoid cyst was located at the quadrigeminal cistern and extended into the supracerebellar cistern and to the floor of the third ventricle, protruding downwards; it also revealed that the fourth ventricle was normal. (c) Heavily T2-weighted MRI image clearly revealed the discontinuity between the anterior part of the cyst wall and the third ventricle.
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F1
The cyst, which was considered as congenital arachnoid cyst, was located at the quadrigeminal cistern extending caudally into the supracerebellar cistern [Figure 1a and b]. However, heavily T2-weighted images revealed a definite discontinuity between the anterior part of the cyst wall and the third ventricle [Figure 1c]. T2-weighted MRI image [Figure 1c], the cyst wall facing the posterior part of the third ventricle was opened widely [Figure 2a]. The aqueduct stenosis was easily apparent [Figure 2b].
(a) Intraoperative endoscopic view showed that the cyst wall facing the posterior part of the third ventricle was opened widely and the cyst wall was confirmed to consist of arachnoid membrane through the endoscopic view. (b) It was demonstrated that the aqueduct was severely narrowed through the endoscopic view.
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F2
T2-weighted MRI image [Figure 1c], the cyst wall facing the posterior part of the third ventricle was opened widely [Figure 2a]. The aqueduct stenosis was easily apparent [Figure 2b].
(a) A postoperative MRI displayed marked reductions in the size of the lateral and third ventricles. (b) The size of the quadrigeminal cistern arachnoid cyst was also reduced, and normalization of the cerebellar tonsillar descent was observed. The flow void artifact through the stoma with ETV was detected (arrow).
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F3
A postoperative MRI of the brain at the 12-month follow-up displayed marked reductions in size of the lateral and third ventricles and the quadrigeminal cyst; it also revealed normalization of the cerebellar tonsillar descent, and patency of the stoma was clearly indicated by the flow artifact, which is depicted on the postoperative T2-weighted image in Figure 3.