Why does endoscopic aqueductoplasty fail so frequently? Analysis of cerebrospinal fluid flow after endoscopic third ventriculostomy and aqueductoplasty using cine phase-contrast magnetic resonance imaging.

[hydrocephalus with stenosis of the aqueduct of sylvius]

The aim of this study was to evaluate and compare CSF flow after endoscopic third ventriculostomy (ETV ) and endoscopic aqueductoplasty (EAP ) in patients presenting with obstructive hydrocephalus caused by aqueductal stenosis .In patients harboring aqueductal stenosis who underwent EAP (n =8 ), ETV (n =8 ), and both ETV and EAP (n =6 ), CSF flow through the restored aqueduct and through the ventriculostomy was investigated using cine cardiac -gated phase-contrast MRI . For qualitative evaluation of CSF flow , an in -plane phase-contrast sequence in the midsagittal plane was used . The MR images were displayed in a closed-loop cine format . Quantitative through-plane measurements were performed in the axial plane perpendicular to the aqueduct and /or floor of the third ventricle .Evaluation revealed significantly higher CSF flow through the ventriculostomies compared with flow through the aqueducts . This was true both when comparing the ETV group with the EAP group and when comparing the flow of the ventriculostomy and aqueduct within the ETV and EAP group . There was no difference in aqueductal CSF flow between patients who underwent EAP alone and patients who underwent ETV and EAP . There was also no difference in ventriculostomy CSF flow between patients who underwent ETV alone and patients who underwent ETV and EAP . Fifty percent of the restored aqueducts became occluded at a mean of 46 months after surgery (range 18 -126 months ). In contrast , all ETVs remained patent in the mean follow-up period of 110 months after surgery , although 1 patient required shunt placement after 66 months .Cerebrospinal fluid flow through ventriculostomies is significantly higher than aqueductal CSF flow after EAP . This could be one factor to explain why the reclosure rate of aqueducts after EAP is higher than the reclosure rate of the ventriculostoma after ETV .