Ultrastructural changes in the Liliequist membrane in the hydrocephalic process and its implications for the endoscopic third ventriculostomy procedure.

AIM Fenestration of Liliequist membrane (LM) during endoscopic third ventriculostomy (ETV) is extremely important for the success of the procedure. It is noteworthy that LM usually shows a tough and dense stucture in long-standing hydrocephalus cases different from its usual arachnoidal membrane-like structure observed in new-onset hydrocephalus cases. The structural variation of LM in different hydrocephalic states was investigated histologically in this study. MATERIAL AND METHODS Specimens of LM obtained during endoscopic fenestration in 11 cases were examined under transmission-electron-microscopy. Six cases had long-standing hydrocephalus and five had new-onset triventricular hydrocephalus. None of the cases had a history of infection or hemorrhage. RESULTS In cases with long-standing hydrocephalus, ultrastructural examinations revealed the existence of regular and dense bundles of type-I collagen among the fibroblast-like cells, which were closely connected by dense desmosomes and gap-junctions. In cases with new-onset hydrocephalus, it was observed that the cells usually had long cytoplasmic extentions and were connected with loose desmosomes. Sparse type-I collagen bundles were observed rarely among the cells. CONCLUSION These results suggest that the structure of LM may change with the duration of the hydrocephalic process. This may help explain the tough and dense LM stucture observed during the ETV procedure in cases with long-standing-hydrocephalus.