An endoscopic assisted retrosigmoid approach to the cerebello-pontine angle for resection of an epidermoid cyst.

Epidermoid cysts are rare lesions accounting for 1% of intracranial tumors with approximately 50% located within the cerebello-pontine angle (CPA). Resection is complicated by their close anatomical relation to critical neurovascular structures and their tendency to be densely adherent making complete removal a significant neurosurgical challenge. We present a 35-year-old woman with left sided tongue numbness and lower lip paresthesias with a CPA epidermoid. An endoscopic assisted retrosigmoid approach was utilized for resection. A 30-degree endoscope was used to assist in removal of unseen tumor in Meckel's cave, medial to the lower cranial nerves, and along the ventral pons. The video can be found here: http://youtu.be/bv0lMPbX7BY .

Cerebral aneurysm wall thickness analysis using intraoperative microscopy: effect of size and gender on thin translucent regions.

OBJECTIVE: Wall thickness is a poorly documented characteristic of cerebral aneurysms which may provide insight into adaptive aneurysmal growth, aneurysm rupture risk and response to endovascular treatment. The distribution of aneurysm wall thickness, as observed by intraoperative video microscopy, is described. METHODS: 54 unruptured saccular cerebral aneurysms were selected based on the availability of intraoperative video obtained from patients undergoing microsurgical clipping. Aneurysms were assessed for the distribution of wall thickness based on color translucence and quantitation of pixel values at superthin translucent, intermediate and thick regions of the dome. The data were analyzed with respect to aneurysm morphology, location and associated demographic factors. RESULTS: The mean proportions of tissue characteristic among all domes analyzed were found to be 27% superthin, 65% intermediate, and 8% thick. Smaller aneurysms having a maximal dimension Dmax <7 mm had a higher proportion of superthin tissue (p=0.003) and lower thick tissue (p=0.001) content. Female gender was associated with a significantly higher proportion of superthin tissue at the aneurysm dome (p=0.038), with no statistical dependence seen with patient age, smoking status or anatomical location. CONCLUSION: The dome of unruptured aneurysms is a highly heterogeneous region with areas of variable thickness that appear to be intimately related to the process of aneurysm development. This inconstant property affects wall tensile stress, may play a role in aneurysm pathogenesis and focal rupture, and should be incorporated into future analyses of aneurysm rupture risk and mechanics.

Colocalization of thin-walled dome regions with low hemodynamic wall shear stress in unruptured cerebral aneurysms.

OBJECT: Wall shear stress (WSS) plays a role in regulating endothelial function and has been suspected in cerebral aneurysm rupture. The aim of this study was to evaluate the spatial relationship between localized thinning of the aneurysm dome and estimated hemodynamic factors, hypothesizing that a low WSS would correlate with aneurysm wall degeneration. METHODS: Steady-state computational fluid dynamics analysis was performed on 16 aneurysms in 14 patients based on rotational angiographic volumes to derive maps of WSS, its spatial gradient (WSSG), and pressure. Local dome thickness was estimated categorically based on tissue translucency from high-resolution intraoperative microscopy findings. Each computational model was oriented to match the corresponding intraoperative view and numerically sampled in thin and normal adjacent dome regions, with controls at the neck and parent vessel. The pressure differential was computed as the difference between aneurysm dome points and the mean neck pressure. Pulsatile time-dependent confirmatory analysis was carried out in 7 patients. RESULTS: Matched-pair analysis revealed significantly lower levels of WSS (0.381 Pa vs 0.816 Pa; p<0.0001) in thin-walled dome areas than in adjacent baseline thickness regions. Similarly, log WSSG and log WSS×WSSG were both lower in thin regions (both p<0.0001); multivariate logistic regression analysis identified lower WSS and higher pressure differential as independent correlates of lower wall thickness with an area under the curve of 0.80. This relationship was observed in both steady-state and time-dependent pulsatile analyses. CONCLUSIONS: Thin-walled regions of unruptured cerebral aneurysms colocalize with low WSS, suggesting a cellular mechanotransduction link between areas of flow stasis and aneurysm wall thinning.