Comparative analysis of endoscopic third ventriculostomy trajectories in pediatric cases

Abstract

E ndoscopic third ventriculostomy (ETV) has emerged as an alternative method of CSF diversion alongside the placement of ventriculoperitoneal shunts. [18][19][20] ETV has been primarily advocated as an aqueductal bypass procedure for obstructive hydrocephalus, 12 but its application has now expanded to treating hydrocephalus of nonobstructive etiologies 1,5,8 with an overall success rate ranging from 68.5% to 83% in large mixed series. 1,2,13,23 Parallel to these high success rates, a recent review demonstrates an overall complication rate of 8.5%, permanent morbidity of 2.4%, and mortality of 0.21% for ETVs.3 In addition to the conceptual advantage of hardware-free CSF diversion, ETV presents the option of acquiring tissue biopsy if needed. 15,16,25 ETV also benefits from a potentially better cost effectiveness 9,11,12 and shorter surgical time compared with the placement of ventriculoperitoneal shunts.A safe and successful ETV requires good surgical visualization and atraumatic neuroendoscope passage through OBJect Endoscopic third ventriculostomy (ETV) has become a widely used method for CSF diversion when treating obstructive hydrocephalus. There are multiple recommendations on the transcortical ETV entry points, and some are specifically designed to provide a trajectory that avoids displacement to the eloquent periventricular structures. However, the morphology of the ventricular system is highly variable in hydrocephalus, and therefore a single best ETV trajectory may not be applicable to all cases. In the current study, 3 frequently quoted ETV entry points are compared in a cohort of pediatric cases with different degrees of ventriculomegaly. methOdS The images of 30 consecutive pediatric patients with varying degrees of ventriculomegaly were reviewed. Three-dimensional models were created using radiological analysis of anatomical detail and preoperative MRI scans in order to simulate 3 frequently quoted ETV trajectories for rigid neuroendoscopes. These trajectories were characterized based on the frequency and depth of tissue displacement to structures such as the fornix, caudate nucleus, genu of the internal capsule, and thalamus. The results are stratified based on ventricle size using the frontal horn ratio (FHR). reSultS Eloquent areas were displaced in nearly all analyzed entry points (97%-100%). Stratifying the data based on ventricle size revealed that 1) lateral structures were more likely to be displaced in cases of intermediate ventriculomegaly (FHR < 0.4) using all 3 trajectories, whereas 2) the fornix was less likely to be displaced using more posteriorly placed trajectories for severe ventriculomegaly (FHR > 0.4). Allowing for minimal (2.4 mm) tissue displacement, a more posterior entry point was less traumatic for severe ventriculomegaly. cOncluSiOnS There is no single best ETV trajectory that fully avoids displacement of the eloquent periventricular structures. Larger ventricles require a more posteriorly placed entry point in order to reduce injury to the eloquent structures, and interme...

Operative planning aid for optimal endoscopic third ventriculostomy entry points in pediatric cases

“…With regards to underlying neurosurgical diagnosis, posterior fossa neoplasm (22/30 patients) was the most common (including medulloblastoma, ependymoma, and meningioma), followed by primary CSF circulation abnormalities (8/30 patients). Mean frontal horn ratio was 0.38 and ranged between 0.24-0.5 (as previously reported [14]). …”

“…Our anonymized database contained 30 consecutive pediatric patients aged 6 months-16 years with varying degrees of ventriculomegaly who underwent treatment for newly diagnosed hydrocephalus (as previously reported [14]). We excluded cases with supratentorial mass lesions.…”

“…Radioanatomical data has been used to compare variants of the transpetrosal approach confirming the expected increments of working areas and angle with progressive bone removal [23]. The extent of tissue displacement in ETVs has been quantified by several investigators using intraoperative neuronavigation and paralleled with clinical safety of the procedure [14,16,17,24]. Furthermore, several studies advocate surgical simulation that uses virtual platforms or physical heads as adjunct models of surgical training as well as preoperative planning [25][26][27].…”

“…The location of these points however varies considerably which is paralleled by the highly diverse morphology of the ventricles in hydrocephalus [9,11,12]. These observations suggest that ETV entry points should be planned on a case-by-case basis with adjustments based on the ventricle sizes [13,14]. Neuronavigation is now wellaccepted in neurosurgical practice, however, it has not been widely used for ETV planning as most studies report using a single conventional transcortical entry point [1,[4][5][6]14].…”

“…These observations suggest that ETV entry points should be planned on a case-by-case basis with adjustments based on the ventricle sizes [13,14]. Neuronavigation is now wellaccepted in neurosurgical practice, however, it has not been widely used for ETV planning as most studies report using a single conventional transcortical entry point [1,[4][5][6]14]. Furthermore, the infrastructure to this adjunct is not always available to the surgeon.…”