Comparative analysis of endoscopic third ventriculostomy trajectories in pediatric cases.
OBJECTIVE
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 intermediate ventricles would dictate a medial entry point. These results suggest that the optimal entry point should be selected on a case-by-case basis after incorporating ventricle size.
Department of Pediatric Neurosurgery, Royal Manchester Children's Hospital, Manchester;|Department of Neurosurgery, Greater Manchester Neuroscience Centre, Salford Royal NHS Foundation Trust, Salford, United Kingdom.
Zsolt
Z
Zador
Department of Pediatric Neurosurgery, Royal Manchester Children's Hospital, Manchester;|Wolfson Molecular Imaging Centre, The University of Manchester, Manchester; and.|Department of Neurosurgery, Greater Manchester Neuroscience Centre, Salford Royal NHS Foundation Trust, Salford, United Kingdom.
David J
DJ
Coope
Department of Pediatric Neurosurgery, Royal Manchester Children's Hospital, Manchester;
Ian D
ID
Kamaly-Asl
D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D006849:Hydrocephalus / Q000175:diagnosis / Q000601:surgery*; D007223:Infant; D007231:Infant, Newborn; D008279:Magnetic Resonance Imaging; D008297:Male; D044583:Neuroendoscopy / Q000379:methods; D012720:Severity of Illness Index; D020542:Third Ventricle / Q000473:pathology / Q000601:surgery*; D016896:Treatment Outcome; D014696:Ventriculostomy / Q000379:methods*
ETV = endoscopic third ventriculostomy; FHR = frontal horn ratio; endoscopic third ventriculostomy; minimally invasive surgery; neuroendoscopy; optimal ETV trajectory; pediatric hydrocephalus