Intra-operative Evaluation of the External Ventricular Drain Catheter Position With Structured Light

External ventricular drainage (EVD) is a life-saving procedure used to release cerebrospinal fluid and relieve elevated intracranial pressure due to acute hydrocephalus, often secondary to subarachnoid hemorrhage, spontaneous intracerebral hemorrhage or traumatic brain injury (TBI). To drain cerebrospinal fluid (CSF) from the ventricular system and relieve pressure on the brain, a catheter is inserted into the ipsilateral frontal horn of the lateral ventricle (IFHLV) close to the Foramen of Monro (FoM). Twist-drill trephination is utilized to create a frontal burr hole at Kocher's point, approximately 11.5cm superior to the nasion and 2-3cm lateral of the midline. The dura is perforated, and the catheter is inserted with a rigid stylus. The current standard of care is a freehand technique which is often performed by neurosurgeons at the bedside in the ICU. It relies on surface anatomical landmarks to guide the catheter trajectory towards the FoM perpendicular to the calvarial slope at Kocher's point. However, the freehand technique is challenging to accurately perform, often requiring multiple passes of the catheter through the brain, with trajectory deviation most critical to malpositioning. Up to 24% of malpositioned EVDs require revision or reinsertion which can significantly increase catheter-associated infection. Up to 45.5% of EVD procedures require multiple passes for successful catheter insertion (6). This can lead to hemorrhage along the catheter tract (up to 34%, catheter dysfunction (up to 38%, and catheter-associated infection (up to 36% which increase EVD-associated health care costs (up to 20%). EVD malpositioning outside of the IFHLV (up to 60%) has been associated with other rare but significant complications including coma and diabetes insipidus. Large deviations in catheter placement have resulted in catheter insertion into significant brain regions (thalamus, hypothalamus, basal ganglion, internal capsule. Angular error within the coronal plane is the primary determinant of successful catheter insertion.

Bullseye is a novel intra-procedural system the investigators initially developed for glenoid guidepin placement. Bullseye EVD uses a verification workflow (guess and check) to identify EVD catheter position and trajectory with reference to the diagnostic CT image prior to catheter insertion using structured-light imaging. Structured-light scanning currently has several medical applications due to its speed, accuracy, and robust 3D surface reconstruction, and has been investigated in planning bedside subdural evacuation port system placement. In vitro performance of Bullseye EVD was demonstrated through testing on 3 cadaveric specimens to localize EVD placement on both sides of each of the heads (N=6 trials in total). The success of this in vitro work motivated further development of the technology including clinical evaluation for EVD.

Reducing EVD malpositioning and associated complications is a priority for neurosurgeons, however costly and cumbersome navigation solutions have had limited uptake in this urgent procedure that is often conducted at the bedside. Bullseye EVD represents a portable, safe, low-cost technology that can identify catheter positioning on existing preprocedural CT imaging. The proposed work, including integration into the existing clinical workflow, evaluation of in vivo accuracy and automation to enable rapid feedback during EVD placement, is critical to translating this technology from the bench to the bedside.