External ventricular drain (EVD) placement is a life-saving surgical procedure that treats hydrocephalus, a build-up of fluid and pressure in the center of the brain.


The Problem: A 'Blind' procedure

EVD placement (also known as ventriculostomy) typically occurs at the bedside in the ICU or in the operating room (OR), and the targeting of the cerebral ventricles (the fluid-filled center of the brain) is done in a 'blind' or freehand fashion: no imaging guidance is used. The optimal path for EVD insertion in an individual patient is estimated by the surgeon, using surface landmarks. 

Two very serious problems arise from 'blind' EVD placement:

  • malplacement (at the end of the procedure, the EVD catheter is in the wrong place
  • multiple passes (during the procedure, the catheter may need to be passed across the brain multiple times)

The literature shows that the rate of EVD malplacement is extremely high: about 17% of the time, the catheter is not in the correct location.

“The results of this study lead us to ask whether there is a better way to perform ventriculostomy.”
— Huyette, et al., Journal of Neurosurgery (2008) 108:88.

The Solution: Ultrasound-guided VENTRICULOSTOMY

Bedrock's solution is an easy-to-use ultrasound guidance system that allows Neurosurgeons and Neurointensivists to accurately place EVDs, ventriculoperitoneal shunts, and Ommaya reservoirs at the bedside or in the OR. 

The following sequence demonstrates how the system works. In the photographs, a laser locator is used for illustrative purposes in lieu of the ultrasound probe:

The ultrasound guidance system is attached to the cranial access twist drill hole in the skull model. A large hemicraniectomy skull defect has been created so we can see inside the skull model. Several targets are drawn surrounding the foramen magnum (the hole at the base of the skull model). 

The laser guide is turned on and the device is swiveled until the target is painted with the laser. Once the target is acquired, the device is use to lock this trajectory.

With the trajectory locked off, the laser guide is removed and a spacer insert in put in place that allows the EVD catheter to be advanced down the center of the determined trajectory.

The catheter is advanced along the locked-off trajectory.

Zoomed image showing accuracy of the system.

After the stylet is removed from the catheter, a thin profile stopper is placed and the alignment system is removed off the back of the catheter. 


For much more detailed information on how ultrasound-aligned EVD placement works, click here to read the granted U.S. patent (Flint 2015, #9,039,615), or here to read the 1st divisional patent (Flint 2016, #9,408,629)