Technical Background —The brain is normally cushioned in the skull by cerebrospinal fluid (CSF). When CSF cannot drain properly, pressure builds up and can cause brain herniation, a displacement of brain tissue from its normal position that is often fatal. The pressure can be relieved by an operation to remove CSF from the place in the center of the brain that it fills. The CSF is removed through an external ventricular drain (EVD) that is placed by drilling a hole

through the skull 10-11 cm back from the bridge of the nose and 2.5-3 cm over from the midline.

 

Problem Statement —The ideal location for placing the EVD catheter is the so-called foramen of Monroe, which lies at the point of intersection where a line from the ear canal crosses a second line through the edge of the eye closest to the nose. The placement is a difficult procedure and the first attempt often fails, even with experienced neurosurgeons, causing unwanted damage to nearby brain tissue. While the free-hand technique is recognized to be inadequate, alternative methods have drawbacks. Image-guided catheter placement using electromagnetic technology requires a special type of high-resolution CT scan to place landmarks beforehand and a special navigation device brought to the patient’s room, which are expensive and not available in all hospitals, besides which the technique is difficult to set up and to learn. A specialized ultrasound probe is another alternative, but this requires specialized training and is difficult to use. The Ghajar guide, a small tripod mounted on the skull to guide the catheter on a perpendicular path into the skull, is affected by differences in the slope of the skull at the point of entry and cannot be used when midline shift occurs. Another problem with EVD is the need to maintain the patient’s head in a stationary position. The Mayfield clamp used in the OR is not practical outside the OR due to its bulkiness, the need for anesthesia to apply the pins and the lack of a place to secure the clamp to the bed. There are no commercially available devices for beside head stabilizing. In the absence of such as device, a second medical employee can hold the head steady, but positioning will be sub-optimal if there is no one available to do this.

 

Technical Solution —The present invention provides an interactive means of guiding the placement of the EVD catheter to avoid unnecessary damage to healthy brain tissue. The device consists in a c-shaped gel roll with ridge rubber base that attaches to two adjustable brackets, one inserted into the ear space and the other localized near the edge of the eye closest to the nose (the medial epicanthal fold). The two brackets serve as reference points for EVD placement. An electromagnetic proximity sensor attached to the EVD catheter and senses its position in space relative to the two adjustable bracket settings and relays the information to a cell phone application, which then displays an image to guide the navigation of the catheter into the skull. A routine CT scan performed on patients can reveal elevated brain pressure and will indicate an anatomical abnormality, such as midline shift, then the appropriate corrections can be programmed into the cell phone application to guide the trajectory accordingly. The ability to take individual anatomy into account thus constitutes an improvement over the Ghajar guide, which cannot be used when midline shift is present. Compared to current electromagnetic navigation systems, the present invention is much less expensive and easier to set up, since it does not require additional imaging. The image-guided navigation of the present invention is a clear improvement over freehand estimate placement without head stabilization, the current standard of practice owing to the difficulty of implementing existing alternatives.

 

Feasibility —Some university studies have demonstrated the technical feasibility of estimating midline shift and computing target parameters, as well as syncing with imaging. The challenge is to bring together the software with the catheter guide and positioning device. The implementation of the link between the software and the catheter guide could be a fairly low technology solution, involving a flat pack and cardboard that unfolds. Thus, the real technical problem to solve lies in programming the software for the mobile phone application that brings in the more advanced capability that currently does not exist at the bedside. Developing an algorithm to translate information from CT/MRI scans into a computed trajectory and to generate the image guidance for the catheter based on input from the electromagnetic proximity sensors calls for more expertise than a typical software programming project. Hence, the main cause for reserve about the invention’s feasibility rests in the relatively complicated nature of the problem the software has to be designed to solve.

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Market Potential

 

Market Definition— The bedside EVD system is intended to address the issue of patient head positioning, while decreasing the chances of damaging healthy brain tissue in placing catheters. It is claimed that these advantages will be accomplished by utilizing adjustable guides and a proximity sensor attached to the EVD catheter. In addition, a mobile application is suggested to be paired to this device to provide image-guided navigation. The primary target market segment

for the present invention is the United States intracranial pressure monitoring devices market.

 

Market Quantification— The U.S. intracranial pressure monitoring devices market is segmented on the basis of application into traumatic brain injury (TBI), intracerebral hemorrhage (stroke) and meningitis, among others. 1 The two most common occurrences appear to be TBI and intracerebral hemorrhage; both of which require life saving procedures that include the use of either an EVD device or an intracranial pressure monitor (ICP) device.