Freehand Frontal EVD Insertion in Case of Small Ventricle: How to Navigate Easily?

The freehand technique for EVD insertion into the anterior horn of the ventricle remains the most reliable method to date, despite recent technological advancements. It is simple, easy, and can be performed by junior residents. Despite these merits, there is one obstacle that may make the procedure seem difficult to complete smoothly: navigating the ventricle with the correct trajectory, especially on the first attempt, minimizing the risk of possible complications that may arise from multiple trials. The degree of dilatation of the anterior horn of the ventricle significantly influences the success of the procedure, particularly on the first attempt. A small anterior horn of the ventricle in the EVD insertion procedure can be characterized as a non-hydrocephalic ventricle, with a slightly dilated appearance that does not exceed the ipsilateral medial canthus (IMC) line, which is approximately 15 mm lateral to the midline and does not reach the ipsilateral midpupillary line (IMPP). The average width of the anterior horn of the ventricle in non-hydrocephalic patients is approximately 17 mm. The new proposed entry point and trajectory of this study are based on such measurements as solid anatomical facts to precisely navigate small ventricles seen in early EVD candidate cases. The technique involves drawing a line from the ipsilateral medial canthus to intersect with a horizontal line representing the coronal suture. At the meeting point, a linear incision is made, and a burr hole is created immediately anterior to the coronal suture. A small round durotomy is performed with diathermy while using artery forceps, and then the ventricular catheter is inserted vertically downward, not guided by any landmarks or directions as in the trajectory for the classical Kocher’s point. This is the advantage of this point and trajectory; once the entry point is identified as mentioned, the trajectory's direction is not based on any specific structure or landmark. Given the proximity of this new entry point to the midline, the central position of the superior sagittal sinus should be confirmed to prevent injury. Entry into the ventricle, based on this proposed point, can be predicted by taking simple measurements from the axial cut of the image (CT or MRI) using a sheet of paper to draw a vertical line passing from the ipsilateral medial canthus to the lateral wall of the anterior horn in the image below, as demonstrated in the figures. This proposed point can be added to other suggested points to facilitate EVD insertion using the freehand technique. It should be utilized by others, and reports should be made to the literature for further evaluation and study.