Neuroanatomical and cranial geometry of the frontal horn of the lateral ventricle.

In common practice ventricular catheterisation is dependent on accurate targeting of the lateral ventricles from external cranial landmarks. A ventricular catheter guide has been developed for rapid and accurate placement of ventricular catheters using a percutaneous technique and a narrow twist drill. Correct intraventricular placement is dependent on the width of the lateral ventricle and its distance from the midline, as well as depth from the cranial surface. In the present report data is presented obtained from coronal MRI studies describing the relationship between ventricular anatomy and cranial geometry. Within the frontal quadrant the centre of the frontal horn projection to the cranial surface where right angle intersection with the ventricle occurs is 3.28 cm (standard deviation, s.d. = 0.26) from the midline, at which point the mean depth from skin surface to the frontal horn is 5.97 cm (s.d. = 0.21). Optimal criteria for frontal ventriculostomy therefore comprises ventricular catheter passage at right angles to the scalp, approximately 3 cm from the midline to a depth of 6 cm from the skin where ventricular CSF should be encountered.