RESUMEN
Why a catheter can be correctly placed in the ventricle by inserting perpendicular to the frontal bone on the ventricular drainage? We performed a study on the accuracy of a path perpendicular to the skull surface into the anterior horn using computed tomography (CT), and a clinical study. Twenty patients were studied on CT images. Using the curved multi-planar reconstruction method, the curved frontal skull and brain were reconstructed to flat structures, and perpendicular lines were drawn from the flat surface to the foramen of Monro on the reconstructed images. In clinical practice, we made a device which guided a catheter inserting perpendicular to the frontal skull surface, and used it in the ventricular drainage surgery for 148 hydrocephalic patients (158 surgeries). We discovered that the curved surface of the frontal bone around Kocher's point represents the surface of a globe (mean radius, 75.9 ± 4.3 mm) centering on the foramen of Monro. The distribution of points ranged from 13.5-43.5 mm (mean, 43.5 ± 6.1 mm) to the midline, with points appearing more laterally as ventricular size increased. A catheter was placed in the ventricle in 148 surgeries (99.4%), and the catheter reached the ventricle with correct orientation toward the foramen of Monro in 128 (81.0%). The reason why the ventricular insertion perpendicular to the frontal bone surface can provide a consistent path toward the foramen of Monro is that the curved surface of the frontal bone around Kocher's point represents the surface of a globe centered on the foramen of Monro.