Object: Frontal ventriculostomy is one of the most frequent and standardized procedures in
neurosurgery. However, many first and subsequent punctures miss the target, and suboptimal
placement or misplacement of the catheter is common. We therefore re-examined the
landmarks and rules to determine the entry point and trajectory with the best hit
rate (HtR).
Methods: Computed tomography scans of 50 patients with normal ventricular and skull anatomy,
and without ventricular puncture were selected. Using a 5 × 5 cm frontal grid with
25 entry points referenced to the bregma, we examined trajectories 1) perpendicular
to the skull, 2) toward classical facial landmarks in the coronal and sagittal plane
and 3) toward an idealized target in the middle of the ipsilateral anterior horn.
Three-dimensional (3D)-virtual reality ventriculostomies were performed for these
entry points and trajectories and the HtRs were recorded, resulting in an investigation
of 8000 different virtual procedures.
Results: The best HtR for the ipsilateral anterior horn (ILAH) was 86% for an ideal trajectory,
84% for a landmark trajectory, and 83% for a 90° trajectory, but only at specific
entry points. The highest HtRs were found for entry points 3 or 4 cm lateral to the
midline, but only in combination with a trajectory toward the contralateral canthus,
and 1 or 2 cm lateral to the midline, but only paired with a trajectory toward the
nasion. The same “pairing” exists for entry points and trajectories in the sagittal
plane. For perpendicular (90°) trajectories, the best entry points were at 3–5 cm
lateral to the midline and 3 cm anterior to the bregma, or 4 cm lateral to the midline
and 2 cm anterior to the bregma.
Conclusions: Only a few entry points offer a chance of >80% of hitting the ILAH, and then only
in combination with a specific trajectory. This “pairing” between entry point and
trajectory was found both for landmark targeting and for perpendicular trajectories,
with very limited variability. Surprisingly, the ipsilateral medial canthus (IMC),
a commonly quoted landmark, had low HtRs and should not be recommended as a trajectory
target.
