50 Anthropometry for Ventricular Puncture • Acute hydrocephalus. • Intracranial hypertension: ◦ Cerebrospinal fluid (CSF) drainage. ◦ Direct measurement of intracranial pressure. • Subarachnoid/intraventricular hemorrhage. • Intraoperative brain relaxation. • CSF infection. • Position: The patient is positioned supine. • Head: The head is slightly flexed (30°), in neutral position. • Side: The side is usually the nondominant (unless clinically indicated). • Starting point: Incision starts about 3 cm lateral to midline, over the coronal suture (usually located 11–13 cm along the nasion-to-inion line) or just posterior to it. • Course: It runs straight anteriorly, parallel to the midline. • Ending point: It ends about 2 cm anterior to the coronal suture. • Burr hole ◦ The burr hole is made about 2.5–3 cm lateral to the midline, 1 cm anterior to the coronal suture. • Arachnoid granulations. • Dural venous lakes. • Underlying brain parenchyma. • The dura is opened in a cruciate fashion. • Bipolar electrocautery is used for dural opening. • Venous lakes and bridging veins. • The cortical surface is coagulated with bipolar electrocautery. • The catheter is directed perpendicularly to the cortical surface by aiming in the coronal plane, toward the medial canthus of the ipsilateral eye and in the antero-posterior plane toward the tragus. Fig. 50.1 Kocher’s point. • The catheter is further advanced without stylet for about 1 cm. • The stylet has not to be advanced for more than 7 cm. • If CSF does not come out, following aspects have to be taken into consideration: ◦ Wrong site of burr hole or incorrect direction of catheter insertion. ◦ Slit ventricles. ◦ Brain shift. ◦ Air entrance in ventricles. ◦ Catheter obstruction by brain tissue, blood clot, or air lock. • Intra-cerebral hematomas along catheter’s path. • Intraventricular bleeding from choroid plexus. • Entry point: Catheter entry point is 4 cm above the orbital rim and 3 cm lateral to the midline. • Direction: The stylet is directed toward the midline. • Depth: The stylet must be advanced for 6-7 cm. • Ventricular target: Ventricular target corresponds to the frontal horn. Occipital horn can be reached by the same trajectory. • Advantage: Accuracy rate might exceed that of Kocher access. • Critical issues: Minimal cosmetic deficit. • Technique: ◦ Superior eyelid has to be retracted forward and upward. ◦ Ocular globe is displaced downward. • Entry point: A 18-gauge spinal needle is placed in the rostral third of the orbital roof (1 cm behind the supra-ciliar arch), just medial to the mid-pupillary line. • Direction: The stylet is directed 45° according to the axial plane (orbito-meatal line) and 15–20° medial to a vertical line (cranio-caudal line). • Depth: The stylet must be advanced from 3 to 8.5 cm, according to the ventricular size. • Ventricular target: Ventricular target corresponds to the frontal horn (1–2 cm superior to the foramen of Monro). • Critical issues: ◦ Risk of damage at supraorbital neurovascular bundle, or frontal lobe vessels. ◦ Intra-orbital CSF leakage. • Supine position ◦ Head: The head is flexed 15-20°, rotated as much as possible to the contralateral side. ◦ Possible positioning of a roll under the ipsilateral shoulder. • Prone position ◦ The patient is prone, in neutral position.
50.1 Indications
50.2 Frontal Horn (Kocher’s Point) (Fig. 50.1)
50.2.1 Patient Positioning
50.2.2 Skin Incision
50.2.3 Craniectomy
Critical Structures
50.2.4 Dural Opening
Critical Structures
50.2.5 Intradural Exposure and Catheter Insertion
50.2.6 Critical Issues
50.3 Alternative Access To The Frontal Horn
50.3.1 Kaufman’s Point (Supraorbital) (Fig. 50.2)
50.3.2 Transorbital (Fig. 50.3)
50.4 Occipital Horn
50.4.1 Patient Positioning
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