Ventriculostomy

Ventriculostomy, like a ventricular tap, allows direct access to the ventricular system. It allows CSF to be drained for a longer period of time without the need for multiple punctures and is the 'gold standard' for measuring ICP when coupled to a fluid-filled manometer or transducer. At some institutions all emergency ventriculostomies are performed at the bedside in the Pediatric ICU. Our preferred hardware is a long (35 cm) catheter with a disposable trocar that allows rapid tunneling for some distance from the entry site. In an emergency, if a commercial ventricular catheter is unavailable, a small, red, rubber catheter with a K-wire as a sylet can be used.

Indications

1. Raised ICP. Situations requiring continuous ICP monitoring and drainage (i.e., severe head injury, obstructive hydrocephalus from a brain tumor, postoperative drainage when the ventricular system is entered).

2. Hydrocephalus. As a temporizing measure until resolution of pathology or shunt placement.

3. Shunt infection. Used to drain CSF for pressure reasons and also diagnostic purposes when a shunt infection is present.

Procedure in a Neonate

The right side is preferred. The scalp is shaved, prepped, draped and local anesthetic is infiltrated. The entry point for the catheter is the same as for a ventricular tap. A 1.5 cm curvilinear incision is made over the lateral aspect of the anterior fontanelle. This places the suture line away from the catheter. In addition, the incision should be planned for the eventuality of a VP shunt, if the right frontal area is needed. Care should be taken not to puncture the dura at this point. The scalp flap is then gently retracted laterally with a small retractor to tamponade bleeding. The dura in the corner of the fontanelle is dissected off the inner surface of the skull and a small opening is made using either a #11 blade or a hand-held cautery device set on low current. A 35-cm catheter and stylet are then inserted perpendicular to the surface of the brain and passed approximately 2 to 3 cm into the brain, or until CSF is seen. In infants, the ICP may not be sufficient to allow the CSF to exit from the top of the cathter. It should be lowered to allow gravity to assist flow. The stylet is then removed and once the ICP has been measured, the catheter is tunneled laterally and brought through the skin as far from the insertion point as possible. Care must be taken to hold the catheter while tunneling in order to prevent accidental removal. Nonabsorbable sutures (4-0) are used to secure the catheter to the skin while an absorbable suture is used to close the incision.

Procedure in an Older Child

Once the cranial sutures fuse and the anterior fontanelle closes, the landmarks chosen for the placement of the ventriculostomy are the same as in an adult (Fig. 1). The right (non-dominant) side is chosen and the site of the burr hole is usually placed 2 to 3 cm lateral to midline and 1cm anterior to the coronal suture (Kocher's point). This point avoids the sagittal sinus and the motor strip. Several other possible insertion sites can be used (Fig. 2).

The right frontal quadrant of the scalp is shaved, prepped and draped. A 2 cm incision is made and a burr hole is drilled with a 0.5 cm bit. (Either a standard burr hole can be made or a smaller one with bits available in many commercial kits that are available). The dura is incised with a #11 blade and a flexible venticular catheter is passed into the lateral ventricle using the ipsilateral medial canthus and external auditory meatus (EAM) as landmarks in the coronal and saggital planes, respectively. The catheter should be inserted 5-7 cm and the stylet removed once CSF is obtained. If there is some difficulty cannulating the ventricle, the trajectory can be altered to cannulate the contralateral ventricle by aiming towards the contralateral medial canthus. The catheter is tunneled laterally under the galea, as with the neo-nate, and connected to a fluid filled manometer.

Occasionally it is necessary to use an occipital burr hole for ventriculostomy placement. The technique involved is the same except that the landmarks are changed. In the neonate, the entry point is usually along the lambdoid suture 2 cm lateral to the midline. In older children a classic Frasier burr hole is placed 3 cm lateral to the midline and 5 to 6 cm rostral to the inion. The catheter is directed towards the middle of the forehead and passed approximately 7 to 8 cm.

Troubleshooting

1. Inability to obtain CSF. The distance entered should be checked. The catheter can be advanced but not more than 7 cm from a coronal entry point (no more than 5 cm in an infant). Advancing more than this risks injury to deeper structures. If unsuccessful, the catheter should be withdrawn, the landmarks rechecked, and a new trajectory chosen. Generally, the ventricle is missed either laterally or anteriorly. No more than 3 attempts should be made. If unsuccessful, either another entry point should be chosen, or techniques such as ultrasound, or CT guidance should be considered. If the ICP is low, the end of the tubing should be dropped below the level of the head to promote drainage. Gentle aspiration with a syringe is sometimes necessary to clear an airlock or debris from the catheter.

2. Bloody CSF. Usually this is not a major problem. CSF drainage usually clears rapidly. For visually apparent bloody CSF, irrigation with warm saline can be done until the CSF begins to clear. If brisk or arterial in nature, the catheter should be left in place and an urgent CT should be obtained.

Troubleshooting a Ventricular Drain and ICP Monitor

Failure to Drain

1. Check that all stopcocks are open and check for leaks in the system. Remove any trapped air.

2. Check that the air filter on the drainage bag is not clogged or wet; this will cause a build-up of pressure in the system.

3. Lower the drainage bag below the level of the external auditory meatus. If the system is patent, it will drain even if the ICP is close to 0.

Figure 2. Various landmarks for entering the ventricular system. (Reprinted by permission, Wilkins, Rengachary, eds. Neurosurgery. McGraw Hill, 1985.)

Figure 2. Various landmarks for entering the ventricular system. (Reprinted by permission, Wilkins, Rengachary, eds. Neurosurgery. McGraw Hill, 1985.)

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