Ventricular Shunt

This is one of the most frequently performed procedures in neurosurgery, however there is a potential risk of infecting the shunt system or damaging the hardware if not performed properly. As noted in the chapter on hydrocephalus, there are many different types of shunts available, each with a different site at which a tap can be performed. A plain X-ray film 2 of the skull in 2planes can often help determine which type of shunt is being used. Most modern shunts have an integral reservoir that can be accessed percutaneously, although some shunts do not have such a reservoir.

Indication

1. Suspected shunt malfunction or infection.

2. Measurement of ICP in a patient with a VP shunt.

Procedure

Once the site for the tap has been identified, the scalp over the region is shaved and prepped. We typically use a 23-gauge butterfly needle to percutaneously access the reservoir and connect it to a manometer to measure the opening pressure. The needle should enter the reservoir at an angle to increase the likelihood of entering the reservoir. Once the needle passes the dome of the reservoir, there is usually a 'give,' or loss of resistance. The needle tip should not be pushed too far because it can become obstructed in the far wall of the reservoir. If free flow of fluid is not observed, then a 3-cc syringe is used to draw back CSF. A proximal occlusion is suspected if there is still no flow of CSF. In cases where infection is of concern, CSF is removed and sent for culture, cell count and protein and glucose analysis.

Suggested Readings

1. Evans RW. Complication of lumbar puncture. Neurol Clin 1998; 16:83-105.

2. Gower DJ, Baker AL, Bell WO, Ball MR. Contraindications to lumbar puncture as defined by computed cranial tomography. J Neurol Neurosurg Psychiatry 1987; 50:1071-1074.

3. Mayhall CG, Archer NH, Lamb A et al. Ventriculostomy-related infections. A prospective epidemiologic study. N Engl J Med 1984; 310:553-559.

4. McComb JG, Little FM. Cerebrospinal fluid diversion. In: Apuzzo MLJ, ed. Surgery of the Third Ventricle. Baltimore: Williams and Wilkins, 1987.

5. Rekate HL. Treatment of hydrocephalus. In: Cheek WR, ed. Pediatric Neurosur-gery. 3rd ed. Philadelphia: Saunders, 1994.

6. Rennick G, Shann F, de Campo J. Cerebral herniation during bacterial meningitis in children. BMJ 1993; 306:953-955.

7. Rosner MJ. Techniques for intracranial pressure monitoring. In: Tindall GT, Cooper PR, Barrow DL, eds. The Practice of Neurosurgery. Baltimore: Williams and Wilkins, 1996.

8. Stenager E, Gerner-Smidt P, Kock-Jensen C. Ventriculostomy-related infection— An epidemiological study. Acta Neurochir 1986; 83:20-23.

9. Wood JH. Cerebrospinal fluid: Techniques of access and analytical interpretation. In: Wilkins RH, Rengachary SS, eds. Neurosurgery. 2nd ed. New York: McGraw-Hill, 1996.

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