External ventricular drainage

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In neurosurgery, external ventricular drainage (also known as EVD in everyday clinical practice) is a drainage of cerebrospinal fluid ( liquor cerebrospinalis , or CSF for short ) from the ventricular system of the brain .

The liquor is pressed out of the blood in the choroid plexus mainly in the lateral ventricles (but also in parts of the third and fourth ventricles) and reaches the fourth ventricle via the third ventricle and the aqueductus mesencephali and from there through openings ( apertures ) into the outer cerebrospinal fluid space outside the brain. This is where the cerebral water is taken up again ( resorption ) in the venous blood conductors . So it is a circulating system.

If the CSF production is too strong or if the CSF cannot drain off properly because a tumor , cerebral hemorrhage or other swelling blocks the drainage, then hydrocephalus internus develops , a congestion of the cerebral fluid in the ventricular system. This can put pressure on the brain ( intracranial pressure ), which can be life-threatening. To avert this danger to life, the pressure must be diverted from the ventricle. Therefore, in a small operation, which can be performed either in the operating room or on the bedside in the intensive care unit , a tube or a thin needle ( Duisburg needle ) is inserted through the skull into the ventricular system. The liquor can then escape through this drainage and the danger is initially averted.

Since such an external ventricular drainage is a potential entry point for germs, it cannot remain indefinitely. So it is only suitable as a temporary derivative. Require a permanent Liquorableitung must operationally a so-called internal cerebral shunt , are laid out in a ventriculoperitoneal or ventriculo-atrial shunt.

Technical implementation

An external ventricular drain can be inserted in two ways: On the one hand, an external ventricular drain can be inserted in the operating room and the drain is then tunneled under the skin and drained away. The second option is the bedside insert with a bolt system. Here an opening is drilled into the skull with a hand drill and a retaining bolt is inserted; the external ventricular drainage can then be advanced over this bolt. The Kocher point is used as a typical entry point for both intraoperative and bedside insoles. The quick, technically correct implementation of an external ventricular drainage can be a life-saving measure with increased intracranial pressure.

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