Hydrocephalus is a state in which there is a build up of brain fluid (Cerebrospinal fluid CSF) in the head, and this generally results in a build up in pressure. Symptoms usually include headache, vomiting, visual disturbance (double vision or loss of vision), and if severe there may be drowsiness or even reduced consciousness.
The build up in CSF is due to failure to absorb the fluid. Commonly this can arise following haemorrhage or infection.
Around 15% of aneurysmal subarachnoid haemorrhage patients need temporary CSF drainage. This may be via lumbar punctures, a lumbar drain, or an external ventricular drain (EVD - drain inserted directly into a lateral ventricle through a burrhole).
Half of these patients need permanent CSF diversion - via a shunt procedure.
Following meningitis, sometimes hydrocephalus can develop. This may be due to pyogenic bacteria, or due to Tuberculosis.
These patients can safely have lumbar puncture - both for diagnostic and therapeutic reasons.
Benign Intracranial Hypertension (BIH)
This is a condition that presents mostly in young women, characterised by very high CSF pressures but small ventricles. There is a risk of permanent blindness. Initial management for secondary causes, diagnosis, trial of medications, is with neurologists. Sometimes a shunt may be required.
Normal Pressure Hydrocephalus (NPH)
This is an important potentially reversible cause of dementia. The classical triad includes apraxic gait (slow shuffling walking), cognitive decline, and urinary incontinence. A number of simple tests can be undertaken to predict the response to a shunt. Overdrainage of CSF is an important complication.
There is a build up of CSF in the brain due to a blockage in the CSF pathway.
The blockage may be due to a variety of reasons. In children a congenital narrowing - aqueduct stenosis, is a common cause.
A range of tumours - benign and malignant can cause different patterns of obstructive hydrocephalus. A lumbar puncture is not feasible in these cases.
Treating the cause can cure the hydrocephalus in many cases, in others CSF diversion may still be needed.
An internal bypass - endoscopic third ventriculostomy avoids any implants.
Shunts for these cases need to drain CSF from the ventricles (fluid chambers in the brain), most commonly to the peritoneal cavity in the abdomen, where the CSF gets absorbed via the lymphatics and is returned to the venous system.
A shunt is an implanted device, which allows drainage of excess CSF in order to normalise the pressure. Shunts are usually permanent implants. These mechanical devices can fail due to overdrinage, under drainage, blockage, infection, fracturing, and migration. The failure rate in adults is quite low.
The Ventriculoperitoneal (VP) shunt is the commonest type. A thin catheter is carefully placed through a burrhole in the skull into a lateral ventricle. A small valve is connected to regulate the flow of CSF. A longer thin tube is tunnelled from the valve under the skin to a small wound in the abdomen. The tip of the tubing is placed into the peritoneal cavity.
It is quite rare to drain the CSF to either the pleural cavity (ventriculo-pleural) or the heart (ventriculo-atrial shunt).
A lumboperitoneal shunt is in essence a permanent lumbar puncture, and may be quite effective for the treatment of communicating hydrocephalus. Historically a thin silicone tubing would drain from the lumbar spinal canal to the peritoneal cavity. Modern valve systems can overcome over drainage issues.