You are asked to clerk in a 48 year old gentlemen who has presented to A-E with headaches, nausea and vomiting. He had a VP Shunt in situ, and the GP is worried that the shunt maybe blocked.
In a shunt related problem there are some important general questions to ask in the history:
- Type of Shunt (is it VPeritoneal, VAtrial, VPleural)
- Location of the distal end of the shunt (eg peritoneal etc)
- Why the shunt was put in the first place
- Number of revisions required for the shunt
When exploring a patient with suspected Shunt dysfunction I tend to look 3 aspects:
If you think of a shunt as a piece of tubing it consists of a number of different parts:
- Proximal part (ventricular part)
- Valve
- Resevoir
- Distal Catheter
Any disconnection or migration will produce mechanical shunt dysfunction or it can become blocked with choroid plexus cells, exudate from infection or blood leading to obstructive hydrocephalus.
If you think of a shunt as a piece of tubing that drains CSF at different rates:
- It will either drain too much
- It will drain too little
If you think of a shunt as a piece of tubing as a foreign object:
- There is a significant increased risk of infection
Hence in a shunt related problem specific questions to ask in the history are:
- Under-drainage: headaches, nausea, vomiting and visual disturbance
- Over-drainage: low pressure headaches, confusion, weakness (secondary to sub-dural haematoma)
- Infection-ventriculitis/ventriculomeningitis
- Any swelling in the neck/abdomen
- Any palpable defects in the tube
Examination
- Bedside Investigations: Neuro-observations (GCS, Pupils, Blood glucose) Regular Obervations (temperature), Include Fundoscopy to look for Papilloedema
- Look for abdominal swelling, palpate the tube examining for disconnections, look for swelling around the shunt tubing and importantly in the neck (most common site for shunt disconections)
- With appropriate senior support: Pressing on the reservoir may indicate whether the proximal part is working. Press the valve, and if it refills than the proximal part is working. This does not exclude distal obstruction.
- With appropriate senior support: ‘Tapping’ a shunt involves passing a narrow needle into the reservoir of the shunt valve and attach a manometer. If CSF can be aspirated at high pressure it could suggest distal obsturuction, if difficult to aspirate could suggest proximal blockage. CSF aspirate can also get sent to the Labaratory for further analysis.
Imaging
- CT Scan- often used as first line investigation, can give size of ventricles, position of ventricular catheter tip. Please do remember that it is important to compare previous imaging and remember the radiation risk this posses to children.
- Shunt Series X-Rays (x-rays of the skull, chest and abdomen) looking for signs of any mechanical shunt dysfunction. They should not be used as first line investigations, firstly due to the low sensitivity (30%, Pujara et al referrals for suspected VP Shunt dysfunction) and the radiation risk it poses to patients. 1 Shunt Series X-Rays is equivalent to 2 years of background environmental radiation
Blood Tests
- Checking Inflammatory Markers looking for signs of infection e.g. CRP
Surgical Options
- Shunt Revision- either replacing part of the shunt hardware or total insertion of a new shunt.