How can you confirm a cerebrospinal fluid leak in a base of skull fracture?
Basilar skull fractures (i.e. base of skull fractures) have a high incidence of dural tears and thus a higher than average risk of meningitis – although it is controversial whether or not to give prophylactic antibiotics. The basics to know about this condition are as follows:
Firstly, skull X-rays are almost never of any help in diagnosing basilar skull fractures. You need to go by clinical signs.
Clinical signs include:
Raccoon eyes – this refers to a periorbital (around the eyes) bruising, and is a result of blood tracking down from the skull fracture site to the soft tissue around the eyes.
Battle’s sign – named after a guy (unsurprisingly) called Battle, this is bruising around the mastoid process (behind the ears). As with raccoon eyes, this bruising is due to blood tracking there from the skull fracture, not from damage directly to the mastoid process.
Cerebrospinal fluid (CSF) otorrhoea -this is leakage of CSF out your ear, via a combination of a ruptured tympanic membrane and nearby basilar skull fracture.
CSF rhinorrhoea – similar to the otorrhoea story, this is leakage of CSF out your nose. Usually (but not exclusively) the ethmoid cribriform plate is the part fractured.
Cranial nerve palsies – many of the cranial nerves run nearby enough to be injured or compressed by a fractured base of skull.
A good question that might now arise is how you tell if fluid coming out the nose or ears is CSF – it could be pure blood, or (in the case of nasal discharge) it could be the normal nasal secretions. There are a number of tests you can do.
Firstly, CSF should have glucose in it, whereas this is unlikely in normal nasal secretions, and so measuring the glucose (initially on dipstix, and then formally) is helpful.
Secondly, if you are dealing with a bloody fluid, you could try to look for the halo sign (or ring sign). Get some of the blood on a tissue If there is CSF mixed with the blood, it will move by capillary action further away from the centre than the blood will. You’ll get something like this:
These tests are helpful , but they aren’t accurate. If you want to be more sure, measure the level of beta-2-transferrin in the fluid. This protein is only found in CSF, so if you are finding it in fluid coming from the nose or ears, you have a CSF leak.
If you have any of these signs present, you may be dealing with a basilar skull fracture. To confirm your diagnosis, you need to organise a CT scan of the area. This is more or less the diagnostic procedure followed in most hospitals.
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