A lumbar puncture is most commonly carried out to help diagnose three conditions:
- meningitis
- subarachnoid haemorrhage
- Guillain-Barré syndrome
Meningitis
The most common reason for a lumbar puncture is to help confirm or rule out a diagnosis of meningitis.
Meningitis is an infection of the outer layers of the brain and spinal cord. These layers are known as the meninges. The infection can be:
- viral – which can cause unpleasant flu-like symptoms but is not particularly serious
- bacterial – which is a medical emergency and, if not treated, can lead to coma, brain damage or death
Children under five years of age are most vulnerable to developing bacterial meningitis, which needs immediate treatment. The symptoms of meningitis can include:
- drowsiness
- confusion
- sometimes a blotchy red rash that does not fade when a glass is placed against it
A lumbar puncture can be used to check for the presence of bacteria or viruses in the cerebrospinal fluid (CSF).
Levels of white blood cells and sugar are also measured. A high white blood cell count and a low sugar count are often signs of infection.
Subarachnoid haemorrhage
A subarachnoid haemorrhage is an uncommon cause of a stroke, where blood leaks out of blood vessels over the surface of the brain.
As with all strokes, a subarachnoid haemorrhage is a medical emergency. It requires immediate treatment to prevent serious complications, such as brain damage and death.
The most common symptom of a subarachnoid haemorrhage is a sudden and severe headache, which feels like suddenly being hit on the head and is often unlike anything ever experienced before.
A lumbar puncture can be used to determine whether there is any blood in the CSF, which is often a sign of bleeding inside or around the brain.
Guillain-Barré syndrome
Guillain-Barré syndrome is a rare condition that affects around 1,500 people in the UK every year. It causes inflammation of the nervous system which disrupts its normal working.
The symptoms of Guillain-Barré syndrome, such as tingling in the hands and feet, start gradually and steadily get worse. Someone with the condition may eventually be unable to walk or swallow food.
A lumbar puncture can be used to check the protein level in the CSF. In Guillain-Barré syndrome, the amount of protein is usually higher than normal.
A lumbar puncture is also useful for ruling out other possible causes of the symptoms, such as a subarachnoid haemorrhage.
Providing treatment
As well as being used to diagnose conditions, a lumbar puncture is sometimes used to give treatments, including antibiotics or chemotherapy medicine for cancer.
A lumbar puncture can also be used to remove CSF to relieve pressure placed on the skull by the brain and fluid inside the skull cavity (known as high intracranial pressure). For example, this might be used in a condition called idiopathic intracranial hypertension, which mainly affects overweight women of childbearing age.
A lumbar puncture is an effective way of providing short-term symptom relief until a more permanent method of treatment can be provided.
