A lumbar puncture is often used to diagnose certain conditions that affect the brain and spinal cord. 

Meningitis

Meningitis is the inflammation of the membrane layers covering the brain and spinal cord. It can develop from a number of different causes, including infection by bacteria or viruses. Bacterial meningitis can be life-threatening.

A lumbar puncture is needed to diagnose meningitis and ensure appropriate treatment is started.

Subarachnoid haemorrhage

A subarachnoid haemorrhage occurs when a blood vessel within or underneath the brain bursts (ruptures). It's usually diagnosed using a computerised tomography (CT) scan, but sometimes it may be necessary to perform a lumbar puncture to detect the presence of blood in the cerebrospinal fluid (CSF).

Guillain-Barré syndrome

Guillain-Barré syndrome is a rare condition that causes inflammation of nerves supplying the arms and the legs. A lumbar puncture is needed to check the protein level in the CSF, which is usually higher with this condition.

Providing treatment

A lumbar puncture can also be used to administer treatments by injecting medication into the CSF. Medications include:

• antibiotics for bacterial meningitis
• chemotherapy medicines for cancers affecting the central nervous system
• spinal anaesthetic, so operations on the lower half of the body can be carried out without a general anaesthetic

A lumbar puncture can also be used to relieve a pressure build-up within the skull (known as raised intracranial pressure) by removing some CSF. This can give short-term relief of symptoms until a more permanent treatment can be provided.