Lumbar puncture

A lumbar puncture (also called a spinal tap) is normally done to help diagnose meningitis (usually Cryptococcus) or certain viral infections that can cause neurological problems. It is an essential part of establishing the etiology (cause) of persistent headache, fever, or other problems such as weakness and numbness in the legs. It may also be used to assess the tumour severity.

After use of a local anaesthetic, a needle is inserted into the base of the spine and a small amount of cerebrospinal fluid is removed. The procedure is normally done in a hospital or clinic on an outpatient basis. Afterwards,  the patient is asked to remain lying flat for four to 24 hours to reduce the risk of a post-lumbar puncture headache. If swelling of the brain tissue is clinically suspected, a brain scan must be done before the lumbar puncture to ensure patient safety.

Cryptococcus and other causes of meningitis, such as tuberculosis, can be readily diagnosed and treated. Viruses that may be implicated in certain neurological problems can also be detected in CSF and their detection will confirm a diagnosis. These viruses include CMV, herpes simplex virus, and JC virus. Occasionally, a lumbar puncture may be performed to assess the response to treatment for cryptococcal meningitis or to help confirm or exclude a clinical relapse.