How the procedure works

A LUMBAR puncture is a diagnostic test where a long hollow needle is inserted between the vertebrae into the spinal cord.

A fluid sample is taken and analysed in a lab. If a patient has Alzheimer’s disease, one or two proteins linked to the condition are present. Other types such as vascular or Lewy body dementia cannot be detected. For the procedure, also known as a spinal tap, patients must undress from the waist up and curl into ball lying on their side.

Afterwards, patients must lie down for about an hour and not drive for 24 hours.

The test, which some find painful, is considered generally safe but side effects can include severe headaches for up to a week, swelling and lower back pain.