Lumbar puncture

In medicine, a lumbar puncture (or spinal tap) is a diagostic procedure that is done to collect a sample of cerebrospinal fluid (CSF) for biochemical and microbiological analysis. Lumbar puncture may also be done to inject medications into the cerebrospinal fluid. The most common indication for a lumbar puncture is to collect cerebrospinal fluid in a case of suspected meningitis.

A lumbar puncture must be done with aseptic technique by qualified medical practitioners.

In performing a lumbar puncture (in an adult), first the patient is usually placed in a left (or right) lateral position with his/her neck bent in full flexion and knees bent in full flexion up to his/her chest, approximating a foetal position as much as possible. It is also possible to have the patient sit on a stool and bend his/her head and shoulders forward. The area around the lower back should be prepared using aseptic technique. Once the appropriate location is palpated, a spinal needle is inserted, usually between the lumbar vertebrae L3/L4 or L4/L5 and pushed in until there is a "give" that indicates the needle is past the dura mater. The stylet from the spinal needle is then withdrawn and drops of cerebrospinal fluid are collected. The opening and closing pressures of the cerebrospinal fluid may be taken during this collection. The procedure is ended by withdrawing the needle while placing pressure on the puncture site. The patient should then lie on his/her back for at least six hours and be monitored for any signs of neurological problems. The technique described is almost identical to that used in spinal anesthesia, except that spinal anesthesia is more often done with the patient in a sitting position.

Adverse side effects from a lumbar puncture range from introduced infection to headache. Headache is the most common complication. Serious complications of a lumbar puncture include damage to the spinal cord or spinal nerve roots resulting in weakness or loss of sensation, or even paraplegia.

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