The main reason for a lumbar puncture is to help diagnose diseases of the central nervous system, including the brain and spine.

Young infants commonly require lumbar puncture as a part of the routine workup for fever without a source.

Infants also do not reliably show classic symptoms of meningeal irritation (meningismus) like neck stiffness and headache the way adults do.

[7] In any age group, subarachnoid hemorrhage, hydrocephalus, benign intracranial hypertension, and many other diagnoses may be supported or excluded with this test.

CSF containing less than 10 red blood cells (RBCs)/mm3 constitutes a "negative" tap in the context of a workup for subarachnoid hemorrhage, for example.

While mainstays of treatment are medication, in some cases lumbar puncture performed multiple times may improve symptoms.

[11][12] Additionally, some people with normal pressure hydrocephalus (characterized by urinary incontinence, a changed ability to walk properly, and dementia) receive some relief of symptoms after removal of CSF.

[13] Lumbar puncture should not be performed in the following situations: Post-dural-puncture headache with nausea is the most common complication; it often responds to pain medications and infusion of fluids.

It was long taught that this complication can be prevented by strict maintenance of a supine posture for two hours after the successful puncture; this has not been borne out in modern studies involving large numbers of people.

A headache that is persistent despite a long period of bedrest and occurs only when sitting up may be indicative of a CSF leak from the lumbar puncture site.

[21] Contact between the side of the lumbar puncture needle and a spinal nerve root can result in anomalous sensations (paresthesia) in a leg during the procedure; this is harmless and people can be warned about it in advance to minimize their anxiety if it should occur.

The latter is exceedingly rare, since the level at which the spinal cord ends (normally the inferior border of L1, although it is slightly lower in infants) is several vertebral spaces above the proper location for a lumbar puncture (L3/L4).

In any case, computed tomography of the brain is often performed prior to lumbar puncture if an intracranial mass is suspected.

[23][24][25][26] The brain and spinal cord are enveloped by a layer of cerebrospinal fluid, 125–150 mL in total (in adults) which acts as a shock absorber and provides a medium for the transfer of nutrients and waste products.

[citation needed] The upright seated position is advantageous in that there is less distortion of spinal anatomy which allows for easier withdrawal of fluid.

Some practitioners prefer it for lumbar puncture in obese patients, where lying on their side would cause a scoliosis and unreliable anatomical landmarks.

Use of ultrasound reduces the number of needle insertions and redirections, and results in higher rates of successful lumbar puncture.

[28] If the procedure is difficult, such as in people with spinal deformities such as scoliosis, it can also be performed under fluoroscopy (under continuous X-ray imaging).

There was a higher success rate in obtaining CSF in the first attempt in infants younger than 12 months in the sitting flexed position.

Therefore, it is difficult to assess when the needle passes through them into the subarachnoid space because the characteristic "pop" or "give" may be subtle or nonexistent in the pediatric lumbar puncture.

[27] Decreased CSF pressure can indicate complete subarachnoid blockage, leakage of spinal fluid, severe dehydration, hyperosmolality, or circulatory collapse.

[citation needed] The finding of erythrophagocytosis,[33] where phagocytosed erythrocytes are observed, signifies haemorrhage into the CSF that preceded the lumbar puncture.

[56] The technique for needle lumbar puncture was then introduced by the German physician Heinrich Quincke, who credits Wynter with the earlier discovery; he first reported his experiences at an internal medicine conference in Wiesbaden, Germany, in 1891.

[58][59] The lumbar puncture procedure was taken to the United States by Arthur H. Wentworth an assistant professor at the Harvard Medical School, based at Children's Hospital.

During this quite painful procedure, CSF was replaced with air or some other gas via the lumbar puncture in order to enhance the appearance of certain areas of the brain on plain radiographs.