Lumbar puncture

Lumbar puncture (LP), also known as a spinal tap, is a medical procedure in which a needle is inserted into the spinal canal, most commonly to collect cerebrospinal fluid (CSF) for diagnostic testing. The main reason for a lumbar puncture is to help diagnose diseases of the central nervous system, including the brain and spine. Examples of these conditions include meningitis and subarachnoid hemorrhage. It may also be used therapeutically in some conditions. Increased intracranial pressure (pressure in the skull) is a contraindication, due to risk of brain matter being compressed and pushed toward the spine. Sometimes, lumbar puncture cannot be performed safely (for example due to a severe bleeding tendency). It is regarded as a safe procedure, but post-dural-puncture headache is a common side effect. The procedure is typically performed under local anesthesia using a sterile technique. A hypodermic needle is used to access the subarachnoid space and fluid collected. Fluid may be sent for biochemical, microbiological, and cytological analysis. Using ultrasound to landmark may increase success. Lumbar puncture was first introduced in 1891 by the German physician Heinrich Quincke. The reason for a lumbar puncture may be to make a diagnosis or to treat a disease. The chief diagnostic indications of lumbar puncture are for collection of cerebrospinal fluid (CSF). Analysis of CSF may exclude infectious, inflammatory, and neoplastic diseases affecting the central nervous system. The most common purpose is in suspected meningitis, since there is no other reliable tool with which meningitis, a life-threatening but highly treatable condition, can be excluded. A lumbar puncture can also be used to detect whether someone has 'Stage 1' or 'Stage 2' Trypanosoma brucei. Young infants commonly require lumbar puncture as a part of the routine workup for fever without a source. This is due to higher rates of meningitis than in older persons. Infants also do not reliably show classic symptoms of meningeal irritation (meningismus) like neck stiffness and headache the way adults do. In any age group, subarachnoid hemorrhage, hydrocephalus, benign intracranial hypertension, and many other diagnoses may be supported or excluded with this test. It may also be used to detect the presence of malignant cells in the CSF, as in carcinomatous meningitis or medulloblastoma. 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. Taps that are 'positive' have an RBC count of 100/mm³ or more. Lumbar punctures may also be done to inject medications into the cerebrospinal fluid ('intrathecally'), particularly for spinal anesthesia or chemotherapy. Serial lumbar punctures may be useful in temporary treatment of idiopathic intracranial hypertension (IIH). This disease is characterized by increased pressure of CSF which may cause headache and permanent loss of vision. While mainstays of treatment are medication, in some cases lumbar puncture performed multiple times may improve symptoms. It is not recommended as a staple of treatment due to discomfort and risk of the procedure, and the short duration of its efficacy. 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.