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A lumbar puncture (also known as a spinal tap) is a diagnostic procedure where samples of cerebrospinal fluid (CSF) are collected and analyzed to help with the diagnosis of certain conditions such as infections (e.g. meningitis), demyelinating processes (e.g. multiple sclerosis), elevated pressures within the brain (hydrocephalus), ruptured aneurysms and brain cancer. While at the end of a lumbar puncture the needle used to withdraw CSF is removed, occasionally, a catheter can be placed through the needle into the space that contains the CSF in order to continuously drain this fluid for treatment or diagnosis of various conditions -- this procedure is called a lumbar drain placement.
In performing a lumbar puncture, the patient is positioned on his/her side and asked to flex the neck and bring the knees up to his/her chest (in a fetal position). Alternatively, the patient may be asked to sit with his/her head and shoulders forward flexed forward. The skin around the lower back is prepared using an antiseptic solution and a local anesthetic (numbing medication) is injected. A long and thin needle, called a spinal needle, is then inserted through the skin and deeper tissues, and between two lower lumbar vertebrae into the space that contains the CSF (also known as the subarachnoid space). Once the appropriate volume of CSF has been collected, the needle is withdrawn and a bandage is placed on the puncture site. The diagram below depicts the typical positioning for a lumbar puncture.
In placing a lumbar drain, a similar procedure to a lumbar puncture is performed with the exception that the needle used is slightly thicker and after collection of CSF, a thin plastic catheter is placed through the needle in to the subarachnoid space. The needle is then removed, leaving the catheter in place, which is then connected to appropriate drainage and monitoring devices. The drain is typically removed after one to several days, depending on the diagnostic or therapeutic procedure to be performed. Insertion of a lumbar drain through the spinal needle is shown below.
Headache with occasional nausea is the most common complication of this procedure which often responds well to analgesics and infusion of fluids and can often be prevented by laying flat for one to two hours. A headache that is persistent despite these measures can be treated by more bed rest or by an epidural blood patch, which is a procedure where the patient's own blood is injected into the site of leakage to cause a clot to form and seal off the leak.
Contact between the spinal needle and a nerve in the subarachnoid space can result in painful sensations in the leg during the procedure. This is harmless and patients can be warned about it in advance to minimize their anxiety if it should occur.
Serious complications of a properly performed lumbar puncture or lumbar drain placement are extremely rare, and include infections, bleeding around the spine, and trauma to nerves resulting in weakness or loss of sensation.
