A lumbar puncture is also called a spinal tap, spinal puncture, thecal puncture, or rachiocentesis.
A lumbar puncture is usually not painful, as a patient is first given a local anesthetic. Most patients feel nothing except for the mild sting of the local anesthetic needle. It is possible to feel a pressure sensation as the needle goes in. The procedure is done in the hospital or outpatient facility by a doctor or nurse practitioner and usually takes 30 to 45 minutes. After about one or two hours of monitoring, patients are able to leave the facility.
There are many nerves in the spinal canal and if one of them is touched by the needle, there might be a sharp pain, mostly in the leg. Some might feel a burning sensation or nerve twinges. The patient should inform the physician if they feel any undue pain.
What is a lumbar puncture?
A lumbar puncture (LP) is a procedure performed in the lumbar region of the spine to collect cerebrospinal fluid (CSF) that surrounds the spinal cord and brain. The doctor inserts a needle in the space between two lumbar vertebrae to enter the spinal canal. A lumbar puncture is also called a spinal tap, spinal puncture, thecal puncture, or rachiocentesis.
Why is a lumbar puncture done?
The cerebrospinal fluid acts as a support of buoyancy for the brain and spinal cord, protecting them from injury. An analysis of CSF is done for diagnosing life-threating conditions such as:
- cancers and tumors of the brain or spinal cord
- bleeding around the brain
- inflammatory diseases such as meningitis, encephalitis and syphilis
- autoimmune diseases such as multiple sclerosis
- increased fluid pressure from hydrocephalus
A lumbar puncture may be done for the following reasons:
- to collect cerebrospinal fluid for diagnostic purposes
- to measure the pressure of the cerebrospinal fluid
- to administer anesthesia before a surgery
- to administer medications for certain conditions
- to inject dye for imaging and scanning
How is a lumbar puncture performed?
A lumbar puncture is usually performed as an outpatient procedure. Patients lie on their side in a curled or fetal position for a lumbar puncture. This extends the space between the lumbar vertebrae, making the target larger and procedure easier. An LP might also be done while sitting in a bent over position.
The doctor first cleans the area and injects a local anesthetic in the spot chosen for the LP. The LP is most commonly done between the third and fourth lumbar vertebrae. After the local anesthetic takes effect, they insert a long thin needle, which enters the spinal canal. They can then use the needle with a manometer to measure the spinal fluid pressure, or a syringe to withdraw fluid sample, or inject medication or dye.
It is important for the patient to remain still during the procedure, though the doctor might recommend a slight change of position. After the procedure, the puncture site is covered with a dressing or bandage. Immediately after the procedure, the patient will lie flat and stay still for about an hour or more.
How long is the recovery after a lumbar puncture?
A lumbar puncture usually takes 30 to 45 minutes. After about one or two hours of monitoring, patients are able to leave the facility, depending on underlying illness. There may be tenderness in the lower back and swelling at the needle site.
About 25 percent of the patients get a headache after an LP, which might last up to a week. Lying flat and taking painkillers help ease the headache. During recovery, you should:
- lie down flat and rest as much as possible,
- move carefully when you have to,
- drink plenty of fluids,
- take painkillers as needed,
- avoid driving and strenuous activities.
What are the complications and risks of a lumbar puncture?
Rarely, other complications besides a headache might occur. This may depend on the age, health, or underlying medical condition of the individual. Some of the risks involved in a lumbar puncture are:
- persistent cerebrospinal fluid leak
- bleeding from the LP site
- infection at the LP site
- irritation of nerves or nerve roots
- brain herniation
It is advisable to return to the doctor if any of the following are experienced after a lumbar puncture:
- severe persistent headache that isn’t relieved by a pain reliever
- fever and chills
- nausea
- high blood pressure
- any other abnormal reaction