Neuroradiology

What is a Lumbar Puncture?

A lumbar puncture (also called a spinal tap) is a minimally invasive, image-guided diagnostic test that involves the removal of a small amount of cerebrospinal fluid—the fluid that surrounds the brain and spinal cord—or an injection of medication or other substance into the lumbar (or lower) region of the spinal column. Cerebrospinal fluid is a clear, colorless liquid that delivers nutrients to and cushions the brain and spinal cord.

What are some common uses of the procedure?

A lumbar puncture is typically performed to:

• Collect a sample of cerebrospinal fluid to be analyzed in a laboratory
• Measure the pressure of fluid in the spinal canal
• Remove some cerebrospinal fluid to decrease pressure in the spinal canal
• Inject chemotherapy drugs or other medications into the cerebrospinal fluid.
• The lumbar puncture procedure helps physicians diagnose:
• Bacterial, fungal and viral infections, including meningitis, encephalitis and syphilis
• Bleeding around the brain (subarachnoid hemorrhage)
• Cancers involving the brain and spinal cord
• Inflammatory conditions of the nervous system, including Guillain-Barre syndrome and multiple sclerosis.

How is the procedure performed?

This examination is usually done on an outpatient basis. You will be positioned lying face down on your stomach on the examining table. You may be connected to monitors that track your heart rate, blood pressure and pulse during the procedure. The area of your body where the catheter is to be inserted will be sterilized and covered with a surgical drape. Your physician will numb the area with a local anesthetic.

Guided by real-time x-ray images (fluoroscopy), the physician will insert the needle through the skin between two lumbar vertebrae and into the spinal canal. Once the needle is in place, you may be asked to change your position slightly while fluid pressure in the spinal canal is measured.

Depending on the reason for your lumbar puncture:

• A small amount of fluid may be withdrawn through the needle to be tested in a laboratory
• Cerebrospinal fluid may be removed to relieve pressure in the spinal canal
• Anesthesia medication may be injected into the spinal canal.

The needle is then removed. Pressure will be applied to prevent any bleeding and the opening in the skin is covered with a bandage. No sutures are needed. Your intravenous line will be removed. You may be asked to lie on your back or side for a few hours following the procedure. This procedure is usually completed within 45 minutes.

What is Myelography?

Myelography is an imaging examination that involves the introduction of a spinal needle into the spinal canal and the injection of contrast material in the space around the spinal cord and nerve roots (the subarachnoid space) using a real-time form of x-ray called fluoroscopy.

When the contrast material is injected into the subarachnoid space, the radiologist is able to view and evaluate the status of the spinal cord, the nerve roots and the meninges. The meninges are the membranes which surround and cover the spinal cord and nerve roots. Myelography provides a very detailed picture (Myelogram) of the spinal cord, nerve roots, subarachnoid space and spinal column. The radiologist views the passage of contrast material in real-time within the subarachnoid space as it is flowing using fluoroscopy but also takes permanent images, called x-rays or radiographs, of the contrast material around the spinal cord and nerve roots in order to document abnormalities involving or affecting these structures. In most cases, the Myelogram is followed by a computed tomography (CT) scan to better define the anatomy and any abnormalities.

What are some common uses of the procedure?

Magnetic resonance imaging (MRI) is often the first imaging exam done to evaluate the spinal cord and nerve roots. However, on occasion, a patient has a medical device, such as a cardiac pacemaker, that may prevent him or her from undergoing MRI. In such cases, Myelography and/or a CT scan, in lieu of MRI, is performed to better define abnormalities.

Myelography is most commonly used to detect abnormalities affecting the spinal cord, the spinal canal, the spinal nerve roots and the blood vessels that supply the spinal cord, including:

To show whether a herniation of the intervertebral disk between the successive vertebral bodies is compressing the nerve roots or the spinal cord. To depict a condition that often accompanies degeneration of the bones and soft tissues surrounding the spinal canal, termed spinal stenosis. In this condition, the spinal canal narrows as the surrounding tissues enlarge due to the development of bony spurs (osteophytes) and thickening of the adjacent ligaments.

Myelography can also be used to assess the following conditions when MR imaging cannot be performed, or in addition to MRI (when MR does not provide sufficient information):

• Tumors involving the bony spine, meninges, nerve roots or spinal cord
• Infection involving the bony spine, intervertebral discs, meninges and surrounding soft tissues
• Inflammation of the arachnoid membrane that covers the spinal cord
• Spinal lesions caused by disease or trauma

A Myelogram can show whether surgical treatment is promising in a given case and, if it is, can help in planning surgery. In patients with spinal instrumentation (screws, plates, rods, etc.), MR imaging may not be optimal because of artifacts generated by these instruments. In these cases your doctor may decide to order CT Myelography.

What are the benefits vs. risks?

Benefits

Myelography is relatively safe and painless. When a contrast material is injected into the subarachnoid space surrounding the nerve roots and spinal cord, it allows the radiologist to view outlines of the different areas of the spine that usually are not visible or distinguishable on x-rays. X-rays usually have no side effects when used in the diagnostic range necessary for this procedure.

Risks

Although it is uncommon, headache associated with the needle puncture is a risk. The headache, when it occurs following Myelography, usually begins when the patient begins to sit upright or stand. One of the common features of this type of headache is that it is improved when the patient lays flat. When present, the headache usually begins within 2-3 days after the procedure. Rest while lying flat and increased fluid intake readily relieve mild headaches, but more severe headaches may call for medication. In rare circumstances some patients may continue to experience spinal headaches, which may necessitate a special, but simple, procedure to help with the headache called a blood patch.
Adverse reactions to the injection of contrast material during a Myelogram are infrequent and usually mild in nature, including itching, rash, sneezing, nausea or anxiety. The development of hives or wheezing is rare, but may require treatment with medication. More severe reactions involving the heart or lungs are rare.

Other rare complications of Myelography include nerve injury from the spinal needle and bleeding around the nerve roots in the spinal canal. In addition, the meninges covering the spinal cord may become inflamed or infected. Seizures are a very uncommon complication of Myelography. There is a very small risk that pressure changes within the spinal canal caused by the introduction of a needle below the site of an obstruction will block the flow of fluid within the subarachnoid space of the spinal canal, which can make urgent surgery necessary.
A Myelogram uses X-rays and a special dye called contrast material to make pictures of the bones and the fluid-filled space (subarachnoid space) between the bones in your spine (spinal canal). A Myelogram may be done to find a tumor, an infection, problems with the spine such as a herniated disc, or narrowing of the spinal canal caused by arthritis.

The spinal canal holds the spinal cord, spinal nerve roots, and the subarachnoid space.

During the test, a dye is put into the subarachnoid space with a thin needle. The dye moves through the space so the nerve roots and spinal cord can be seen more clearly. Pictures may be taken before and after the dye is used. To get more information from the test, a CT scan is often done after the X-rays, while the dye is still in your body.

Why is it done?

A Myelogram is done to check for:

• The cause of arm or leg numbness, weakness, or pain.
• Narrowing of the spinal canal (spinal stenosis).
• A tumor or infection causing problems with the spinal cord or nerve roots.
• A spinal disc that has ruptured (herniated disc).
• Inflammation of the membrane that covers the brain and spinal cord.
• Problems with the blood vessels to the spine.
• A Myelogram may help find the cause of pain that cannot be found by other tests, such as an MRI or a CT scan.

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What are the discs?

The discs are soft, cushion-like pads, which separate the hard vertebral bones of your spine. A disc may be painful when it bulges, herniates, tears or degenerates and may cause pain in your neck, mid-back, low back and/or arms, chest wall, abdomen and legs. Other structures in your spine may also cause similar pain such as the muscles, joints and nerves. Often, we will have first determined that these other structures are not your sole pain source (through history and physical examination, review of x-rays, CT/MRI, and/or other diagnostic injection procedures such as facet, sacroiliac joint injections, and nerve root blocks) before performing discography.

What is discography and why is it helpful?

Discography confirms or denies the disc(s) as a source of your pain. It is a relatively simple procedure that uses a small needle to inject contrast dye into your disc. MRI and CT scans only demonstrate anatomy and cannot absolutely prove your pain source. In many instances, discs are abnormal on MRI or CT scans but are not a source of pain. Only discography, which is a functional test, can tell if the disc itself is a source of your pain. Discography is usually done only if you think your pain is significant enough for you to consider more advanced treatment options, directed at the disc itself, such as surgery.

What will happen to me during the procedure?

An IV will be started so that antibiotics (to prevent infection) and relaxation medicine can be given. You will lie on your back for cervical discography, or on your stomach for thoracic and lumbar discography. Your skin will then be cleansed with an antiseptic solution. The physician will numb a small area of skin. Next, the physician will use x-ray guidance to direct a small needle into the center of your disc. You may feel temporary discomfort as the needle passes through the muscle and other soft tissues near your spine. The physician may repeat this at several adjoining disc levels. After the needles are in their proper locations, a small amount of contrast dye is injected into each disc. If a disc is the source or your usual pain, the injection will temporarily reproduce discomfort in the area of your usual symptoms. If a disc is not the source of your pain, then the injection will not produce any discomfort, or will not reproduce your usual symptoms.

What should I do and expect after the procedure?

Immediately afterwards, you may be taken for a CT scan so that the anatomy of your disc can be better appreciated. On the day of the injection, you should not drive and should limit your activities. Over the next 2-3 days, your muscles may be sore and your usual pain aggravated. Ice will usually be more helpful than heat during this period. You can take your regular pain medicine as prescribed. You will also be given, if desired, a prescription for stronger pain medication. On the second to third day, you may return to your regular activities. Your soreness should improve by the third day and your pain should go back towards your baseline level. When your pain is improved, start your regular exercises/activities in moderation.

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What is it?

A block is performed to confirm that a facet joint is the source of pain and decrease pain and inflammation in a facet joint or joints.

How is it done?

The patient is given a local skin anesthetic – a needle is then inserted into the facet joint or facet capsule and an anesthetic and steroid are injected by the physician. This is done under fluoroscopy.

Expected Results

A Facet Joint Block can cause a decrease in or relief of back pain.

How long does it take?

Thirty minutes.

Blocks are done in conjunction with physical therapy.

GLOSSARY

Facet Joints – Joints located on the back of the spine on each side where one vertebra slightly overlaps the adjacent vertebrae. They guide and restrict movement of the spine.

Fluoroscopy – X-ray imaging of a part of the body that is displayed on a screen or monitor in the block suite – this facilitates and assures proper placement of the needle and medication.

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Prior to Magnetic Resonance Imaging (MRI), the patient is instructed to remove any metal objects (i.e. jewelry, hairpins) and change into a gown. During the scan, the patient lies comfortably on a motorized table inside the scanner surrounded by huge powerful magnets.

The technician observes the patient throughout the exam through large windows to the adjacent control room. The technician converses with the patient by means of an intercom. Typically, the test takes up to an hour to complete.

Magnetic resonance imaging does not require the patient to change bodily positions. Instead, the patient is instructed to be still. Magnetic resonance imaging generates images in the sagittal (left/right), coronal (front/back), axial (head/toe), and oblique (slanted) planes without moving the patient. Certain MRI studies utilize a contrast medium to enhance particular body structures.

Magnetic resonance imaging produces vivid and complex images in 256 levels of gray that characterizes the relationship between vertebrae, intervertebral discs, spinal cord, and nerve roots. It is a valuable diagnostic and pre-surgical planning tool, and replaces some invasive diagnostic procedures.

IMPORTANT CONSIDERATIONS

If the patient’s MRI scan is to include a contrast medium, known allergies to intravenous dyes should be discussed with the referring physician prior to the test. Patients should tell their physician if their body contains any ferromagnetic objects such as shrapnel, a pacemaker, or aneurysm clips. These patients cannot undergo magnetic resonance imaging. Ferromagnetic objects are attracted by the MRI’s powerful magnet.

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X-ray technology is the ‘workhorse’ of fundamental diagnostic imaging. Testing is fast, easy, and painless. Radiographs are produced by means of a source that radiates x-rays through a particular body part (i.e. spine). As the x-rays pass through the body they are weakened by the many types and levels of tissue encountered. That is why bony structures appear more prominently (i.e. whiter) than soft tissue – bone is denser and absorbs a greater amount of radiation. The energy is directed into a film cassette that has been placed into a receptacle under/behind the targeted body part. The film is exposed and developed in much the same manner as a photograph.

Computed Tomography (CT) imaging is also known as CAT scanning (Computed Axial Tomography). The machine resembles a large square with a ring in the middle. CT has the unique ability to image soft tissues (e.g. blood vessels) and renders more detail of bony structures than MRI (Magnetic Resonance Imaging). CT images reveal the relationships between soft tissue and bone.

In orthopaedic medicine, CT is an important diagnostic tool. Following trauma, it often is the imaging method of choice because the exams are fast and simple. The images help diagnose intervertebral disc herniation, fractures, and other spinal disorders. The images appear as cross-sectional slices of the patient’s anatomy.

Prior to the exam, the patient is instructed to remove any metal objects (i.e. belt, jewelry, hairpins) and change into a gown. Some CT examinations require a contrast agent to be injected (or intravenously) into the patient’s bloodstream. A contrast agent serves to enhance a particular body part (i.e. intervertebral discs).

After the patient is comfortably positioned on the table, the technician leaves the room and enters the adjacent control room. Throughout the exam the technician observes the patient through large windows and will converse with the patient by means of an intercom.

During the test, the patient must lie still and may be asked to hold their breath for a several seconds from time to time. The patient may hear the scanner rotating during the study. This noise may be soft or more audible. Depending on the type of study, the CT scanner or table will move slightly as low intensity x-ray beams are rotated at many angles around the patient. A computer collects the data from the scanner, calculates the density of a given cross-sectional slice, and produces the image onto film for study by a radiologist.

IMPORTANT CONSIDERATIONS

If the patient’s CT scan is to include a contrast agent, any known allergies should be discussed with the referring physician prior to the test. The test may be postponed, if the patient is pregnant or nursing.