Myelography | |
---|---|
ICD-10-PCS | 3.AW.10.^^ |
ICD-9-CM | 87.21 |
MeSH | D009192 |
OPS-301 code | 3-130 |
Myelography is a type of radiographic examination that uses a contrast medium (e.g. iodised oil [1] ) to detect pathology of the spinal cord, including the location of a spinal cord injury, cysts, and tumors. Historically the procedure involved the injection of a radiocontrast agent into the cervical or lumbar spine, followed by several X-ray projections. Today, myelography has largely been replaced by the use of MRI scans, although the technique is still sometimes used under certain circumstances – though now usually in conjunction with CT rather than X-ray projections. [2]
This procedure is used to look for the level of where spinal cord disease occurs or compression of the spinal cord at the neck region for those who are unable or unwilling to undergone MRI scan of the spine. [3]
This procedure is to look for the level of spinal cord disease such as lumbar nerve root compression, cauda equina syndrome, conus medullaris lesions, and spinal stenosis. This is done for those who are unwilling or unable to do MRI scan of the spine. Lumbar puncture is done before injected contrast into the thecal sac. However, it is dangerous to do lumbar puncture in those who have raised intracranial pressure (ICP). [3] For those who had recently done lumbar puncture in one week time, there may be some cerebrospinal fluid (CSF) accumulates in the subdural space. Thus needle maybe mistakenly inserted into subdural space rather than the targeted subarachnoid space. [3]
AP, lateral, and oblique radiographic views of the lumbar spine are taken. The oblique view is used to examine the exiting nerve roots from cauda equina. [3]
To image the thoracic spine, lumbar puncture is done and contrast medium is injected into the puncture site. The subject lie down on one side, then head of the table is lowered, with subject's head supported by bolster or pad to prevent the contrast from flowing up into the neck. [3]
Contrast media is injected into the thecal sac. The subject is then rotated longitudinally a few times to ensure even coating of the contrast around spinal cord and reduce the possibility of layering of the contrast media just before CT scan. [3]
General anesthesia is required for all children before 6 years old, and most of the children before 12 years old. For those children with spinal cord diseases, lumbar puncture may damage the spinal cord due to possibility of tethered spinal cord syndrome where the spinal cord is located below than the usual spinal termination level. [3] Therefore, lumbar puncture should be done at the lowest position as possible for such cases. However, spinal cord injury is rare. There is also a possibility of herniation of cerebellar tonsils when C1/C2 puncture is done laterally. [3]
Water-soluble non-ionic iodinated contrast agent is used nowadays and cause very little complication, unlike oil-based dye that was used previously which can cause arachnoiditis. However, history of allergy to iodine is contraindicated for the use of iodinated contrast. [3]
A CT scan is typically performed after radiographic contrast media (dye) has been placed with fluoroscopic guidance into a sac-like lining (the first- and hardest and outermost- layer of the spinal meninges, the spinal dura mater) surrounding the spinal cord and nerves. The material is typically water-soluble, which has largely replaced nonsoluble oil-based fluids, while CT has largely replaced the conventional X-ray projections used for image acquisition in the past.
The process usually involves lying face down on a table, with the lower extremities secured tightly with straps to the table. After the skin area has been numbed, the dye is injected into the thecal sac, then the table is slowly rotated in a circular motion, first down at the head end for approximately 4 to 6 minutes, then rotated up at the head end for the same duration. Several more minutes lying flat and the process is complete. This movement ensures the contrast has sufficiently worked its way through the spinal cord, followed by X-rays or a CT scan.
Post-procedure care centers around ensuring that infection (especially skin or subcutaneous infections, myelitis or meningitis or encephalitis, or sepsis) does not set in and that the "plug" at the site of the spinal tap does not become dislodged. Patients are usually instructed to avoid strenuous activity and heavy lifting, for example. Some patients are given instructions to keep their heads elevated at least 30 degrees for a specified number of hours. Complications from the surgery can cause a loss of cerebrospinal fluid (CSF), which could cause severe headaches. This can be corrected by returning to the medical facility and having them perform a blood patch. In this procedure, a small amount of blood is taken from the arm and injected into the exact spinal tap location to stop the leaking of CSF.
Nowadays, MRI has all but replaced myelography. [4] MRI is preferable because injection of contrast medium into the spinal canal is infrequently needed for better images. However, a CT myelogram may be useful for patients who cannot undergo MRI (e.g., those with pacemakers or cochlear implants). CT is preferred when MRI images are limited by metallic artifact from titanium disc replacement implants, screws, and other metals reactive with MRI device components.
Prior to the late 1970s, iofendylate (trade names: Pantopaque, Myodil) was the radiocontrast agent typically employed in the procedure. It was an iodinated oil-based substance that the physician performing the spinal tap usually attempted to remove at the end of the procedure. This step was both difficult and painful and complete removal could not always be achieved. The process of removing the contrast agent necessitated removing some of the patient's CSF along with it and the resulting deficiency of CSF gave rise to severe headache if the patient was raised from the prone position, requiring bed rest in the laying position. Moreover, iofendylate's persistence in the body might sometimes lead to arachnoiditis, a potentially painful and debilitating lifelong disorder of the spine. [5] [6] This led to extensive litigation around the world since the substance was administered to millions of myelography patients over the course of more than three decades. [7] After water-soluble agents (such as metrizamide) became available it was no longer necessary to remove the contrast agent as it would eventually be absorbed into the body although the water-soluble agent sometimes gave rise to severe headaches if it got into the head, requiring bed rest in the upright position.
Headache occurs in about 25% of the cases after the procedure and the incidence is more frequent in females. 5% of those who undergone the procedure may experience nausea and vomiting. There is also a risk of contrast medium being injected into the subdural space when part of the bevel of the needle is in the subarachnoid space and another part is in the subdural space. The contrast medium would flow freely in the subdural space, mimicking the flow as if it was in the subarachnoid space. If there is doubt that the needle is in the subdural space, AP and lateral views of the radiograph should be taken and the subject is to be rebook for another date for the same procedure. [3]
Cerebrospinal fluid (CSF) is a clear, colorless body fluid found within the tissue that surrounds the brain and spinal cord of all vertebrates.
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 is a contraindication, due to risk of brain matter being compressed and pushed toward the spine. Sometimes, lumbar puncture cannot be performed safely. It is regarded as a safe procedure, but post-dural-puncture headache is a common side effect if a small atraumatic needle is not used.
Spinal anaesthesia, also called spinal block, subarachnoid block, intradural block and intrathecal block, is a form of neuraxial regional anaesthesia involving the injection of a local anaesthetic or opioid into the subarachnoid space, generally through a fine needle, usually 9 cm (3.5 in) long. It is a safe and effective form of anesthesia usually performed by anesthesiologists that can be used as an alternative to general anesthesia commonly in surgeries involving the lower extremities and surgeries below the umbilicus. The local anesthetic with or without an opioid injected into the cerebrospinal fluid provides locoregional anaesthesia: true anaesthesia, motor, sensory and autonomic (sympathetic) blockade. Administering analgesics in the cerebrospinal fluid without a local anaesthetic produces locoregional analgesia: markedly reduced pain sensation, some autonomic blockade, but no sensory or motor block. Locoregional analgesia, due to mainly the absence of motor and sympathetic block may be preferred over locoregional anaesthesia in some postoperative care settings. The tip of the spinal needle has a point or small bevel. Recently, pencil point needles have been made available.
A laminectomy is a surgical procedure that removes a portion of a vertebra called the lamina, which is the roof of the spinal canal. It is a major spine operation with residual scar tissue and may result in postlaminectomy syndrome. Depending on the problem, more conservative treatments may be viable.
Intracranial hemorrhage (ICH), also known as intracranial bleed, is bleeding within the skull. Subtypes are intracerebral bleeds, subarachnoid bleeds, epidural bleeds, and subdural bleeds.
Radiocontrast agents are substances used to enhance the visibility of internal structures in X-ray-based imaging techniques such as computed tomography, projectional radiography, and fluoroscopy. Radiocontrast agents are typically iodine, or more rarely barium sulfate. The contrast agents absorb external X-rays, resulting in decreased exposure on the X-ray detector. This is different from radiopharmaceuticals used in nuclear medicine which emit radiation.
Spondylosis is the degeneration of the vertebral column from any cause. In the more narrow sense it refers to spinal osteoarthritis, the age-related degeneration of the spinal column, which is the most common cause of spondylosis. The degenerative process in osteoarthritis chiefly affects the vertebral bodies, the neural foramina and the facet joints. If severe, it may cause pressure on the spinal cord or nerve roots with subsequent sensory or motor disturbances, such as pain, paresthesia, imbalance, and muscle weakness in the limbs.
A subdural hygroma (SDG) is a collection of cerebrospinal fluid (CSF), without blood, located under the dural membrane of the brain. Most subdural hygromas are believed to be derived from chronic subdural hematomas. They are commonly seen in elderly people after minor trauma but can also be seen in children following infection or trauma. One of the common causes of subdural hygroma is a sudden decrease in pressure as a result of placing a ventricular shunt. This can lead to leakage of CSF into the subdural space especially in cases with moderate to severe brain atrophy. In these cases the symptoms such as mild fever, headache, drowsiness and confusion can be seen, which are relieved by draining this subdural fluid.
Cisternography is a medical imaging technique to examine the flow of cerebrospinal fluid (CSF) in the brain, and spinal cord. The gold standard for diagnosis of a cranial cerebrospinal fluid leak is CT cisternography. For the diagnosis of a spinal CSF leak radionuclide cisternography also known as radioisotope cisternography is used. The false negative rate of cisternography is high (30%), so the radiographic study of choice is CT myelography. The third type of cisternography is MR cisternography.
A suboccipital puncture or cisternal puncture is a diagnostic procedure that can be performed in order to collect a sample of cerebrospinal fluid (CSF) for biochemical, microbiological, and cytological analysis, or rarely to relieve increased intracranial pressure. It is done by inserting a needle through the skin below the external occipital protuberance into the cisterna magna and is an alternative to lumbar puncture. Indications for its use are limited. Subarachnoid hemorrhage and direct puncture of brain tissue are the most common major complications. Fluoroscopic guidance decreases the risk for complications. The use of this procedure in humans was first described by Ayer in 1920.
A laminotomy is an orthopaedic neurosurgical procedure that removes part of the lamina of a vertebral arch in order to relieve pressure in the vertebral canal. A laminotomy is less invasive than conventional vertebral column surgery techniques, such as laminectomy because it leaves more ligaments and muscles attached to the spinous process intact and it requires removing less bone from the vertebra. As a result, laminotomies typically have a faster recovery time and result in fewer postoperative complications. Nevertheless, possible risks can occur during or after the procedure like infection, hematomas, and dural tears. Laminotomies are commonly performed as treatment for lumbar spinal stenosis and herniated disks. MRI and CT scans are often used pre- and post surgery to determine if the procedure was successful.
Leptomeningeal cancer is a rare complication of cancer in which the disease spreads from the original tumor site to the meninges surrounding the brain and spinal cord. This leads to an inflammatory response, hence the alternative names neoplastic meningitis (NM), malignant meningitis, or carcinomatous meningitis. The term leptomeningeal describes the thin meninges, the arachnoid and the pia mater, between which the cerebrospinal fluid is located. The disorder was originally reported by Eberth in 1870. It is also known as leptomeningeal carcinomatosis, leptomeningeal disease (LMD), leptomeningeal metastasis, meningeal metastasis and meningeal carcinomatosis.
An epidural blood patch (EBP) is a surgical procedure that uses autologous blood, meaning the patient's own blood, in order to close one or many holes in the dura mater of the spinal cord, which occurred as a complication of a lumbar puncture or epidural placement. The punctured dura causes cerebrospinal fluid leak. The procedure can be used to relieve orthostatic headaches, most commonly post dural puncture headache (PDPH).
Metrizamide is a non-ionic iodine-based radiocontrast agent. It is also a density gradient medium for the centrifugation of biological particles.
A cerebrospinal fluid leak is a medical condition where the cerebrospinal fluid (CSF) that surrounds the brain and spinal cord leaks out of one or more holes or tears in the dura mater. A CSF leak is classed as either spontaneous (primary), having no known cause, or nonspontaneous (secondary) where it is attributed to an underlying condition. Causes of a primary CSF leak are those of trauma including from an accident or intentional injury, or arising from a medical intervention known as iatrogenic. A basilar skull fracture as a cause can give the sign of CSF leakage from the ear, nose or mouth. A lumbar puncture can give the symptom of a post-dural-puncture headache.
Tarlov cysts, are type II innervated meningeal cysts, cerebrospinal-fluid-filled (CSF) sacs most frequently located in the spinal canal of the sacral region of the spinal cord (S1–S5) and much less often in the cervical, thoracic or lumbar spine. They can be distinguished from other meningeal cysts by their nerve-fiber-filled walls. Tarlov cysts are defined as cysts formed within the nerve-root sheath at the dorsal root ganglion. The etiology of these cysts is not well understood; some current theories explaining this phenomenon have not yet been tested or challenged but include increased pressure in CSF, filling of congenital cysts with one-way valves, and/or inflammation in response to trauma and disease. They are named for American neurosurgeon Isadore Tarlov, who described them in 1938.
Lumbar provocative discography is an invasive diagnostic procedure for evaluation for intervertebral disc pathology. It is usually reserved for persons with persistent, severe low back pain (LBP) who have abnormal spaces between vertebrae on magnetic resonance imaging (MRI), where other diagnostic tests have failed to reveal clear confirmation of a suspected disc as the source of pain, and surgical intervention is being considered.
The thecal sac or dural sac is the membranous sheath (theca) or tube of dura mater that surrounds the spinal cord and the cauda equina. The thecal sac contains the cerebrospinal fluid which provides nutrients and buoyancy to the spinal cord. From the skull the tube adheres to bone at the foramen magnum and extends down to the second sacral vertebra where it tapers to cover over the filum terminale. Along most of the spinal canal it is separated from the inner surface by the epidural space. The sac has projections that follow the spinal nerves along their paths out of the vertebral canal which become the dural root sheaths.
Spinal stenosis is an abnormal narrowing of the spinal canal or neural foramen that results in pressure on the spinal cord or nerve roots. Symptoms may include pain, numbness, or weakness in the arms or legs. Symptoms are typically gradual in onset and improve with leaning forward. Severe symptoms may include loss of bladder control, loss of bowel control, or sexual dysfunction.
Magnetic resonance myelography is a noninvasive medical imaging technique that can provide anatomic information about the subarachnoid space. It is a type of MRI examination that uses a contrast medium and magnetic resonance imaging scanner to detect pathology of the spinal cord, including the location of a spinal cord injury, cysts, tumors and other abnormalities. The procedure involves the injection of a gadolinium based contrast media into the cervical or lumbar spine, followed by the MRI scan.