Myelography is a generic term to refer to an imaging procedure performed to evaluate the subarachnoid spaces within the spinal canal and is performed after the intrathecal injection of either contrast media (for fluoroscopy, xrays, CT and MRI) or radiopharmaceuticals.
Although conventional myelography has been largely supplanted by MRI, and to a lesser degree CT, of the spine, it remains a useful problem-solving tool in the evaluation of spondylosis in patients who cannot undergo MRI, the identification of the cause of spontaneous intracranial hypotension, or in a variety of other situations where routine CT or MRI are unable to give a definitive answer.
Myelography can be performed in various ways, and these are discussed separately.
conventional myelography (fluoroscopic & x-ray)
History
The concept of using a contrast agent to better image the contents of the spinal canal was first proposed in 1919 by Walter Dandy (1886-1946, American neurosurgeon) who had pioneered pneumoencephalography, wherein air was instilled into the subarachnoid space as a negative contrast agent for evaluating structures of the brain 5. This was first carried out in 1921 6,7. Although crude, requiring extraction of an equivalent volume of cerebrospinal fluid to instilled air, and extremely painful, air-contrast myelography (or pneumomyelography) techniques allowed some visualization of the intraspinal soft tissues as imaged by fluoroscopy.
In the same year, Jean-Athanase Sicard (1872–1929, French physician) who had been experimenting with injection of an iodized oil called Lipiodol® into the epidural space for the treatment of chronic pain, accidentally injected it into the intrathecal space. It was known that Lipiodol was markedly radiopaque and the patient was fine. And thus, positive contrast myelogrphay was born 8,9.
Contrast would be injected either via a suboccipital injection or via a lumbar puncture. The patient was tilted to allow the contrast to travel undergravity outlining any obstructions to its free passage using a tilting table 8.
Concerns regarding the safety of Lipiodol were soon raised as it resulted in extensive arachnoiditis and spinal cord cyst formation in experimental animals 8. Although Abrodil® , a water soluble agent, was introduced in the 1930s it never gained widespread use outside of Scandinavia due to its associated headache, ocular pain and leptomeningeal irritation 11.
In 1941, after many years of debate over the safety of leaving these contrast agents in the CSF space for life, as they were not readily absorbed, europathologist Charles Kubik (1891-1982, neuropathologist) and radiologist Aubrey Hampton (1900-1955, radiologist) demonstrated the removal of most of the contrast by aspiration 10.
In 1944 Iofendylate (Myodil/Pantopaque) was introduced and was thought to be safer than older agents and remained popular myelography agent until the 1970s. Nonetheless, as an oil-based agent, it was not readily reabsorbed and thus often remained trapped within the subarachnoid spaces for decades 4,8. As with many of its pharmacological predecessors, it was notorious for causing arachnoiditis. It was withdrawn from clinical use in 1988 4.
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