Gaseous myelography or pneumomyelography

«Myelography developed as an imaging technique to assess the status of the thecal sac, spinal cord, and nerve roots in diverse pathologic conditions. Before the development of myelography, the only definitive means of evaluating these structures was laminectomy and direct inspection [1].»

«Myelographic techniques have evolved over time. The requirement for dural puncture, although invasive, offered the opportunity to acquire cerebrospinal fluid (CSF) specimens for laboratory analysis as a part of the procedure. (...). After spinal puncture, a myelographic contrast agent was slowly injected into the subarachnoid space with fluoroscopic confirmation. (...). Myelography is an invasive procedure, requiring puncture of the subarachnoid space. The spinal puncture is generally done below the L1-2 disc space level. Subarachnoid puncture also can be performed in the cervical spine at the C1-2 level via a lateral approach, or at the craniocervical junction via a posterior midline approach. (...). Although myelography has become a relatively safe test, it is invasive. MR imaging of the spine with its improved soft tissue delineation and excellent ability to depict and characterize extradural, intradural, and intramedullary lesions has led to a significant decrease in the use of myelography [1].»

«Several contrast agents have been used for myelography»: air and other gases, Thorotrast® (a suspension containing particles of the radioactive compound thorium dioxide), Lipiodol (ethiodized oil), Abrodil (sodium iodomethane sulfonate), Conray (iothalamate meglumine), Pantopaque (iophendylate), Dimer-X (methylglucamine iocarmate), metrixamide, iohexol and other nonionics [1].

«In 1919, Dr. Walter Dandy [2] suggested that the intraspinal air that was used for pneumoencephalography could be also used for the diagnosis of intraspinal pathology. A few years later, Dandy [1922, cited by 1] reported his experience with pneumomyelography in the diagnosis of spinal cord tumors. Attractive features of gas, specifically air, as a contrast medium include low cost, lack of allergic reactions, and spontaneous reabsorption. Other gases, such as oxygen, were also used for pneumomyelography because of their greater diffusibility and more prompt resorption. Gas is a negative contrast agent, and the optical contrast provided by plain radiography or tomography was poor. Although not chemically toxic, a variety of unpleasant side effects, such as headache, nausea, and transient neurologic symptoms, were common with air myelography. (...). The other disadvantage of pneumomyelography was that fluoroscopic images could not be used; rather, radiographs were obtained using overpenetrated technique. Even with the best technique, these studies were extremely challenging to perform and interpret [1].» «Advancements in contrast media development have led to significant improvement in their safety profile [1].» «The development of water-soluble contrast media allowed the use of post-myelographic computed tomography, which was a major advance [1].»

«Although myelography has largely been supplanted by MRI [magnetic resonance imaging], it will continue to be a necessary tool and is most useful in evaluation of cerebrospinal fluid leaks and in patients unable to undergo MRI [1].»

Bibliographic references:

[1] Price DB, Ortiz AO. Myelography: From Lipid-Based to Gadolinium-Based Contrast Agents. Magn Reson Imaging Clin N Am. 2017 Nov;25(4):713-724. Available at: https://doi.org/10.1016/j.mric.2017.06.005.

[2] Dandy WE. Roentgenography of the brain after the injection of air into the spinal canal. Ann Surg. 1919 Oct;70(4):397–403. Available at: https://doi.org/10.1097/00000658-191910000-00004.