50TH ANNIVERSARY PERSPECTIVES Neuroradiology Back to the Future: Spine Imaging E.G. Hoeffner SUMMARY: Although radiography of the spine began shortly after Roentgen’s discovery in 1895, there S.K. Mukherji was little written in the medical literature about spine imaging until nearly 25 years later with the development of myelography, first by using air and then a variety of positive contrast agents. The A. Srinivasan history of spine imaging before CT and MR imaging is, in large part, a history of the development of D.J. Quint contrast agents for intrathecal use. The advent of CT and, more important, MR imaging revolutionized spine imaging. The spinal cord and its surrounding structures could now be noninvasively visualized in great detail. In situations in which myelography is still necessary, advances in contrast agents have made the procedure less painful with fewer side effects. In this historical review, we will trace the evolution of spine imaging that has led to less invasive techniques for the evaluation of the spine and its contents and has resulted in more rapid, more specific diagnosis, therapy, and improved outcomes. ABBREVIATION: LP ϭ lumbar puncture here was very little in the medical literature about spine eign bodies.2 Tomography was introduced as early as 1914.9 Timaging until nearly 25 years after Roentgen’s discovery of This allowed the detection of subtler abnormalities such as the x-ray in 1895. The development of contrast studies of the complex fractures, bone fragments within the spinal canal, spine in the 1920s, first by using air and later various ra- and cortical erosions; however, it was still only osseous diopaque contrast agents, was the first major development. changes that were detectable.8,10 Despite these limitations, During the next 50 years, a variety of contrast agents was in- spine x-rays have remained a mainstay of imaging for a variety troduced with the goal of improving diagnostic specificity of traumatic and nontraumatic conditions of the osseous with less toxicity. The advent of CT and MR imaging dramat- spine, unlike skull x-rays, which are now virtually obsolete. ically changed the way the spine was imaged. These discoveries PERSPECTIVES have advanced the field of neuroradiology and improved the Contrast Studies of the Spinal Canal ANNIVERSARY lives of patients via easier, safer, more rapid diagnosis and Walter E. Dandy, the noted neurosurgeon, published the first 50TH treatment. description of pneumoencephalography and its use in diag- nosing intracranial tumors and hydrocephalus in 1919.11 In The Beginning: Spine X-Rays this article, he noted that the normal spinal cord could be seen Unlike imaging of the skull and brain, about which textbooks outlined by the air injected into the spinal canal. He postulated were published as early as 1912, there is very little in the med- that the same technique could be used to localize spinal cord ical literature on spine imaging until the 1920s.1 Historic re- tumors with the air column extending up to the level of the views indicate spine x-rays came into use shortly after Roent- lesion. However, he did not publish any more on this topic gen’s discovery in 1895.2 The main use was to identify until 1925.12 In 1921, the injection of air into the subarachnoid fractures and foreign bodies.3,4 As early as 1897, the noted space followed by x-ray examination was described indepen- neurosurgeon Harvey Cushing, in his first publication, re- dently by 2 Scandinavian physicians. Hans Christian Jaco- ported on a patient with Brown-Sequard syndrome after a baeus, a Swedish internist, reported on the use of pneumomy- gunshot wound, in which spine x-rays showed the bullet elography to diagnose spinal cord tumors.13 This development lodged in the C6 vertebra.5 It took at least 10–15 minutes, if evolved from his earlier unsuccessful attempts to treat tuber- not longer, to obtain an exposure of the spine, and there was 13,14 no way to angle the x-ray tube or eliminate scattered radia- culous meningitis by replacing 100 mL of CSF with air. 6-8 Sofus Widero¨e, a Norwegian surgeon, described a similar pro- tion. The reason for the dearth of literature on spine imag- 15 ing before approximately 1920 is not entirely clear. Bull7 sug- cedure to diagnose a spinal cord tumor. gests that clinical localization of spinal lesions presented less of A year later, French physician, Jean-Athanese Sicard, and a dilemma than intracranial lesions; thus, there was little im- his student, Jacques Forestier, reported on the intrathecal use petus to develop imaging of the spine beyond x-rays. Others of iodized poppy seed oil, Lipiodol (Andre Guerbet, Aulnay- 14,16 suggest, however, that little useful information was obtained sous-Bois, France), for diagnosing spinal masses. This was from early spine x-rays beyond identifying fractures and for- a somewhat fortuitous development. Although it was known at the time that Lipiodol was radiopaque, Sicard injected it into lumbar muscles or the epidural space to treat sciatica and From the Division of Neuroradiology, Department of Radiology, University of Michigan 16,17 Health System, Ann Arbor, Michigan. other neuralgias. Occaionally, he took x-rays after the epi- 16 Please address correspondence to Ellen G. Hoeffner, MD, Division of Neuroradiology, dural injection of Lipiodol to assess tumor or infection. It Department of Radiology, University of Michigan Health System, 1500 East Medical Center was by accident that a student of Sicard injected the Lipiodol Dr, UH B2A 209G, Ann Arbor, MI 48109; e-mail: [email protected] into the thecal sac.17 After ensuring that there were no ill- effects to the patient, Sicard looked at the patient’s spine on the Indicates open access to non-subscribers at www.ajnr.org fluorescent screen and saw that the Lipiodol had descended to http://dx.doi.org/10.3174/ajnr.A3129 the bottom of the spinal canal. Sicard then placed the patient AJNR Am J Neuroradiol 33:999–1006 ͉ Jun-Jul 2012 ͉ www.ajnr.org 999 Fig 1. Myelogram in a 30-year-old man with radicular pain. A, Lateral lumbar myelographic image shows a typical extradural defect indenting the ventral dural sac at L4-L5 (arrow). B, Frontal lumbar myelographic image shows the defect, which is also resulting in poor filling of the right L5 nerve root sleeve (black arrow). Note that the needle remains in place (white arrow), presumably for removing the contrast. in the Trendelenburg position and was able to see the cranial to diagnose spinal cord tumors and cord compression in the flow of Lipiodol within the dural sac.14,17 A year later, Sicard late 1920s and early 1930s.22 Because these conditions were and Forestier began injecting Lipiodol into the subarachnoid relatively rare, many clinicians in the United States at the time space by cisterna magna puncture.17 In 1932, Sicard and For- thought that the benefits of making a correct diagnosis with estier published a book on the diagnostic and therapeutic uses Lipiodol myelography likely outweighed the complications in of Lipiodol, which, in addition to myelography, included im- these infrequent situations.22,23 aging of the respiratory, gastrointestinal, and genitourinary systems.18 Introduction of Additional Contrast Agents In 1925, Dandy reported on more than 30 spinal cord le- In 1931, Christian Georg Schmorl published his study on disk sions that had been localized by gas myelography; however, he degeneration by using both radiographic and pathologic find- was aware of Sicard’s discovery and even indicates in the arti- ings.24 Three years later, Mixter and Barr published their clas- cle that he had used Lipiodol himself via both LP and cisternal sic article on ruptured (their preferred terminology) interver- puncture.12 Dandy preferred injecting the Lipiodol by cister- tebral disks as a cause of radicular symptoms and sciatica, with nal puncture because he thought it was more comfortable for surgery being the preferred treatment.25 Before this, radicular the patient compared with LP, for which the patient had to lie symptoms were generally thought to be due to cartilaginous head down.12 The same year, an American neurosurgeon, Wil- neoplasms. Most of the patients in their series had a Lipiodol liam Mixter, also reported on the use of Lipiodol in diagnosing myelogram before the operation. Two years later, Hampton spinal cord tumors.19 and Robinson published their classic article on the myelo- Lipiodol was originally developed in 1901 for therapeutic graphic findings of ruptured intervertebral disks (Fig 1).26 use, which in addition to the aforementioned treatment of These developments led to an increased demand for myelog- sciatica and neuralgias, included syphilis, cardiovascular and raphy, for which Lipiodol was the only available positive con- respiratory diseases, leprosy, and goiter.20 Its use for myelog- trast agent.22,23 In 1941, Kubik and Hampton published the raphy was widely accepted in France after the publication of first description of removing iodized oil by lumbar puncture Sicard and Forestier’s article. However, its acceptance in other after myelography to prevent its irritating effects. The authors countries was tempered by concern over its safety.21 Even in hoped this technique would alleviate some of the trepidation their original article, Sicard and Forestier noted that patients associated with myelography and allow more patients with experienced pain for 2–3 days after intrathecal injection of disk herniations to be correctly diagnosed and treated.27 Lipiodol.16 Later, it became known