Downloaded from by on 10/16/15 from IP address Copyright ARRS. For personal use only; all rights reserved



MR Imaging Advances Gordon

of the Spinal



and Future


The advent of MR imaging has dramatically altered the evaluation of suspected myelopathy. MR is far less invasive than traditional imaging techniques and often offers a degree of un-


of an abnormality

achievements vances, such introduction

not previously

have closely followed recent as the development of contrast

of sequences



a reduction



technologic agents and in both



time and artifacts. The current role of MR in the imaging of spinal cord disorders, including intramedullary tumors, infectious and inflammatory myehitis, demyehinating diseases, vascular lesions, trauma, synngomyehia/hydromyehia, and neurodegenerative disorders, is reviewed. While further improvements will undoubtedly occur, the field of spinal MR imaging appears to be entering a




Technique Technically, assessment of the spinal cord presents one of the greatest challenges in the use of MR to evaluate the neuraxis. Early images were markedly degraded by motion artifacts, especially from respiration, cardiac pulsation, and CSF pulsation [2, 3]. Several techniques have evolved to compensate for involuntary motion, and high-quality images of the For


are now

the evaluation




of a suspected, both


and long TR (e.g., 2200/30,80)

and possibly

TR (e.g.,




small, [TR/TE])

are essential.

Short TR sagittal sequences generally contain excellent morphohogic detail. Long TR sagittal sequences often show subtle


The advent of MR imaging has permitted direct visualization of the spinal cord for the first time [1 ]. Although the presence or absence of cord lesions could be inferred on myelography and postmyehographic CT by the shape of the surrounding contrast column, MR imaging allows specific assessment of the cord parenchyma itself. This review focuses on the MR imaging findings in diseases of the spinal cord, including tumors, cysts, demyehinating diseases, infections, vascular diseases, and trauma. The article concludes with a discussion of recent advances in the techniques available for MR imaging of the cord.

lesions that are not visualized on the short TR sagittal Sequences, and also provide further characterization of lesions. These acquisitions are best obtained with cardiac gating and/ or gradient-moment nulhing techniques in order to decrease the effect of flow artifacts, especially on high-field-strength units [2, 3]. For both short TR and long TR images, it is necessary to obtain sufficiently thin sections, preferably 3 mm or less with minimal interslice gaps. The use of a higher matrix improves resolution and helps to reduce the effect of the Gibbs artifact, which may produce a thin linear longitudinal line down the center of the cord that can be mistaken for a syrinx [4].

Received December 6, 1991 ; accepted after revision February 3, 1992. Presented at the annual meeting of the American Roentgen Ray Society, Boston, May 1991. I Department of Diagnostic Radiology, Yale University School of Medicine, 333 Cedar St. , P.O. Box 3333, G. Sze. AJR 159:149-159,


July 1992 0361 -803X/92/1


© American


Ray Society

New Haven,

CT 0651 0. Address





Downloaded from by on 10/16/15 from IP address Copyright ARRS. For personal use only; all rights reserved


Although much of the information in an MR study of the cord is obtained in the sagittal plane, axial images can also be vital. In general, if further morphologic detail is desired, axial short TA sections are usually acquired. If further characterization of lesions or if confirmation of a subtle lesion seen on the long TR sagittal images is desired, then short TR sequences are not optimal. Rather, gradient-echo (e.g., 800/ 35/20#{176} [TR/TE/flip angle]) or long TA axial sections may be necessary. In the cervical spine, volumetric gradient-echo sequences that allow one to obtain sections as thin as 1 mm are used. These sequences are very sensitive to subtle disturbances

of the cord parenchyma,


as multiple


(MS) plaques. Intramedullary


The advent of MR has tremendously increased the ability to detect and characterize tumors of the cord. Short TA sagittal sequences readily disclose the marked cord widening often associated with intramedullary neoplasms. Long TA sagittal scans reveal high signal within the substance of the cord, consistent with either tumor or surrounding edema. Because of MR’s sensitivity to hemorrhage, areas of bleeding are easily detected. A number of different appearances may be seen. If hemorrhage into a tumor cyst occurs, fluid levels may result. Owing to the evolution of hemoglobin breakdown products

and to other


the relative




the inferior and superior components may vary. In addition, hemorrhagic cord tumors are often associated with hemosidem deposition, which appears as peripheral marked hypointensity on long TA sequences. While unenhanced MR images generally can be used to detect tumors of the cord accurately, gadopentetate dimeglumine can help in further


and delineation


9]. Enhancement with gadopentetate dimeghumine is most useful in cases of focal masses, especially hemangioblastomas and metastases [6] (Fig. 1). Both of these lesions tend

Fig. 1.-Spinal A and B, Short


July 1992

to be fairly well circumscribed and produce extensive surrounding edema. Because of this, cord swelling far beyond the region of the actual tumor is often seen. The use of gadopentetate dimeghumine can be very effective in pinpointing the exact location of the lesion [5, 6]. Although the area of cord enlargement can be extensive, the actual lesion may be small, less than one vertebral body in height. Results with primary cord ghiomas are less dramatic. First, as in the brain, it is likely that areas of enhancement do not coincide with the actual boundaries of these infiltrative tumors. Second, unlike that seen with hemangioblastomas and metastases, enhancement is often variable. It does appear, however, that primary tumors tend to enhance in the cord much more often than in the head [6-9]. In ghiomas of the cord, enhancement again tends to be fairly focal [5-9] (Fig. 2). Areas of enhancement may be representative of more active tumor and good areas for biopsy, as is the case in the brain. Often, these tumors are associated with cysts. Cysts can be either intratumoral or rostral and caudal. Rostral and caudal cysts tend to be benign [1 0, 1 1]. Even though the fluid within them might be proteinaceous or hemorrhagic, these cysts are usually not lined by tumor nor do they contain tumor cells. Unlike tumor cysts, they do not require excision but are merely drained at surgery. Contrast enhancement has proved useful in identifying the nature of cysts associated with tumors [6-9]. Tumor cysts are generally surrounded by enhancement, while the walls of benign


lack associated



Although 40-50% of ghiomas of the brain do not enhance, the large majority of ghiomas of the cord do, regardless of grade [5-9]. In fact, unenhancing ghiomas of the cord are unusual,








how-grade tumors tend to show some enhancement. Of the 55 reported cases of cord ghioma in which contrast-enhanced MA was used, enhancement was seen in 54 [5-9, 12]. Because of this, the use of contrast material can be helpful in differentiating suspected neoplasms from other disorders, for

cord hemangioblastoma.

TR (600/30) and gradient-echo (800/35/20#{176}) sagittal MR images show an enlarged cervical cord with central edema. A small nodule Is noted along wall of cystic cavity posteriorly. C, Short TR (600/30) sagittal MR image after administration of contrast material shows enhancing nodule along posterior

cystic aspect


and surrounding

of cyst.

Downloaded from by on 10/16/15 from IP address Copyright ARRS. For personal use only; all rights reserved



July 1992

Fig. 2.-Cord

MR image shows a diftusely expanded cord. In addition, area of cystic change is noted in upper portion of thoracic cord. MR image confirms superior cyst. Also noted Is area of heterogeneity within cord inferior to cyst. MR image after administration of contrast material shows marked enhancement of main tumor nidus, with rostral cyst.

example, infection or benign syrinx. If no enhancement is seen, the likelihood of a ghioma of the cord is significantly reduced. and Inflammatory


As with the brain, multiple infectious agents can affect the cord and cause myelopathic symptoms, including bacterial, granulomatous, viral, and even parasitic diseases. As a rule, however, inflammatory diseases that affect the cord tend to be seen earlier than those in the brain. Therefore, certain lesions that require time to develop, such as the well-formed abscess capsule, are comparatively unusual in the cord. Viral agents are probably the most common ones to directly involve the cord. Often, the exact virus may be difficult to determine. Regardless of the specific agent, the response of the cord parenchyma is stereotypical [1 3, 14]. An inflammatory cellular infiltrate, usually composed of lymphocytes and plasma cells, predominates, although neutrophils may be numerous early in the disease. Edema, both vasogenic and cytotoxic, occurs. Cellular destruction may be limited to mdividual neurons and small foci, or it may be extensive and fail to respect anatomic boundaries. Vessel thrombosis may lead to secondary ischemia. Short TA images generally reveal mild enlargement of the cord, often quite extensive. Long TA images show high intensity within the cord, often extending beyond the area that might be expected from the degree of cord swelling. The presence of a skip area separating multiple regions matory



A, Short TR (600/20) saglttal B, Long TR (2136/80) saglttal C, Short TR (600/20) sagittal



of enlarged cord is strongly suggestive of an inflamcondition rather than tumor [1 5]. After the administra-

tion of contrast material, enhancement may be nodular and resemble that of tumor. Alternatively, enhancement may be diffuse, peripheral, or even punctate and speckled [15] (Fig. 3). All of these patterns of enhancement are unusual for tumor.

Granuhomatous diseases, such as tuberculosis or sarcoid, also affect the cord. In these cases, short and long TA images

generally show focal enlargement of a limited segment of the cord. After the administration of contrast material, nodular enhancement is usually seen [1 5]. This pattern strongly resembles that of tumor, and differentiation between the two may be difficult.



MS is the most common demyehinating disease to affect the cord. Eighty percent of cases involve the cord, and 2033% show symptoms referable to the cord alone [1 6]. Lesions may involve any region of the cord, regardless of anatomy, although the cervical cord is involved more often. Devic’s disease, also known as neuromyehitis optica, represents the association of transverse myehitis with acute visual loss due to optic neuritis. Pathologically, the typical regions of demyehination are seen [1 6]. In acute plaques, the axons are relatively preserved while the myehin is fragmented. These changes are often associated with microghial and perivascular hymphocytic infiltration. In chronic plaques, dense fibrillary ghiosis is typical. In severe cases, atrophy is common. The majority of patients with cord lesions documented with the use of MR imaging will also have brain lesions, occurred at different times. amination may be performed

although these lesions may have Therefore, a screening head exin lieu of a spinal examination if

the diagnosis is in doubt [1 7]. However, if evaluation of the cord is desired, MS plaques in the cord can be detected. Good-quality cardiac-gated long TA images, with flow-cornpensation techniques, are essential for the visualization of cord plaques in the sagittal plane. In the axial plane, gradientecho images are often very sensitive in showing MS plaques that disrupt the otherwise easily visualized border between gray and white matter in the cord. As in the head, MS plaques generally appear of high intensity compared with the remainder of the cord on long TA or gradient-echo images. Large and acute plaques may have

Fig. 3.-Inflammatory myelitis. A, Swollen areas of spinal cord show diffuse high signal on long TR (2200/80) MR image. B, After contrast administration, long TR (2200/

80) MR image shows diffuse enhancement




skip area.

This pattern

is unlike

Downloaded from by on 10/16/15 from IP address Copyright ARRS. For personal use only; all rights reserved

usually seen in tumor.

mass effect and resemble tumors. Acute plaques generally enhance after the administration of contrast material while chronic plaques do not [1 8] (Fig. 4). While the natural history of plaques in the brain has been described both without and with treatment, this research has not been done in the spine. Presumably, acute cord plaques also enhance for several weeks initially before repair of the blood-brain barrier takes place. Radiation change is another entity that may cause myelopathy. The development of myehopathy is dependent on the dose of radiation received, the interval at which the radiation was administered, and the number of fractions [1 9-23]. Radiation myelopathy may be divided into acute and chronic forms. The acute form is best known as the transient myelopathy of Lhermitte and is manifested by shockhike sensations down the back when flexing the neck. It usually occurs 3 months after radiation treatment and resolves spontaneously. Findings on MA imaging are normal. Chronic radiation myehopathy has been described in three forms [1 9-23]. First, lower motor neuron disease can occur as a result of injury to the anterior horn cells. Second, acute paraplegia due to radiation-induced vascular changes and secondary cord ischemia has been seen. Third, and by far the most common, is chronic progressive radiation myelopathy. It primarily involves the lateral columns. These patients have sensory or motor changes and frequently Brown-Sequard syndrome. Symptoms are often slowly progressive and may result in death. The cause of these changes is unclear, but they may result from either radiation-induced vascular change or primary neuronal damage. Chronic radiation myehopathy of all types usually occurs approximately 1 year after

radiation therapy and has been described as late as 13 years after irradiation. As with MS, radiation myelopathy may have a variety of appearances on MR [24]. When it is fulminant, chronic progressive radiation myelopathy often can be seen as an area of focal cord swelling on short TA images with associated high intensity on long TA images. In particularly severe cases, contrast enhancement can occur [24]. The appearance can markedly resemble that of tumor. In the late stage of chronic radiation myehopathy, the cord may appear totally normal on both short TA and long TA images or may even appear atrophic.

Acute disseminated encephahomyehitis, also known as postvaccinal or postinfectious encephalomyehitis, typically occurs several weeks after an antecedent innoculation or viral syndrome. Patients have focal lesions, often in the white matter; as in MS, these lesions appear random in distribution [16]. Pathologically, although the syndrome is associated with previous infection, no infectious agents can be found. Most often, one sees a perivascular lymphocytic infiltration, associated with areas of demyehmnation that follow the course of the vessels. In severe cases, hemorrhage may occur. The reaction is presumed to be immune in nature, possibly owing to antigen-antibody




hal damage, and vascuhitis. The brain is most often involved, but a very small proportion of cases involve the cord. Imaging findings, in general, resemble those seen in the acute phase of MS. Short TA images may show a normal cord or a slightly enlarged cord. Long TA images show corresponding





of high signal


(Fig. 5). In more

may be seen. Since acute


seminated encephahomyelitis is a monophasic disease, unlike MS, it has been speculated that the enhancement pattern should also be monophasic, unlike MS, in which different lesions may enhance, subside, and reenhance at different intervals.

Downloaded from by on 10/16/15 from IP address Copyright ARRS. For personal use only; all rights reserved



Vascular lesions of the cord can be separated into infarcts and malformations. Cord infarcts generally present acutely. Although they may have a wide array of causes, they are most often associated with surgery for aortic aneurysms [25]. As in the head, mass effect on short TA images and high signal on long TA images is generally seen. In the subacute phase, contrast enhancement, generally diffuse in nature, can be demonstrated. Presumably, the time course of enhancement reflects that seen in brain infarcts, although there is a hack of research on this topic. Early exaggerated enhancement due to incomplete ischemia has not been described in the cord. Many types of malformations may involve the cord, including intramedullary arteriovenous malformations (AVM5), cayernous hemangiomas, and extramedullary vascular malformations [26]. Intrameduhhary AVM5 generally occur in young adults, are fed most often by the anterior spinal artery, and present acutely as cord hemorrhage or as subarachnoid hemorrhage





is involved



Short TA and long TA images may reveal a normal or swollen cord, often with areas of hemorrhage. Serpiginous signal voids representing the nidus are seen in the cord, consistent with the actual malformation [27, 28] (Fig. 6). Large serpiginous signal voids may also be present in the subarachnoid space owing to feeding and draining vessels. Atrophy or syrinx formation can be caused by the AVM. Hemosiderin deposition is usually present, indicative of previous hemorrhage. Cobb syndrome is a metameric angiomatosis associated with an intramedullary AVM, an epidural AVM, vertebral or superficial angiomas, or any combination of these abnormahities. Extramedullary arteriovenous fistuhas, also known as dural arteriovenous fistulas or as radiculomeningeal fistuhas, generahhy occur in older patients, especially men, and are due to a fistula between a dural branch of a radicuhar artery and the perirnedullary veins [26]. These fistuhas are generally fed by the posterior circulation, and symptoms are usually those of

Fig. 4.-Multiple


A, Long TR (2235/30) sagittal MR image shows high intensity in cord over a short segment. B, Short TR (500/12) saglttal MR Image after administration of contrast material shows en-


cord claudication or a progressive myeloradiculopathy, often a conus medullaris syndrome. These lesions can be very difficult to visualize on MA (Fig. 7). Conus enlargement and intramedullary

high signal

on long TA images

may be present.

surface of the cord may be caused by the enlarged perimedullary veins. If gadopentetate dimeglumine is given, punctate enhancement of the posteriorly draining medullary veins can be seen along the surface of the cord in about one fourth of cases [29, 30] (Fig. 7). On delayed scans, diffuse cord enhancement has been reported, possibly due to venous engorgement and secondary ischemia. Finally, cryptic vascular malformations of the cord may occur, as in the head; the most common of these, cavernous hemangiomas, are seen with increasing frequency [31]. Their appearance in the cord is similar to their appearance in the head (Fig. 8). Generally, these lesions appear either as a central focus of high signal intensity, surrounded by a lowintensity rim, due to the breakdown products of blood, or, in smaller lesions, as how intensity due to hemosiderin deposiScalloping



In general,

of the posterior


is unusual

very little contrast







is seen.


Pathologic changes that occur in the injured spinal cord can be divided into acute and chronic [32]. Acutely, the trauma can result in a wide spectrum of iniurv, ranging from mild cord contusion to severe disruption of cord architecture and hemorrhage. Secondary edema can head to vascular compromise of adjacent areas. Most of these changes occur in the first few days following trauma. After the first week, the subacute phase begins, as the body attempts to heal from the results of the injury. Macroscopically, edema and the smaller areas of hemorrhage are resorbed. The acute infiltrate is replaced by mononuclear cells. Astrocytic ghiosis may also be seen at the periphery of the injury. Chronically, fibrous tissue fills in the regions of necrosis and hemorrhage. Secondary atrophy of the cord may be present. In the acute setting, MA imaging permits the visualization of changes in the traumatized cord directly as long as the patient is sufficiently stable and cooperative to be imaged [33, 34]. Imaging may be particularly important when the trauma is incomplete, that is, when some motor and/or sensory function below the level of the injury persists [32]. In these cases, aggressive treatment may be indicated in order to




Fig. 5.-Acute


July 1992



Downloaded from by on 10/16/15 from IP address Copyright ARRS. For personal use only; all rights reserved

A, Long TR (1333/80) sagittal MR image shows focal high intensity at C6-C7. B, Short TR (600/30) sagittal MR image after administration of contrast material shows focal

and marked enhancement

prevent further deterioration. These incomplete injuries may be characterized by varying clinical characteristics. The central cord syndrome is often seen in elderly patients with cervical spinal stenosis, in which even minor trauma can result in hemorrhage into the central gray matter of the cord. These patients have decreased function in the upper extremities but relatively normal function in the lower extremities. Other incomplete cord injuries may present as Brown-Squard syndrome, anterior cord syndrome, or mixed motor and sensory deficits. The MA characteristics of the acutely injured spinal cord reflect the clinical symptoms. If the injury is mild, with only temporary neurologic dysfunction, MA imaging may show a normal cord. With increasing cord injury, short TA images may be normal or may reveal cord swelling [32]. The long TA

A Fig. 6.-Arteriovenous malformation of cord. Short TR saglttah MR image shows marked serpiginous sig. nal voids permeating substance of cord, especially visible


at Cl and on axial image (not shown). In addition, marked large serpiginous signal voids are present along cord periphery superiorly, consistent with large draining veins.

of lesion.

images, however, are the most sensitive in showing cord edema, which is seen as areas of high signal intensity within the substance of the cord (Fig. 9). Areas of hypointensity on both short TA and long TR images, with hater evolution to hyperintensity,


at first,

are typical

of hemorrhagic


The presence of hemorrhage has been associated with a poor prognosis [33]. Also important to note are any retropulsed bone fragments or disk fragments that may impinge on the cord. Rarely, rapidly ascending spinal necrosis can result from thrombosis of the anterior spinal artery or other interruption in the blood supply. In cases of penetrating injury of the spinal cord, such as in knife or gunshot wounds, actual transection of the cord may be visualized. In the chronic stage, an imaging examination may be mdicated if new or progressive signs of neurohogic dysfunction


Fig. 7.-Dural arteriovenous fistula. A, Gradient-echo (367/15/15#{176}) sagittal MR image of thoracic ing of posterior surface of cord. B, Short TR (550/20) sagittal MR image after administration subtie punctate enhancement of some focal and serpiginous cord.





of contrast material shows hypointensities posterior to



July 1992



Fig. 8.-cryptic vascular malformation of distal thoracic cord in a patient with long-standing fluctuating conus symptoms. A, ShortTR(600/20)sagittal MR Image obtained during a period of exacerbation shows focal high

Downloaded from by on 10/16/15 from IP address Copyright ARRS. For personal use only; all rights reserved

signal intensity in conus, consistent with evolving products

of hemorrhage.






mixed increased and decreased signal intensity extending superiorly, representing hemorrhage at other stages of evolution and extension of the bleeding. B, Long

TR (2368/70)


MR image


shows multiple areas of mixed signal intensity within cord, consistent with evolving hemorrhage. In this case, because of acute nature of hemorrhage, high signal intensity is also noted in surrounding cord, probably because of edema.

[32, 35]. In these cases, the development of intramedullary cysts, myelomalacia, or adhesions may be treated. Areas of cord injury or transection are well demonstrated (Fig. 1 0). Myelomalacia is generally visualized as a poorly defined area of how intensity within the cord on short TR images [32]. Long TA images disclose high intensity in the corresponding occur



to a well-defined


can be detected

on MA by the presence of a well-defined low-intensity region on short TA images, with a sharp interface between the surrounding normal cord and the cyst itself. The cyst contents appear uniformly hypointense or may show evidence of flow, unlike in myehomalacia. If the lesion is extensive, then a cyst is more likely, since myelomalacia is characterized by relatively short segments of involvement. Clearly, the differentation is clinically important, since myehomahacia cannot be treated with shunting. prominent

Those are


in which flow artifacts appear especially good candidates for treatment,


since active pulsations further extension.


the cyst

may predispose




and the syrinx





Chiari-associated hydromyehia. The syrinx itself is often well defined and smooth, but occasionally septa are detected. If arachnoiditis is present, extensive adhesions may typical


blur the interface


the cord and the surrounding

[36]. If the cyst shows any suspicious features loss of definition in a focal region, then contrast is indicated

to ensure


that a neoplasm



at all, such as enhancement

is less likely.

of the Spinal


A small number of neurodegenerative disorders involve the cord [13]. Different disorders involve different tracts, and involvement of structures other than the cord, such as the cerebellum or other parts of the brain, is frequently associated. The pathogenesis of most of these disorders is unknown. Pathologically, these diseases are typified little inflammatory reaction and by progressive,

by very



of cells, usually neurons. ataxia is believed to be due to a mutation on chromosome 9 and occurs in both autosomal recessive and Friedreich’s



Although cord cysts may be commonly associated with trauma or neoplasm, true syringomyehia or hydromyehia is usually found related to Chiari malformation or is idiopathic in origin [1 3]. Hydromyehia is due to congenital dilatation of the central canal. Syringomyehia represents a cavity in the cord itself. The pathogenesis is highly debatable. The dysraphic theory suggests that a closure defect of the neural tube at the level of the posterior raphe is responsible. The hydrodynamic theory maintains that disturbances of CSF outflow from the fourth ventricle heads to hydromyehia, followed by syringomyelia as a result of rupture of the dilated ependymal canal. Occasionally,


can also occur

as a result

of arachnoid

adhesions with secondary alteration in CSF flow [36-38]. These cases typically involve the thoracic region, unlike other syrinxes, which are usually located in the cervical cord. Symptoms depend on the location of the syrinx. Pathologically, syrinxes may be lined by fibrous astrocytosis. On MA, short TA images accurately show the morphology of the cyst. Typically, there is a sharp interface between the





olescents or young adults and present picture of gait ataxia, upper extremity


are typically a mixed



clumsiness, and dysarloss and ghiosis focused on the posterior columns, spinocerebellar tract, and corticospinal tract are seen, with secondary atrophy. MR imaging reveals an atrophic spinal cord with normal signal intensity [40]. While Friedreich’s ataxia is the prototypical progressive ataxia, several other degenerative disorders of the cord can also occur. These include hereditary spastic paraplegia (Strumpelh-Lorain disease) and hereditary posterior column ataxia (Biemond syndrome) [41]. Other syndromes may involve the brain, especially the cerebellum, as well as the cord and include ohivopontocerebellar atrophy and Shy-Drager syndrome. Other types of neurodegenerative disorders primarily involve the motor neurons. Of these, the prototype is amyotrophic lateral sclerosis. Although most cases are sporadic, thria. Pathologically,



in elderly





the disease

is transmitted

in approximately

in an

5% of cases




July 1992

Fig. 9.-Posttraumatic cord contusion in patient with bullet wound to soft tissues of neck and

secondary quadriparesis. Long TR (2308/80) sagthaI MR image shows diffuse high intensity in

Downloaded from by on 10/16/15 from IP address Copyright ARRS. For personal use only; all rights reserved



of cord.

Fig. 10.-chronic disruption of cord after direct stab wound. 5hort TR (600/20) sagittal MR image shows disruption of distal thoracic cord with significant atrophy both above and below area of trauma.

[42]. distal ties, fects

The clinical triad consists of atrophic weakness of the upper extremities, mild spasticity of the lower extremiand generalized hyperreflexia. Innervation atrophy afthe muscles.



of the corticospinal



lower motor neurons is seen [1 3, 14]. Because corticospinal tract degeneration can extend superiorly to involve the cerebral peduncles, posterior portion of the posterior limb of the internal capsule, and corona radiata, MR reports have focused on the hyperintense foci seen on long TA sequences in the brain. However, the cord may also appear to be atrophic and flattened in its anterior and lateral portions owing to loss of motor


in the



in corticospinal


of the





known as monomehic amyotrophy or benign focal amyotrophy. Characteristic unilateral muscular atrophy in the distal upper extremity due to selective anterior horn cell involvement in the lower cervical cord is seen. Unlike amyotrophic lateral sclerosis, this disease usually occurs in boys and stabilizes after a few years. Focal atrophy of the cervical cord, often limited to the anterior horn cell region, has been described [43].


Clinically, most metabolic and toxic disorders affect the brain far more than the cord. A very few, however, target the cord. Subacute combined degeneration of the cord occurs in patients with pernicious anemia due to vitamin B12 deficiency, but









and malabsorptive conditions [1 3, 14]. Pathologically, degeneration of myelin results in demyehination of the white matter, especially

the dorsal

Subacute nancy,


and lateral

and axons







the cord











and other








of image

the scope and versatility

to expand


of the Cord

of tumors



in the thoracic


in MR Imaging

the appearance has







of MR imaging

of the cord.


Hyperintense foci in the cord have not been reported. Other more unusual forms of motor neuron disease have been described clinically but not by imaging. One exception is juvenile



necrotizing myelopathy accompanies mahiga lung carcinoma [1 3, 14]. Necrosis of myelin

New Pulse Sequences

Often, plaques,

cord lesions, especially subtle lesions such as MS are first detected with long TA images. Unfortunately, long TA images of the cord are often time-consuming and marred by motion artifacts. Aecently, fast spin-echo (FSE) techniques have been developed that promise to provide images with a sensitivity to pathology comparable to that of long TA images, but in a much shorter time. These techniques are all variants of the original RARE (rapid acquisition with relaxation enhancement) sequence devised by Hennig et al. in 1 986 [44-47]. Modification of the original sequence allows adaptation for clinical use [48, 49]. Although many variations exist, all of the FSE sequences consist of a single 90#{176} pulse, followed by multiple 180#{176} refocusing pulses. Each refocusing pulse is associated with its own



The TE occurs

lowest-order phase encodes, responsible placed. The length of the echo train is crucial time

of the acquisition,

contrast, typical





the presence


to the



of certain




in determining

of sections,

or absence

the FSE sequences, of the interecho spacing of


for contrast,

the image


such as blurring [49]. The is also important and similarly sections,






July 1992

and the presence

Downloaded from by on 10/16/15 from IP address Copyright ARRS. For personal use only; all rights reserved


of certain artifacts.

new parameters,

Thus, in specifying

such as the length


of the echo

train and the interecho spacing, become important in addition to the familiar TA, TE, matrix size, and number of excitations. FSE images strikingly resemble the routine long TA spinecho images (Fig. 1 1). One crucial difference involves the persistent




of lipid on FSE images,


when parameters apparently similar to those of routine spin echo are used. This persistent high signal intensity of lipid has been explained by the homonuclear coupling interaction of adjacent






that the FSE

sequences are as sensitive in the detection of intramedullary disease as routine spin-echo sequences are [50]. MR imaging of the spine is characterized by long acquisition times and susceptibility to motion artifacts, factors that are less of a problem in brain imaging. Therefore, FSE images offer tremendous potential in the spine. Early reports on the evaluation of extradurah disease suggest that FSE sequences are equivahent to gradient-echo sequences in the sagittal plane but are still inferior

in the axial plane

The rapidity dimensional

(Sze G, unpublished

of the FSE sequences



a volumetric acquisition where N is the number phase-encoding



a three-

the time


is equal to (TA x N x S x S)/P, of excitations, S is the number of


and P is the number


also makes

S is the number

of slice select

of phase-encoding



per TA, in

routine spin echo, a volumetric acquisition would be prohibitive in the time required. However, with the FSE sequences,

the volumetric acquisition can be obtained in a reasonable length of time [51 ]. Preliminary clinical evidence indicates that these sequences are also sensitive in the detection of intramedullary


A small number sequences:


of disadvantages

(1) FSE sequences

of these




can be minimized with optimization of all the parameters. (2) The number of sections that can be obtained in a given acquisition is less than that of routine spin-echo imaging for a given TR. In MR imaging of the spine, the limited number of sections is not a clinical problem. (3) There is a theoretical loss of small object definition. Preliminary reports indicate that in the spine, detection of even small lesions, such as MS plaques, has not been compromised. The theoretical loss of small object definition applies to extremely small objects (two pixels), which also have short T2 relaxation times, a phenomenon very different from the majority of cord lesions. (4) Motion compensation techniques, such as gradient-moment nulhing, are more difficult to apply in FSE imaging owing to the very short interecho spacing. Nevertheless, gradient-moment nulhing can be applied to FSE imaging with slight limitations of other parameters, such as interecho spacing or TE.

Phased-Array Increasingly,


do exist with the FSE



Coils clinicians







Imaging of the length of the cord may be indicated to assess a diffuse process, such as tumor, MS, or inflammatory or infectious disease, or in cases of myelopathy in which exact localization is difficult. Both unenhanced and enhanced scans



may be necessary.

These clinical demands

capability in spinal must be performed



head to a need for

MA imaging. more rapidly

Either individual or large portions

of the cord must be imaged on one acquisition, imaging

limiting patient


In the past, only one surface coil could be used at a time, permitting only a limited field of view (FOV) in each acquisition [52, 53]. Increasing the FOV invariably led to decreased





at the extremes


the end of the coil. Increasing the size of the surface coil reduced the advantages of the surface coil and decreased SNA. A single surface coil, therefore, could not always meet clinical


With phased-array coils, several surface coils can be used together, combining the benefits of the small surface coil with the large FOV. These surface coils are arranged in a linear fashion. Coupled together to act as one, they markedly increase the length of the FOV, up to 48 cm (Fig. 12). The advantages of the phased-array coils are thus twofold: a larger FOV and increased SNA. With phased-array coils, one can routinely image the entire cord in a single acquisition (Fig. 12). The



of receivers and separate receiver. processed at this



are matched

by an equal


memory boards. Each coil feeds into a The information from a particular coil is receiver and stored in one of the memory

processing recoils is thus processed and stored. Because each receiver only processes signal from one specific coil, the noise heard by a particular receiver is limited to that transferred by a single surface coil. This allows for less noise coupling at the level of the receiver, ceiver.





in increased

and memory




solely with the particular from





The information

is then coupled



all receivers

by using


of algorithm.

Because of their advantages, phased-array coils will likely the most versatile of all coils for routine scanning of the spine. If a large FOV is required, such as a scan of the entire prove

cord to evaluate an extensive syrinx, phased-array coils clearly the method of choice. However, if only a limited is required, phased-array coils still can be used because provide better SNR and resolution than a single surface Phased-array coils, therefore, are extremely versatile in

are FOV they coil. their




Significant advances have been made recently in the field of image display. The development of three-dimensional reformations promises to be one of the most important advances in MA imaging of the cord [54]. The ability to acquire very thin sections with gradient-echo sequences has permitted data acquired in one plane to be reconstructed and displayed in other planes. If isotropic voxels are obtained, minimal distortion or artifact exists in the reconstructions. Three-dimensional reconstructions can be combined with enhancement when spoiled




gradient-echo sequences that display tion in a “Ti -weighted” fashion are used. One major



Downloaded from by on 10/16/15 from IP address Copyright ARRS. For personal use only; all rights reserved



Fig. 1 1.-Multiple



TR (2188/80) cardlac-gated sagittal MR image of cervical spine, obtained sec, shows a small high-intensity lesion consistent with multiple sclerosis plaque. B, Fast spin-echo (2000/112) MR image obtained in 3 mm 12 sec also shows lesion. A, Long

Fig. 12.-Syrinx. Short TR (500/12) sagittal MR image with phased-array area of how signal intensity within cord, consistent with a syrinx.

still must be addressed, namely, the sensitivity of spoiled gradient-echo sequences to contrast enhancement. Although spoiled gradient-echo sequences appear markedly Ti weighted, it has been noted that these sequences do not appear to show contrast enhancement after the administration of gadopentetate dimeglumine as clearly as short TA spin-echo sequences do (Augenstein HM et al., presented at the Radiological Society of North America meeting, November 1990; Rand SD et al., presented at the American Society of Neuroradiology meeting, June 1991). Cine MA is another recent advance in the assessment of the cord and may be used to assess the pulsatihity of cord cysts and to evaluate cord motion itself [55, 56]. As mentioned, cord cysts that are pulsatihe are often considered better candidates for surgery, since persistent pulsatihity may be associated with cyst expansion. These changes are optimally


technique, readily




July 1992



of a cardiac-gated

in cine. from


In addition, cyst


myelomalacia can be formation, since it fails to

in 12 mm 48

coils shows small focal

display pulsatihity or turbulence. Use also facilitate understanding of the Although it has been suggested that connected to the fourth ventricle by flow







of this technique may origin of syringomyehia. congenital

the obex, syrinx



a continuous has not been

observed. Cord motion can be assessed with similar techniques. In these studies, a cardiac-gated spin-echo pulse sequence can be used to obtain phase information [56]. Peak caudal velocity of the cord has been noted to occur in early systole and to be 12.4 mm/sec. These velocities are decreased in patients with tethered cord or spinal cord compression, but not in those





REFERENCES 1. Norman D, Mills C, Brant-Zawadzki M, Yeates A, Crooks LE, Kaufman L. Magnetic resonance imaging of the spinal cord and canal: potential and limitations. AJNR 1984;5:9-14



July 1992

Downloaded from by on 10/16/15 from IP address Copyright ARRS. For personal use only; all rights reserved

2. Rubin JB, Enzmann DR. Imaging AJNR 1987;8:297-306

of spinal

CSF pulsation



by 2DFT MR.

G, Brown J, Niendorf HP, et al. Enhancement of cervical intraspinal in MR imaging with intravenous gadolinium-DPTA. J Comput Assist 1985;9:847-851 Krol G, Zimmerman RD, Deck MDF. Intramedullary disease of the diagnosis using gadolinium-DPTA enhanced MR imaging. AJNR



1 1.

12. 13. 14.

lesions. AJNR 1988;9:345-350 Dillon WP, Norman D, Newton TH, Bolla K, Mark A. Intradural spinal cord lesions: Gd-DPTA-enhanced MR imaging. Radiology 1989;170:229-237 Parizel PM, Bal#{233}riauxD, Rodesch G, et al. Gadolinium-DPTA-enhanced MR imaging of spinal tumors. AJNR 1989;10:249-258 Goy AMC, Pinto RS, Raghavendra EN, et al. Intramedullary spinal cord tumors: MR imaging, with emphasis on associated cysts. Radiology 1986;161 :381-386 Poser CM. The relationship between syringomyelia and neoplasm. In: American Lecture Series, #262: American Lectures in Neurology. Springfield,IL: 1956:28-32 Breger RK, Williams AL, Daniels DL, et al. Contrast enhancement in spinal MR imaging. AJNR 1989;10:633-637 Okazaki H. Fundamentals of neuropathology. New York: Igaku-Shoin, 1983:61-184 Rosenberg R, Grossman R, Schochet S Jr, Heinz E, Willis W Jr. The clinical neurosciences. New York: Churchill Livingstone, 1983


M, Fariow

patients spinal

M, Stevens

with isolated

18. Larsson


J. Cranial

MR in spinal cord MS: diagnosing

cord symptoms.



EM, Holtas 5, Nilsson 0. Gd-DPTA-enhanced multiple




MR of suspected



19. Boden

G. Radiation myelitis of the cervical spinal cord. Br J Radiol 1948;21 :464-469 20. Kim YH, Fayos Jv. Radiation tolerance of the cervical spinal cord. Radiology 1981;139:473-478 21 . Maier JF, Perry RH, Saylor W, Sulak MH. Radiation myelitis of the dorsolumbar





AJ, Liang MK. Radiation tolerance of the cervical spinal cord. Oncol Biol Phys 1989;16:675-678 23. Reagan TJ, Thomas JE, Colby MY. Chronic progressive radiation myelopathy. Its clinical aspects and differential diagnosis. JAMA 1968;203: mt J Radiat

and intraoperative

34. 35.



ischemia after resection of thoracoabdominal ings in 24 patients. AJNR 1990;1 1:987-991



R, Rey A, Dhindjian

MR find-

M. Arteriovenous

malformations of the spinal cord. Prog Neurol Surg 1978;9:238-266 27. Dormont D, Gelbert F, Assouline E, et al. MR imaging of spinal cord arteriovenous malformations at 0.5 T: study of 34 cases. AJNR 1988;9:833-838 28. Minami S. Sagoh T, Nishimura K, et al. Spinal arteriovenous malformation: MR imaging. Radiology 1988;169: 109-115 29. Terwey B, Becker H, Throm A, Vahidiek G. Gadolinium-DPTA enhanced MR imaging of spinal dural arteriovenous fistulas. J ComputAssist Tomogr

1989;13:30-37 30. Gaensler EHL, Jackson cervicomedullary 51 8-520


DE, Halback as a cause

VV. Arteriovenous of myelopathy.

fistulas AJNR

of the 1990;11:




Am 1988;26:


FJ, Rose SL, Narayana PA. 1 .5 Tesla magnetic

BT, Sanchez J, Manelfe C, Peck W, Norman D. MRI

JHM. The pathogenesis

of syringomyelic



with arachnoiditis localised to the spinal canal. In: Bamett HJM, Foster JB, Hudgson P, eds. Syringomyeila. London: Saunders, 1973:245-259 Chamberlain 5, Shaw J, Rowland A, et al. Mapping of mutation causing Friedreich’s ataxia to human chromosome 9. Nature 1988;334:248

Wessel K, Schroth G, Diener HC, Muller-Forell W, Dichgans J. Significance of MRI-confirmed atrophy of the cranial spinal cord in Friedreich’s ataxia. Eur Arch Psychiatry Neurol Sci 1989;238:225-230 41 . Schoene WC. Degenerative diseases of the central nervous system. In: Davis RL, Robertson DM, eds. Textbook of neuropathology. Baltimore: Williams & Wilkins, 1985:788-823 42. Adams RD, Victor M. Principles ofneurology, 4th ed. New York: McGrawHill Information Services Co., Health Professions Div., 1989:35-77, 334346, 488-500, 921-967

43. Biondi A, Dormont D, Weitzner I Jr, et al. MR imaging of the cervical cord in juvenile amyotrophy of distal upper extremity. AJNR 1989;10:263-268 44.

Hennig J, Naureth A, Friedburg H. RARE imaging: a fast imaging method for clinical MR. Magn Reson Med 1986;3:823-833 45. Hennig J, Friedburg H, Strobel B. Rapid nontomographic approach to MR myelography without contrast agents. J Comput Assist Tomogr

1986;10:375-378 46. 47.

Hennig J, Friedburg H, Ott D. Fast three-dimensional imaging of cerebrospinal fluid. Magn Reson Med 1987;5:380-383 Hennig J, Friedburg H. Clinical applications and methodological developments of the RARE technique. Magn Reson Imaging 1988;6: 391-395

48. Mulkem RV, Wong STS, Winalski C, Jolesz FA. Contrast manipulation and artifact assessment of 2D and 3D RARE sequences. Magn Reson Imaging 1990;8:557-566 49. Melki PS, Mulkem RV, Panych LP, Jolesz FA. Comparing the FAlSE with




J Magn



1991;1 :319-326 50.

1990;1 1:1188-1190

R, Djindjian



of the cervical spinal cord: MR

25. Mawad ME, Rivera V, Crawford ES, Ramirez A, Breitbach W. Spinal cord

26. Hurth M, Houdart

G. Cavernous

of syringomyelia secondary to arachnoid adhesions (arachnoiditis) with emphasis on associated arachnoid cysts. In: Book of Abstracts: Society of Magnetic Resonance in Medicine. Berkeley, CA: Society of Magnetic Resonance in Medicine, 1987: 251 Bamett JHM. Syringomyelia associated with spinal arachnoiditis. In: Barnett HJM, Foster JB, Hudgson P, eds. Syringomyeila. London: Saunders, 1973: 220-243

method AJNR

R, Bertrand

resonance imaging of acute spinal trauma. RadioGraphics 1988;8: 1059-1 082 Mirvis SE, Geisler FH, Jelinek JJ, Joslyn JN, Gellad F. Acute cervical spine trauma: evaluation with 1 .5-T MR imaging. Radiology 1988;166:807-816 Yamashita Y, Takahashi M, Matsuno Y, et al. Chronic injuries ofthe spinal cord: assessment with MR imaging. Radiology 1990;175:849-854

38. Bamett


24. Zweig G, Russell EJ. Radiation myelopathy findings.

D, Cosgrove

33. Kulkami MV, Bondurant


22. McCunniff


S, Melanson

of the spinal cord: MR imaging. Radiology 1988;66:839-842 32. Quencer RM. The injured spinal cord. Evaluation with magnetic resonance

in MR of spinal

15. Goro B, Sze G, Sharif H. MR imaging of intradural inflammatory diseases of the spine. AJNR 1991;12: 1009-1019 16. Helgason CM, Amason BGW. Demyelinating diseases affecting the spinal cord. In: Davidoff RA, ed. Spinal cordhandbook, vol. 4. New York: Dekker, 1986:345-366 17.


36. Mark AS, Andrews

1988;9:847-858 7. valk J. Gadolinium-DPTA




3. Rubin JB, Enzmann DR, Wright A. CSF-gated MR imaging of the spine: theory and clinical implementation. Radiology 1985;167:225-232 4. Bronskill MG, Mcveigh ER, Kucharczyk W, Henkelman RM. Syrinx-like artifacts on MR images of the spinal cord. Radiology 1988;166:485-489 5. Bydder tumors Tomogr 6. Sze G, spine:




Sze G, Merriam M, Oshio K, Jolesz F. Fast spin echo imaging in the evaluation of intramedullary spinal lesions. AJNR (in press) 51 . Oshio K, Jolesz F, Melki PS, Mulkem RV. T2-weighted thin slice imaging with multi-slab 3D RARE. J Magn Reson Imaging 1991;1 :695-700 52. Carison JR, Arakawa M, Kaufman L, McCarten BM, George C. Depthfocused radio-frequency coils for MR imaging. Radiology 1987;165:251 53. Kneeland JB, Hyde JR. High resolution MR imaging with local coils. Radiology 1989;171 :1-4 54. Sherry CS, Harms SE, McCroskey WK. Spinal MR imaging: multiplanar representation from a single high resolution 3D acquisition. J Comput Assist Tomogr 1987;1 1:859-864 55. Quencer AM, Post MJ, Hinks AS. Cine MR in the evaluation of normal and abnormal CSF flow: intracranial and intraspinal studies. Neuroradiology 1990;32:371 -391 56. Levy LM, DiChiro G, McCullough D, Dwyer AJ, Johnson D, Yang S. Fixed spinal cord: diagnosis with MR imaging. Radiology 1988;169:773-778

MR imaging of the spinal cord: current status and future advances.

The advent of MR imaging has dramatically altered the evaluation of suspected myelopathy. MR is far less invasive than traditional imaging techniques ...
2MB Sizes 0 Downloads 0 Views