Imaging of the Spine in Multiple Sclerosis

Updated: Feb 27, 2016
  • Author: Djamil Fertikh, MD; Chief Editor: James G Smirniotopoulos, MD  more...
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Overview

Overview

Magnetic resonance imaging (MRI) was first used to visualize multiple sclerosis (MS) in the upper cervical spine in the late 1980s. [1] Spinal MS is often associated with concomitant brain lesions; however, as many as 20% of patients with spinal lesions do not have intracranial plaques. Contrary to the brain, white and gray matter can both be affected in the spine. No strong correlation has been established between the extent of the plaques and the degree of clinical disability. (See the image below).

Sagittal, T2-weighted magnetic resonance image of Sagittal, T2-weighted magnetic resonance image of the cervical spinal cord in a woman aged 27 years showing a fusiform area of increased signal intensity representing a multiple sclerosis plaque.

Careful review of the patient's medical history and an evaluation of the brain with MRI can prove helpful in the diagnosis, especially in young females. MS is considered to be the most common demyelinating process involving the central nervous system (CNS). [2, 3]

Imaging plays an important role in MS as included in McDonald criteria, which were introduced in 2001, then revised and simplified in 2005 and finally 2010. It is important to note that McDonald criteria were largely collected from adult white European and North American populations. MRI is used to demonstrate lesion dissemination in time (DIT) and space (DIS).

MRI criteria for DIS are as follows:

  • At least 1 T2-weighted lesion in at least 2 of 4 locations considered characteristic for MS (juxtacortical, periventricular, infratentorial, and spinal cord)
  • If brain imaging fails to demonstrate DIS, then imaging of the spinal cord may be helpful in demonstrating a least a single T2-weighted hyperintense lesion of 3 mm or greater dimension, less then 2 vertebral bodies in length, and involving less than the cord cross-section.

MRI criteria for DIT are as follows:

  • A new T2-weighted and/or gadolinium-enhancing lesion(s) on follow-up MRI, with reference to baseline MRI irrespective of time of initial imaging
  • Simultaneous presence of asymptomatic gadolinium enhancing and nonenhancing lesions at any time

Radiologically isolated syndrome (RIS)

RIS describe cases in which McDonald imaging criteria meet DIT and DIS but lack corresponding clinical symptoms. The exact significance is still a subject of debate. Some authors suggested that this could represent a stage preceding clinical isolated syndrome (CIS). In an extensive review of the RIS literature, Granberg et al [4] emphasize that approximately two thirds of cases show radiological progression and one third develop clinical symptoms at 5-years follow-up. They also point out that clinical conversion is more likely when cervical cord lesions are present. However, further studies are needed to determine patient stratification and define the role of disease-modifying drugs in RIS.

Race-, sex-, and age-related demographics

MS affects whites more frequently, although other ethnic populations such as Africans, Asians, and Hispanics also can be affected. Even though MS is more common in countries above 40° latitude, it is almost nonexistent in some populations, such as Yakutes, Hutterites, Hungarian Romani, Norwegian Lapps, Australian Aborigines, and New Zealand Maoris.

MS is 2-3 times more common in females than in males.

Most people affected by the disease are diagnosed between ages 20 and 50 years, although children can also be affected.

Preferred examination

MRI is presently considered to be the most sensitive diagnostic imaging modality for revealing demyelinating plaques, as recommended by the Consortium of Multiple Sclerosis Centers. [5] No specific field strength is recommended. Gadolinium is typically favored. MRI shows abnormalities in 95% of patients with clinically definitive MS. [6, 7]

On long TR sequences, MRI scans show areas of demyelination as high-signal areas. Lesions of other etiologies (eg, viral myelitis, acute disseminated encephalomyelitis [ADEM]) may resemble MS plaques and must be considered along with the clinical history and the patient's presenting signs and symptoms. For patient education information, see Multiple Sclerosis.

According to an international group of neurologists and radiologists, the spinal cord MR imaging protocol for MS should include sagittal T1-weighted and proton attenuation, STIR or phase-sensitive inversion recovery, axial T2- or T2-weighted imaging through suspicious lesions, and, in some cases, postcontrast gadolinium-enhanced T1-weighted imaging. [8]

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Computed Tomography

Because computed tomography (CT) scanning has poor sensitivity, the detection, evaluation, and characterization of MS lesions and enhancement patterns are limited with this modality. As a result, with the advancement of MRI, evaluation of the spinal cord using axial CT scanning was abandoned.

On CT scans, large, masslike lesions can occasionally mimic a neoplasm, and characterizing them can be difficult. Primary and secondary neoplasms of the spinal cord (astrocytomas, ependymomas), infection, transverse myelitis, acute infarction, sarcoidosis, and systemic lupus erythematosus may mimic demyelinating MS plaques on CT scans.

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Magnetic Resonance Imaging

MRI far exceeds CT scanning in the ability to demonstrate intramedullary pathology; MRI is currently used for the first-line investigation of spinal MS. [9] Depending on their age, MS plaques appear on unenhanced, T1-weighted images as areas of slightly low to low signal intensity. Spinal plaques may appear as nodules, rings, or arcs and generally are less than 2 vertebral bodies in length. [10] Plaques usually demonstrate prompt enhancement after the administration of a gadolinium-based contrast agent, which most often indicates active disease. [11] The enhancement may last 2-8 weeks. Steroids typically do not suppress the enhancement of the active plaques. Classic chronic lesions do not demonstrate contrast enhancement. (See the image below.)

Sagittal, T1-weighted image following gadolinium c Sagittal, T1-weighted image following gadolinium contrast showing arciform enhancement along the edge of the plaque, typical of demyelination.

Most MS plaques appear hyperintense on T2-weighted images. The spinal cord may or may not be focally enlarged. Enlargement of the cord is usually seen with active disease. Larger active lesions may have extensive edema with associated cord expansion. Chronic lesions often demonstrate focal cord atrophy. Spinal lesions usually coexist with more severe concomitant brain plaques. As many as 20% of spinal MS lesions are isolated. Spinal cord narrowing due to atrophic changes is present in 10% of patients with spinal cord involvement. [12] (See the images below.)

Sagittal, T2-weighted magnetic resonance image of Sagittal, T2-weighted magnetic resonance image of the cervical spinal cord in a woman aged 27 years showing a fusiform area of increased signal intensity representing a multiple sclerosis plaque.
Axial, T2-weighted magnetic resonance image in a w Axial, T2-weighted magnetic resonance image in a woman aged 27 showing a multiple sclerosis plaque located in the left dorsolateral region of the left hemicord.
Sagittal, T2-weighted image showing areas of signa Sagittal, T2-weighted image showing areas of signal hyperintensity in the cervical spinal cord and pons.
Axial, T2-weighted image showing a large area of s Axial, T2-weighted image showing a large area of signal hyperintensity in the right lateral aspect of the cord.
Sagittal, T2-weighted image showing a focal area o Sagittal, T2-weighted image showing a focal area of spinal cord atrophy in a patient with long-standing multiple sclerosis.

Tumefacient MS may mimic a neoplasm; a demyelinating process should always be considered if a masslike lesion is encountered. As is the case in the brain, a ring or arc of enhancement can often be found, as opposed to a more nodular or masslike enhancement. Follow-up studies are helpful.

Although not widely implemented, newer methods may be more specific in evaluating MS plaques. [13] These methods include magnetization transfer and diffusion, as well as proton MR spectroscopy (MRS). [14, 15, 16]

Typically, fast-FLAIR (fluid-attenuated inversion recovery) sequences have been shown to have a lower sensitivity than do fast spin-echo sequences (FSE) for depicting spinal cord MS lesions. [17, 18, 19]

Studies have suggested that more cervical cord MS lesions can be revealed with magnetization transfer–prepared gradient-echo and fast-STIR (short TI inversion recovery) sequences than with FSE sequences, with fast-STIR demonstrating the greatest sensitivity. [18, 20, 21, 22, 23]

In one study, 3.5-mm axial T2-weighted images with full spinal cord coverage showed 22% more lesions in patients with MS compared with 3-mm sagittal scans, especially for lesions with small axial diameters. In the study, 449/509 lesions (88.2%) were detected on 3.5-mm axial scans and 337/509 (66.2%) on 3-mm sagittal scans. Only 277/449 (61.7%) axial lesions were also detected on sagittal images. [24]

Gadolinium-based contrast agents have been linked to the development of nephrogenic systemic fibrosis (NSF), also known as nephrogenic fibrosing dermopathy (NFD). The disease has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or MR angiography (MRA) scans. NSF/NFD is a debilitating and sometimes fatal disease. Characteristics include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of the eyes; joint stiffness with trouble moving or straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness.

Differentials

The main differentials include, but are not limited to, the following:

  • Primary or metastatic spinal cord neoplasms - Eg, astrocytomas, ependymomas
  • ADEM
  • Sarcoidosis
  • Transverse myelitis
  • Infarct
  • Radiation myelitis

Neoplasms

The presence of cysts and hemorrhage support the diagnosis of neoplasm

ADEM

This may show enhancement. The concomitant presence of brain lesions is the rule. ADEM typically runs a monophasic course; therefore, it does not have the relapsing course of MS. A history of viral infection within the previous 3-4 weeks should alert the radiologist.

Sarcoidosis

This involves the CNS in approximately 5% of cases. Concomitant pial involvement is frequently encountered. Enhancement is usually the rule.

Transverse myelitis

This term is usually used for idiopathic inflammatory myelopathy. Cord swelling and enhancement may be present, often involving a longer segment than does MS. MRI of the brain may be helpful for showing additional lesions in case of MS or ADEM. Transverse myelitis usually responds to steroid therapy; therefore, a treatment trial is often considered before proceeding with biopsy. This process is typically monophasic.

Infarct

This is more common at the thoracic level. Usually, only a single lesion is present. Contrast may be present, although this is not the dominant feature. Signal alteration usually and initially involves the anterior gray matter (anterior spinal artery distribution). The patient's clinical presentation will be acute. Particularly consider the possibility of an infarct if the patient is older and/or has a history of aortic/vascular surgery.

Vasculitis

Processes such as systemic lupus erythematosus can result in spinal lesions that mimic MS. Often, multiple lesions are present. However, the clinical history is often known and can help to establish the correct diagnosis.

Radiation myelitis

Generally, doses higher than 4000cGy are required to cause this condition. The latency period is 1-3 years. Chemotherapy may be synergistic. Images may show some peripheral enhancement.

Arteriovenous fistula

Usually, this occurs at the thoracolumbar level, and patients are usually older than 50 years, with a long history of back pain. The cord signal abnormality can involve a very long segment. Look for a serpiginous flow void along the cord surface.

Degree of confidence

Although MRI is not specific, it is considered the most sensitive imaging modality for diagnosing spinal cord MS, for evaluating its extent, and for following up the response to treatment. MRI is more sensitive for identifying active plaques than is double-dose CT scanning or clinical examination.

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