Felis ISSN 2398-2950

Magnetic resonance imaging: spine

Synonym(s): MRI

Contributor(s): Ruth Dennis, Fraser J McConnell, Laurent Garosi

Introduction

  • MRI Magnetic resonance imaging: basic principles is the best imaging modality for investigation of many spinal diseases, due to its multiplanar imaging capability (cross-sectional images can be obtained in any plane) and the high resolution of the resulting images Spine: cervical thoracic normal anatomy (sagittal T2W) MRI  Spine: cranial L2 disk normal anatomy (transverse T2W) MRI  Spine: thoracic normal anatomy (dorsal T2W) MRI .
  • CT Computed tomography (CT) is also helpful, but soft tissue contrast is poorer, and images in the sagittal and dorsal planes may require reformatting from the transverse plane.

Advantages of MRI over myelography and CT 

  • It is non-invasive, as no subarachnoid injection of contrast medium is required.
  • It can differentiate types of spinal cord swelling, eg solid and cystic.
  • It will show lesions which do not produce a mass effect and which therefore are not seen on myelography Radiography: myelography.
  • It detects early disk degeneration and other soft changes in the disk space, such as diskospondylitis Diskospondylitis.
  • Acquisition of images in the transverse plane Spine: cranial L2 disk normal anatomy (transverse T2W) MRI provides a dimension that cannot be assessed radiographically.
  • Spinal nerves can be seen.
  • The investigation is often quicker than myelography, dependant on scanner type, and is physically easier as no repositioning of the patient is needed.
  • If the clinical signs are multifocal, the brain can easily be scanned at the same time.
  • Paraspinal soft tissues can be assessed for involvement in pathology.
  • MRI provides superior contrast resolution than CT and is better suited for imaging soft tissues, such as the spinal cord, nerve roots, and intervertebral disks.

Disadvantages of MRI compared with myelography and CT

  • It is more expensive, and is often not immediately available for acute cases requiring urgent surgery.
  • Localization of lesions with respect to the meninges may be harder, eg differentiation of extradural and intradural lesions.
  • Stressed and traction views are more difficult; in particular, stressed views which may compress the cord further cannot be justified because of the length of time for which the position must be maintained.
  • There is reduced fine bone detail compared with radiography, and periosteal new bone is hard to see (although medullary and subchondral bone changes are better demonstrated).
  • Whole spine screens can take a long time.
  • CT provides superior spatial resolution and is better suited for imaging bone.
  • Thinner slice acquisition (submillimeter) is possible with CT.
  • CT is cheaper to buy, requires fewer maintenance requirement and associated expenses as well as rapidity of imaging.
  • CT can be used to successfully guide needle aspirations or biopsies once a lesion is localized, but this is not generally done with MRI guidance because of prolonged imaging times and inability to use metal implements for tissue sampling.
  • Interpretation requires considerable experience, and false positive diagnoses are easy to make.
  • Resolution may be inadequate for some small cats.

Restraint and positioning

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Scanning procedure

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Normal appearance

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Pathology

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • De Risio L (2015) A review of fibrocartilaginous embolic myelopathy and different types of peracute non-compressive intervertebral disc extrusions in dogs and cats. Front Vet Sci 2, 24 PubMed.
  • Rylander H, Eminaga S, Palus V et al (2014) Feline ischemic myelopathy and encephalopathy in secondary to hyaline arteriopathy in five cats. J Feline Med Surg 16 (10), 832-839 PubMed.
  • Palus V, Volk H A, Lamb C R et al (2012) MRI features of CNS lymphoma in dogs and cats. Vet Radiol Ultrasound 53 (1), 44-49 PubMed.
  • da Costa R C, Samii V F (2010) Advanced imaging of the spine in small animals. Vet Clin Small Anim 40 (5), 765-790 PubMed.
  • Gonçalves R, Platt S R, Llabrés-Díaz F J et al (2009) Clinical and magnetic resonance imaging findings in 92 cats with clinical signs of spinal cord disease. J Feline Med Surg 11 (2), 53-59 PubMed.


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