Intervertebral disk disease is a common neurologic condition in dogs. It is the process of IVD degeneration followed by protrusion or extrusion of disk material into the vertebral canal with focal compression of the spinal cord or adjacent nerve roots and attendant vascular structures.1 The clinical signs associated with IVDD range from spinal hyperesthesia to hind limb ataxia, nonambulatory hind limb paraparesis, and complete hind limb paralysis with or without loss of deep pain perception, together with various degrees of loss of sensory and motor function.2,3 Dachshunds are 12.6 times as likely to develop IVDD as any other breed of dog.4 Priester5 reported that 49% (3,898/8,117) of dogs with IVDD were Dachshunds; in another report,6 Dachshunds comprised 24.5% of the breeds affected by IVDD. The incidence of IVDD among high-risk dog breeds peaks between 4 and 6 years of age.5 The thoracolumbar junction (vertebral bodies T11 through L2) is the area most commonly affected by disk extrusion or protrusion; in dogs evaluated at Auburn University between 1952 and 1975, 1,718 of 2,620 of all disk protrusions and extrusions occurred in this anatomic region.7
Surgery is recommended in most IVDD-affected dogs that have marked and deteriorating neurologic signs.8 For surgical candidates, specialized diagnostic imaging procedures are undertaken to confirm focal extradural cord compression and to anatomically localize and characterize the extent of the lesion. The imaging findings enable the surgeon to limit access to the appropriate portion of the cord and to approach the lesion in the least invasive manner.9–11 Myelography and computed tomography have been used for spinal cord assessment but with specific limitations. Myelography provides an outline of the spinal cord but does not definitively reveal the nature of the pathologic change and can be unreliable in the presence of severe spinal cord swelling or epidural hemorrhage.12 Compared with MR imaging, computed tomography is claimed to be more versatile but provides relatively limited soft tissue definition. It has been recommended that computed tomography or MR imaging is used instead of myelography for assessment of the vertebral column in dogs.13
Magnetic resonance imaging is frequently used in the veterinary field for assessment of suspected neurologic conditions. The principal advantage is enhanced soft tissue imaging with 3-dimensional delineation of lesions. This imaging technique is noninvasive and safe for the patient. In humans, it has been proven to be the method of choice for imaging the nervous system.14–16 There are a number of reports12,17-24 describing the clinical application of MR imaging in dogs. Of these studies, some have assessed clinically normal vertebral columns,21,25–29 whereas others have assessed degenerative changes in IVDs.23,29 Magnetic resonance imaging has been reported17–19,21,23,24,28 to be a reliable diagnostic tool for IVDD in dogs and cats.
In a retrospective study28 of 40 dogs of different breeds that had IVDD and for which MR imaging and subsequent decompressive surgery had been performed, the MR imaging findings correlated with surgical observations with regard to localization and degree of disk material dispersion. Dispersed disk material was described as material that had lost contact with the originating IVD space, whereas nondispersed material retained contact with the disk space. In that study,28 there was complete agreement between the MR imaging and surgical findings with regard to left, right, or central positioning of the EIDM.
To our knowledge, there are no published prospective studies of dogs with TLIDE that have determined the accuracy of MR imaging findings; no comparison between the size and localization of the extruded material as determined via MR imaging and findings at the time of surgery has been reported. Seemingly, no study has compared different MR imaging sequences to determine which, if any, is the most accurate for assessment of the size of the extruded material. Similarly, we are not aware of any published case series to describe the MR image appearance of TLIDE in dogs and standardize findings with respect to breed, duration of clinical signs, first-time event, and anatomic location of disk extrusion. The purpose of the study reported here was to evaluate the accuracy of specific MR imaging sequences in determining the site, lateralization, and extent of EIDM, compared with surgical findings, in Dachshunds with TLIDE. Our hypotheses were that estimates of extent and location of extruded IVD material obtained via MR imaging do not differ from measurements obtained during surgery and that no differences exist among T1weighted, T2-weighted, and STIR sequences with regard to determination of the length of EIDM.
Intervertebral disk disease
Extruded intervertebral disk material
Thoracolumbar intervertebral disk extrusion
Short tau inversion recovery
Balanced-turbo field echo
Time to echo
Time to repetition
Philips Gyroscan Intera T15, Eindhoven, The Netherlands.
Domitor, Novartis, Kempton Park, Gauteng, South Africa.
Intraval sodium, Merial, Halfway House, Gauteng, South Africa.
Lactated Ringer's solution, Adcock Ingram Cirical Care, Johannesburg, Gauteng, South Africa.
Augmentin, Aspen, Pharmacare, Johannesburg, Gauteng, South Africa.
Rimadyl, Pfizer Animal Health, Sandton, Gauteng, South Africa.
Stata 8.2, StataCorp, College Station, Tex.
NCSS 2004, NCSS, Kaysville, Utah.
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