Dynamic Lumbosacral Magnetic Resonance Imaging in a Dog with Tethered Cord Syndrome with a Tight Filum Terminale

Development of Real-Time Kinematic Magnetic Resonance Imaging (kMRI) Techniques for Studying the Kinematics of the Spine and Joints in Dogs-Preliminary Study on Cadavers

Simple Summary

Many orthopedic and neurological pathologic conditions can potentially lead to or be affected by joint instability. Standard magnetic resonance imaging, as a static technique that examine joints and body parts in functional rest, can underestimate or overlook key diagnostic findings. As a result, kinematic magnetic resonance imaging techniques were developed to evaluate joints and body parts under stress and load conditions or during movement. In human medicine, the real-time acquisition technique is one of the modalities for acquiring kinematic magnetic resonance imaging, and has gained popularity in recent years. This proof-of-concept study was designed to test the feasibility of real-time acquisition techniques in veterinary medicine for the first time. Based on the results of this preliminary cadaveric study, real-time kinematic magnetic resonance imaging may be a feasible and valuable procedure to be applied to the canine cervical spine and stifle joints. Moreover, given the ease of execution and the concise duration of acquisitions, it could be applied in a regular standard protocol MRI with little additional effort, risk, and cost. In this proof-of-concept study, a good visualization of the canine cervical spine and stifle joint was achieved, showing the potential of real-time acquisition techniques for clinical and research applications.

Abstract

Kinematic MRI (kMRI) is a novel human imaging technique that couples the excellent soft tissue contrast and multiplanar capabilities of traditional MRI with kinematic potential. The study’s goals are: (1) testing the feasibility of spinal cord and joints real-time kMRI; and (2) evaluating the quality of these kinematic studies as a new diagnostic option in veterinary medicine. Standard and real-time kinematic MRI were performed on cervical spine, elbow, and stifle joints of seven cadavers. Studies were repeated after a surgical insult aimed to create a certain degree of joint instability. A total of 56 MRI were performed—7 cervical spinal tracts, 3 elbow joints, and 4 stifle joints were examined. The technique was feasible in all the three regions examined. The images were considered of excellent quality for the stifle joint, good to fair for the cervical spine, whereas two of three elbow studies were considered to have unacceptable image quality. Additionally, real-time kMRI provided good to excellent information about stifle instability. Therefore we consider kMRI a promising technique in veterinary medicine. Further studies and an in vivo setting are needed to increase the quality of the kMRI images, and to fully evaluate clinical usefulness.

Translocation of the conus medullaris during dynamic lumbosacral magnetic resonance imaging in dogs

OBJECTIVE

To investigate the change in the lumbosacral angle (ΔLSA) and conus medullaris (CM) displacement in healthy dogs undergoing dynamic MRI with changes in the posture of their pelvic limbs from neutral posture to flexion or extension posture and to evaluate for potential correlation between ΔLSA and CM displacement.

ANIMALS

9 healthy adult Beagles.

PROCEDURES

Dogs underwent dynamic MRI with their pelvic limbs positioned in neutral, flexion, and extension postures. From T2-weighted sagittal midline plane MRI images, 2 observers measured the lumbosacral angle and CM location in duplicate for each posture for each dog. Intra- and interobserver agreement was assessed, and the Spearman rank correlation coefficient (ρ) was used to assess for potential correlation between ΔLSA and CM displacement for changes in pelvic limb posture from neutral to flexion or extension.

RESULTS

Overall, the mean ΔLSA and CM displacement for changes in posture were 23° and 9.09 mm (caudal displacement) for the change from neutral to flexion posture, 8.4° and -2.5 mm (cranial displacement) for the change from neutral to extension posture, and 32.2° and 11.64 mm (caudal displacement) for the change from extension to flexion posture. The ΔLSA strongly correlated (ρ = 0.705; 95% CI, 0.434 to 0.859) with displacement of the CM.

CONCLUSIONS AND CLINICAL RELEVANCE

The use of dynamic MRI, compared with conventional MRI, will better help to characterize clinically normal and abnormal features of the lumbosacral region of the vertebral column and associated spinal cord during postural changes. Further, when limited translocation of the CM is evident on dynamic MRI, veterinarians should suspect underlying lumbosacral pathophysiologic processes or anatomic abnormalities.

Association between filum terminale internum length and pain in Cavalier King Charles spaniels with and without syringomyelia

Background

Lumbar syringomyelia (SM), lumbosacral pain, and more caudal spinal cord termination are reported in Cavalier King Charles spaniels (CKCS). Data are lacking on the clinical relevance of alterations in their spinal cord terminal structures.

Objectives

To compare spinal cord termination level and filum terminale internum length (FTIL) with presence of lumbar SM and clinical signs in CKCS.

Animals

Forty‐eight CKCS.

Methods

In this prospective study, pain was quantified using owner and clinician assessments. Vertebral level of spinal cord and dural sac termination, presence of SM, and FTIL were determined from sagittal magnetic resonance imaging (MRI) sequences. Kappa and intraclass correlation (ICC) analyses determined interobserver reliability. The MRI findings were compared to owner and clinician‐reported pain quantification.

Results

Interobserver reliability was good for spinal cord and dural sac termination (kappa = 0.61 and 0.64, respectively) and excellent for FTIL (ICC: 92% agreement). The spinal cord terminated at 6th lumbar vertebra in 1, 7th lumbar vertebra in 31, and the sacrum in 15 dogs, and termination level was associated with lumbar SM (P = .002) but not clinical signs. Mean FTIL was 2.9 ± 1.08 mm; it was associated with owner‐reported pain (P = .033) and spinal palpation scores (P = .023). Painful CKCS without SM had shorter FTIL compared to normal CKCS and painful CKCS with SM (P = .02).

Conclusions

Painful CKCS without SM have decreased distance between the termination of the spinal cord and dural sac, suggesting a shorter FTIL. More caudal spinal cord termination is associated with development of lumbar SM.

Comparison of inherited neural tube defects in companion animals and livestock

Neural tube defects (NTDs) are congenital malformations resulting from the improper or incomplete closure of the neural tube during embryonic development. A number of similar malformations of the protective coverings surrounding the central nervous system are also often included under this umbrella term, which may not strictly fit this definition. A range of NTD phenotypes exist and have been reported in humans and a wide range of domestic and livestock species. In the veterinary literature, these include cases of anencephaly, encephalocele, dermoid sinus, spina bifida, and craniorachischisis. While environmental factors have a role, genetic predisposition may account for a significant part of the risk of NTDs in these animal cases. Studies of laboratory model species (fish, birds, amphibians, and rodents) have been instrumental in improving our understanding of the neurulation process. In mice, over 200 genes that may be involved in this process have been identified and variant phenotypes investigated. Like laboratory mouse models, domestic animals and livestock species display a wide range of NTD phenotypes. They remain, however, a largely underutilized population and could complement already established laboratory models. Here we review reports of NTDs in companion animals and livestock, and compare these to other animal species and human cases. We aim to highlight the potential of nonlaboratory animal models for mutation discovery as well as general insights into the mechanisms of neurulation and the development of NTDs.

Canine Degenerative Lumbosacral Stenosis: Prevalence, Impact And Management Strategies

Canine degenerative lumbosacral stenosis (DLSS) is a syndrome of low back pain with or without neurologic dysfunction associated with compression of the cauda equina. Most commonly occurring in medium- to large-breed dogs of middle to older age, German shepherd and working dogs are predisposed. Diagnosis is based on a combination of clinical signs, advanced imaging and ruling out other differential diagnoses. The volume of the intervertebral foramina at the lumbosacral junction is naturally reduced on extension but degenerative changes lead to a more marked reduction that can impinge the L7 nerve roots. Evidence is lacking on which to base decision-making for treatment of dogs with DLSS. However, surgical intervention may be indicated in dogs that do not respond to conservative management, or for dogs in which there is a requirement to work that prevents lifestyle adjustments. Improvements in electrodiagnosis and novel intra-discal treatments may improve the management of DLSS in the future.

Morphometric analysis of spinal cord termination in Cavalier King Charles Spaniels

BACKGROUND

There is an association between Chiari malformations, syringomyelia (CMSM) and tethered cord syndrome (TCS) in people, suggesting Cavalier King Charles Spaniels (CKCS) with CMSM could also have TCS. Currently there are no data on the position of the caudal spinal cord structures in CKCS.

OBJECTIVE

To describe and compare location of spinal cord termination in CKCS with weight-matched controls and to examine the relationship between SM and spinal cord termination.

ANIMALS

Thirty-nine CKCS and 33 controls with thoracolumbar MRIs; 34 of 39 CKCS also had cervical MRIs.

METHODS

Blinded retrospective study. Spinal cord and dural sac termination were determined from T2-weighted sagittal and transverse images and half-Fourier acquisition single-shot turbo spin echo sequences. Intra-observer reliability was determined using kappa analysis. Presence of SM was compared with location of spinal cord and dural sac termination.

RESULTS

Intra-observer reliability was moderate for identifying spinal cord termination (Kappa = 0.6) and good for dural sac termination (Kappa = 0.8). The spinal cord terminated at lumbar vertebra 6 (L6) in 1, 7 (L7) in 22, and sacrum in 16 CKCS versus 9 at L6, 23 at L7, 1 at sacrum in controls. Spinal cord (P < .001) and dural sac (P = .002) termination were significantly more caudal in CKCS compared to controls. The presence of thoracolumbar SM was associated with more caudal dural sac termination in CKCS (P = .03).

CONCLUSIONS AND CLINICAL IMPORTANCE

The relationship between TL SM and possible spinal cord tethering because of a more caudal dural sac termination should be investigated.