Cervical Spondylomyelopathy - Exploring the Diagnosis and Complexities

1. What makes cervical spondylomyelopathy a challenging diagnosis?

Cervical spondylomyelopathy (CSM), often referred to as ‘wobbler disease’, is a multifactorial condition affecting the cervical spine in larger breed dogs – resulting in progressive compression of the spinal cord and nerve roots. Morphologic and biomechanical abnormalities of the cervical spine have been classified as either Disc-Associated Wobbler Syndrome (DAWS) or Osseous Associated Wobbler Syndrome (OAWS).

Dobermans are predisposed to DAWS, but the disease can also occur in breeds such as Labradors and Dalmatians. Great Danes and Basset Hounds can be predisposed to OAWS. DAWS involves protrusion of one or more degenerative cervical discs into the spinal canal, usually affecting C5-6 and C6-7, causing compression of the spinal cord or nerve roots. In OAWS the spinal cord is compressed as a result of malformation and proliferation of the osseous boundaries of the spinal canal (facets and neural arch). In both presentations, the spinal cord can be compressed chronically without major symptoms and then a minor incident can trigger deterioration, manifested as cervical pain (nerve root compression) or ataxia (spinal cord compression), which can progress to para or tetra-paresis / plegia.

Post-mortem sample of a vertebra and an MRI scan of intervertebral disc protrusions

(A) A post-mortem sample of a vertebra affected by osseous compression of the spinal canal (OAWS). (B) Sagittal plane T2-weighted MRI scan of intervertebral disc protrusions at C5-6 and C6-7 (DAWS).

 

2. Why is advanced imaging crucial for an accurate diagnosis?

Survey radiography is not sufficient for the diagnosis of either DAWS or OAWS. MRI scans are considered fundamental to elucidate the degree of spinal cord impingement. Dynamic MRI imaging can be performed to investigate if a disc protrusion causes more compression in extension (dynamic) or if the degree of compression reduces when traction is applied to the neck (traction-responsive). A high-powered scanner which allows variable positioning is essential. CT scans optimally illustrate osseous margins and are important for measurement if surgery using implants is planned.

MRI sagittal and transverse images of intervertbral disc protrusion

Images A-F are T2-weighted MRI sagittal and transverse images of a C6-7 intervertebral disc protrusion in a five-year-old Doberman affected by DAWS illustrating three different positions.
A,B Neutral; B,C Hyperextended; E, F Traction.

The spinal cord is more compressed in hyperextension and less compressed when traction is applied. Note the increased signal intensity within the cord due to vasogenic oedema, gliosis and/or malacia. This may not resolve even after surgical treatment.

 

Author: Dr. Noel Fitzpatrick

Link: https://www.fitzpatrickreferrals.co.uk/blog/2019/07/cervical-spondylomyelopathy-exploring-the-diagnosis-and-complexities-of-wobbler-disease/?utm_source=linkedin&utm_campaign=nfpatient&utm_medium=social

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