Degenerative lumbosacral stenosis (DLSS) is the most common cause of compression of the cauda equina and seventh lumbar (L7) nerve roots in dogs. DLSS is characterised by lumbosacral (LS) intervertebral disc (IVD) protrusion, subluxation or inflammation of the facet joints with associated thickening of the joint capsule and hypertrophy of the interarcuate ligament. The lumbosacral joint is the most mobile functional spinal unit (FSU) in dogs. Pathological static or dynamic alteration in load transmission across the L7-S1 joint is thought to be the most common contributor to lumbosacral intervertebral disc degeneration in dogs. A common sequel to disc-associated DLSS is impingement of the nerve roots or vasculature of the cauda equina and/or L7 nerveroots, either by the disc itself or by secondary inflammatory, fibrous or osseous impingement. Abaxial disc protrusion and spondylosis can be a significant cause of pain and lameness in large breed dogs whilst lower motor neuron deficits are much less common in our case population in the UK.
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