Changes

==Introduction==

==Introduction==

[[File:Intervertebral disc degeneration.jpg|200px|right|thumb|Intervertebral disc degeneration (Courtesy of Bristol Biomed Image Archive)]]

[[File:Intervertebral disc degeneration.jpg|200px|right|thumb|Intervertebral disc degeneration (Courtesy of Bristol Biomed Image Archive)]]

The term ''''Intervertebral Disc Disease'''' ('''IVDD''') refers to several pathological processes involving the intervertebral discs. It is common in the '''dog''', and the type of degeneration of the disc is normally related to the breed of dog. Although any disc in the [[Spinal Column - Anatomy & Physiology|spinal column]] may be affected it is normally the '''cervical, thoracic or lumbar discs''' that are affected as they are less supported by surrounding structures.  

The term ''''Intervertebral Disc Disease'''' ('''IVDD''') refers to several pathological processes involving the intervertebral discs. It is common in the '''dog''', and certain breeds of dog have a genetic predisposition to early-onset IVDD. Any disc in the [[Spinal Column - Anatomy & Physiology|spinal column]] may be affected with the most prevalent clinical signs resulting from lesions in the '''cervical, thoracic or lumbar discs'''.

==Hansen Type I==

==Hansen Type I==

In '''[[Chondrodysplasia|chondrodystrophic breeds]]''' such as the '''dachshund''' and the '''bassett hound''', the [[Spinal Column - Anatomy & Physiology|nucleus pulposus]] undergoes '''chondroid degeneration'''. This is normal in these breeds and changes such as '''[[Mineralisation - Pathology|mineralisation]]''' are normally apparent in more than one disc by the time the dog is one year old. However '''extrusion''' of the degenerate nuclei can occur at any point, causing '''acute''' [[Spinal Cord - Anatomy & Physiology|spinal cord]] '''trauma'''. The initial impact of the nucleus causes '''contusion''' of the spinal cord, and the extruded nucleus continues to '''compress''' the cord. This is known as '''Type I (Hansen) IVDD'''.  

In '''[[Chondrodysplasia|chondrodystrophic breeds]]''' such as the '''dachshund''' and the '''bassett hound''', the [[Spinal Column - Anatomy & Physiology|nucleus pulposus]] undergoes '''chondroid degeneration'''. These breeds are genetically predisposed to such pathology and changes such as '''[[Mineralisation - Pathology|mineralisation]]''' are normally apparent in more than one disc by the time the dog is one year old. The abnormal disc may bulge, chronically impinging on the ventral cord and producing slow onset of clinical signs. However dorsal '''extrusion''' of the degenerate nucleus pulposus - which ruptures through the annulus fibrosis into the spinal canal - can occur at any point, causing '''acute''' [[Spinal Cord - Anatomy & Physiology|spinal cord]] '''trauma'''. The initial impact of the nucleus causes '''contusion''' of the spinal cord, and the extruded nucleus continues to '''compress''' the cord. This is known as '''Type I (Hansen) IVDD'''.  

Type I IVDD most commonly occurs in '''small and [[Chondrodysplasia|chondrodystrophic breeds]]''', but it can occur in any dog. It is most likely to occur in '''young to middle-aged''' dogs. Clinical signs are '''acute''' in onset. Neurolocalisation will depend on which disc is affected but the classic signs are a T3-L3 myelopathy (the most common localisation) are '''a non-ambulatory pelvic limb para-paresis, poor paw placement and the presence of withdrawal and patellar reflexes'''.  

Type I IVDD most commonly occurs in '''small and [[Chondrodysplasia|chondrodystrophic breeds]]''', but it can occur in any dog. It is most likely to occur in '''young to middle-aged''' dogs. Clinical signs are '''acute''' in onset. Neurolocalisation will depend on which disc is affected but the classic signs are a T3-L3 myelopathy (the most common localisation) are '''a non-ambulatory pelvic limb para-paresis and poor paw placement (proprioception)'''. Withdrawal reflexes may be absent or abnormal, deep pain perception may be absent, and patellar reflexes  may be absent or abnormal (e.g. crossed extensor reflex) dependent on the location and severity of the lesion.

* '''Cervical discs''' - neck pain is the most common clinical sign, paresis is less common as there is more space in the vertebral canal at this point, so compression is less severe.

* '''Cervical discs''' - neck pain is the most common clinical sign, paresis is less common as there is more space in the vertebral canal at this point, so compression is less severe.

* '''Thoracolumbar discs''' - paresis and ataxia are the most common clinical signs.

* '''Thoracolumbar discs''' - pelvic limb paresis and ataxia are the most common clinical signs.

* '''Lumbosacral discs''' - pelvic limb lameness and pain and incontinence are the most common clinical signs.

* '''Lumbosacral discs''' - pelvic limb lameness, spinal pain and urinary incontinence are the most common clinical signs.

==Hansen Type II ==

==Hansen Type II ==