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==Introduction==

==Introduction==

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 affects 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 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.  

=Hansen Type I IVDD=

==Hansen Type I==

In '''[[Chondrodysplasia|chondrodystrophic breeds]]''' such as the '''dachshund''' and the '''bassett hound''', the [[Spinal Column - Anatomy & Physiology|nucleus propulsus]] 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'''. 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'''.  

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 localistaion) are '''a non-ambulatory pelvic limb para-paresis, poor paw placement and the presence of withdrawl 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, poor paw placement and the presence of withdrawal and patellar reflexes'''.  

* '''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''' - 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 and pain and incontinence are the most common clinical signs.

=Hansen Type II IVDD=

==Hansen Type II ==

'''Type II IVDD''' is more common in '''older, large breed dogs''' such as the German Shepard Dog. IVDD type II involves '''fibroid degeneration of the [[Spinal Column - Anatomy & Physiology|nucleus propulsus]]''' and '''protrusion of the [[Spinal Column - Anatomy & Physiology|annulus fibrosis]]'''. Over time the fibroid tissue in the disc is replaced by '''collagenous tissue'''. At the same time '''hypertrophy''' of the surrounding '''annulus''' occurs, causing '''progressive compression of the spinal cord'''. Mineralisation of the discs is rare.  

'''Type II IVDD''' is more common in '''older, large breed dogs''' such as the German Shepard Dog. IVDD type II involves '''fibroid degeneration of the [[Spinal Column - Anatomy & Physiology|nucleus pulposus]]''' and '''protrusion of the [[Spinal Column - Anatomy & Physiology|annulus fibrosis]]'''. Over time the fibroid tissue in the disc is replaced by '''collagenous tissue'''. At the same time, '''hypertrophy''' of the surrounding '''annulus''' occurs, causing '''progressive compression of the spinal cord'''. Mineralisation of the discs is rare.  

Clinical signs are normally '''insidious''' but the dog may present acutely. It is common for the dog to only show signs of '''dynamic compression''' of the spinal cord, for example when jumping. As the onset of disease is normally '''gradual''' and '''progressive''', so clinical signs are normally less severe on presentation. These include:   

Clinical signs are normally '''insidious''' but the dog may present acutely. It is common for the dog to only show signs of '''dynamic compression''' of the spinal cord, for example when jumping. As the onset of disease is normally '''gradual''' and '''progressive''', so clinical signs are normally less severe on presentation. These include:   

* Restlessness and panting

* Restlessness and panting

=Fibrocartilagenous Embolic Myelopathy ([[Embolism|FCE]])=

==Fibrocartilagenous Embolic Myelopathy (FCE)==

This '''vascular''' disease most is typically seen in '''young medium to large breed dogs''' but it can occur in any dog or cat. It occurs when a '''[[Embolism|fibrocartilagenous emboli]]''' causes an '''[[Infarction|infarction]] of the [[Spinal Cord - Anatomy & Physiology|spinal cord]] parenchyma'''.  

This '''vascular''' disease is typically seen in '''young medium to large breed dogs''' but it can occur in any dog or cat. It occurs when a '''[[Embolism|fibrocartilagenous embolus]]''' causes an '''[[Infarction|infarction]] of the [[Spinal Cord - Anatomy & Physiology|spinal cord]] parenchyma'''.  

It is typically '''peracute''' in onset and clinical signs are '''non-progressive''', with a classic history of a dog jumping for a toy, yelping, and collapsing with paresis. The disease is '''non-painful''' as no pain receptors are present in the spinal cord '''parenchyma'''.

It is typically '''peracute''' in onset and clinical signs are '''non-progressive''', with a classic history of a dog jumping for a toy, yelping, and collapsing with paresis. The disease is '''non-painful''' as no pain receptors are present in the spinal cord '''parenchyma'''.

='Explosive Disc'=

=='Explosive Disc'==

Explosive disc is the '''low volume, high velocity traumatic extrusion of the normal nucleus propulsus'''. This causes an '''non-compressive contusion injury to the spinal cord'''. The signalment, clinical signs and history are normally similar to FCE, with the dog presenting with a non-progressive paresis of peracute onset.  

Explosive disc is the '''low volume, high velocity traumatic extrusion of the normal nucleus pulposus'''. This causes a '''non-compressive contusion injury to the spinal cord'''. The signalment, clinical signs and history are normally similar to FCE, with the dog presenting with a non-progressive paresis of peracute onset.  

=Diagnosis=

==Diagnosis==

A thorough '''history, clinical exam and neurological exam''' should be performed on presentation. The neurological exam should reveal the '''severity and neuro-localisation''' of the disease. Motor function, proprioception, spinal reflex arcs, the location of spinal pain and most importantly the presence or absence of conscious pain perception can provide an overall picture of location and severity.

A thorough '''history, clinical exam and neurological exam''' should be performed on presentation. The [[Neurological Examination - Dog & Cat|neurological exam]] should reveal the '''severity and neuro-localisation''' of the disease. Motor function, proprioception, spinal reflex arcs, the location of spinal pain and most importantly the presence or absence of conscious pain perception can provide an overall picture of location and severity.

Once this has been achieved imaging modalities can be used to further localise and classify the lesion.  

Once this has been achieved imaging modalities can be used to further localise and classify the lesion.  

* '''Presence of disc material in the spinal canal'''

* '''Presence of disc material in the spinal canal'''

Radiographs are normally taken when the animal in '''anaesthatised''' to allow appropriate positioning. '''Lateral and VD views''' should be taken. Should these radiographs fail to demonstrate the full extent of the lesion, a '''CSF sample''' should be taken to provide more information.  

Radiographs are normally taken when the animal in '''anaesthetised''' to allow appropriate positioning. '''Lateral and ventrodorsal views''' should be taken. Should these radiographs fail to demonstrate the full extent of the lesion, a '''[[Cerebral Spinal Fluid - Anatomy & Physiology|CSF]] sample''' should be taken to provide more information.  

===Myelography===

===Myelography===

Myelography involves injection of '''non-ionic contrast medium''' into the '''subarachnoid space''', which '''outlines the spinal cord'''. It should be performed in all cases which showed no clear signs on survey radiographs, cases where the survey radiographs do not match the clinical signs, cases where the extent of the lesion in unknown and any potentially surgical cases. The procedure should be performed under general anaesthesia - often the animal will be moved directly to theatre following myelography. Myelography can identify the lesion and confirm IVDD:

Myelography involves injection of '''non-ionic contrast medium''' into the '''subarachnoid space''', which '''outlines the spinal cord'''. It should be performed in all cases which showed no clear signs on survey radiographs, cases where the survey radiographs do not match the clinical signs, cases where the extent of the lesion is unknown and any potentially surgical cases. The procedure should be performed under general anaesthesia - often the animal will be moved directly to theatre following myelography. Myelography can identify the lesion and confirm IVDD:

'''1) Extradural'''

'''1) Extradural''' - The contrast medium bulges towards the cord - this is the sign you would expect to see in Type I and II IVDD.

The contrast medium bulges towards the cord - this is the sign you would expect to see in Type I and II IVDD.

'''2) Intramedullary''' - The contrast lines are further pushed apart by an intramedullary lesion. This pattern is seen with FCE. Common differentials are neoplasia and spinal cord oedema.

'''3) Intradural-extramedullary''' - The contrast medium surrounds the lesion in these cases, producing a fork-shape in the contrast line. This is most commonly caused by a nerve root tumour.

 

 

'''3) Intradural-extramedullary'''

 

The contrast medium surrounds the lesion in these cases, producing a fork-shape in the contrast line. This is most commonly caused by a nerve root tumour.

===MRI===

===MRI===

MRI is the '''gold-standard''' for identifying IVDD, however it is generally only available in '''referral hospitals''' and is very expensive.

MRI is the '''gold-standard''' for identifying IVDD, however it is generally only available in '''referral hospitals''' and is very expensive.

=Treatment=

==Treatment==

With '''Type I IVDD''' you may consider '''immediate referral'''. Providing there are no cost constraints, performing '''prompt surgery''' to relieve the pressure on the spinal cord results in an '''improved prognosis''' and specialist refferal units are equipped to do this. '''Conservative treatment''' may be considered if signs are '''mild''' (presence of peen pain) and '''non-progressive''', if performing surgery is against the owners wishes or there are significant '''cost constraints'''. '''Type II IVDD''' is treated in the same way as type I but as clinical signs are less acute, a rapid decision about the choice of treatment is rarely necessary.   

With '''Type I IVDD''' you may consider '''immediate referral'''. Providing there are no cost constraints, performing '''prompt surgery''' to relieve the pressure on the spinal cord results in an '''improved prognosis''' and specialist referral units are equipped to do this. '''Conservative treatment''' may be considered if signs are '''mild''' (presence of mild pain) and '''non-progressive''', if performing surgery is against the owners wishes or there are significant '''cost constraints'''. '''Type II IVDD''' is treated in the same way as type I but as clinical signs are less acute, a rapid decision about the choice of treatment is rarely necessary.   

===Surgery===

===Surgery===

The surgical procedure performed depends on the location of the lesion. The procedure performed on a '''thoracolumbar lesion''' is a '''hemilaminectomy'''. A '''ventral slot''' is performed on '''cervical lesions'''. Generally a fenestration is made in the vertebral canal and the extruded disc material is cooped out to relieve pressure on the spinal cord. Prophylactic laminectomies may be performed on unaffected discs to prevent recurrence.

The surgical procedure performed depends on the location of the lesion. The procedure performed on a '''thoracolumbar lesion''' is a '''hemilaminectomy'''. A '''ventral slot''' is performed on '''cervical lesions'''. Generally a fenestration is made in the vertebral canal and the extruded disc material is cooped out to relieve pressure on the spinal cord. Prophylactic laminectomies may be performed on unaffected discs to prevent recurrence.

Post-operatively it is essential that the dog is placed on a program of '''strict cage rest and physiotherapy''' for a minimum of '''6 weeks'''. NSAIDs may also be given.

Post-operatively, it is essential that the dog is placed on a program of '''strict cage rest and physiotherapy''' for a minimum of '''6 weeks'''. [[NSAIDs]] may also be given.

===Conservative Treatment===

===Conservative Treatment===

The aims of conservative treatment are to; allow the '''extruded disc material time to dissipate''', relieving pressure on the spinal cord and; to allow the '''dorsal annulus to heal''', preventing further extrusion of disc material. This involves '''strict cage rest for a minimum of 6 weeks''', very short '''lead walk''' and '''physiotherapy'''. NSAIDs may also be given.  

The aims of conservative treatment are to:

:allow the '''extruded disc material time to dissipate''', relieving pressure on the spinal cord  

:allow the '''dorsal annulus to heal''', preventing further extrusion of disc material.

This involves '''strict cage rest for a minimum of 6 weeks''', very short '''lead walk''' and '''physiotherapy'''. NSAIDs may also be given.  

FCE and 'explosive disc' are non-progressive the appropriate treatment is '''supportive care''' (management of the recumbent animal), '''time''' and '''physiotherapy'''.  

FCE and 'explosive disc' are non-progressive and the appropriate treatment is '''supportive care''' (management of the recumbent animal), '''time''' and '''physiotherapy'''.  

Steroid treatment is now contraindicated in acute spinal trauma.  

Steroid treatment is now contraindicated in acute spinal trauma.  

=Prognosis=

==Prognosis==

Prognosis for IVDD type I depends on the '''severity and duration of clinical signs and the treatment options'''. If '''[[Sensory Pathways - Anatomy & Physiology|deep pain''' sensation]] is present and surgery is performed immediately then prognosis is good. Prognosis worsens the longer deep pain is absent - prognosis is grave with a loss of deep pain longer than 48 hours.

Prognosis for IVDD type I depends on the '''severity and duration of clinical signs and the treatment options'''. If '''[[Sensory Pathways - Anatomy & Physiology|deep pain''' sensation]] is present and surgery is performed immediately then prognosis is good. Prognosis worsens the longer deep pain is absent - prognosis is grave with a loss of deep pain longer than 48 hours.

RVC staff (2009) '''Nervous System and Special Senses''' RVC Integrated BVetMed Course, ''Royal Veterinary College''

RVC staff (2009) '''Nervous System and Special Senses''' RVC Integrated BVetMed Course, ''Royal Veterinary College''

[[Category:Joints - Degenerative Pathology]]

[[Category:Joints - Degenerative Pathology]]

[[Category: To Do - Siobhan Brade]]

[[Category:Neurological Diseases - Dog]]

[[Category:To Do - Manson review]]

[[Category:Expert Review - Small Animal]]