SPINAL SURGERY and DISC DISEASE
The most common spinal surgery performed in the dog is for intervertebral disc disease.
Intervertebral disc disease is the most common spinal disease in dogs and is increasingly recognised in cats. The intervertebral discs (IVD) are fibrocartilaginous cushions between the vertebrae (except the first 2 cervical vertebrae) that allow movement, are supportive and act as shock absorbers. They consist of a fibrous outer rim, the anulus fibrosis, and a jelly like centre, the nucleus pulposus. IVD degeneration results in diminished shock-absorbing capacity, and can ultimately lead to IVD herniation and spinal cord compression. The types of IVD herniation are often described as Hansen type I (nucleus pulposus degeneration and extrusion) and Hansen type II (anulus fibrosis degeneration and protrusion).
What are the clinical signs of disc disease?
The most common sign is pain localised to the back or neck. Apart from yelping, common signs of spinal pain are abnormal posture (e.g. hunched back with head down), shivering, panting, unwillingness to move and difficulty jumping / doing stairs. In more severe cases there may be difficulty walking - ranging from poor control of the hindlimbs to complete paralysis. Most severe cases have a paralysed bladder and may be unable to urinate and / or dribble urine. The most severe cases are paralysed, have lost bladder function and have lost the ability to feel painful sensations.
How is disc disease diagnosed?
Disc disease may be strongly suspected on the basis of clinical signs especially in predisposed breeds however diagnostic imaging is required to confrim the diagnosis. Spinal radiographs (x-rays) may reveal characteristic changes of disc disease e.g. calcified disc material within the vertebral canal or narrowing of the IVD space or the foramen however radiographs rarely provide the accurate conformation and localisation required for surgical management. In some cases myelography is recommended. This is a radiograph where a contrast agent (i.e. similar to dye) is put into the space surrounding the spinal cord so that the outline of the spinal cord can be appreciated.
At Stone Lion veterinary centre we predominantly use MRI for the diagnosis of spinal cord problems. This is less invasive for the animal and provides more information for diagnosis and surgical planning.
Degenerate and Calcified IVD in a Lucas terrier
Lateral spinal radiograph and myelogram demonstrating a L1/L2 disc extrusion in a Dachshund (arrow)
Standard Dachshund with a disc extrusion
Gadolinium Enhanced T1W Dorsal MRI of the spinal cord in a 5 year old Dachshund.
The spinal cord is compressed by a large disc extrusion (arrow)
T1W Sagittal MRI of the lumbosacral area in a 10 year old male Border Collie.
The caudal equina nerves are impinged by a lumbosacral disc protrusion (arrow).
Do you have to operate?
Many cases will do well when managed conservatively (see below) however in cases with paralysis the prognosis is better with surgery i.e. the dog or cat is more likely to regain walking function and be pain free; is more likely to improve quickly; and is less likely to have recurrences. Cases where pain sensation is absence (i.e. when the toe is pinched hard but the dog or cat is unaware of discomfort) are a surgical emergency and have a poor prognosis for improvement.
What is conservative management for disc disease?
Conservative management has the advantage that it is comparatively inexpensive and avoids surgery. The most important aspect is restriction of movement i.e. cage or crate confinement. This limits further IVD extrusion and exacerbation of the injury. The animal’s natural healing process can then repair the damage to the spinal cord. Pain relief should be given as necessary however the animal must be restricted otherwise they can exacerbate the injury. For pain relief the author prefers to use licenced NSAID analgesics in combination with opioids. The author avoids corticosteroids for treating IVD disease.
Conservative management is indicated for patients with pain only or for those with mild deficits although there may be success with more severe case. Dogs which have lost pain sensation are a surgical emergency and are extremely unlikely to respond to conservative management. Disadvantages of conservative management include a higher rate of recurrence of clinical signs and a higher chance of deterioration or persistent neurological deficits. In addition diagnostic tests may not be performed so the animal may be receiving inappropriate treatment. A protocol for conservative management is detailed below.
What does the surgery involve?
There are two categories of disc surgery. The easiest and one that does not require specialised equipment is fenestration. In this procedure the nuclei pulposus of T11/T12 to L3/L4 (in the case of a thoracolumbar disc extrusion) or all the cervical intervertebral spaces (in the instance of cervical disc disease) are removed through a small window in the anulus fibrosis. This is a prophylactic procedure limiting further disc extrusions. The disc material within the vertebral canal is not removed and if the dog has severe spinal cord compression then the neurological recovery will be prolonged and/or there will be residual neurological deficits. At Stone Lion Veterinary Centre fenestrations are usually done in combination with a decompressive technique (below).
The second type of surgery is decompressive i.e. the extruded disc material is removed from the vertebral canal. This surgery is more technically difficult and requires specialised equipment and training. The type of decompressive surgery performed depends on the site of the problem. In the neck a ventral approach is favoured (ventral slot) and a window is drilled through the vertebral bodies. For the thoracolumbar spine, the most common procedure is a hemilaminectomy, where entry into the vertebral canal is made from the side, directly above the disc space and the vertebral foramen. For lumbosacral problems a dorsal laminectomy is used where the “roof” is taken off the vertebral canal allowing direct visualisation of the cauda equina and the lumbosacral disc.
How long does spinal surgery for disc disease take?
1-3 hours - depending on the complexity of the procedure
What sort of aftercare is there?
At the Stone Lion Veterinary Centre spinal patients receive physiotherapy from trained veterinary nurses and from chartered physiotherapists. When the pet discharged from Stone Lion Veterinary Centre the owner is taught how to perform any ongoing physiotherapy and / or the animal will continue to have sessions with the physiotherapist.
Physiotherapy plays a vital part in the treatment of animals with spinal cord disease.
Inactivity and recumbency results in decreased joint movement and muscle contracture. To prevent this, the joints are passively exercised and each muscle group massaged
When can my dog go home after spinal surgery?
The average hospital stay is 5 days after surgery. Patients are discharged when no longer requiring injectable pain killers and, for most cases, when they able to urinate voluntarily and starting to show signs of recovery
How long before my paralysed dog will walk again?
This is very variable - typically recovery occurs several weeks. Some cases improve more quickly and, sadly, in some cases there is no improvement. The success rate of spinal surgery at Stone Lion Veterinary Centre is ~ 90%.
Are there any solutions if my dog does not regain a functional walking ability?
Some dogs continue to enjoy life in carts however a limiting factor can be bladder control. Many patients paraplegic after spinal injury have to have their bladder emptied manually or they have an automatic bladder (i.e. involuntarily empties when full like a baby)
Freddy lost the use of his hindlimbs following a disease called degenerative myelopathy. However this didn’t stop him enjoying a full life
Chondrodystrophic dogs (characteristically have disproportionably short limbs) for example the Bassett Hound, Dachshund, Lucas terriers, Sealyhams and Shih Tzus are predisposed to intervertebral disc disease
Intraoperative view of removal of a dermoid sinus – a cyst associated with the skin and attached to the spinal cord.
Frequently asked questions
Will the problem recur?
If the spinal surgery has been successful then it is unusual for there to be a problem with the same disc. However there may be a problem with other remaining degenerate discs - limited follow up studies have suggested a recurrence rate of 6-13% with Dachshunds being more at risk of recurrence. If possible other “at risk” IVD are fenestrated at the original surgery to reduce the risk of recurrence.
How common is disc disease in Dachshunds?
A Finnish study (Lappalainen and others) looked at 124 randomly selected miniature dachshunds, representing 4.5% of the population and found calcified discs in 75.9% of the longhaired miniature dachshunds and in 86.7% of the wirehaired ones. The occurrence of signs associated with IVD was 16.5% in longhaired and 15.6% in wirehaired miniature dachshunds. The occurrence of signs of IVD in dogs with calcified discs was 20.0% and 17.9% in longhaired and wirehaired miniature dachshunds, respectively.
Reference: Lappalainen A, Norrgård M, Alm K, Snellman M, Laitinen O. Calcification of the intervertebral discs and curvature of the radius and ulna: a radiographic survey of Finnish miniature dachshunds Acta Vet Scand. 2001;42(2):229-36
Is disc disease inherited?
The Lucas Terrier club has become concerned about a number of the breed developing intervertebral disc disease. After consulting Dr Clare Rusbridge it was proposed that they would recommend an (unproven) protocol used by Danish and Finnish Dachshund clubs (for more information click here). In this scheme radiographs are obtained of the dog’s spinal – specifically regions C1-C7 and T11-L7. If the dog has no or one calcified intervertebral discs it is considered to be ‘fit for breeding’.
A Danish study looked at the inheritance of disc calcification in the dachshund. A strong correlation was found in the occurrence of disc calcification between offspring and mean parent (P < 0.001) and between offspring and dams (P < 0.005) on an either/or scale. Statistically significant estimates of heritability of 0.60 and 0.87 were found based on the offspring-sire relationship using the total score and three-class scale, respectively. Higher correlation estimates were found based on the dam-offspring relationship than based on the sire-offspring relationship, suggesting an effect of maternal environmental factors
Reference: Jensen VF, Christensen KA. Inheritance of disc calcification in the dachshund. J Vet Med A Physiol Pathol Clin Med. 2000 Aug;47(6):331-40.
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Why does the disc have early degeneration in chondrodystrophic dogs?
IVD degeneration is thought to occur because of loss of notochordal cells which produce proteoglycans which “hold water” in the disc. Chondrodystrophic dogs (characteristically have disproportionably short and curved limbs), for example the Bassett Hound, Dachshund, Lucas terriers, Sealyhams and Shih Tzus, are predisposed to intervertebral disc disease. This is due to a primary deficiency of notochordal cells associated with being chondrodystrophic. Research found that large notochordal cells in the nucleus pulposus of chondrodystrophoid dogs formed 13% of the cell population in young dogs and fell to 0.4% in adults, whereas they were the predominant cell type in the nonchondrodystrophoid dogs at all ages (Cappello and others 2006). Thus chondrodystrophoid dogs suffer early degenerative changes in the disc and a concomitant reduction in proteoglycan content, increased collagen, and loss of water content making the discs likely to herniate (Cappello and others 2006). When discs of chondrodystrophic dogs degenerate they also calcify making the discs visible on radiographs. The consequence of disc herniation is pain and in more severe cases there may be difficulty walking - ranging from poor control of the hindlimbs to complete paralysis. Very severe cases may develop myelomalacia (spinal cord rot) and die.
In addition to be predisposed to IVD herniation because of chondrodystrophism, these dogs may have an increased likelihood because of other conformational changes eg a long back (Dachshund) or a comparatively heavy head (Bassett Hound).
Reference: Cappello R, Bird JL, Pfeiffer D, Bayliss MT, Dudhia J.Notochordal cell produce and assemble extracellular matrix in a distinct manner, which may be responsible for the maintenance of healthy nucleus pulposus. Spine. 2006 Apr 15;31(8):873-82; discussion 883.