Canine Intervertebral Disc Disease

Original Editor - Ansi van der Walt Top Contributors - Jess Bell, Tarina van der Stockt, Kim Jackson, Rucha Gadgil and Lucinda hampton

Introduction

IVDD more common in eg Dachshunds

Intervertebral disc disease (IVDD) is the most common spinal condition in canine patients. It occurs most often in the thoracolumbar region. There is no gender predisposition, but certain dogs are more predisposed to IVDD, particularly chondrodystrophic breeds (i.e. short-legged phenotype).

The most common presenting breeds are: dachshund, pug, bull dog, bassett, pekinese, lhasa apso, shih tzu, beagle, poodle, cavalier King Charles spaniel and boston terrier.

Dogs are usually affected when they are aged between three and six years. If a predisposed breed presents with spinal pain, IVDD must be considered in a differential diagnosis. The overall prevalence of disc herniation in dogs is two percent, but between 19 and 24 percent of dachshunds present with clinical signs of IVDD during their lifetime.

There are two types of IVDD:

• Hansen Type I: Intervertebral disc extrusion
  • This is an acute disease process caused by the extrusion of disc material (i.e. the nucleus pulposus) through a tear in the annulus and into the vertebral canal. This causes cord and / or nerve root compression. It is usually associated with chondroid degeneration and is more common in young and middle-aged chondrodystrophic breeds
• Hansen Type II: Intervertebral disc protrusion
  • This chronic process occurs secondary to tearing of the annulus fibrosus, which results in bulging of the disc dorsally and compression of the spinal cord. It is usually associated with fibroid degeneration. In contrast to Type I, it tends to occur in older non-chondrodystrophic dogs (i.e. dogs aged over 7 years). Breeds commonly affected include labrador retrievers and german shepherds

Various imaging techniques have been used to identify IVDD in dogs including radiographs, myelography, CT and MRI:

• Radiographs, while unable to identify disc prolapses or disc extrusions, can identify disc calcifications and spondylitic changes around the vertebra. They can also exclude other potential causes of disc pain
• Myelography allows evaluation of compressive lesions of the spinal cord and can be used to evaluate and identify disc extrusions and protrusions. It has, however, largely been replaced by cross-sectional imaging in areas where CT and MRI are available
• MRI is a more advanced imaging technique that allows better evaluation of areas of disc pathology and the spinal cord itself. It is considered the gold standard for IVDD imaging

Key Features

66 to 87 percent of dogs present with thoracolumbar intervertebral disc herniation and 12.9 to 25.4 percent present with cervical disc herniation. Older dogs have a higher incidence of cervical disc disease.

Cervical Spine

• Commonly produces only neck pain without major loss of nerve function to the limbs - this may be because the cervical vertebral column has a larger vertebral canal / spinal cord ratio
• Unilateral or bilateral lameness (caused by lower cervical nerve root compression) is reported in 15 to 50 percent of cases
• This is one of the few conditions that can cause dogs to vocalise pain during sudden movements or when they are picked up
• Patients adopt a stiff gait
• They often refuse to flex or extend their neck to eat and adopt a low head and neck carriage
• In severe cases, ataxia (front and / or hind limbs) and loss of ambulation can occur

Thoracolumbar Spine

Thoracolumbar IVDD causes varying degrees of pain and neurological deficits (mild paraparesis to paraplegia). Characteristic gait abnormalities begin to develop and progress, usually in the following order. The dog:

1. Starts to refuse to do 'normal activities' (e.g. avoids jumping onto couch, walks and usual games)
2. Develops an ataxic gait (has variable weakness, refuses / is unable to walk or stand
3. Has complete loss of motor function (bladder and bowel function are usually also lost)
4. Has a loss of deep pain

Treatment

Conservative management of IVDD can be considered if:

• There is no neurological fallout
• Cord compression is mild
• Nerve root compression is the primary finding

Treatment will focus on pain management, combined with cage rest or strict confinement at home to help prevent further disc extrusion.

A multi-drug approach is typically used:

• Muscle relaxants such as diazepam, anti-inflammatory medications (non–steroidal) and NDMA receptor antagonists, such as gabapentin, have been found to be effective
• Steroids may initially be used to reduce inflammation, but their use should be limited to between 2 and 4 days before they are replaced with non-steroidal medications

Treatment should be continued for a month after all pain has been controlled. If conservative management fails, or if there is neurological fallout, then surgery is warranted (ventral slot decompression for cervical IVDD; hemilaminectomy with fenestration for thoracolumbar decompression).

Supportive Care for Neurological Patients

A key treatment objective is to prevent or mitigate secondary complications. It is imperative that decubitus ulcers, urine scalding, and infection are prevented / managed.

Bedding

• Immobile and non-ambulatory patients must be provided with adequate bedding
• Ideally, bedding should be smooth, stable, nonporous (or easily cleaned and replaced), and deformable
• It should be checked frequently (sometimes as often as hourly) for soiling. Bedding that is wet with water, urine, faeces or discharge needs to be replaced immediately

Because the patient’s skin may require frequent cleaning, gentle products that will not disrupt the protective epidermal layer should be used. Patients that are not yet able to hold themselves in a sternal position, or who preferentially lie on one side should be turned every 4 to 6 hours.

Harnesses

Harnesses assist in lifting heavy patients and support mobility until the patient regains sufficient strength and coordination to be independently ambulatory. They should be constructed of a durable yet soft, lightweight, and breathable material. Edges should be smooth or padded to prevent rubbing / pinching of the skin and catching of the fur.Click on this link to view different walking accessories.

Booties

Patients with reduced / absent proprioception and sensory capacity are more likely to develop skin lesions. These range from hair loss and abrasions to full thickness wounds on the digits and bony prominences of the lower limbs. They may be caused by pressure necrosis, scuffing on the ground, or self-mutilation. Abrasions can quickly progress to full thickness lesions and may become infected.

The toes and distal limbs can be protected from trauma with the use of bandages or commercial booties. These should fit securely but not constrict the thin, soft tissue layers of the extremities. It is, however, important to note that the use of booties can be problematic. Booties that provide adequate protection to the skin may also limit sensory input to the distal limb, which can potentially hinder proprioceptive signalling. Moreover, the weight of the bootie may complicate locomotion in dogs with weakness (e.g. weak hock flexion secondary to sciatic neuropathy or weak carpal extension secondary to radial nerve palsy). Many patients will object to the feel of the booties or be inclined to chew at the unfamiliar article. It is, therefore, important to consider these issues when selecting a bootie.

Bladder Management

Many patients with spinal cord disease also have bladder and urethral dysfunction. There should be continuous monitoring for signs of urinary tract compromise. If the patient is unable to initiate or complete micturition, the bladder needs to be manually expressed. Bladder management may also be facilitated with the use of medications.

Owners of canine patients managed as outpatients should be advised to watch for any change in the frequency or amount of urine production, changes in colour or odour, and the presence of blood, fibrin or mucus. Even when there are no outward signs of infection, routine monitoring is recommended (i.e  urine cultures every 4 weeks to 3 months for as long as the dog remains non-ambulatory). This is especially important for dogs participating in hydrotherapy.

Faecal Incontinence

Faecal incontinence is a frequent challenge, but medical management options are limited. Appropriate sanitation and nursing care (as described above) are the primary management goals. Commercially available dog nappies can be used. Neonatal nappies can also be adapted for use.

Physiotherapy Management

The goals of physiotherapy management are to:

• Prevent secondary complications
• Promote neurorecovery
• Maximise function by maintaining and strengthening all innervated muscle groups and facilitating functional patterns of activity
• Support and educate the patient, carers, family and staff

Physiotherapy should start as soon as patients are medically stable and can tolerate the required treatment intensity. There are no evidence-based guidelines for IVDD rehabilitation protocols in dogs. Management has, therefore, been adapted from human clinical guidelines:

• Standing
  • Soft Tissue Effects : Standing has been found to result in reduced muscle tone and improved range of motion or muscle length. This may be of most value for canine patients who have hip flexor or adductor spasticity
  • Bone Health Effects: High frequency standing that is introduced soon after injury and maintained can significantly reduce bone demineralisation in human patients with spinal cord injury
  • Exercise Effects:  Standing helps to improve postural control, strengthen the antigravity muscles, enhance balance reactions and maintain functional range of movement. It can also help to enhance skill acquisition during gait retraining. This is most easily achieved by supporting the dog in standing with its hind limbs placed in a functional position (e.g. while the dog is eating). This can be progressed to more challenging positions as the dog’s strength increases, such as placing the dog’s front feet on a slightly raised surface

• Gait training should include conventional overground walking, supported by body weight–supported treadmill training (or underwater treadmill training) where possible
• Functional electrical stimulation

When the patient has pain, any diagnosis of neuropathic pain must be informed by the patient's complete patient history, as well as a physical examination using the International Spinal Cord Injury Pain (ISCIP) Classification System. It is essential to screen for Red Flags to help identify any serious underlying conditions that may cause, aggravate or mimic neuropathic pain.

• Acute or chronic nociceptive pain can be visceral or musculoskeletal (or other nociceptive pain):
  • Visceral pain may arise from trauma, disease or inflammation of the viscera
  • Musculoskeletal pain may arise from trauma, disease or inflammation of the musculoskeletal system
• Neuropathic pain can occur above, at or below the level of injury:
  • Above-level neuropathic pain is not exclusive to SCI and may occur secondary to complex regional pain syndromes or peripheral nerve injury
  • At-level neuropathic pain may occur secondary to trauma to the spinal cord or nerve roots
  • Below-level neuropathic pain also occurs secondary to trauma to the spinal cord

Therapeutic Interventions for IVDD

Spasticity and Contracture Management

• Manual Stretching
• Weight Bearing (standing)
• Vibration (low frequency—5—50Hz)

Gait Training

It is suggested that whole body vibration increases tone in functional positions (50 - 100Hz). It appears to be safe and well-tolerated. It may also improve muscle oxygenation and the patient’s body awareness during treatment.

Treadmill training (including underwater treadmill training) provides an opportunity for dogs to repetitively practise walking. It has been found that the repeated activation of sensorimotor pathways during task-specific training may reinforce the circuits and synapses needed to complete the task at hand.

A harness can be used for patients who have significant functional limitations. Harnesses provide the opportunity to grade the amount of body weight support provided. In the case of underwater treadmill walking, the dog's weight is supported by the buoyancy in water. Therapists help to facilitate alternating stepping and weight-bearing.

Balance Training

Balance training focuses on providing more challenging positions and surfaces.

Pain Management

• Physical modalities such as TENS, heat and cold
• Soft tissue techniques such as massage
• Specific strengthening and stretching exercises
• Graded exercise or activity programmes
• Hydrotherapy
• Education on activity pacing

Exercise Guidelines

It has been found that human adults with SCI should engage in:

• 20 minutes of moderate to vigorous intensity aerobic exercise 2 x per week AND 3 sets of strength training exercises for each major functional group at a moderate to vigorous intensity 2 x per week to achieve cardiorespiratory and muscle strength benefits
• 30 minutes of moderate to vigorous intensity aerobic exercise 3 x per week for cardiometabolic health

These guidelines can be carried over to canine patients. Fitting canine patients with a wheelchair can help them to reach this level of activity:

• Canine wheelchairs can only be worn for short periods at a time (i.e. 20 to 40minutes), so they are not a solution for all-day mobility
• Wheelchairs can only be used under supervision
• Wheelchairs should be well-fitting to reduce pressure areas and musculoskeletal strain

Hydrotherapy is also a practical way of maintaining cardiovascular fitness in non-ambulant of poorly-ambulating patients.