Disc Herniation

Frequently asked questions about Disc Herniation in dog and cat

What is the spinal disc herniation?

Disc herniation is one of the most frequent spinal disorders in the dog and only occasionally found in the cat. It consists in the release of the intervertebral disc from its physiological site and a subsequent compression of the spinal cord.

The intervertebral disc is a fibrocartilaginous structure interposed between the vertebrae of the spine, consisting of a nucleus of a gelatinous substance (core nucleus) and an external fibrous ring. The discs act as bearings that can cushion the stresses and loads of the spine. However, when discs start with degenerating (age-related or breed predisposed) they become particularly fragile and are prone to displacement from their usual location; these conditions often cause disc herniation (Figure 1). Among the most prevalent breeds, we can include the so-called "chondrodystrophic breeds " such as the dachshunds and the French Bulldog, but all the dogs, including crossbreeds, can develop this illness.

Figure 1. Schematic picture of intervertebral disc with herniation, and consequent spine compression.

What are the typical clinical signs of the disc herniation?

The first clinical signs of canine and feline disc herniation are pain and reluctance to move. Clinical worsening may also be rapid (within a few days or even hours). Starting with incoordination of the limbs, weakness (paresis) followed by a complete disappearance of voluntary movement (paralysis).

Figure 2. Schematic sketch of nervous system. Blue lines represent the nervous system, and red cross shown the interruption of nervous impulse in the thoracic-lumbar spine. In this case, neurological signs are shown in hind limbs (red oval).

Clinical signs may involve only the hind limbs or all 4 limbs, depending on where the disc herniation is located. Clinical signs are divided into degrees of gravity, based on the level of neurological deficits.

When the disc herniation originates from the thoracolumbar spine (Figure 2), we will find motor dysfunctions only on the hind limbs, therefore it is a paraparesis or paraplegia. If the hernia involves the cervical spinal cord, neurological deficits will be present on both hind and fore limbs, thus it is a tetraparesis or tetraplegia (Figure 3).

Figure 3. Schematic sketch of nervous system. Blue lines represent the nervous system, and red cross shown the interruption of nervous impulse at cervical spine. In this case, neurological signs are shown in all limbs (red oval).

A very important aspect for the prognosis is the level of neurological deficits. In veterinary neurology, the severity of this pathology is classified in degrees (Table 1).

Table1. Description of the severity level of animals with spinal cord disease.

Level

Clinical signs

Medical therminology

1

“Pain"

Pain at the palpation of the spine, reluctant to move, however, in walking the dog appears coordinated and not weak.

Spontaneous or evoked algia

2

" Badly walking "

Weakness of the legs and incoordination but deambulation ability is maintained.

Ataxia and/or ambulatory paresis

3

“No walking”

Inability to walk but limbs movement are conserved. The animal can walk if just sustained by some person.

Non-ambulatory paresis

4

“Limbs are not moving”

Lack of movement of the limbs, but pain is present.

Plegia with deep pain sensitivity is conserved

5

 “Limbs are not moving and absence of limbs perception”

Lack of movement of the limbs and absence of deep pain.

Plegia and absence of deep pain sensitivity

 

When do you need to call the vet? Hurry up!

Disc herniation is a severe problem. It can cause permanent damage due to the compression that the herniated disc performs on the spinal cord. Clinical signs may start suddenly, with a rapid deterioration, thus the veterinarian specialist should be contacted immediately if any of the cited signs previously described develop. As a rule, the higher  the neurological level, the more urgent the situation is. In grades 3 and 4 it is advisable to refer your dog to the neurologist on the same day, while in grade 5 surgery must be performed within 12-24 hours of the onset of neurological signs. Patients with grades 3, 4 and 5 are not able to urinate autonomously and therefore need assistance to void their bladder.

How is a disc herniation diagnosed?

The diagnosis of canine and feline herniation of the intervertebral disc is based on a proper neurological examination and on the use of advanced diagnostic techniques such as computerized tomography and magnetic resonance imaging. Advanced Diagnostic Examinations are procedures that require general anaesthesia and may therefore require additional tests (i.g. bloodwork, echocardiography and ECG if indicated), in order to allow low risk anaesthesia.

How is disc herniation treated?

Treatment of canine and feline disc herniation depends on the severity of the clinical signs, and on the degree of compression the hernia is causing on the spinal cord. In most cases, surgical treatment is the only option, even if some cases may have an improvement with medical treatment.

  • Conservative treatment: indicated in patients with small hernias and/or with mild neurologic signs (grades 1). It consists of an absolute rest period for at least 30 days, possibly associated with pain relief medication.
  • Surgical treatment: indicated in patients with herniation that causes moderate or severe spinal cord compression (Video 1). The surgical technique varies depending on the type of hernia and location. After surgery, strict rest is imperative, and a period of postoperative hospitalization for few days for pain management, serial neurological evaluation and monitoring for possible complications is recommended.

After the disc herniation surgery, will my pet walk again?

Prognosis to obtain a functional recovery of the limbs and urination depends largely on the diagnosed neurological grade. If surgery was performed before the absence of deep sensitivity of the limbs (grades 1-4), 80% of dogs regain the ability to walk and run independently. However, in grade 5 cases, prognosis is severe; a fast intervention improves chance of recovery and prognosis gradually worsens the longer surgery is postponed. Recovery times varies from patient to patient, and in some cases it is recommended to perform a post-surgical physiotherapy at a specialized clinic.

Video 1. Dachshund with spinal disc herniation, and thoracic-lumbar syndrome with IV grade, before and after neurosurgery. The recovery of hind limbs function is apparent.

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