Intervertebral Disc Disease

TL;DR. Intervertebral Disc Disease (IVDD) is a common, painful spinal condition where a herniated disc presses on the spinal cord, causing symptoms ranging from mild back pain to complete paralysis.

A cross-section showing how a herniated disc presses directly on the spinal cord.

What is it?

Intervertebral Disc Disease (IVDD) is a degenerative condition affecting the shock-absorbing cushions, or discs, that sit between the bones of the spine (vertebrae). Each disc consists of two main parts: a tough, fibrous outer ring called the annulus fibrosus, and a soft, gelatinous center called the nucleus pulposus. In a healthy animal, these discs allow the spine to bend, flex, and absorb the impact of daily activities like running, jumping, and walking.

When IVDD occurs, these discs undergo degenerative changes that compromise their structural integrity. This degeneration typically leads to one of two types of herniation, historically classified as Hansen Type I and Hansen Type II:

• Hansen Type I (Acute Extrusion): This type involves a sudden rupture of the disc. The gelatinous center of the disc dehydrates, mineralizes, and hardens over time. Under normal physical stress, this hardened center suddenly erupts through the outer fibrous ring, shooting directly into the spinal canal. This causes acute bruising, inflammation, and compression of the spinal cord.
• Hansen Type II (Slow Protrusion): This type is a slower, more progressive bulging of the disc. The outer fibrous ring gradually thickens and protrudes upward into the spinal canal over months or years, slowly compressing the spinal cord. This type is more akin to a bulging disc in humans.

Regardless of the type, the resulting pressure on the spinal cord disrupts the transmission of nerve signals between the brain and the rest of the body. This leads to severe pain, loss of coordination, and, in severe cases, permanent paralysis. While predominantly diagnosed in dogs, IVDD can also occur in cats, though it is far less common in the feline population.

Causes & risk factors

The primary driver of IVDD is genetic predisposition, particularly in chondrodystrophoid breeds—dogs bred for short legs and long bodies. In these dogs, abnormal cartilage development causes the intervertebral discs to age and degenerate prematurely, often within the first year of life.

As noted in a leading veterinary internal medicine reference:

"With normal aging the nucleus is gradually replaced by fibrocartilage. In some dogs, particularly the chondrodystrophoid breeds, the nucleus matrix degenerates, dehydrates, and mineralizes, making these dogs prone to acute disk rupture."
— Internal Medicine, p. 1087

While genetics play the largest role, physical trauma, repetitive strain from jumping off high furniture, and obesity also contribute to disc failure. Excess body weight places continuous, abnormal mechanical stress on the spinal column, accelerating the wear and tear on already vulnerable discs.

Signs to watch for

The clinical signs of IVDD depend on the location of the affected disc (usually the neck or the mid-to-lower back) and the severity of the spinal cord compression. Symptoms can appear suddenly or progress gradually over several weeks.

• Spinal pain (Cardinal) – Your pet may shiver, whimper, tense their abdominal muscles, or cry out when touched or picked up.
• Ataxia (Common) – An uncoordinated, wobbly, or "drunken" gait, particularly in the hind limbs.
• Tetraparesis (Common) – Weakness in all four limbs, which typically indicates a disc herniation in the neck (cervical spine).
• Neck pain (Common) – Reluctance to turn the head, holding the head low, or muscle spasms in the neck.
• Arched back (Common) – A hunched posture (kyphosis) as the animal attempts to relieve pressure on the spinal cord.
• Proprioceptive deficits (Common) – Knuckling over on the paws, where the pet stands on the tops of their toes because they cannot sense where their feet are in space.
• Paraparesis (Common) – Weakness in the hind limbs only, indicating a disc issue in the mid-to-lower back (thoracolumbar spine).
• Root signature (Occasional) – Holding up a single leg in pain, which occurs when a herniated disc presses directly on a nerve root. This is often mistaken for a leg injury.
• Paralysis (Occasional) – Complete loss of voluntary motor function in the limbs.
• Loss of deep pain perception (Occasional) – The inability to feel a deep, painful pinch on the toes. This is a critical neurological emergency.

An arched back (kyphosis) is a common sign of spinal pain in dogs with IVDD.

How vets diagnose it

Your vet will begin with a comprehensive physical and neurological examination. During this exam, they will assess your pet's reflexes, check their conscious proprioception (paw-flipping test), and carefully palpate the spine to locate the source of pain. This helps the vet determine the general area of the spinal cord lesion.

To obtain a definitive diagnosis, advanced imaging is required:

• Survey Radiographs (X-rays): While standard X-rays cannot show the spinal cord or soft disc material, they are useful for ruling out other conditions like spinal fractures, infections, or bone tumors. They may also show narrowed disc spaces or calcified discs.
• Magnetic Resonance Imaging (MRI): This is the gold standard for diagnosing IVDD. It provides highly detailed images of the spinal cord, nerves, and surrounding soft tissues. As detailed in veterinary literature:

"MRI is the best diagnostic method for localizing the site and the side of extruded disks with nearly 100% accuracy... MRI also allows evaluation of the cord parenchyma for injury and edema, which may be associated with prognosis for recovery in patients with loss of deep pain sensation."
— Internal Medicine, p. 1089

• Computed Tomography (CT): CT scans are highly effective, particularly when the extruded disc material has calcified. It is faster than MRI but provides less detail regarding internal spinal cord damage.
• Myelography: This older technique involves injecting a contrast dye around the spinal cord before taking X-rays. It has largely been replaced by MRI and CT due to the risk of side effects, but it may still be used if advanced imaging is unavailable.

Treatment options

Treatment for IVDD is categorized into conservative (medical) management and surgical intervention. The choice depends on the severity of the neurological signs, the level of pain, and how long the symptoms have been present.

Conservative Management

Conservative management is typically reserved for pets with mild neurological deficits (such as mild weakness or knuckling) and those who still have intact pain sensation.

1. Strict Crate Rest: This is the most critical component of medical management. Your pet must be confined to a small crate or pen for 4 to 6 weeks. This strict confinement prevents further movement of the spine, allowing the torn outer ring of the disc to heal and scar over. Physical activity must be limited strictly to short, leashed walks solely for elimination purposes.
2. Medical Therapy: Your vet will prescribe medications to manage pain and reduce inflammation. These commonly include:
   • Glucocorticoids (Corticosteroids): Used to reduce severe inflammation and swelling around the compressed spinal cord.
   • Methocarbamol (Muscle Relaxants): Prescribed to alleviate painful muscle spasms along the spine.
   • Pain Relievers: Non-steroidal anti-inflammatory drugs (NSAIDs) or other analgesics may be used instead of steroids (they must never be given together due to the risk of severe gastrointestinal ulceration).

Surgical Decompression

Surgery is indicated for pets with severe neurological deficits, progressive worsening of symptoms despite medical therapy, or recurrent episodes of spinal pain. The most common procedure is a hemilaminectomy (for back discs) or a ventral slot (for neck discs). During surgery, the veterinary surgeon removes a portion of the vertebral bone to access the spinal canal and carefully extracts the herniated disc material, relieving the pressure on the spinal cord.

Following surgery, intensive physical rehabilitation—including passive range-of-motion exercises, laser therapy, and underwater treadmill therapy—is highly beneficial to help the pet regain strength and coordination.

Prognosis

The prognosis for pets with IVDD is highly dependent on their neurological status at the time of presentation, particularly whether they can still feel deep pain.

For dogs with intact deep pain sensation, the prognosis is generally good to excellent, with an 80% to 95% success rate for recovery, whether treated conservatively or surgically. However, if a pet has lost deep pain sensation, the prognosis drops significantly. In these cases, conservative management yields less than a 10% success rate, while prompt surgical decompression offers approximately a 64% chance of recovery.

If the spinal cord undergoes a rare but devastating process called progressive myelomalacia, the prognosis becomes hopeless. As described in veterinary texts:

"In approximately 10% of dogs presenting for rapid-onset complete paralysis and loss of deep pain perception, focal spinal cord damage and edema result in spinal cord ischemia and progressive myelomalacia of the cord cranial and caudal to the original lesion (i. e. , ascending descending)"
— Internal Medicine, p. 1092

Myelomalacia is the progressive dying of spinal cord tissue. It is irreversible, painful, and ultimately fatal as it ascends to the nerves controlling respiration.

For feline patients, long-term prognosis data is limited due to the rarity of the condition in this species. However, clinical guidance is extrapolated from canine protocols, and recovery rates similarly depend on the severity of the initial spinal cord injury.

MRI is the gold standard for identifying the exact location of disc herniation.

Prevention

While you cannot change your pet's genetics, you can take steps to minimize the risk of disc herniation:

• Weight Control: Keep your pet at a lean, healthy weight to reduce mechanical stress on the spine.
• Use a Harness: Walk your dog on a harness rather than a collar to distribute pressure away from the neck.
• Avoid Jumping: Install ramps or steps next to beds, couches, and vehicles to prevent your pet from jumping from high surfaces.
• Avoid High-Impact Activities: Limit activities that involve twisting or sudden twisting jumps, such as catching frisbees or balls mid-air.

There are currently no reliable genetic screening tests available to predict which individual dogs will develop clinical IVDD, making lifestyle management the primary line of defense.

When to call your vet

IVDD can progress rapidly. If your pet shows any of the following signs, contact your veterinarian immediately. Treat these as emergencies:

• Sudden loss of the ability to walk or stand.
• Knuckling of the paws or dragging the hind legs.
• Severe, unmanageable spinal pain (shivering, crying out, or refusing to move).
• Loss of bladder or bowel control.

Delaying treatment, especially once a pet has lost the ability to walk, can significantly reduce the chances of a successful recovery.

For specific breeds

Chondrodystrophoid breeds are highly predisposed to Hansen Type I IVDD. These include the Dachshund, Basset Hound, Beagle, [Cardigan Welsh Corgi](/p/breeds/cardiganwelshcorgi_dog), Welsh Corgi, Chihuahua, Chinese Shar-Pei, Shar Pei, Lhasa Apso, Pekingese, Shih Tzu, Toy Poodle, and Miniature Schnauzer.

Non-chondrodystrophoid breeds, such as the Doberman Pinscher, Dalmatian, Rottweiler, [English Cocker Spaniel](/p/breeds/englishcockerspaniel_dog), Cocker Spaniel, Staffordshire Bull Terrier, German Shepherd Dog, Labrador Retriever, and Border Collie, are more prone to the slowly progressive Hansen Type II IVDD.

Additionally, a highly specific hereditary spinal condition occurs in young Shiloh Shepherds:

"A similar syndrome with degeneration and bony proliferation of multiple thoracolumbar articular facets causing spinal cord compression has been reported as a hereditary condition in 4- to 10-month-old Shiloh Shepherds."
— Internal Medicine, p. 1099

If you own one of these predisposed breeds, maintaining a lean body weight and implementing spinal safety measures early in life is highly recommended.

Sources

• Internal Medicine, 5th Edition, pages 1087, 1089, 1092, 1099.

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