29. Diseases of the intervertebral disc. Diseases of the thoraco- lumbar vertebrae. Discospondylitis Spondylosis deformans. DISH. Fractures, luxation and neoplasia. Aetiology, symptoms, diagnosis and therapy.

What are the two main parts of an intervertebral disc (IVD)?

Annulus fibrosus and nucleus pulposus

What is the main disease of the intervertebral discs?

Intervertebral Disc Disease (IVDD)

What happens to the IV disc in degenerative disc disease?

Degeneration and herniation, leading to spinal cord/nerve/nerve root compression

Which regions of the spine are most commonly affected by IVD disease?

Cervical and thoracolumbar

What are the different types of disc herniation?

1. Bulging: nucleus pulposus causes a bulge by stretching intact annulus fibrosus. No herniation

2. Protrusion/Prolapse: discal mass bulges into vertebral canal; herniation. Annulus and nucleus remain intact

3. Extrusion: nucleus has broken through the annulus into the epidural space. Herniation

4. Sequestration: part of the nucleus pulposus is discontinuous with the native disc

What is the pathogenesis of IVD degeneration?

Progressive dehydration of the nucleus pulposus

What are some clinical signs of IVD disease?

Depends on the location

1. Cervical

   1. severe neck pain, altered stiff gait, lowered head carriage, neck/muscle shoulder spasms, neuropathic pain in forelimb, paresis/paralysis (worse in hind limbs)

2. Thoracolumbar

   1. neck and back pain, “sawhorse” back, hindlimb paresis with altered proprioception, with/out urinary incontinence

What are the two types of disc degeneration according to Hansen?

Hansen I (chondroid metaplasia) and Hansen II (fibrous metaplasia)

Which breeds are typically affected by Hansen I disc degeneration?

Chondrodystrophic breeds (Dachshund, Beagle). Young.

What is the pathogenesis of Hansen I IVDD?

Dehydration of the disc → granulation and mineralisation of the nucleus pulposus → annulus fibrosus degenerates & loses its capacity to contain nucleus → extrusion → acute spinal cord compression → severe neurological signs (paralysis of extremities)

What are the radiographic features of Hansen I disc degeneration?

Soft tissue radiopacity (mineralisation) in the nucleus pulposus (instead of radiolucent). Can be focal (central zone of nucleus), Ring-like (periphery of nucleus) or involve whole nucleus.

Which breeds and age groups are typically affected by Hansen II disc degeneration?

Older, non-chondrodystrophic breeds (Doberman) and cats

What is the pathogenesis of Hansen II IVDD?

Desiccation of nucleus pulposus → fibrous nuclear material, usually not mineralised → protrusion/prolapse of disc into the spinal canal → spinal cord compression

What are the radiographic features of Hansen II disc degeneration?

Desiccated, fibrous, usually non-mineralised nucleus pulposus, disc bulging

How is IVD disease diagnosed?

MRI, X-ray, myelography, neurological examination, history (breed)

What are the treatment options for IVD disease?

1. Conservative: strict confinement, pain relief (not NSAIDs), muscle relaxer, rehab

2. Surgical: Fenestration (removal of nucleus pulposus, not extruded disc material) or Decompression by ventral slot or hemilaminectomy (removal of extruded disc material from vertebral canal)

What are the radiographic features of IVD disease?

1. Narrowing of disc space and articular process joint space

2. Small IV foramen

3. Increased opacity of IV foramen

4. Extruded, mineralised disc material within vertebral canal.

5. Mineralisation of IVD

What type of lesion is seen on myelography in IVD disease?

Extradural

What are examples of diseases of the thoraco-lumbar vertebrae?

1. Discospondylitis

2. Spondylosis deformans

3. Diffuse Idiopathic Skeletal Hyperosteosis (DISH)

4. Fractures

5. Luxation

6. Neoplasia

What is discospondylitis?

Bacterial infection of the intervertebral disc, vertebral endplates, and vertebral bodies → progressive bone lysis & proliferation occurring ventral & lateral to IV spaces

Which bacteria is most commonly involved in discospondylitis?

Staphylococcus

Which dogs are most commonly affected by discospondylitis?

Older, large dogs

Where does the infection in discospondylitis originate?

1. Spread from another system (urinary, prostate)

2. Local infection in disc space

What are the clinical signs of discospondylitis?

Progressive, non-specific; back/neck pain, reluctance to walk, stiff gait, proprioceptive deficits, lethargy, pyrexia, inappetence, lameness

How is discospondylitis diagnosed?

X-ray (bone proliferation/lysis, vertebral sclerosis, narrowed IV space), MRI, CT, FNA + culture

What are the treatment options for discospondylitis?

1. Conservative: Long-term antibiotics, pain relief (codeine), cage rest, physiotherapy

2. Surgery: remove affected bone (if deteriorating neurologically)

What is spondylosis deformans?

Presence of osteophytes along the edges of vertebral bodies, forming bridges

Where is spondylosis deformans most commonly seen?

T9-T10 and L7-S1

Which dogs are most commonly affected by spondylosis deformans?

Older dogs

What are the clinical signs of spondylosis deformans?

Often asymptomatic; stiff back, pain

How is spondylosis deformans diagnosed?

X-ray, spinal MRI

What are the treatment options for spondylosis deformans?

Analgesics, surgery (to remove spurs)

What is DISH?

Diffuse Idiopathic Skeletal Hyperostosis

What characterises DISH?

Hyperostosis (excessive bone growth) forming flowing ossification along the ventrolateral aspect of vertebrae

Which regions of the spine are most commonly affected by DISH?

Thoracic and lumbar

Which breed is most commonly affected by DISH?

Boxers

What are the clinical signs of DISH?

Often asymptomatic; reduced spinal flexibility → decreased agility/mobility, rarely painful nerve compression

How is DISH diagnosed?

X-ray, MRI, CT

What are the treatment options for DISH?

NSAIDs/corticosteroids, analgesics, surgery (severe cases to reduce nerve compression)

Where are spinal fractures most common?

Vertebral body

What are the common causes of spinal fractures?

Trauma

What radiographic view is crucial for spinal fracture assessment?

Horizontal beam radiography

What are some radiographic signs of spinal fractures?

Abnormal spinal alignment, narrowed IV disc space, distorted shape

How do compression fractures appear radiographically?

Smaller and more radiopaque vertebrae

What is luxation?

Displacement of a bone from a joint with or without fracture

What diagnostic tool is helpful in suspected spinal luxation/subluxation?

Myelography. May not be visible on every view.

What are the most common spinal tumours?

Meningioma and lymphoma

Are primary or secondary spinal tumours more common?

Primary brain tumours are more common than spinal cord/peripheral nerve tumours

What are examples of neuroepithelial tumours?

Astrocytoma, oligodendroglioma

What are examples of secondary tumours of the spine?

Nephroblastoma, osteosarcoma, fibrosarcoma, peripheral nerve sheath tumours

Are benign or malignant spinal tumours more common?

Malignant

What are some examples of benign spinal tumours?

Osteoma, chondroma, multiple cartilaginous exostoses (MCE)

What are some examples of malignant spinal tumours?

Osteosarcoma, multiple myeloma, metastatic prostatic carcinoma

What are the clinical signs of spinal neoplasia?

Vary depending on progression, size, and location. Pain and myelopathy

How is spinal neoplasia diagnosed?

X-ray, CT, MRI, scintigraphy, biopsy

What are differential diagnoses of spinal neoplasia?

IVDD, discospondylitis, meningomyelitis, fibrocartilaginous embolism

What are the treatment options for spinal neoplasia?

Surgical removal, radiation, chemotherapy

How and why does spondylosis form on the spine?

Spondylosis forms as a degenerative response to instability in the spine, with the body creating bone spurs to stabilize and limit movement between vertebrae.