Flash Cards: Hansen Type I and Hansen Type II Disc Disease

Definition

Intervertebral Disc Disease (IVDD) is a condition involving the degeneration and displacement of intervertebral discs, leading to spinal cord compression and/or nerve root irritation. It is classified into Hansen Type I and Hansen Type II based on the mechanism of degeneration and extrusion.

Hansen Type I IVDD

Pathophysiology: Acute extrusion of the nucleus pulposus into the spinal canal due to chondroid degeneration of the disc. The extrusion causes spinal cord compression and inflammation.
Signalment: Common in chondrodystrophic breeds (e.g., Dachshunds, Beagles, Shih Tzus), typically aged 3-7 years.

Hansen Type II IVDD

Pathophysiology: Gradual protrusion of the annulus fibrosus into the spinal canal due to fibroid degeneration, leading to chronic spinal cord compression.
Signalment: Seen in large, non-chondrodystrophic breeds (e.g., German Shepherds, Labradors) and older dogs.

Clinical Signs: Hansen Type I

Acute onset: Pain, ataxia, paresis, or paralysis depending on severity.
Localization: Most common in the thoracolumbar region (T11-L3).
Signs: Proprioceptive deficits, absent pain sensation in severe cases, and possible urinary incontinence.

Clinical Signs: Hansen Type II

Gradual onset: Progressive ataxia, paresis, and difficulty rising.
Localization: Commonly affects the lumbosacral and thoracolumbar regions.
Signs: Chronic pain, proprioceptive deficits, and muscle atrophy.

Diagnostic Approach

• Neurological Exam: Gait analysis, proprioceptive testing, and reflex evaluation.
• Radiography: Screening tool to identify narrowed disc spaces or mineralized discs.
• Advanced Imaging: MRI (preferred) or CT to confirm disc extrusion or protrusion and assess spinal cord compression.

Grading System for IVDD

Grade I: Spinal pain only.
Grade II: Ambulatory paresis.
Grade III: Non-ambulatory paresis.
Grade IV: Paralysis with intact deep pain.
Grade V: Paralysis with loss of deep pain perception (poor prognosis).

Treatment: Hansen Type I

Conservative: Strict cage rest (4-6 weeks), analgesics (NSAIDs, gabapentin), and muscle relaxants.
Surgical: Hemilaminectomy or mini-hemilaminectomy for Grades III-V or failed medical management.

Treatment: Hansen Type II

Conservative: Physical therapy, weight management, and anti-inflammatory medications.
Surgical: Decompression techniques (e.g., hemilaminectomy, dorsal laminectomy) for severe or progressive cases.

Prognostic Factors

Positive Prognosis: Presence of deep pain perception, early intervention.
Negative Prognosis: Loss of deep pain for >48 hours, severe myelomalacia.
Recovery rates are higher for Hansen Type I with surgical intervention compared to Hansen Type II.