CNS Degenerative Diseases - Pathology

()Map NERVOUS SYSTEM (Map)

Equine Laryngeal Hemiplegia

• These horses are also known as "roarers"
• Equine laryngeal hemiplegia is a very common condition.

Pathogenesis

1. The disease starts with an idiopathic degeneration of the left recurrent laryngeal nerve.
2. This leads to atrophy of the left dorsal cricoarytenoid muscle.
3. Without the use of this muscle, the horse is unable to abduct the left arytenoid cartilage and vocal fold.
4. Airways are therefore partially obstructed on inspiration.

View images courtesy of Cornell Veterinary Medicine

Lysosomal Storage Disease (LSD)

• Occurs in many breeds of dogs and cats.
• Genetic defects give deficiencies of specific enzymes of degradation.
  • Disease only occurs in animals homozygous at the gene pair controlling enzyme activity.
    • The genes are co-dominant.
  • Enzyme activity is extremely low or entirely absent.
• Large amounts of waste products accumulate within cells.
  • Nervous system cells are predisposed.
  • Cells become engorged.
  • Normal function is prevented.

• Image 1, courtesy of Cornell Veterinary Medicine
  
• Image 2, courtesy of Cornell Veterinary Medicine
• Image 3, courtesy of Cornell Veterinary Medicine

Clinical Signs

• Nervous system cells are predisposed to the disease, and so progressive neurological signs predominate.
  • Develop between 2 weeks and 12 months of age.
  • The disease is ultimately fatal.
• For example, Siamese cats show:
  • Ganglisidosis
  • Mucopolysaccharidosis

Diagnosis

• Clinical signs are considered.
• Urine enzyme assays may be helpful.
• Post-mortem diagnosis is possible.
• More recently, gene tests have been available.

Cognitive Dysfunction Syndrome (CDS)

• CDS causes signs of senility.
• Increasing numbers of dogs and cats are suffering from CDS.
  • Prevalence is similar to that seen in humans: an 85 year-old human is roughly equivalent to a 15 year-old cat, and a 13-14 year-old dog.
    • Aging in dogs id breed specific.

Pathology

• A number of changes are seen in the brains of geriatric animals which may cause the signs of CDS.
  • Vascular insufficiency leads to:
    • Hypoxia
    • Increased free redical production
    • Deposition of amyloid plaques
    • Modification of other brain proteins

Treatment

• There are no published studies related to treatment of CDS in animals.
• Potential therapies include:
  • Dietary modification
    • Diets are enriched with antioxidants, vitamin E, beta-carotene and essential fatty acids.
  • Environmental stimulation
  • Drugs
    • Selegiline
    • Propentofylline
    • Nicergoline