Myoclonus

Sporadic myoclonus occurs as a reflex response.
- A sudden response to an auditory stimulus.

In repetitive myoclonus, contractions and relaxations are rhythmic.
- They occur one to two seconds apart.
- May occur when the animal is at rest or during movement.
Repetitive myoclonus may be due to a functional disturbance of lower motor neurons.
- This may be caused, for example, by distemper or another encephalomyelitis.

Tremors are induced by movement.
- Myoclonus disappears when the patient is relaxed or sleeping.
May be caused by:
- Cerebellar conditions
- Myelin defects
- Toxic insult
- Problems with neurons

Maltese terrtiers and West Highland white terriers are predisposed.
- Gives rise to the name "white shakers" for the sufferers.
Caused by meningoencephalitis.
- Toxicosis is a common cause of meningoencephalitis, for example:
  - Metaldehyde
  - Pyrethrins
  - Hexachlorophene
  - Organophosphate
  - Food born mycotoxins
  - Macadamia nuts
Takes the form of postural repetitive myoclonus.
- Postural muscles are affected while they are supporting weight.
The young and old are differentially affected.
- Young animals
  - The head and neck are affected.
    - Gives head bobbing, which stops when the animal is distracted.
  - Most common in Dobermans, English Bulldogs and Boxers.
- Aged dogs
  - Pelvic limbs are affected, although only when standing.
    - Orthostatic tremors
  - Whole muscles are affected.
  - Most common in Great Danes.
Aquired action-related myoclonus is responsive to steroid or immunosuppressive drugs.

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