Difference between revisions of "Myotonia"

Revision as of 10:58, 18 August 2008

Myotonia congenita is caused by an ion channel defect.
Certain breeds of dogs are predisposed to myotonia congenita.
- Chow chow
  - The condition is caused by a defect in the sodium channel.
- Schnauzer
  - The condition is caused by a defect in the chloride channel.

Stiffness is present from birth.
- Signs improve with exercise.
Hypertrophy of the tongue and appendicular muscles.
Percussion dimple formation
Biopsy results may:
- Be normal, or
- Show type 1 fibre predominance or hypertrophy.

Acquired myotonia may be caused by:
- Herbicides
  - For example, (2,4-D) and dicamba.
- Hyperadrenocorticoidism
  - This may be natural (i.e. increased endogenous steroid production), or iatrogenic (i.e. prolonged corticosteroid administration).

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+==Myotonia==
+* Myotonia is the term given to sustained muscle contraction.
+* Myotonia may be congenital or acquired.
+===Congenital===
+* Myotonia congenita is caused by an ion channel defect.
+* Certain breeds of dogs are predisposed to myotonia congenita.
+** Chow chow
+*** The condition is caused by a defect in the sodium channel.
+** Schnauzer
+*** The condition is caused by a defect in the chloride channel.
+====Clinical Signs====
+* Stiffness is present from birth.
+** Signs improve with exercise.
+* Hypertrophy of the [[Oral Cavity - Tongue - Anatomy & Physiology|tongue]] and appendicular muscles.
+* Percussion dimple formation
+* Biopsy results may:
+** Be normal, or
+** Show type 1 fibre predominance or hypertrophy.
+====Treatment====
+* Exercise avoidance.
+* Drugs:
+** Metilxantine
+** Procainamide
+===Acquired===
+* Acquired myotonia may be caused by:
+** Herbicides
+*** For example, (2,4-D) and dicamba.
+** Hyperadrenocorticoidism
+*** This may be natural (i.e. increased endogenous steroid production), or iatrogenic (i.e. prolonged corticosteroid administration).