Canis ISSN: 2398-2942

Muscular hypertonicity

Synonym(s): Movement disorders, cramping, peripheral nerve hyperexcitability, involuntary muscle contractions, hyperkinesis, Scotty cramp

Contributor(s): G Diane Shelton, Paul Cuddon

Introduction

  • Identified in many breeds including Scottish Terrier, Norwich Terrier, Jack Russell Terrier, Yorkshire Terrier, Wheaton Terrier and Border Terrier, Bichon Frise, Boxer, Cavalier King Charles Spaniel and Springer Spaniel.
  • Signs: causes collapse without loss of consciousness, limb rigidity. May or may not be associated with visible "continuous muscle fiber activity" or rippling muscles.
  • Usually following exercise or excitement.
  • Diagnosis: laboratory and pathologic testing to rule out primary muscle and peripheral nerve diseases, family history of movement disorder is suggestive.
  • Treatment: recovery usually within 10-60 mins, although stiffness may last for hours. Daily dose of benzodiazepines or membrane stabilizing drugs may improve or control clinical signs.
  • Prognosis: although most of the conditions are non-progressive or life threatening, persistent muscle contraction may result in hyperthermia and death.

Pathogenesis

Etiology

  • Where determined, no structural changes seen in muscles or in central or peripheral nervous systems.
  • The underlying cause in most of these disorders has not yet been determined.
  • Antiserotonin agents make the clinical conditions worse (Scottish Terrier).

Predisposing factors

General

  • Many Terrier breeds.
  • Cavalier King Charles and Springer Spaniel breeds.

Pathophysiology

  • Physiological diseases.
  • No structural abnormalities identified to date.
  • Defect may be in neurons that control muscle contractions, hyperactivity of abnormal peripheral nerve motor axons, or ion channel abnormalities in nerve or muscle.
  • In Scottish Terriers (Scotty cramps) pharmacological studies suggest the disorder may be due to defects in serotonergic transmitters. Most likely due to spinal cord disturbance that may involve the myotactic reflex mechanism:
    • A defect of serotonin-producing neurons that control muscle contraction.
    • Inherited autosomal recessive disease.
    • Compounds that inhibit prostaglandin synthesis increase the severity of signs.
    • Antiserotonin agents such as methylsergide make clinical signs worse and can induce the condition.

Timecourse

  • A non-progressive condition.
  • In Cavalier King Charles Spaniels, may find improvement with age.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Urkasemsin G & Olby N (2015) Clinical characteristics of Scottie Cramp in 31 cases. JSAP 56 (4), 276-280 PubMed.
  • De Lahunta A, Glass E N, Kent M (2006) Classifying involuntary muscle contractions. Compend Contin Educ Vet 28 (7), 516-530 VetMedResource.
  • Van Ham L, Bhatti S, Polis I, Fatzer R, Braund K, Thoonen H (2004) 'Continuous muscle fiber activity' in six dogs with episodic myokymia, stiffness and collapse. Vet Rec 155 (24), 769-774 PubMed.
  • Penderis J, Franklin J M (2001) Dyskinesia in an adult Bichon Frise. JSAP 42 (1), 24-25 PubMed.
  • Ramsey I K, Chandler K E, Franklin R J (1999) A movement disorder in boxer dogs. Vet Rec 144 (7), 179-180 PubMed.
  • Furber R (1984) Cramp in Norwich terriers [Correspondence]. Vet Rec 115 (2), 46 VetMedResource.
  • Herrtage M E, Palmer A C (1983) Episodic falling in the Cavalier King Charles spaniel. Vet Rec 112 (19), 458-459 PubMed.

Other sources of information

  • DeLahunta A, Glass E (2008) Veterinary Neuroanatomy and Clinical Neurology. 3rd edn.
  • Lorenz M D, Kornegay J N (2004) Handbook of Veterinary Neurology. 4th edn. pp 265-281.
  • Shelton G D (2004) Muscle pain, cramps and hypertonicity. Vet Clin North Am Small Anim Pract 34(6), 1483-1496.
  • Canine epileptoid cramping syndrome-Spikes disease. Border terrier WebRing. Accessed December 2008 at: www.borderterrier-cecs.com/index.htm


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