From Dog

Myokymia (peripheral nerve hyperexcitability syndrome) is defined as continuous involuntary skeletal muscle fibre activity.

This may occur with localized muscles such as facial or eyelid muscles or can affect all body muscles and in many cases often progresses to muscle stiffness, delayed muscle relaxation and eventual collapse[1].

Unlike seizures, myokymia does not usually affect limb movement and dogs can usually remain conscious and move normally, although ataxia may be evident.

Causes include:

In Jack Russell Terriers, myokymia is an autosomal-recessive disease associated with facial muscle twitching, intense facial rubbing and hyperthermia[5][6].

Diagnosis is usually based on visual confirmation of spontaneous muscle twitching and confirmed by electromyography[7] and brainstem auditory-evoked potentials[8].

Elimination of other causes of spontaneous muscle fasciculation needs to be confirmed, such as polyneuropathy, temporary shivering due to fever or hypothermia and seizures.


  1. Van Ham L et al (2004) 'Continuous muscle fibre activity' in six dogs with episodic myokymia, stiffness and collapse. Vet Rec 155(24):769-774
  2. Holland CT et al (2010) Unilateral facial myokymia in a dog with an intracranial meningioma. Aust Vet J 88(9):357-361
  3. Bhatti SF et al (2011) Myokymia and neuromyotonia in 37 Jack Russell terriers. Vet J 189(3):284-288
  4. Vanhaesebrouck AE et al (2010) Inspiratory stridor secondary to palatolingual myokymia in a Maltese dog. J Small Anim Pract 51(3):173-175
  5. Walmsley GL et al (2004) Facial myokymia in a puppy. Vet Rec 158(12):411-412
  6. Van Poucke M et al (2012) Experimental validation of in silico predicted KCNA1, KCNA2, KCNA6 and KCNQ2 genes for association studies of peripheral nerve hyperexcitability syndrome in Jack Russell Terriers. Neuromuscul Disord 22(6):558-565
  7. Reading MJ & McKerrell RE (1993) Suspected myokymia in a Yorkshire terrier. Vet Rec 132(23):587-588
  8. Vanhaesebrouck AE et al (2010) Clinical and electrophysiological characterization of myokymia and neuromyotonia in Jack Russell Terriers. J Vet Intern Med 24(4):882-889