An owner guide to understanding involuntary movement disorders in dogs and cats
What is paroxysmal dyskinesia?
Paroxysmal dyskinesia (PD) is a movement disorder in which an otherwise normal dog or cat develops sudden episodes of involuntary movement before returning completely to normal. The word ‘paroxysmal’ means that the signs occur in episodes, while ‘dyskinesia’ simply means abnormal involuntary movement.
Importantly, paroxysmal dyskinesia is the disease process—not the movement itself. During an episode, different types of involuntary movement may be seen. The most common are dystonia and chorea, although tremor, myoclonus or other abnormal movements can occasionally occur. Different animals may show different combinations of these movements, and the appearance may even vary between episodes in the same pet.
What do the abnormal movements look like?
The two movement patterns most commonly seen in PD are dystonia and chorea.
Dystonia is a sustained involuntary muscle contraction that produces abnormal postures. Dogs may arch their back, become stiff, extend or flex one or more limbs, or hold the neck or body in unusual positions. These postures may fluctuate during the episode but are usually maintained for several seconds or longer.
► Watch Video 1 to see an example of dystonia.
Chorea consists of irregular, unpredictable ‘dance-like’ movements. Rather than becoming stiff, affected animals continually reposition their limbs with flowing movements that seem to move from one body part to another.
► Watch Video 2 to see an example of chorea.
Many dogs show both dystonia and chorea during the same episode.
What causes paroxysmal dyskinesia?
PD is thought to result from abnormal function within parts of the brain responsible for controlling movement, particularly the basal nuclei. In most dogs and cats no structural abnormality is found and the condition is believed to be inherited or developmental (primary PD).
Less commonly, similar episodes may develop secondary to another problem affecting the brain, including inflammation, stroke, tumours or, rarely, certain medications. In these cases other neurological abnormalities are often present between episodes.
Which breeds are affected?
PD has been recognised in many breeds including Border Terriers, Cavalier King Charles Spaniels, Scottish Terriers, Cairn Terriers, Jack Russell Terriers, Miniature Schnauzers, Labradors, Norwich Terriers, Pugs, Bichon Frisé and Sphynx cats, although it can occur in any breed.
How would I recognise an episode?
During an episode your pet may:
• become stiff or develop abnormal postures (dystonia)
• show irregular dance-like limb movements (chorea)
• stumble or have difficulty walking
• tremble or shake
• remain standing, or occasionally fall because of the abnormal movements.
One of the most important features is that affected animals usually remain aware of their surroundings. They will often recognise their owner, respond to their name and attempt to interact despite being unable to control their movements.
Could this be epilepsy?
Epileptic seizures are the main condition that PD can be mistaken for.
Features that support PD include:
• awareness is usually preserved throughout the episode
• salivation, urination and defaecation are usually absent
• there is no prolonged confused behaviour afterwards
• episodes may last several minutes or occasionally much longer
• many dogs attempt to walk during an episode.
Your veterinary surgeon or neurologist will use the history together with video footage to distinguish the two conditions.
How is PD diagnosed?
There is no single blood test for PD. Diagnosis is based on recognising the characteristic involuntary movements while excluding other diseases.
Depending on your pet, investigations may include:
• blood and urine tests
• MRI of the brain
• cerebrospinal fluid (CSF) analysis
• breed-specific genetic tests where available.
Smartphone video recordings are often one of the most valuable diagnostic tools, so we strongly encourage owners to record an episode whenever it is safe to do so.
Are all forms of PD the same?
No. Different breeds have different forms of PD.
Border Terriers most commonly develop paroxysmal gluten-sensitive dyskinesia. Episodes usually consist of dystonia and chorea in varying combinations, and many affected dogs also have gastrointestinal signs. A strict gluten-free diet is often highly effective.
Cavalier King Charles Spaniels develop episodic falling syndrome, characterised predominantly by progressive dystonia affecting all four limbs during excitement or exercise.
Scottish and Cairn Terriers develop Scottie Cramp, producing sustained dystonia of the pelvic limbs and characteristic gait abnormalities.
Many other breeds have their own distinctive forms of PD.
Can PD be treated?
Treatment depends on the underlying type of PD.
Border Terriers frequently respond well to a strict gluten-free diet.
Dogs with episodic falling syndrome often improve with acetazolamide.
For many other forms there is no universally effective medication, although treatment may be considered if episodes are frequent or significantly affect quality of life. Unlike epilepsy, most forms of PD do not respond to conventional anti-seizure medication.
What is the outlook?
The prognosis is generally excellent. PD is not usually life-threatening and affected animals are completely normal between episodes. In many dogs the episodes become less frequent with age, and some stop altogether. Treatment is usually recommended only when episodes are frequent or interfere significantly with quality of life.