Paroxysmal dyskinesia (movement disorder)

Some dogs are affected by a disease that affects their movement so that they occasionally show muscle spasms or being wobbly or develop tremors. These signs can be present all the time or may come and go. The term paroxysmal means that affected dogs are generally normal and then periodically develop signs associated with disease before returning to normal again. Dyskinesia means an involuntary movement of the body. So, in this condition apparently normal dogs suddenly have episodes where they develop tremors or other movement disorders. Although these conditions are being recognised more commonly, they are often mistaken for an epileptic seizure, both by owners and by veterinarians. Although initially very frightening many of these conditions can be managed very successfully.

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Paroxysmal dyskinesias (PDs) are episodic movement disorders in which abnormal movements are present only during attacks.

The attacks can last anything from a few minutes to a couple of hours and can sometimes occur in clusters. PDs occur in many breeds such as Cavalier King Charles spaniel, Border terrier, Cairn terrier, Scottish terrier, Dalmatian, Norwich terrier, Boxer, Bichon Frise, Pug, and Chinook. They are increasingly being reported in Jack Russell terriers (JRT) and Labradors.

It is thought that PD occurs due to dysfunction in a specific area of the brain that plays an important role in controlling movement. The underlying cause is often unknown. In people, some forms are caused by genetic abnormalities. Some patients develop paroxysmal movement disorders as a result of brain damage due to a tumor, inflammation, infection, or stroke.

Dogs often develop PD at a young age, and attacks are often triggered by startling or sudden movements. Males are particularly affected (75%) and most of these are entire.

The most common appearance of affected dogs is ‘cramping’/’spasm’ of the hind limbs, but all 4 limbs can be affected. During attacks, animals can be severely incapacitated, since the spasm overcomes any attempts at voluntary movement; however, many dogs will still attempt to walk. In some cases, episodes can be triggered by excitement or exercise. If your dog develops any usual movement problems or you think it might have had a seizure (convulsion) then you should contact your veterinarian for advice. Since the abnormalities are often only present during an attack if you can take a video of an episode it will be very helpful in making a diagnosis.

Dogs and people with PD are often misdiagnosed as having unusual epileptic seizures. One part of the history that can help your veterinarian distinguish these conditions from seizures is whether your dog loses consciousness during an attack and whether signs such as loss of bladder/bowel function or excessive salivation are present. If you are able to video an episode it can be really useful to show this to your veterinarian.

Your veterinarian will want to rule out a physical brain lesion by performing an MRI scan of the brain, along with collected a sample of fluid from around the brain (cerebrospinal fluid (CSF)) for analysis. Blood and urine tests will help rule out underlying metabolic or hormone disorders.

Although many breeds of dog are affected by these disorders a number of breed-specific paroxysmal movement disorders have been described. These only occur in the particular breed and each form is subtly different. If your dog is from one of the commonly affected breeds diagnosis may be more straightforward.

Cavalier King Charles Spaniels
In CKCS this condition is often called ‘episodic falling syndrome’ (EFS). Episodes are triggered by exercise, stress or excitement and affected dogs develop a gradually worsening muscle spasm in the fore and hind limbs during an attack, with the trunk also affected; this results in a characteristic ‘deer-stalking’ or ‘praying’ position. Episodes begin between 14 weeks and 4 years of age and dogs are normal between episodes. The condition gets its name from the fact that all 4 limbs will often cramp during exercise and cause the dog to fall over. Other clinical signs that sometimes occur include facial muscle stiffness, stumbling, a ‘bunny-hopping’ gait, arching of the back or vocalization. A genetic test is available, so if the condition is suspected a blood sample can be taken and submitted for analysis. Most dogs respond to treatment with acetazolamide. Clonazepam can be used as add-on treatment to acetazolamide in difficult to control cases, though its beneficial effects sometimes diminish with time; other drugs can also be considered.

Scottish or Cairn terriers
In these breed the condition may be referred to as ‘Scottie cramp’. During excitement, the hindlimbs of young adult dogs typically become stiff and extended, although affected dogs occasionally have exaggerated flexion of the limbs and the forelimbs can also cramp. Severely affected dogs arch their back and may fall onto their side, with their head and tail flexed. Diagnosis is based on a dog having typical episodes and no evidence of other conditions that might appear similar. Treatment is aimed at using drugs to improve muscle relaxation or to increase serotonin levels.

Border terriers
Probably the best documented form occurs in Border terriers, and is often known as canine epileptoid cramping syndrome (CECS) or ‘Spike’s disease’. Episodes are very variable, ranging from a wobbly gait to an inability to stand, or cramping of belly, neck and back muscles. Currently, the most effective way to manage CECS in Border terriers is to use a gluten-free diet, although it can take several weeks for an improvement to be noted and not all dogs will respond. See the owner factsheet on this condition for more information.

Paroxysmal dyskinesia can be extremely frustrating to treat. Apart from CKCSs who respond to acetazolamide and Border terriers who generally respond to exclusive gluten free diets, most cases of PD do not respond to medication. In particular, the large majority of PD do not respond to anti-epileptic medication. Treatment may be helpful if the episodes of PD occur more than once a week. Anecdotally, keppra (levetiracetam) has helped some affected Labradors.

One-third of dogs will stop having episodes and three quarter of dogs improve with time without treatment. Dogs with cluster episodes are less likely to stop having episodes.