RCVS recognised Specialist in Veterinary Neurology
EBVS® European Specialist in Veterinary Neurology
DVM MVetMed DipECVN MRCVS
What are paroxysmal dyskinesias?
Paroxysmal dyskinesias (PD) are a group of conditions characterised by episodes of abnormal posture and movement that are self-limiting. The term ‘paroxysmal’ indicates that the signs can start and stop suddenly. The term ‘dyskinesia’ broadly refers to a movement of the body that is involuntary and or to diminished voluntary movements. This means that the patient struggles to execute planned movements, executes them in an abnormal way or movements are executed which are not planned for. This all happens while the patient is fully aware of its surroundings. Episodes are painless, autonomic signs are absent (salivation, urination…), consciousness is not impaired and abnormal behaviour following the episode is not observed. Episodes can last minutes or hours (rare), with the beginning and end of the abnormal movement being abrupt. Many of these features help distinguish PD from epileptic seizures, which are one of the other main causes for episodes of abnormal movements in pets.
What causes paroxysmal dyskinesias in dogs?
Based on research in humans it is most likely that PD results from dysfunction in an area of the brain called the basal nuclei that are important in planning, executing and controlling movement. The underlying cause of many PDs is unknown, with the majority being described as idiopathic (meaning of unknown cause). In some dogs, PD is recognised to be caused by a genetic abnormalities and can be familial in origin. It is very rare but not impossible that PD is a result of a structural disease (e.g. tumour, inflammation, infection, stroke) or in response to some medications (phenobarbital, propofol). Border Terriers suffer from a very specific form of PD which is caused by a gluten hypersensitivity: Paroxysmal Gluten‐Sensitive Dyskinesia. We can test this by looking for Antibodies against transglutaminase‐2 and gliadin.
Which pets experience paroxysmal dyskinesias?
PD can occur in any dog but have been increasingly described in certain breeds including: Cavalier King Charles spaniel, Border terrier, Cairn terrier, Scottish terrier, Dalmatian, Norwich terrier, Boxer, Bichon Frise, Pugs and Chinook, in which they have been ‘labelled’ as breed-specific entities (and sometimes even a genetic test exists for these). More recently PD have been reported for Jack Russell terriers (JRT) and Labrador Retrievers in the UK but there is a current effort to describe this disease in a variety of other breeds (Dachshunds, Yorkshire Terrier, Chihuahuas…). Overall, it should be assumed that any breed of dog can present for PD.
What are the signs of paroxysmal dyskinesias?
The most common appearance of affected dogs is ‘cramping’/’spasm’ of the limbs, which is seen as an increase in the muscle tone of the limbs and markedly abnormal postures. While all four limbs may be affected, the pelvic limbs are often affected to a greater degree than the thoracic limbs. During an attack, animals can be severely incapacitated and can appear distressed, since the spasm overcomes any attempts at voluntary movement; however, many dogs will still attempt to walk. Other signs observed might be tremors, swaying from side to side, kyphosis, walking backwards or even inability to move (being frozen) In some cases, episodes can be triggered by excitement or exercise. Episodes can last seconds, minutes or hours, with the beginning and end of the PD being abrupt.
How is paroxysmal dyskinesia diagnosed?
Diagnosing a PD is extremely challenging as antibody or genetic tests are only available for some specific breed. The episodes must be precisely characterised, and this requires taking a detailed history and reviewing any videos of the episodes you may have as well as conducting a physical and neurological examination. The most important differential diagnosis for PD is focal seizures activity which can cause similar muscle movements. If the animal shows convincing signs of PD, is neurological normal and has remained neurological normal in between the episodes for a prolonged time further diagnostics are often not performed. If this does not apply to a patient an MRI scan of the brain +/- cerebrospinal fluid (CSF) analysis will be performed to exclude structural disease of the brain.
What treatment options are available?
In cases of idiopathic (primary) PD treatment is often not necessary nor available. Different classes of medications have been used experimentally including skeletal muscle relaxants, anti-seizure medications and drugs that work on ion channels in the brain and muscle. The majority of them did not show any convincing effect. For some of the breed specific forms of PD there are specific ways of treatment: Cavalier King Charles Spaniels, who respond to muscle relaxants and Border terriers who generally respond to gluten free diets.
What is the prognosis?
Due to a lack of progression and a lack of harm to the patient by primary PD the prognosis for a good quality of life should be considered very good. It is very rare that the episodes are frequent and intense enough to cause an impairment of quality of life (but we have seen cases like that). In many dogs the condition is self-limiting over time with a third entering remission and an improvement over time seen in three quarters of dogs. Remission was significantly lower in dogs with cluster episodes than those without. The frequency of many episodes can also be improved by reducing levels of stress and excitement (if identified as a trigger).
- Get a video!
- Based on the video and an exact history we will have a good idea if we are dealing with epileptic seizures or a movement disorder
- The amount of advanced investigations needed is very depending on how convinced we are that the observed episode indeed is a PD
- Especially, if a patient is neurological abnormal between the episodes or there is an obvious progression it is worthwhile ruling out an underlying cause that is leading to the events of PD