Auteur: dr. Paul Mandigers
Movement disorders (MD) are without saying in most cases dramatic neurological presentations for owners and very challenging disorders for veterinary neurologist (1, 2). The most well known MD in humans is without saying Parkinson disease. A similar disorder is unknown in cats and dogs but various manifestations have been described in the recent years. And thanks to the invention of the smart phone with a camera function more and more movement disorders are recognized and put on media such as You Tube are get known to the public before local veterinarian get aware of it. Sometimes they are just put there to ‘laugh’ but they also help us to properly investigate and diagnose and facilitate treatment. Just google on ‘head tremor’ and you will find several hits a video’s to illustrate them. But despite our growing knowledge much is still unknown and veterinary nomenclature tends to follow human medicine. Not always is this possible or logical as we lack specific knowledge on localisation and type of disorder.
Movement disorders are neurological disorders that affect the central nervous system causing abnormal involuntary movements (AIM) without ictal seizure activity on EEG recordings (3). Of course this is difficult to perform in practice as well as in the open air which undermines proper diagnosis in all these rare involuntary movement disorders. Most likely there are also some peripheral disorders that can cause movement disorders but even in human medicine this is still under debate and not discussed here. The goal of this manuscript is simply to introduce the term and briefly introduce a few described AIM that are seen in companion animals. This will by all means far from complete.
Some terminology used in human (and veterinary) medicine (4):
Akathisia Inability to sit still
Athetosis Involuntary writing movements
Akinesia Lack of movement (kinesia = to move)
Ballismus Violent involuntary irregular rapid movements (Hemiballismus = affecting just one side)
Bradykinesia Slow movement
Chorea Rapid involuntary irregular movements: resembles dancing
Dyskinesia Abnormal movement
Dystonia Sustained contraction / movement or torsion
Myoclonus Involuntary contraction of a muscle or group
Tics Involuntary compulsive repetitive stereotypic movements
Tremors Agonistic / antagonistic contractions. Subdivided into resting tremor, postural tremors, kinetic tremors and essential tremors.
The term paroxysmal simply mean that it suddenly arises and is reversible. Affected animals do not lose consciousness.
Abnormal involuntary hyperkinetic movement or muscle tone. This may include dystonia, ballismus, hemiballismus, chorea, and athetosis. These involuntary movements do not include clonic movements or automatisms as observed in generalized seizures.
One of the first AIM described it the muscular hypertonicity in the Scottish terrier dogs described as Scotty Cramp (5). It has also been seen in similar breeds such as the West Highland White terrier, Norwich terrier. The dogs get affected between 6 weeks to 18 months of age. It may be triggered or evoked by excitement, exercise and stress. The syndrome starts with an abduction of the front legs, arching of the vertebral column and stiffness of the hind legs. By description the disorder is most likely caused by a lesion in the extrapyramidal system causing this rigidity. This rigidity is caused by dysfunction of the normal inhibitory glycinergic neurotransmission or GABAergic interneuron transmission may. In scotty cramp it is believed to be caused by a relative deficiency of the inhibitory neurotransmitter serotonin. NSAID’s do not work. Benzodiazepines and acepromazine have been used although it should only be given in severely affected animals (5).
Episodic falling in the Cavalier King Charles Spaniels
Episodic falling in the CKCS has also been described as hypertonicity or hyperexplexia. Again it is believed that the disorder is most likely caused by a lesion in the extrapyramidal system causing rigidity. The disease was first described in 1983 (6) and just recently the mutation causing the disorder has been found (7). The affected dogs are between 3 to 8 months of age. After exercise the dogs develop a stiffness of the hind legs that get abducted. The dogs may show a ‘bunny hopping’ locomotion and may either fall over or to their sides. Treatment, with good results, consists of the use of benzodiazepines. Breeders can screens their dogs as the mutation has been found.
Similar disorders are seen in various breeds and are often called paroxysmal dyskinesias. Just recently it has been well documented in Chinook Dogs (3). It has also been seen in Labrador retrievers, Belgian Shepherds, Markiesje (own work) and various other breeds.
Paroxysmal dyskinesias may be classified as one of the following (4)
(1) paroxysmal kinesigenic choreoathetosis/ dyskinesias (PKC/PKD)
(2) paroxysmal dystonic choreoathetosis/ paroxysmal nonkinesigenic dyskinesias (PDC/ PNKD)
(3) paroxysmal exertion-induced dystonia (PED)
(4) episodic ataxia (EA-1 or EA-2)
Generalized Muscular Stiffness in Labradors retrievers
Just recently a novel movement disorder has been described in the Labrador. The dogs have muscular stiffness even at rest and show difficulty walking. In necropsied dogs astrocytosis was found throughout the spinal cord grey matter, reticular formation and caudate nuclei (8).
Tremors are most likely one of the most common movement disorders seen (2). Tremors are divided into resting tremors (only visible at rest) and tremors that are seen during action (such as intention tremors).
In Parkinson’s disease (humans) tremors are most likely a very important clinical hallmark. Tremors following after the intend to do something are so called intention tremors. They are not present at rest. These tremors are subdivided into postural and kinetic tremors. A true intention tremor such as in cerebellar disease should be seen as a kinetic tremor. This type of tremor is not seen if the animal is at sleep or at rest.
Generalised tremors can occur secondary to congenital disorders of myelination, intoxications, metabolic problems, inflammatory diseases and degenerative diseases.
A very well known generalised tremor is the so-called White Shaker Syndrome especially seen in Maltesers, WHWT and other breeds (9, 10). Animals can be of any age although it is predominantly seen in young dogs. The disorder is benign. It is believed to be (in part?) caused by an aseptic meningo-encephalitis (10).
Postural tremors are seen in standing animals in the muscles that support the body against gravity. Garosi et all described in detail a postural or orthostatic tremor in the great Dane which is also seen in other breeds such as New foundlanders (11). These tremors (not to be confused with the tremors visible at old age) are only visible standing upright. The tremors can be seen in the legs (even the front legs) as well as other muscles (neck). The dogs are young of age. When the dog lays down the tremor disappears. It has been treated with benzodiazepines and fenobarbital.
Perhaps the most frequently seen tremor is that seen in the pelvic limbs of the old dog. It appears to be benign. Again this tremor is only present while standing. Some of these dogs may show, if an X-ray of the lumbar vertebral column is made spondylosis. But this is just a coincidental finding as until now the etiology and pathogenesis of this disorder remains unknown.
Head tremors, often seen in the English Bulldog and American Bulldog, might also be called postural tremors. As these tremors all occur in typical breeds it is believed to be genetic of origin. Striking is however the fact that the head tremor seen in the bulldogs (all between 1 to 3 years of age) suddenly comes and even quickly seems to disappear. The author of this manuscript has performed in most of the cases seen extensive bloodwork, MRI scans and CSF taps without clear results.
A head tremor that appears to stay present is the so-called head bobbing of the CKCS and Doberman. It resembles the head bobbing of these phony dogs located at the rearshelf of cars. Just recently a study has been published investigating the head tremor seen in the Doberman that suggested a clear genetic cause(12). The head ‘bobbing’ can be either vertical or horizontal and again disappears when the dog is at rest or lays down.
Trancing Bull terriers
Bull terriers may be presented with a syndrome what has been published on the web as ‘trancing Bullterriers’. The dogs appear to ‘trance’ (or ‘ghost walk’ or ‘weed walk’). The trancing seems to be trigged by walking under a bush so that the leaves tickle the dog’s back. The dog’s eyes glaze and movement is in ultra slow motion; the dog almost looks as though it is stalking prey whilst sleep walking. It is seen in a frequency up to 80% of all dogs (13). And although breeders and owners regard it as typical for the breed it is most likely a neurological disorder of unknown origin.