A movement disorder in boxer pups

International veterinary canine dyskinesia task force ECVN consensus statement: Terminology and classification

Movement disorders are a heterogeneous group of clinical syndromes in humans and animals characterized by involuntary movements without changes in consciousness. Canine movement disorders broadly include tremors, peripheral nerve hyperexcitability disorders, paroxysmal dyskinesia, and dystonia. Of these, canine paroxysmal dyskinesias remain one of the more difficult to identify and characterize in dogs. Canine paroxysmal dyskinesias include an array of movement disorders in which there is a recurrent episode of abnormal, involuntary, movement. In this consensus statement, we recommend standard terminology for describing the various movement disorders with an emphasis on paroxysmal dyskinesia, as well as a preliminary classification and clinical approach to reporting cases. In the clinical approach to movement disorders, we recommend categorizing movements into hyperkinetic vs hypokinetic, paroxysmal vs persistent, exercise‐induced vs not related to exercise, using a detailed description of movements using the recommended terminology presented here, differentiating movement disorders vs other differential diagnoses, and then finally, determining whether the paroxysmal dyskinesia is due to either inherited or acquired etiologies. This consensus statement represents a starting point for consistent reporting of clinical descriptions and terminology associated with canine movement disorders, with additional focus on paroxysmal dyskinesia. With consistent reporting and identification of additional genetic mutations responsible for these disorders, our understanding of the phenotype, genotype, and pathophysiology will continue to develop and inform further modification of these recommendations.

Levetiracetam-responsive paroxysmal exertional dyskinesia in a Welsh Terrier

A 5-and-a-half-year old, 9-kg, spayed, female Welsh Terrier presented with a 12 month history of paroxysmal exertion-induced dyskinesia (PED) characterized by recurrent episodes of involuntary hyperkinetic movements, abnormal muscle tone, and contractions triggered by exercise. A single episode occurred within 2 hours after exercise, lasted from 7 to 10 minutes, and resolved without treatment. The owner sought treatment for the dog when the episodes began to last longer (20-30 minutes), and occurred as long as 2.5 to 8 hours after exercise. Diazepam administered intranasally at the start of an episode promptly alleviated the symptoms. Maintenance therapy with levetiracetam proved effective, such that the dog was gradually returned to exercise. However, attempts to wean the dog off the drug resulted in reoccurrence. Although the pathophysiology of PED is not fully understood, the clinical presentation and the positive response to antiepileptic therapy highlight the overlap between disease pathways in epilepsy and PED in dogs.

Mitochondrial PCK2 Missense Variant in Shetland Sheepdogs with Paroxysmal Exercise-Induced Dyskinesia (PED)

Four female Shetland Sheepdogs with hypertonic paroxysmal dyskinesia, mainly triggered by exercise and stress, were investigated in a retrospective multi-center investigation aiming to characterize the clinical phenotype and its underlying molecular etiology. Three dogs were closely related and their pedigree suggested autosomal dominant inheritance. Laboratory diagnostic findings included mild lactic acidosis and lactaturia, mild intermittent serum creatine kinase (CK) elevation and hypoglycemia. Electrophysiological tests and magnetic resonance imaging of the brain were unremarkable. A muscle/nerve biopsy revealed a mild type II fiber predominant muscle atrophy. While treatment with phenobarbital, diazepam or levetiracetam did not alter the clinical course, treatment with a gluten-free, home-made fresh meat diet in three dogs or a tryptophan-rich, gluten-free, seafood-based diet, stress-reduction, and acetazolamide or zonisamide in the fourth dog correlated with a partial reduction in, or even a complete absence of, dystonic episodes. The genomes of two cases were sequenced and compared to 654 control genomes. The analysis revealed a case-specific missense variant, c.1658G>A or p.Arg553Gln, in the PCK2 gene encoding the mitochondrial phosphoenolpyruvate carboxykinase 2. Sanger sequencing confirmed that all four cases carried the mutant allele in a heterozygous state. The mutant allele was not found in 117 Shetland Sheepdog controls and more than 500 additionally genotyped dogs from various other breeds. The p.Arg553Gln substitution affects a highly conserved residue in close proximity to the GTP-binding site of PCK2. Taken together, we describe a new form of paroxysmal exercise-induced dyskinesia (PED) in dogs. The genetic findings suggest that PCK2:p.Arg553Gln should be further investigated as putative candidate causal variant.

Phenotypic characterization of paroxysmal dyskinesia in Maltese dogs

Background

Paroxysmal dyskinesias (PDs) are a group of central nervous system diseases characterized by episodes of abnormal involuntary hyperkinetic movement without altered consciousness that increasingly have been recognized in dogs.

Objectives

To present the phenotypical characterization, treatment, and outcome of a PD observed in Maltese dogs.

Animals

Client‐owned Maltese dogs (n = 19) with presumed diagnosis of PD.

Methods

Data were collected retrospectively from medical records (2014‐2019), and supporting information was added prospectively by using a questionnaire directed to the owners of the affected dogs.

Results

The episodes were characterized mainly by sudden dystonia of ≥1 limbs and generalized body tremors with preserved consciousness. The mean age of clinical onset was 5.4 years. Episode frequency varied widely both among and within individuals. Median episode duration was 4.5 minutes. Most episodes were stress‐ or exercise‐induced. Acetazolamide was administered to 6 dogs, and 4 dogs experienced a decrease in episode frequency. In 7 dogs that received a gluten‐free diet, 6 dogs became episode‐free. In 4 dogs, the episodes stopped spontaneously and in 2 dogs no medication or specific diet was given and the episodes continued at the same frequency.

Conclusions and Clinical Importance

Given the breed predisposition and regional distribution of the disease, additional research should focus on elucidating the underlying genetic cause doing so might advance both our understanding of the pathophysiology and treatment of this disease, not only in dogs, but also in humans. Regardless of the treatment protocol selected, prognosis appears fair to good.

A cross-species approach to disorders affecting brain and behaviour

Structural and functional elements of biological systems are highly conserved across vertebrates. Many neurological and psychiatric conditions affect both humans and animals. A cross-species approach to the study of brain and behaviour can advance our understanding of human disorders via the identification of unrecognized natural models of spontaneous disorders, thus revealing novel factors that increase vulnerability or resilience, and via the assessment of potential therapies. Moreover, diagnostic and therapeutic advances in human neurology and psychiatry can often be adapted for veterinary patients. However, clinical and research collaborations between physicians and veterinarians remain limited, leaving this wealth of comparative information largely untapped. Here, we review pain, cognitive decline syndromes, epilepsy, anxiety and compulsions, autoimmune and infectious encephalitides and mismatch disorders across a range of animal species, looking for novel insights with translational potential. This comparative perspective can help generate novel hypotheses, expand and improve clinical trials and identify natural animal models of disease resistance and vulnerability.

Paroxysmal Dyskinesia in Border Terriers: Clinical, Epidemiological, and Genetic Investigations

Background

In the last decade, a disorder characterized by episodes of involuntary movements and dystonia has been recognized in Border Terriers.

Objectives

To define clinical features of paroxysmal dyskinesia (PD) in a large number of Border Terriers and to study the genetics of the disease.

Animals

110 affected and 128 unaffected client‐owned Border Terriers.

Methods

A questionnaire regarding clinical characteristics of PD was designed at Utrecht University and the University of Helsinki. Thirty‐five affected Border Terriers underwent physical examination and blood testing (hematology and clinical biochemistry). Diagnostic imaging of the brain was performed in 17 affected dogs and electroencephalograms (EEG) between episodes were obtained in 10 affected dogs. A genomewide association study (GWAS) was performed with DNA of 110 affected and 128 unaffected dogs.

Results

One hundred forty‐seven questionnaires were included in the study. The most characteristic signs during episodes were dystonia, muscle fasciculations, and falling over. The majority of owners believed that their dogs remained conscious during the episodes. A beneficial effect of anti‐epileptic therapy was observed in 29 of 43 dogs. Fifteen owners changed their dogs’ diet to a hypoallergenic, gluten‐free diet, and all reported reasonable to good improvement of signs. Clinical examinations and diagnostic test results were unremarkable. The GWAS did not identify significantly associated chromosome regions.

Conclusions and Clinical Importance

The survey results and EEG studies provided further evidence that the observed syndrome is a PD rather than epilepsy. Failure to achieve conclusive results by GWAS indicates that inheritance of PD in Border Terriers probably is complex.

Paroxysmal Dyskinesia in Norwich Terrier Dogs

Background

Episodic muscular hypertonicity in Norwich terrier dogs was first reported in a brief communication in 1984. Since then, the condition has remained poorly characterized.

Objectives

The aims of this study were to characterize the phenomenology, clinical course, and family history of paroxysmal dyskinesia in the Norwich terrier and to estimate its prevalence in the United Kingdom.

Methods

The owners of Norwich terrier dogs born since January 1, 2000 were invited to complete a specifically designed questionnaire aimed at identifying affected and unaffected dogs and investigating the clinical characteristics of this paroxysmal dyskinesia. Pedigrees were collected and reviewed.

Results

The questionnaire was returned for 198 Norwich terrier dogs. Of these, 26 (13%) were classified as affected by paroxysmal dyskinesia after revision of the questionnaires and after obtaining videos of the episodes, veterinary medical records, and telephone interviews with the owners. All dogs were neurologically normal between episodes. No significant abnormalities were detected on diagnostic investigations. Mean age at the first episode was 3 years. The episodes were characterized by sustained muscular hypertonicity in the pelvic limbs, lumbar region, and thoracic limbs, impairing posture and locomotion without loss of consciousness. Episode frequency varied both between and within individuals. Stress, anxiety, excitement, and variation in daily routine were recognized as episode triggers in 13 dogs. Episode duration generally was from 2 to 5 minutes (range, from < 2 to 30 minutes). The majority of affected dogs were related.

Conclusions

Paroxysmal dyskinesia segregates in an extended pedigree of Norwich terrier dogs and thus is potentially an inherited disorder in this breed.

Dystonia and Paroxysmal Dyskinesias: Under-Recognized Movement Disorders in Domestic Animals? A Comparison with Human Dystonia/Paroxysmal Dyskinesias

Dystonia is defined as a neurological syndrome characterized by involuntary sustained or intermittent muscle contractions causing twisting, often repetitive movements, and postures. Paroxysmal dyskinesias are episodic movement disorders encompassing dystonia, chorea, athetosis, and ballism in conscious individuals. Several decades of research have enhanced the understanding of the etiology of human dystonia and dyskinesias that are associated with dystonia, but the pathophysiology remains largely unknown. The spontaneous occurrence of hereditary dystonia and paroxysmal dyskinesia is well documented in rodents used as animal models in basic dystonia research. Several hyperkinetic movement disorders, described in dogs, horses and cattle, show similarities to these human movement disorders. Although dystonia is regarded as the third most common movement disorder in humans, it is often misdiagnosed because of the heterogeneity of etiology and clinical presentation. Since these conditions are poorly known in veterinary practice, their prevalence may be underestimated in veterinary medicine. In order to attract attention to these movement disorders, i.e., dystonia and paroxysmal dyskinesias associated with dystonia, and to enhance interest in translational research, this review gives a brief overview of the current literature regarding dystonia/paroxysmal dyskinesia in humans and summarizes similar hereditary movement disorders reported in domestic animals.

Canine paroxysmal movement disorders

Paroxysmal dyskinesias are episodic movement disorders characterized by muscle hypertonicity that can produce involuntary movements. Signs emanate from the central nervous system; consciousness is not impaired, ictal electroencephalography is normal, and there are no autonomic signs, distinguishing them from seizure disorders. In humans they are classified into 3 groups, each responding to different therapies. A mutation in the gene for brevican (BCAN) has been identified as the cause of Episodic Falling in Cavalier King Charles spaniels. Further elucidation of the genetic causes will enhance our ability to identify and treat these canine diseases.

Phenotypic characterisation of canine epileptoid cramping syndrome in the Border terrier

OBJECTIVES

To characterise the phenotype of Border terriers suspected to be affected by canine epileptoid cramping syndrome and to identify possible contributing factors.

METHODS

Owners of Border terriers with suspected canine epileptoid cramping syndrome were invited to complete an online questionnaire. The results of these responses were collated and analysed.

RESULTS

Twenty-nine Border terriers were included. Most affected dogs had their first episode before 3 years of age (range: 0·2 to 7·0 years). The majority of episodes lasted between 2 and 30 minutes (range: 0·5 to 150 minutes). The most frequent observations during the episodes were difficulty in walking (27 of 29), mild tremor (21 of 29) and dystonia (22 of 29). Episodes most frequently affected all four limbs (25 of 29) and the head and neck (21 of 29). Borborygmi were reported during episodes in 11 of 29 dogs. Episodes of vomiting and diarrhoea occurred in 14 of 29, with 50% of these being immediately before or after episodes of canine epileptoid cramping syndrome (7 of 14). Most owners (26 of 29) had changed their dog's diet, with approximately 50% (14 of 26) reporting a subsequent reduction in the frequency of episodes.

CLINICAL SIGNIFICANCE

This study demonstrates similarities in the phenotype of canine epileptoid cramping syndrome to paroxysmal dystonic choreoathetosis, a paroxysmal dyskinesia reported in humans. This disorder appears to be associated with gastrointestinal signs in some dogs and appears at least partially responsive to dietary adjustments.

Characterization and mode of inheritance of a paroxysmal dyskinesia in Chinook dogs

BACKGROUND

Paroxysmal dyskinesias are episodes of abnormal, involuntary movement or muscle tone, distinguished from seizures by the character of the episode and lack of seizure activity on ictal EEG.

HYPOTHESIS

Paroxysmal dyskinesia is an inherited, autosomal recessive disorder in Chinook dogs.

ANIMALS

Families of Chinook dogs with paroxysmal dyskinesia.

METHODS

Pedigrees and medical histories were reviewed for 299 Chinook dogs. A family of 51 dogs was used for analysis. Episodes were classified as seizures, paroxysmal dyskinesia, or unknown, and segregation analysis was performed.

RESULTS

Paroxysmal dyskinesia was identified in 16 of 51 dogs and characterized by an inability to stand or ambulate, head tremors, and involuntary flexion of 1 or multiple limbs, without autonomic signs or loss of consciousness. Episode duration varied from minutes to an hour. Inter-ictal EEGs recorded on 2 dogs with dyskinesia were normal. Three dogs with dyskinesia also had generalized tonic-clonic seizures. One of 51 dogs had episodes of undetermined type. Phenotype was unknown for 6 of 51 dogs, and 28 dogs were unaffected. Segregation was consistent with an autosomal recessive trait.

CONCLUSIONS AND CLINICAL IMPORTANCE

This movement disorder is prevalent in the Chinook breed, and consistent with a partially penetrant autosomal recessive or polygenic trait. Insufficient evidence exists for definitive localization; episodes may be of basal nuclear origin, but atypical seizures and muscle membrane disorders remain possible etiologies. The generalized seizures may be a variant phenotype of the same mutation that results in dyskinesia, or the 2 syndromes may be independent.

Anticonvulsant responsive, episodic movement disorder in a German shorthaired pointer

An episodic movement disorder is described in a young German shorthaired pointer. Movement disorders are rare, but well-described, neurological conditions in human beings. An attempt is made to classify this disorder using current human guidelines. Unlike previously described movement disorders in dogs, this case responded very well to two commonly used anticonvulsant therapies, suggesting that trial therapy with these drugs is worthwhile in similar cases.

Dyskinesia in an adult bichon frise

Dyskinesias are disorders of the central nervous system that result in involuntary movements in a fully conscious individual. This report describes a disorder in a five-year-old male neutered bichon frise characterised by episodic involuntary skeletal muscle activity with normal levels of consciousness that bears some similarity to the previously described movement disorder in boxer puppies and to the human condition descriptively referred to as paroxysmal dystonic choreoathetosis. The disorder was differentiated from partial motor seizure activity by the character of the episodes, absence of identifiable preceding aura, absence of autonomic signs and the fact that multiple limbs were affected in a varying pattern without generalisation and loss of consciousness. Movement disorders are a well documented group of disorders in human neurology, but only rarely described in the veterinary literature. The purpose of this report is to contribute to an increased awareness of movement disorders within veterinary practice.