Phenotypic characterization of paroxysmal dyskinesia in Maltese dogs

Suspected paroxysmal dyskinesia in four small-breed dogs: Clinical presentation, diagnosis, management and prognosis

This case report details the clinical presentation, diagnosis, management and prognosis of paroxysmal dyskinesia (PD) in four small-breed dogs, each weighing under 6 kg: A 7-year-old spayed female Pomeranian, an 8-year-old female mixed breed, a 1-year-old female Pomeranian and a 9-year-old castrated male Poodle. These dogs were referred to our hospital due to movement disorders. Diagnosis was facilitated by video recordings of the episodes, assessing motor activity, consciousness, episode duration, any pre- or post-episodic behaviour as well as the presence of autonomic signs. Magnetic resonance imaging conducted on two of the dogs returned unremarkable results. Treatment trials included a gluten-free diet for all four dogs, with two also receiving acetazolamide. This intervention led to a decrease in the frequency of abnormal movement in all patients. Our findings suggest that PD in dogs can be effectively diagnosed through detailed symptom description using videos and questionnaires. Furthermore, once diagnosed, a combination of nutritional and medical management can be beneficial.

Canine paroxysmal dyskinesia-a review

Paroxysmal dyskinesias (PDs) are a group of involuntary, hyperkinetic movement disorders that recur episodically and may last seconds to hours. An important feature of PD is that there is no loss of consciousness during the episode. Using a clinical classification, three main types of PDs have been distinguished in canine PD: (1) paroxysmal kinesigenic dyskinesia (PKD) that commences after (sudden) movements, (2) paroxysmal non-kinesigenic dyskinesia (PNKD) not associated with exercise and can occur at rest, and (3) paroxysmal exertion-induced dyskinesia (PED) associated with fatigue. Canine PDs are diagnosed based on the clinical presentation, history, and phenomenology. For the latter, a video recording of the paroxysmal event is extremely useful. An etiological classification of canine PDs includes genetic (proven and suspected), reactive (drug-induced, toxic, metabolic, and dietary), structural (neoplasia, inflammatory, and other structural causes), and unknown causes. In this review, an overview of all reported canine PDs is provided with emphasis on phenotype, genotype, and, where possible, pathophysiology and treatment for each reported canine PD.

Dystonic head tremor in paroxysmal dyskinesia in 17 dogs (2021-2023)

BACKGROUND

Dystonia is a common component of the movement disorder paroxysmal dyskinesia (PD) in dogs. However, the incidence of dystonic head tremor (DHT) in these dogs has not previously been evaluated.

METHODS

The medical records of dogs presenting with PD between 2021 and 2023 were retrospectively reviewed, and those with available video footage and the presence of a head tremor were selected for further analysis.

RESULTS

Seventeen of the 39 (43.6%) dogs diagnosed with PD that had video footage available manifested DHT. Poodle or Poodle-cross was the most commonly affected breed (7/17). DHTs were described as fine irregular head tremors accompanied by cervical dystonia (17/17), truncal (11/17) or head (10/17) sway, shifting limb (10/17) or single limb (6/17) dystonia, freezing (8/17), ataxia (6/17), ptyalism (5/17), falling (5/17), kyphosis (4/17) and prayer posture (4/17). Neurological examination and advanced imaging, when available, were within normal limits.

LIMITATIONS

The limitations of the study include its retrospective nature, the lack of video recordings for all PD patients and the lack of electrophysiological evaluation of tremors and electroencephalography.

CONCLUSIONS

DHT exists in dogs with PD; it has characteristic features, and it should be considered in differential diagnoses for dogs with head tremors.

Very-Low-Frequency Spike-Wave Complex Partial Motor Seizure Mimicking Canine Idiopathic Head Tremor Syndrome in a Dog

Canine idiopathic head tremor syndrome (CIHTS) represents a benign condition characterized by episodic, uncontrolled movement of the head. Even though the condition might be an expression of a partial motor epilepsy, to date, there is a limited number of studies describing the electroencephalographic features. In this report, we describe the case of a dog diagnosed with partial motor epilepsy resembling CIHTS symptomatology, a new slow spike-wave complex pattern similar to that of Lennox-Gastaut syndrome in humans identified on electroencephalographic examination. We also studied the efficacy of phenobarbitone therapy over a period of two years.

Long-term nutritional management of an obese German Spitz with paroxysmal dyskinesia, calcium oxalate urolithiasis, and suspected pancreatitis—A case report

Background

To our knowledge, this is the first description of long-term nutritional management in a dog with paroxysmal dyskinesia.

Case summary

An obese 9-year-old, male entire, German Spitz was presented for dietary management after being diagnosed with calcium oxalate urolithiasis and suspected pancreatitis. Since he was seven years old, the dog has had a history of neurological signs, which were thought to be epileptic seizures. He was treated with phenobarbital and potassium bromide and was clinically controlled. For his nutritional advice, aiming to minimize one of the most important risk factors for the diseases, a weight loss program was started and successfully executed. However, 10 months later, the dog restarted presenting neurological episodes at a high frequency (3x/week). Based on videos and the characteristics of the neurological signs, the dog was diagnosed with paroxysmal dyskinesia. To investigate the role of gluten intake on this patient's neurological signs, a dietary trial with a commercial hypoallergenic diet (gluten-free; hydrolyzed protein) was followed. During the 3 months of the dietary trial, four neurologic episodes related to food indiscretion occurred. Upon the decrease in neurological episodes, the anti-seizure drugs were slowly discontinued. During this period, the dog presented only two neurologic episodes that were related to the days that the anti-seizure drugs were decreased. For 4 months the dog remained episode-free. However, a change in the dog's diet to another gluten-free diet (higher fat) led the dog to vomit and experience another neurologic episode. Once the dog was back to the previous gluten-free diet, it clinically improved, and no other clinical signs were reported by the client during the next 5 months.

Conclusion

Although a relationship between gluten and paroxysmal dyskinesia cannot be confirmed, the dog's improvement after the nutritional management and the removal of the anti-seizure therapy is supportive of dietary association.

Emotional Arousal Impacts Physical Health in Dogs: A Review of Factors Influencing Arousal, with Exemplary Case and Framework

Excessive emotional arousal has been shown to impact physiological health in both veterinary species and human animals. The focus of work in many models of veterinary behavioural medicine has predominantly been associated with reducing activation of the protective emotional systems; in particular, fear-anxiety. The management of the engaging emotional systems of desire-seeking, social play, care and lust has not traditionally been considered in the treatment of physiological health of veterinary species. This article reviews the literature in both veterinary and human fields on the relationship between emotional arousal of both protective and engaging emotional systems and physical health conditions. The current literature describing the regulatory control of sleep on emotional arousal is also discussed. An exemplary case report of a seven month old male entire Cocker Spaniel showing fly-snapping behaviour which had been non-responsive to leviteracetam (Keppra) is presented. The emotional health assessment and treatment of this case is described along with the short and long term (fourteen month follow up) outcomes to demonstrate that some patients presenting in this way can be effectively managed with an appropriate behavioural medicine treatment plan. The authors put forward the argument that an emotional health assessment should be considered an essential component of the work up of all such cases.

The role of nutrition in canine idiopathic epilepsy management: Fact or fiction?

In the last decade, nutrition has gained interest in the management of canine idiopathic epilepsy (IE) based on growing scientific evidence. Diets can serve their functions through many pathways. One potential pathway includes the microbiota-gut-brain axis, which highlights the relationship between the brain and the intestines. Changing the brain's energy source and a number of dietary sourced anti-inflammatory and neuroprotective factors appears to be the basis for improved outcomes in IE. Selecting a diet with anti-seizure effects and avoiding risks of proconvulsant mediators as well as interference with anti-seizure drugs should all be considered in canine IE. This literature review provides information about preclinical and clinical evidence, including a systematic evaluation of the level of evidence, suggested mechanism of action and interaction with anti-seizure drugs as well as pros and cons of each potential dietary adaptation in canine IE.

Phenotypic characterisation of paroxysmal dyskinesia in Sphynx cats

OBJECTIVES

The aim of this study was to identify the phenotypic features of a paroxysmal dyskinesia observed in Sphynx cats.

METHODS

The owners of affected Sphynx cats were invited to provide video footage of abnormal episodes for review. Those that demonstrated episodes consistent with paroxysmal dyskinesia were then invited to complete an online questionnaire designed to allow further characterisation.

RESULTS

Ten Sphynx cats were included in the study. All affected cats were <4 years of age at the onset of the episodes (range 0.5-4.0). The episodes had a duration of <5 mins in 9/10 cats (range 0.5-10), while episode frequency was variable between and within individual cats. The episodes were characterised by impaired ambulation due to muscle hypertonicity, most commonly affecting the hips and pelvic limbs (9/10) and shoulders and thoracic limbs (8/10). The head and neck (6/10), tail (5/10), and back and abdomen (3/10) were also involved in some cats. Sudden movement, excitement and stress were identified as possible triggers for the episodes in three cats. Therapeutic intervention was not attempted in 7/10 cases, although two cats were reported to become free of the episodes while receiving acetazolamide. The two cats that were followed beyond 2 years from onset entered spontaneous remission. None of the owners believed that the abnormal episodes had affected the quality of life of their cat.

CONCLUSIONS AND RELEVANCE

The phenotype of paroxysmal dyskinesia in Sphynx cats presented in this study appears to share similarities with paroxysmal kinesigenic dyskinesia described in human classification systems. Some cats appear to achieve episode freedom spontaneously. Subsequent research should focus on evaluating response to treatment and determining an underlying genetic cause.

Clinical characterisation of a novel paroxysmal dyskinesia in Welsh terrier dogs

Breed specific paroxysmal dyskinesias are increasingly recognised in veterinary medicine. We aimed to characterise the phenomenology, clinical course and prevalence of a previously unreported paroxysmal dyskinesia in the Welsh terrier breed. Clinical records of five Welsh terriers with paroxysmal episodes were reviewed. Additionally, owners of Welsh terriers were invited to complete a questionnaire with the aim of characterising paroxysmal episodes in the wider breed population. Clinical examinations (n = 5) and diagnostic investigations (n = 2) of affected Welsh terriers were within normal limits, apart from mild-moderate ventriculomegaly on cranial magnetic resonance imaging (n = 3). The survey of Welsh terrier owners revealed episodes consistent with a paroxysmal dyskinesia in 41 (22.8%) of 177 respondents. Median age of onset was 59 months. Episodes were predominantly characterised by sustained hypertonicity with periods of limb flexion, abnormal head and body posture, with preserved consciousness. Episode duration ranged from 30 s to 30 min (median, 3 min 30 s), with frequency varying widely between dogs. Affected dogs demonstrated a stable to improving clinical course in most cases. This study investigated a previously unreported paroxysmal dyskinesia in Welsh terriers. Similar clinical signs within the breed were potentially consistent with an inherited cause, worthy of further investigation.

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.

A knockout mutation associated with juvenile paroxysmal dyskinesia in Markiesje dogs indicates SOD1 pleiotropy

A juvenile form of paroxysmal dyskinesia segregated in the Markiesje dog breed. Affected pups exhibited clinical signs of a severe tetraparesis, dystonia, cramping and falling over when trying to walk. In most cases, the presentation deteriorated within weeks and elective euthanasia was performed. Pedigree analysis indicated autosomal recessive inheritance. Genome-wide association and homozygosity mapping of 5 affected dogs from 3 litters identified the associated locus on chromosome 31 in the region of SOD1. The DNA sequence analysis of SOD1 showed that the patients were homozygous for a frameshift mutation in the fourth codon. None of the other analyzed dogs of the breed was homozygous for the mutation, indicating full penetrance of the genetic defect. Mutations in SOD1 are known to cause recessive degenerative myelopathy in middle-aged dogs with low penetrance and dominant amyotrophic lateral sclerosis in humans with variable age of onset. Our findings are similar to recent observations in human patients that a loss of function mutation in SOD1 leads to a juvenile neurologic disease distinct from amyotrophic lateral sclerosis.

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.

Phenotypic characterization of PIGN-associated paroxysmal dyskinesia in Soft-coated wheaten terriers and preliminary response to acetazolamide therapy

A hereditary movement disorder in Soft coated wheaten terriers (SCWT) has been associated with a mutation in PIGN which encodes an enzyme involved in synthesis of glycosylphosphatidylinositol (GPI). The objective of this study was to describe and classify the clinical phenotype and assess therapeutic response. Twenty-five SCWT and related dogs homozygous for PIGN:c.398C>T with paroxysmal dyskinesia were available for inclusion. Medical records and video recordings of 17 dogs were evaluated in a retrospective case series. Affected dogs had episodes of involuntary, hyperkinetic movements and dystonia. Median age of onset was 2.5 years. A typical episode consisted of rapid, irregular hyperflexion and extension of the pelvic limbs with some degree of truncal dystonia. A mild episode consisted of spontaneous flexion of one pelvic limb while walking which could resemble a lameness. Episodes lasted several minutes to several hours and occurred up to 10 times/day or more. They were not associated with exercise or fasting but were sometimes triggered by excitement or stress. Acetazolamide therapy improved nine of 11 dogs, in seven cases abolishing episodes. Five of 17 dogs treated with other agents had mild improvement with clonazepam (n = 2), levetiracetam (n = 1), or phenobarbital (n = 2). Paroxysmal dyskinesias must be differentiated from seizure disorders since they often respond to different therapies. The SCWT phenotype consisted predominantly of hyperkinesia, and can respond dramatically to acetazolamide. GPI anchors proteins to the cell surface including carbonic anhydrase IV which modulates synaptic pH in the brain. Altered activity of this enzyme may be the target of acetazolamide therapy.

Clinical features of muscle cramp in 14 dogs

BACKGROUND

Muscle cramps (MCs) are prolonged, involuntary, painful muscle contractions characterized by an acute onset and short duration, caused by peripheral nerve hyperactivity.

OBJECTIVES

To provide a detailed description of the clinical features and diagnostic findings in dogs affected by MCs.

ANIMALS

Fourteen dogs.

METHODS

Multicenter retrospective case series. Cases were recruited by a call to veterinary neurologists working in referral practices. Medical records and videotapes were searched for dogs showing MCs. The follow-up was obtained by telephone communication with the owner and the referring veterinarian.

RESULTS

Three patterns of presentation were identified depending on the number of affected limbs and presence/absence of migration of MCs to other limbs. In 9/14 (64%) of dogs, MCs were triggered by prompting the dogs to move. 8/14 (58%) dogs were overtly painful with 6/14 (42%) showing mild discomfort. The cause of MCs was hypocalcemia in 11/14 (79%) dogs: 9 dogs were affected by primary hypoparathyrodism, 1 dog by intestinal lymphoma and 1 dog by protein losing enteropathy. In 3/14 cases (21%) the cause was not identified, and all 3 dogs were German Shepherds.

CONCLUSIONS AND CLINICAL IMPORTANCE

Muscle cramps can manifest in 1 of 3 clinical patterns. Muscle cramps are elicited when dogs are encouraged to move and do not always appear as painful events, showing in some cases only discomfort. The main cause of MCs in this study was hypocalcemia consequent to primary hypoparathyroidism. In dogs having MCs of unknown etiology, idiopathic disease or paroxysmal dyskinesia could not be ruled out.

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.