With continued advances in veterinary medicine, an increasing number of movement disorders are recognized. These are a heterogeneous group of disorders characterized by episodic and sudden involuntary movements of specific muscle groups. Animals are normal between episodes and do not demonstrate autonomic signs or alterations in consciousness during episodes.¹ Animals with movement disorders are often normal when presented to a veterinary surgeon, clinical signs are difficult to explain by a specific neuro-anatomical localization, and can be difficult to differentiate from seizure disorders.² The clinical approach to animals with movement disorders is further complicated by inconsistent terminology, lack of useful classification systems, and uncertainties in etiology and pathophysiology. Despite these difficulties, movement disorders can often be recognized by a combination of highly consistent and specific clinical signs in a susceptible breed. Because most movement disorders occur in specific breeds, a hereditary etiology is considered likely for most of them. Although specific genetic tests are emerging, diagnosis of movement disorders is often based on recognition of specific signs in a specific breed and exclusion of other, more common, conditions.¹

Episodic Head Tremor Syndrome

('Head bobbing')

Although this syndrome has been described in several dog breeds, it is particularly common in Doberman Pinschers, English Bulldogs, and Boxers.^3,4 Affected dogs typically nod their head horizontally or vertically at a relative high frequency of 5 to 8 Hz. Dogs do not lose consciousness and seem to be aware of the episode.

The majority of dogs can be distracted out of the episode by food, verbal commands, or other interactions. The first episode of head tremors occurs typically at a young age and can occur at every time during the day. Duration and frequency of the episodes is variable between and within dogs. It can vary from just a few seconds to several hours and can occur several times a day to once every few months. This syndrome does not seem to affect quality of life and 50% of dogs 'grow out' of the episodes without specific treatment.⁴ There is no specific treatment available for episodic head tremor syndrome.

Canine Epileptoid Cramping Syndrome in Border Terriers

This disorder was initially referred to as 'Spike's disease' after the first dog in which it was recognized. Episodes do not seem to be triggered by specific events. Although most dogs will have their first episode before 3 years of age, there is a wide variety in age at onset of episodes (0.2 to 7 years). Episodes most often affect all limbs and are characterized by tremors, difficulties walking, difficulties standing, dystonia of the limbs, head, and neck, air licking and stretching.⁵ This condition is possibly linked to gastrointestinal disease. Many owners report borborygmi, vomiting and diarrhea immediately before or after an episode.⁵ This disorder has recently been suggested to represent a gluten-sensitive movement disorder potentially responsive to a gluten-free diet.⁶

Episodic Falling in Cavalier King Charles Spaniels

Affected dogs demonstrate episodic involuntary movements and muscular hypertonicity of all 4 limbs. Episodes are often associated with episodes of stress or exercise and are characterized by lowering of the head, arching of the lumbar spine, stiffness of the limbs resulting in a 'deer-stalking' posture, and falling over. The duration of episodes varies from a few seconds to several minutes and affected dogs are typically younger than 2 years of age when the first episode occurs.⁷ Dogs do not lose consciousness and can often be distracted by the owner. This condition is caused by a mutation in the BCAN gene and a genetic test is commercially available.⁸ Not all dogs homozygous for the mutation will, however, develop clinical signs.⁸ A variable response is seen to medication with clonazepam and acetazolamide.

Scottie Cramp in Scottish Terriers

Episodes are characterized by episodes of hypertonicity and can vary in severity. Mildly affected dogs can demonstrate signs of mild pelvic limb stiffness and bunny hopping, while more severely affected dogs demonstrate episodes similar to those of Cavalier King Charles spaniels with episodic falling syndrome.⁹ Affected dogs are generally young and episodes start early in life (approximately 6 months of age). Episodes are reportedly triggered by stress, exercise, and excitement, and vary between 5 and 20 minutes in duration. Medication with fluoxetine and diazepam has been reported to be beneficial in the majority of affected dogs.⁹ Clinical signs can be elicited by administration of serotonin antagonists, such as methysergide or methionine. A clinically identical syndrome has been observed in West Highland White terriers, Cairn terriers, and Norwich terriers.¹

Paroxysmal Dyskinesia in Chinook Dogs

This familial form of paroxysmal dyskinesia, previously referred to as 'Chinook seizures', typically starts in dogs younger than 3 years of age. Episodes are not triggered by specific events, can last minutes to one hour, and can occur several times a day to only several times a year. The episodes are characterized by flailing or kicking, sustained limb flexion combined with repetitive small limb movements, and head tremor. Dogs do not lose consciousness and remain responsive during the episodes.¹⁰ An autosomal-recessive mode of inheritance is suspected. Interestingly, occurrence of epileptic seizures has been reported in affected and non-affected, but related dogs.¹⁰

References

1.  Urkasemsin G, Olby NJ. Canine paroxysmal movement disorders. Vet Clin Small Anim. 2014;44:1091–1102.

2.  Packer RM, Berendt M, Bhatti S, et al. Inter-observer agreement of canine and feline paroxysmal event semiology and classification by veterinary neurology specialists and non-specialists. BMC Vet Res. 2015;11:39.

3.  Wolf M, Bruehschwein A, Sauter-Louis C, et al. An inherited episodic head tremor syndrome in Doberman pinscher dogs. Mov Disord. 2011;26:2381–2386.

4.  Guevar J, De Decker S, Van Ham LM, et al. Idiopathic head tremor in English bulldogs. Mov Disord. 2014;29:191–194.

5.  Black V, Garosi L, Lowrie M, et al. Phenotypic characterisation of canine epileptoid cramping syndrome in the Border terrier. J Small Anim Pract. 2014;55:102–107.

6.  Lowrie M, Garden OA, Hadjivassiliou M, et al. The clinical and serological effect of a gluten-free diet in border terriers with epileptoid cramping syndrome. J Vet Intern Med. 2015;29:1564–1568.

7.  Garosi LS, Platt SR, Shelton GD. Hypertonicity in Cavalier King Charles spaniels. J Vet Intern Med. 2002;16:330.

8.  Gill JL, Tsai KL, Krey C, et al. A canine BCAN microdeletion associated with episodic falling syndrome. Neurobiol Dis. 2012;45:130–136.

9.  Urkasemsin G, Olby NJ. Clinical characteristics of Scottie cramp in 31 cases. J Small Anim Pract. 2015;56:276–280.

10. Packer RA, Patterson EE, Taylor JF, et al. Characterization and mode of inheritance of a paroxysmal dyskinesia in Chinook dogs. J Vet Intern Med. 2010;24:1305–1313.