Genetic basis of Episodic Falling Syndrome - in Cavalier King Charles Spaniels it is an autosomal recessive inherited disorder caused by a mutation in the brevican gene (BCAN). Brevican encodes a brain-specific extracellular matrix proteoglycan important for neuronal plasticity, synaptic stability, and axonal conduction. Dogs must inherit two copies of the mutated gene (one from each parent) to be affected, while carriers with one copy do not show symptoms but can pass the mutation on. Genetic testing for the BCAN mutation is available and widely used to identify clear, carrier, and affected dogs, which assists breeders in reducing disease incidence.
Pathophysiology - EFS is a paroxysmal hypertonicity disorder characterized by episodes of increased muscle tone and spasticity, primarily affecting the limbs. The BCAN mutation disrupts synaptic stability and nerve conduction, leading to episodic limb stiffness and an inability to relax muscles normally. During episodes, affected dogs exhibit a “praying” or “deer-stalking” posture with locked, extended limbs and may collapse. Episodes are often triggered by exercise, excitement, stress, or frustration, last from a few seconds to several minutes, and resolve spontaneously. Between episodes, dogs appear neurologically normal. The severity and frequency of episodes vary without a clear progressive pattern, and symptoms may improve with age.
Complications - Clinical signs include sudden limb rigidity, stumbling, muscle stiffness, and collapse, often accompanied by facial muscle stiffness and a “bunny-hopping” gait. Episodes can cause overheating due to impaired panting during muscle rigidity. Although not painful or associated with loss of consciousness, severe or frequent episodes can significantly impair quality of life. Some severely affected dogs may be euthanized. There is no evidence of damage to central or peripheral nervous system structures on microscopic examination. The disorder typically begins between 14 weeks and 4 years of age.
Why This Matters to Breeders and Vets - Breeders must utilize genetic testing to avoid breeding two carriers, which has a 25% risk per puppy of producing affected offspring. This is key to reducing disease prevalence in the breed. Veterinarians must recognize the clinical signs and differentiate EFS from epilepsy or other neurological disorders. Confirmation via genetic testing aids diagnosis. Some dogs respond to medications such as clonazepam or acetazolamide, but many cases are managed by avoiding known triggers and supportive care. Early diagnosis can improve care and owner education. EFS is unique to Cavaliers and is a major inherited movement disorder affecting the breed, underscoring the importance of informed breeding and clinical management.
Summary - Episodic Falling Syndrome in Cavalier King Charles Spaniels is an autosomal recessive neurological disorder caused by a BCAN gene mutation leading to episodic muscle hypertonicity and spastic limb rigidity. Episodes are triggered by exercise, excitement, or stress and cause characteristic “praying” postures and occasional collapse but resolve spontaneously. Affected dogs appear normal between episodes. Genetic testing allows for detection and prevention via careful breeding. While no cure exists, some dogs improve with age or treatment, and avoiding triggers aids management. Understanding this disorder is essential for breeders and veterinarians to support affected dogs and control disease within the breed.