Episodic falling syndrome (EFS)
Episodic falling syndrome is a syndrome of muscle stiffness and collapse, a paroxysmal hypertonicity disorder found in Cavalier King Charles spaniels. It is a recessive hereditary condition and is often mistaken with epileptic seizures. It is caused by a deletion in BCAN gene, encoding the brain-specific extracellular matrix proteoglycan brevican which has an essential role in the formation of perineuronal nets governing synapse stability and nerve conduction velocity. Episodes begin between fourteen weeks and four years of age and are triggered by exercise, stress or excitement and characterized by progressive hypertonicity throughout the thoracic and pelvic limbs, resulting in a characteristic ‘deer-stalking’ position and/or collapse. Between episodes, dogs appear to be completely normal neurologically. Carriers are found to be extremely common (12.9%).
Gill, J.L., Tsai, K.L., Krey, C., Noorai, R.E., Vanbellinghen, J.-F., Garosi, L.S., Shelton, G.D., Clark, L.A., and Harvey, R.J. (2012). A canine BCAN microdeletion associated with episodic falling syndrome. Neurobiol Dis 45, 130–136.