Almost 30 years ago a syndrome of exercise-induced muscle hypertonicity and falling (Episodic Falling, EFS) was described in young Cavalier King Charles Spaniels (1-3, and June 2001 Case of the Month). Clinical signs included exercise and excitement-induced “collapse” that was preceded by a “deer-stalking” action with the head held close to the ground and the bottom high in the air. An increasingly stilted gait was observed until there was finally collapse to one side. An increase in extensor tone in the muscles of both the thoracic and pelvic limbs was present during the period of collapse. The time period required for recovery of limb function was usually about 10 minutes. Mentation was normal throughout the episodes. Electromyographic evaluation showed the muscles were electrically silent. Dogs were neurologically normal between episodes.
A microdeletion in the central nervous system gene BCAN1 has been shown to be highly associated with EFS in CKCS dogs and a scientific paper recently published (4). The carrier rate was approximately 13% suggesting that the EFS microdeletion is present at a high frequency in the general CKCS population. Molecular genetic testing for the EFS microdeletion is now available through Laboklin. Information regarding testing can be found at the link below.
1. Herrtage ME, Palmer AC. Episodic falling in the Cavalier King Charles Spaniel. Veterinary Record 1983;112:458-459.
2. Wright JA, Browlie SE, Smyth JBA et al. Muscle hypertonicity in the cavalier King Charles spaniel – myopathic features. Veterinary Record 1986;118:511-512.