Episodic Falling Syndrome
Episodic falling syndrome (EFS) is a unique genetic disorder in the cavalier King Charles spaniel. It has been recognized in the breed since the 1960s. No other breed is known to suffer from it.
EFS is a non-progressive disorder that tends to improve with therapy, and the life spans of affected dogs do not appear to be shortened by the disease.
Veterinarians may refer to it as "episodic hypertonicity" or "hyperexplexia" or "muscle hypertonicity" (and medically known as "paroxysmal exercise-induced dystonia or dyskinesia") However, research has established that EFS is not a muscular condition, but is due to a single recessive gene associated with brain function, a mutation of the BCAN gene, found only in cavaliers. As a result, affected puppies are more likely to be found in cases of line breeding or inbreeding on carrier bloodlines.
Until 2010, EFS appeared to be a life-long condition of the cavaliers affected by it. However, research that year found that milder cases of EFS are more of a common condition in the CKCS, which tend to stabilize by age one year. EFS rarely is life-threatening.
Some researchers have suggested that EFS in cavaliers may be associated with another disorder unique to the breed, called "idiopathic asymptomatic thrombocytopenia", an abnormally low number of blood platelets. Drs. Jens Häggström and Clarence Kvart of Sweden have noted in a 1997 article that thromboembolic events in the cerebral circulation of blood may be involved in EFS.
Symptoms of EFS vary, but they all are attributed to the dog’s muscles being unable to relax. Typical signs include the cavalier engaged in exercise or being excited or stressed, and then suddenly develop a rigid gait in the rear limbs, extending and retracting in an exaggerated, stiff manner, like that of a hopping rabbit. The dog’s back may be arched, and the dog often yelps. One or more limbs may also protract excessively.
The dog may lose its footing while running. It usually loses all coordination and collapses on its side or on its face. When the cavalier collapses, it may hold its forelegs over its head. In some instances, the cavalier’s symptoms follow a “deer-stalking” behavior, with its head held close to the ground and its rear high in the air, as if stalking game. In the most severe cases, the dog may hold its head so low that its hind quarters somersault over its head. The affected cavalier may exhibit these symptoms only when excited or stressed, but in some cases, the behaviors have not been stress-induced. The dog may also overheat during an episode, possibly due to an inability to pant.
The cavalier does not lose consciousness during the episodes, and mentally, it remains normal. Technically, the collapse is not a seizure, although it may be appear as one. The CKCS appears to know what is happening to it, and sees clearly, but loses control of its body. Afterwards, in most instances the dog recovers relatively quickly; it stands up and acts as if nothing unusual had occurred. However, if the cavalier exercises again immediately after recovery, it may induce another episode.
Also, some severely affected cavaliers have been known to lapse into repeated, lengthy episodes of the syndrome, and may even suffer permanent neurological injuries and not be able to recover from the attacks. At least a few CKCSs are known to have been euthanized to avoid continued suffering from the disorder.
It is to be distinguished from presyncope, another disorder to which cavalier King Charles spaniels are predisposed, which has some of the same symptoms. Syncope in cavaliers is associated with late stages of mitral valve disease.
Episodic falling syndrome is the result of a single recessive gene mutation associated with neurological function. Until 2010, EFS had been believed to be a type of metabolic muscle disorder. The ages of cavaliers studied with EFS have varied from two months to four years. Both male and female CKCSs are affected.
The dogs are neurologically normal between episodes. Electromyographic evaluation detects the muscles at rest and engaged in no abnormal spontaneous activity. There is no evidence of heart or respiratory problems during the episode or the collapse. Blood tests, spinal fluid analysis, muscle biopsies, and magnetic resonance imaging (MRI) of the brain have not proved to be helpful in diagnosing the syndrome. Diagnosis, therefore, has been based solely upon the symptoms of the episode.
Since some of the symptoms of EFS are similar to other disorders, such as liver shunt, an epileptic seizure, or syringomyelia, the examining veterinarian may mis-diagnose the episodes and unnecessarily screen the dog for those other maladies. The primary differences between EFS and other disorders are that they usually are induced by exercise, excitement, stress, or apprehension; the EFS-affected dog remains conscious during the episodes; and the dog rarely will experience any continuing pain or discomfort.
Therefore, video recordings of the dog’s EFS episodes are helpful to the veterinarian in diagnosing the disorder. If a video device is not available, the owner should write a precise report of the Cavalier’s behaviors during the episode, to avoid mis-diagnosis, needless testing, and treatment with drugs which may inadvertently aggravate the condition.
In 2011, two UK research groups independently developed DNA swab tests for detecting a recessive gene associated with brain function, the BCAN gene, which, when mutated, is the cause of episodic falling disorder in the CKCS. EFS is inherited as a autosomal recessive trait. If a DNA-tested cavalier is found to not have the mutated BCAN gene, then it is "clear" of EFS. If the dog is found to have two of the mutated gene, then it is "affected" and has EFS, whether it shows symptoms or not. If the dog is found to have only one of the mutated gene, then it is not affected but is "a carrier".
EFS is a non-progressive disorder that tends to improve with therapy, and the life spans of affected dogs do not appear to be shortened by the disease.
Veterinarians may refer to it as "episodic hypertonicity" or "hyperexplexia" or "muscle hypertonicity" (and medically known as "paroxysmal exercise-induced dystonia or dyskinesia") However, research has established that EFS is not a muscular condition, but is due to a single recessive gene associated with brain function, a mutation of the BCAN gene, found only in cavaliers. As a result, affected puppies are more likely to be found in cases of line breeding or inbreeding on carrier bloodlines.
Until 2010, EFS appeared to be a life-long condition of the cavaliers affected by it. However, research that year found that milder cases of EFS are more of a common condition in the CKCS, which tend to stabilize by age one year. EFS rarely is life-threatening.
Some researchers have suggested that EFS in cavaliers may be associated with another disorder unique to the breed, called "idiopathic asymptomatic thrombocytopenia", an abnormally low number of blood platelets. Drs. Jens Häggström and Clarence Kvart of Sweden have noted in a 1997 article that thromboembolic events in the cerebral circulation of blood may be involved in EFS.
Symptoms of EFS vary, but they all are attributed to the dog’s muscles being unable to relax. Typical signs include the cavalier engaged in exercise or being excited or stressed, and then suddenly develop a rigid gait in the rear limbs, extending and retracting in an exaggerated, stiff manner, like that of a hopping rabbit. The dog’s back may be arched, and the dog often yelps. One or more limbs may also protract excessively.
The dog may lose its footing while running. It usually loses all coordination and collapses on its side or on its face. When the cavalier collapses, it may hold its forelegs over its head. In some instances, the cavalier’s symptoms follow a “deer-stalking” behavior, with its head held close to the ground and its rear high in the air, as if stalking game. In the most severe cases, the dog may hold its head so low that its hind quarters somersault over its head. The affected cavalier may exhibit these symptoms only when excited or stressed, but in some cases, the behaviors have not been stress-induced. The dog may also overheat during an episode, possibly due to an inability to pant.
The cavalier does not lose consciousness during the episodes, and mentally, it remains normal. Technically, the collapse is not a seizure, although it may be appear as one. The CKCS appears to know what is happening to it, and sees clearly, but loses control of its body. Afterwards, in most instances the dog recovers relatively quickly; it stands up and acts as if nothing unusual had occurred. However, if the cavalier exercises again immediately after recovery, it may induce another episode.
Also, some severely affected cavaliers have been known to lapse into repeated, lengthy episodes of the syndrome, and may even suffer permanent neurological injuries and not be able to recover from the attacks. At least a few CKCSs are known to have been euthanized to avoid continued suffering from the disorder.
It is to be distinguished from presyncope, another disorder to which cavalier King Charles spaniels are predisposed, which has some of the same symptoms. Syncope in cavaliers is associated with late stages of mitral valve disease.
Episodic falling syndrome is the result of a single recessive gene mutation associated with neurological function. Until 2010, EFS had been believed to be a type of metabolic muscle disorder. The ages of cavaliers studied with EFS have varied from two months to four years. Both male and female CKCSs are affected.
The dogs are neurologically normal between episodes. Electromyographic evaluation detects the muscles at rest and engaged in no abnormal spontaneous activity. There is no evidence of heart or respiratory problems during the episode or the collapse. Blood tests, spinal fluid analysis, muscle biopsies, and magnetic resonance imaging (MRI) of the brain have not proved to be helpful in diagnosing the syndrome. Diagnosis, therefore, has been based solely upon the symptoms of the episode.
Since some of the symptoms of EFS are similar to other disorders, such as liver shunt, an epileptic seizure, or syringomyelia, the examining veterinarian may mis-diagnose the episodes and unnecessarily screen the dog for those other maladies. The primary differences between EFS and other disorders are that they usually are induced by exercise, excitement, stress, or apprehension; the EFS-affected dog remains conscious during the episodes; and the dog rarely will experience any continuing pain or discomfort.
Therefore, video recordings of the dog’s EFS episodes are helpful to the veterinarian in diagnosing the disorder. If a video device is not available, the owner should write a precise report of the Cavalier’s behaviors during the episode, to avoid mis-diagnosis, needless testing, and treatment with drugs which may inadvertently aggravate the condition.
In 2011, two UK research groups independently developed DNA swab tests for detecting a recessive gene associated with brain function, the BCAN gene, which, when mutated, is the cause of episodic falling disorder in the CKCS. EFS is inherited as a autosomal recessive trait. If a DNA-tested cavalier is found to not have the mutated BCAN gene, then it is "clear" of EFS. If the dog is found to have two of the mutated gene, then it is "affected" and has EFS, whether it shows symptoms or not. If the dog is found to have only one of the mutated gene, then it is not affected but is "a carrier".
