Episodic Falling Syndrome is a rare condition that appears in some cavaliers and seems to be a genetic trait inherited when two parents each have the recessive gene for the syndrome.
Most vets and many neurologists will not be familiar with this syndrome or know to look for it as a possible diagnosis in a cavalier exhibiting typical symptoms: these include the dog running with an arched back, favouring its legs, and falling over -- sometimes in a trance-like state -- especially after or during a period of exercise or excitement. Often the dog is fine after it is picked up and held for a few moments and continues as if nothing has happened, but the dog may also clearly be in pain when these episodes happen. You should inform the breeder if you have a dog diagnosed with this syndrome. Below are further descriptions and links. The first is fairly technical but the others are easy to understand:
From: http://www.ivis.org/special_books/Br...isodic_FallingEpisodic Falling
Episodic falling or hypertonicity is a well-recognized paroxysmal disorder in Cavalier King Charles Spaniels in the UK [1,2], and has been seen in the United States and Australia . After a variable period of exercise, affected animals develop a peculiar bounding, pelvic limb gait in which the limbs may be abducted and appear stiff. Other signs may include a bunny-hopping gait, arching of the spine, vocalization and collapse. There is no loss of consciousness. Some affected dogs assume a "deer-stalking" posture, with increasing limb stiffness, falling, and legs held in extensor rigidity . Episodes appear to be triggered by stress, apprehension, and excitement. Signs are typically first observed between 3 and 7 months of age. Animals are neurologically normal between attacks, which appear to be a life-long event. Affected dogs do not respond to anticholinesterases, but slight, temporary improvement may occur following diazepam treatment. A greater clinical improvement is reported following following treatment with the benzodiazepine drug clonazepam which enhances GABA neurotransmission [67,70]. In one trial, clonazepam (at 0.5 mg/kg tid) resulted in almost complete remission of signs over a 2-year period . Frequency of attacks is reportedly increased in some dogs using the antiepileptic drug carbamazepine (Tegretol) . Results of hematology, blood chemistries, and electrodiagnostic testing are within normal limits. There is no evidence of lactic acidosis. No light microscopic lesions are seen in the central nervous system (CNS), peripheral nervous system (PNS), or viscera. Skeletal muscle appears normal microscopically, apart from presence of small vacuoles between myofibrils in some fibres stained with toluidine blue . Histochemical staining using myosin ATPase, succinic dehydrogenase, and phosphorylase is normal. Ultrastructural alterations, however, have been reported in skeletal muscle, which include dilatation and proliferation of sarcotubular elements, mitochondrial swelling and degeneration of cristae, and tubular proliferations in the region of the triads . Wright stated that she was uncertain if the morphological changes were causally related to the clinical signs . The pathogenesis of this paroxysmal condition remains enigmatic, although both genetic and neuropharmacological factors may be involved. In one study, 7 of 8 dogs were males and 5 had a common male ancestor that suggested an inherited trait . It has been suggested [67,70] that this disorder has some similarities to hyperexplexia (startle disease) in people, a hereditary (autosomal dominant) pathological exaggeration of the normal startle response to auditory, somesthetic or visual stimuli which sometimes results in falling [68,69].
More info: http://www.candog.com/cavaliers/Heal...POTPURRI96.htm
Where it says in part:
Some further info on treatment and contacts:The descriptions of the syndrome in these articles suggest this is a transient and intermittently occurring condition, which was first identified in the 1960s. The article "Episodic falling..." documents nine clinical cases, seven of which were female. In fact, in most of the cases the first signs of the syndrome were seen when the dogs were between three and four months of age. The article on "Muscle hypertonicity..." describes eight dogs which had this syndrome; seven of the dogs were male. Their ages ranged from five-and-a-half months old to four years old. Dogs described in both articles were given thorough neurological exams before and after exercising, and none of them showed any evidence of neurological problems. Blood tests all came back with normal values. As with the club member's dog, Tensilon was given and no improvements for dogs described in both articles were seen with the administration of the medication. Muscle biopsies were taken from five of the dogs, with some abnormalities of the muscles seen. It appears the disorder is a type of metabolic muscle disorder. It is probable that the disease is an inherited condition.
The description of what happens when Episodic Collapse occurs is as follows. After a period of exercise, which may be of variable length, animals that are afflicted develop a laboured, bounding gait in the hindlimbs which appear stiff and are partially turned out. The movement resembles the hopping of a rabbit. The dog's back may become arched, with the head close to the ground and the rear high in the air, and the dog often cries out. With the lack of coordinated movement, the dogs collapse on their sides or pitch over on to their noses. There is no loss of consciousness or change in colour, although muscle tone in the legs was noted to be increased in the "Muscle hypertonicity..." article, and the legs were held in 'extensor rigidity'. After a short time, which can vary, the animal gets back on its feet; some were noted to be quite distressed, while others acted as though nothing had happened. Stress, apprehension, and excitement can cause an episode. There is no known effective treatment, although if the owner picks the dog up, this seems to help with the recovery phase.
Until recently, no medications appeared to remedy the condition, and there was no known effective treatment. However, in a study concluded in 2003, a group of affected Cavaliers was treated with Clonazepam, a drug used to treat humans for hereditary hyperekplexia ("startle disease"). With treatment, the episodes decreased in frequency from between 25 and 30 per week to as few as one every two to three months. After two years of treatment with Clonazepam, dogs in the study were described as clinically normal.
However, in a study currently being conducted by Dr Jacques Penderis, senior research neurologist at the Animal Health Trust in the UK, he has found that although some Cavaliers initially respond well to treatment with Clonazepam or Diazepam, the dogs tend to develop tolerance to the drugs after a while and the beneficial effect wears off. Dr. Penderis states that the current treatment options for CKCSs with episodic falling syndrome are extremely limited.
The Animal Health Trust is conducting research to try to establish the pattern of inheritance of episodic falling in the Cavalier. It is collecting pedigrees from affected dogs for pedigree analysis, particularly where the disease status of related dogs (e.g. parents and litter mates) are known.
In an attempt to develop a more effective treatment for dogs that are severely affected, Dr. Penderis is conducting a trial of some other drugs that have been shown to be beneficial in human patients and to which the Cavaliers' tolerance does not develop. He advises that the initial results for one drug have so far been promising. The current trials are restricted to those dogs that have very frequent collapse episodes and are arranged through the owners' veterinarians.
Dr. Penderis also is collecting blood samples for DNA extraction to conduct genetic linkage analysis in order to determine the offending gene. In order to perform genetic linkage analysis, Dr. Penderis requires blood samples from known affected dogs and from as many normal related dogs as possible (particularly litter mates, parents, grandparents and offspring). The study's goal is to develop a genetic test to allow identification of the affected dogs and asymptomatic carriers, so that the disease may be totally eradicated from all tested breeding lines.
In order to reduce the incidence of the disease and eventually develop a genetic test, Dr. Penderis is interested in information from as many affected dogs as possible from the Cavalier King Charles Spaniel breed. He states that what is essential to the research is that no dogs that do not have episodic falling syndrome are inadvertently included in the study (e.g. have similar appearing stiffness or collapse episodes that are not due to episodic falling) as this could severely hamper the genetic analysis. The disease will therefore need to be confirmed by video footage of an episode or examination of the dog at the Animal Health Trust. Please contact Dr Jacques Penderis at the Animal Health Trust if you wish to participate in the research project. He may be reached at Animal Health Trust, Lanwades Park, Kentford, Newmarket, CB8 7UU, UK. Telephone: (+44) (0)1638 552700; Fax: (+44) (0)1638 555600; email: Jacques.Penderis@aht.org.uk