How Do Seizure Alert Dogs Know That a Seizure Is Coming?
The mystery of how dogs predict an oncoming epileptic seizure has been solved
Posted March 9, 2021 | Reviewed by Ekua Hagan
It was back in the early 1990s that people who studied dogs were surprised by a number of reports about dogs like Harley, a golden retriever owned by Victoria Doroshenko. Victoria has epilepsy, and Harley began to spontaneously alert her whenever she was about to have a seizure. Sometimes Harley could predict the oncoming seizure more than 20 minutes in advance, giving Victoria the chance to find herself a safe place to shelter. This was a godsend for Victoria, and she commented, "Before I got my dog, I was afraid and housebound. Harley gave me my life back." The real puzzle for scientists, however, was how Harley knew that a seizure was imminent. Some new data coming out of Northern Ireland gives us some information as to what may be the cues that the dog is using.
Seizures involving convulsions or loss of consciousness are a well-recognized symptom of epilepsy. Epilepsy is one of the most common debilitating neurological diseases, and it is estimated that 65 million people around the world have epilepsy. In the USA, about 1.2% of the population has active epilepsy. This is about 3.4 million people nationwide and it breaks down to around 3 million adults and 470,000 children. Many adults and children suffering from the disease admit that they often avoid many everyday activities out of fear of having an unexpected seizure in public.
There is a class of service dogs called a "seizure response dog" which has been trained to assist people when they have a seizure. Their job is to bark or otherwise alert caretakers when an individual has a seizure. Some dogs learn to lie next to someone having a seizure to prevent injury, often licking their faces to try to stimulate them back into consciousness. Some dogs are trained to activate some kind of pre-programmed device which signals the event to caretakers or to fetch a telephone or medication. These activities can be trained; however, the remarkable thing is that some dogs, like Harley, spontaneously develop the ability to predict an oncoming seizure and to alert their owner in time for them to take protective action. Dogs can't be trained to predict seizures simply because we have not known what information the dogs are using to know that a seizure is about to occur.
Up to now, some scientists have guessed that the dog that was doing the alerting was responding to changes in behavior in the individual, perhaps in the way that they move. Other scientists have suggested that there are changes in the individual's scent, and still others have even speculated that the dogs can detect magnetic effects since it is known that physiological changes and excessive electrical activity in the brain precede epileptic seizures. A team of researchers headed by Neil Anthony Powell of Queens University in Belfast reasoned that the metabolic stress and the physiological changes which accompany the onset of a seizure might release volatile organic compounds, which dissolve in the blood and saliva and are eventually either exhaled as part of the respiratory process or appear as sweat. These volatile organic compounds might be detected by a dog's sensitive nose, thus providing a scent cue that a seizure is about to occur.
Based on this hypothesis, the team collected scent samples from people with epilepsy using special cloth pads. The samples occurring before an actual seizure were taken (when a seizure alert dog indicated an impending seizure), a seizure sample was collected immediately following an event, and a post-seizure sample taken six hours after a seizure.
The researchers also created a special device that could release controlled scent samples around the chair which the dog's owners would sit.
Their subjects for the test were dogs and owners recruited from a local dog training club. The dogs had not been trained to do anything in terms of seizures and the owners were epilepsy-free.
Sessions were videotaped, and the investigators were looking for three commonly observed attention-seeking behaviors that have been reported when observing seizure alert dogs, namely closely hovering around the owner, intense staring, and climbing up or pawing the owner.
The release of the seizure-related odors did have the effect of increasing the frequency of the dog's targeted behaviors. Most significantly, this included the scent sample gathered just prior to a seizure.
This is an important finding since it suggests that changes in an individual's scent might be a cue that indicates an imminent seizure. But more than that it suggests that we now have a means of not only training seizure response dogs but also "seizure alert dogs." The authors summarize the significance of their findings by saying, "The existence of pre-seizure odor(s) is an important finding because it offers a simple and reliable means for training dependable seizure-alert dogs to warn people of an impending epileptic event, an aim which has long been sought."
If we can train dogs to alert to an oncoming epileptic seizure, then just like in the case of Victoria and Harley, many people with epilepsy need no longer be housebound but now can begin to get their lives and their independence back.
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Neil Anthony Powell, Alastair Ruffell, and Gareth Arnott (2021). The untrained response of pet dogs to epileptic seizures. In Review: Scientific Reports, https://doi.org/10.21203/rs.3.rs-199652/v1