Since the late 1980s, when the media reported the case of a woman claiming a dog alerted her before she had seizures, the subject of seizure-alert dogs has garnered both public and scientific attention. While dogs cannot sense epilepsy as a disease, some canines have demonstrated the ability to sense the onset of the seizures that are a hallmark of epilepsy. Anecdotal evidence of such canine-sensing abilities abounds, and the results of various controlled studies cautiously suggest some dogs are indeed able, before training, to alert owners in advance of seizures.
Significance
Epilepsy, a disorder of the central nervous system, produces seizures that can cause reactions ranging from involuntary muscle movements and muscle stiffness to complete unconsciousness and convulsions. Even patients who are medicated to reduce the number of their seizures can still suffer from them, says the Epilepsy Foundation, and seizures offer little warning before striking. Patients who are standing or sitting when a seizure hits can be injured in falls. Thus a dog that can signal a patient to get into a safe, prone position before a seizure can help improve that person's life dramatically.
Scientific Evidence
The question for patients and scientists alike is whether seizure-alert dogs can sense impending seizures without training. A 2003 study conducted by the University of Florida found that some dogs do indeed have an innate ability to discern when a seizure is coming on. This study, executed by the College of Medicine's Department of Neuroscience, also suggested that a dog's alerting success depends in part on the owner's understanding of the dog's cues. And a 1999 study done in conjunction with a support-dog charity in the United Kingdom confirmed that some dogs can be trained to recognize physical changes preceding a seizure and give their owners a signal, which goes beyond innate sensing but relies on the ability of dogs to pick up subtle behavioral cues that might be imperceptible to humans.
Anecdotal Reports
Apart from what science may conclude, many epileptic patients swear by their seizure-alert dogs, says author Sharon Sakson in her book, "Paws & Effect: The Healing Power of Dogs." While many animals can be trained in seizure response--they're taught to bring medications, water and even phones for patients to use when they regain consciousness--some dogs have been observed sensing seizure without prior instruction. Sakson reports that some younger dogs in particular have, even before training has begun, been seen pawing and whining at patients who later experienced seizures. This supports the belief among trainers that some highly sensitive animals posses an inner understanding of seizure and its effects on humans.
Theory of Scent
Among those who believe these canines possess innate instinct, the theory is that dogs, through their keen sense of smell, detect chemical changes in the body caused by seizure activity, according to the website Canine Partners for Life. There are no scientific studies to confirm this theory, however, as there's no way to determine if scents detectable only to dogs really are the trigger for alerting. Some dogs have been known to sense an oncoming seizure while in another room from their owners, which supports the possibility that scent could be a factor.
Theory of Auras
Still others who own alert dogs believe they might be able to sense the auras that sometimes come before an epileptic seizure, says author Sakson. Auras are bodily changes such as irritability, nausea and headache that may precede a seizure by hours, or a sudden feeling of fear or not being able to interact with the world around you. Some seizure-dog owners believe their animals are able to sense these physical changes as seizure warning signs.
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