Can dogs predict seizures? 

I play poker with this guy on a fairly regular basis at the casino. He's got this medical alert dog he brings with him everywhere. Apparently the dog will warn him 20 minutes prior to having a medical emergency that he needs to seek help. How does the dog know? -R.K.

Fact is, there's no such thing as a general-purpose medical alert dog. Closest I know of is a dog that recognizes seizures, due either to epilepsy or, in diabetics, low blood sugar (hypoglycemia). The experts distinguish two types of canine assistant. The first is a seizure response dog, trained to summon help or the like if its owner has an episode. Research suggests dogs do well at this task. The second is a seizure alert dog, which provides advance notice.

Here matters get murkier, as the notion that dogs can sense a looming medical crisis is controversial. One case written up recently involved a diabetic farmer. While driving back to his house for lunch he'd often suffer hypoglycemia, which can lead to convulsions or unconsciousness. The farmer didn't see the attacks coming but his dog, who liked to sleep on the seat next to him, apparently did: on numerous occasions over a 17-year period the dog immediately awakened and barked until the farmer pulled over and ate some sugar.

Or so the farmer said. The problem with these accounts is you're taking somebody's word for it. Even if we accept claims of talented hounds at face value, how would you teach other animals to recognize signs with no notion of what the signs are? Again, researchers are skeptical.

One 2007 report tells of four individuals whose dogs allegedly could anticipate their seizures. On examination, the four were found to suffer not from epilepsy but from psychogenic nonepileptic seizures, or PNES. They didn't have the chaotic brain activity of epileptics; to make a fine but crucial distinction, the problem was in their minds rather than their heads.

One possibility raised: the dog's behavior wasn't a warning of a seizure but the trigger. Another research team reaching a similar conclusion observed: "Without objectively clarifying if patients have epilepsy or PNES, the current literature fails to support that canines can warn of impending seizures." So I won't say it never happens, but it may not happen much.

As I write, everything in my office is shaking. The culprit is the steamroller repaving a nearby road. My question: does a steamroller, which I believe shakes rather than weights the road into place, register on the Richter scale? If so, how much? -David, Florida

The diesel-powered machines you're seeing are properly called asphalt rollers or rollers. While some rollers flatten by sheer weight, others are designed to vibrate, bouncing their heavy steel drums minutely for superior roadway compaction.

The energy thereby transmitted can be measured on the Richter scale. My assistant Una, a professional engineer, has submitted a page of calculations demonstrating that, certain possibly risky assumptions having been made (among them that road crews put in a full eight-hour day), the total energy released by a jumbo asphalt roller would register a bit south of 2.5 on the Richter scale.

That's per day, not in one jolt, which you may say isn't in keeping with the spirit of the thing. You should also know the Richter is a special logarithmic scale where every jump of two whole numbers represents a thousandfold increase in energy. In sum, 2.5 isn't so much.

A better gauge is the Modified Mercalli Intensity scale (MMI). Una judges the MMI rating of a roller to be 3 or 4. Using a table of equivalence prepared by the U.S. Geological Survey and waving our hands, we can then convert this back to Richter, enabling us to say the shaking you're getting approximates what you'd experience near the epicenter of a quake measuring roughly 4.0 on the Richter scale-not San Andreas level, but in there with the New Madrid fault. Hope that'll do.



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Cecil Adams

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