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Much of medical diagnosis is "pattern fitting" in which
patient's story is matched up against typical stories told by patients with different, identified conditions, and best fit wins. Or, said another way: if it looks like a duck, walks like a duck and quacks like a duck, then it must be a duck.
But what if it looks like a duck, walks like a goose and gobbles like a turkey? What is it then? Well, that's what we call an outlier or atypical case, and we just do best we can.
Medical tests are available for some of these conditions, like an electroencephalogram (EEG) for seizure cases, a 5-hour glucose tolerance test for hypoglycemia, and prolonged cardiac monitoring for irregular heartbeats. But each of these tests has its own strengths, weaknesses, and blind-spots that need to be figured into diagnosis. (For example, an EEG might be normal in a patient who really does have seizures.) Then, for some of conditions—like panic attacks, migraines and pseudoseizures—corroborating tests don't even exist.
Sometimes available data permit a confident diagnosis and a specific treatment. In other cases data allow one to narrow possibilities to a short list, but not a single, final, definitive diagnosis. What then?
Sometimes watchful waiting is what's called for, also known as tincture of time. Once every obtainable clue has been assembled and they're still not enough to permit a firm diagnosis, then perhaps best clue just hasn't happened yet and needs to be waited for.
Depending on which items are still on diagnostic short-list, treatment might still be possible. For example, in a case in which it can't be decided if a patient has seizures, pseudoseizures, or both, it might be reasonable to try a decent dose of a good seizure-preventing drug, and watch to see if anything changes for better.
Reading about inexactness in medical diagnosis might make some people uneasy. Perhaps it would be more comforting to believe that "a series of tests" could prove any diagnosis. For many conditions I'm sure that's exactly what happens, but it doesn't seem to be true for things that go bump in night.
(C) 2005 by Gary Cordingley
Gary Cordingley, MD, PhD, is a clinical neurologist, teacher and researcher. For more health-related articles see his website at: http://www.cordingleyneurology.com
