In this era of genuinely marvelous, high-tech, medical devices, it is sometimes surprising that certain diseases are still diagnosed "clinically," meaning that
clinician makes call based on just story of symptoms and physical exam. Parkinson's disease is one such disease. There is no "Parkinson scan" or "Parkinson blood-test" to rely upon. MRI scans, CT scans and blood tests are usually normal in people with this disease.Of course, once upon a time—before scans and blood-tests even existed—this is how all diagnoses were made. So, in a sense, diagnosing Parkinson's disease gets back to very roots of what doctors are supposed to do. But when there are no corroborative tests available to prove or disprove a diagnosis, even doctor sometimes gets it wrong.
Before delving into challenges of diagnosing Parkinson's disease, let's first consider what is known about this condition.
In 1817 James Parkinson, an English surgeon and apothecary, published a classic, short book entitled "An Essay on Shaking Palsy." In it, Parkinson identified a consistent pattern of physical abnormalities in six patients he had examined. Although people with identical abnormalities had doubtlessly been around for thousands of years, Parkinson was first to recognize this pattern of abnormalities as a distinct condition. For this important achievement, disease was eventually named for him.
In book's opening sentence Parkinson wasted no time in laying out prominent features of this disease: "Involuntary tremulous motion, with lessened muscular power, in parts [of body] not in action and even when supported; with a propensity to bend trunk forwards, and to pass from a walking to a running pace: senses and intellects being uninjured."
Subsequently, scientists discovered that degeneration of a limited group of brain cells containing chemical transmitter dopamine was responsible for these clinical changes. (The group of brain cells involved is too slight to show up on brain scans in all but most advanced of cases.)
In 1967, levodopa (one of two ingredients in brand-name Sinemet) a drug body can convert into dopamine, was found helpful in alleviating many of symptoms. Later, other drugs (dopamine agonists) were created that improved symptoms by mimicking action of missing dopamine. These include bromocriptine (brand name Parlodel), pergolide (Permax), pramipexole (Mirapex) and ropinirole (Requip). To date, there are no treatments that reliably stop or reverse underlying disease-process.
As a condition that affects about one percent of people over age of 60, Parkinson's disease is usually on radar screen of patients and doctors alike when new symptoms are present that suggest disease. That other conditions can resemble it was not news to James Parkinson who devoted a chapter of his 1817 book to "Shaking palsy distinguished from other diseases with which it may be confounded."
