False-positive Parkinson's disease diagnoses common; avoid the pitfalls.
The false-positive rate for a Parkinson's disease (PD) diagnosis is about 35% at the initial diagnosis and 24% at final diagnosis, according to data from several autopsy studies. Autopsy results remain the preferred method for confirming a diagnosis of PD, said Dr. Reich, professor of neurology at the University of Maryland and codirector of its Maryland Parkinson's Disease and Movement Disorders Center.
Not everyone with PD has a resting tremor, but many do, and it improves with movement. Classic PD starts on only one side of the body, unrelated to hand dominance. Although some patients with only Parkinson's-like syndromes will have an initial response to levodopa, it won't be sustained.
Dr. Reich presented his choices for the top 10 pitfalls of PD diagnosis. "The first six are false positives; these are patients who don't have PD, but you may be tempted to make the PD diagnosis, although the condition is really one of the following," he said.
* Essential tremor. Essential tremor (ET) is the condition most often misdiagnosed as PD. "The best way to distinguish ET from PD is the history and physical," Dr. Reich said. "With a few features from the history and physical, you should be able to make the distinction between essential tremor and Parkinson's." For example, a longer duration of symptoms usually tilts the diagnosis toward ET.
Patients with essential tremor usually report that the tremor has been present for years before presentation. "If you ask, 'Mrs. Jones, how long have you had your tremor?' and she says 'About 20 years,' it's an essential tremor; that's not the history of PD," he said. Most tremor patients with PD present to a primary care physician within about 6 months of the initiation of symptoms. Also ask the tremor patient about his or her response to alcohol. "About 60% or more of patients with essential tremor will have noticed that a small amount of alcohol temporarily alleviates the problem. If you ask these few simple questions, you may have a good idea of the diagnosis before you begin the physical exam," he said.
When conducting the physical exam, remember that PD is a resting tremor and thus tends to improve with movement, but essential tremor worsens with movement. A strictly unilateral tremor is probably PD. "Essential tremor, although it might be asymmetrical, is almost always bilateral," he said, adding that tremor of the head or voice is usually an essential tremor.
Handwriting in patients with PD tends to be micrographic, but it is not tremulous, even if patients have tremor at rest. Patients with essential tremor have full-sized handwriting, but it looks shaky. Patients with PD have other associated symptoms and signs, such as cogwheel rigidity, a masked face, and trouble rising from a chair.
"If you have made a mistake initially in diagnosis, it should be obvious later on," Dr. Reich explained. PD is progressive, and the symptoms in most PD patients become obviously worse from year to year, whereas ET is insidious and may appear to be stable.
* Lower-half Parkinsonism. "These are the patients geriatricians see day in and day out. They are disproportionately fine from the waist up," Dr. Reich said.
This is not PD; it appears clinically as a shuffling, broad-based gait, difficulty rising from a seated position, with impaired posture and balance. Most patients with this condition present at an age older than 70 years, and the symptoms occur below the waist. Patients' arms and upper bodies are usually reported as "fine."
Some of these patients respond well to shunts for normal-pressure hydrocephalus, he noted. "I like to count how many steps it takes the patient to make a 360-degree turn. The fact that symptoms occur only from the waist down is the key to distinguishing this condition from PD."
* Drug-induced Parkinsonism. This condition often goes unrecognized because it might take up to 1 year to resolve after taking a particular drug. "You have to ask what medicines patients have taken in the past," Dr. Reich said. Check their hospital records to confirm medications, and be cautious about diagnosing PD--especially if patients have taken antipsychotics, metoclopramide, or dopamine depleters such as reserpine, because the PD symptoms might resolve with time.
* Parkinson's disease vs. Parkinson's syndrome. Red flags that differentiate a Parkinson's syndrome (such as progressive supranuclear palsy or multiple system atrophy) from PD include impaired downward gaze, little or no response to levodopa, early hallucinations, early dementia, and falls early in the course, as well as symmetrical onset and an absence of tremor. However, a patient might display no symptoms on the first visit. "I have not infrequently misdiagnosed a patient with PD on the first visit and changed it after a year or two as new signs have emerged," Dr. Reich said.
* Alzheimer's disease presenting as Parkinsonism. Sometimes the Parkinsonism that accompanies Alzheimer's disease is the first hint to family members that an elderly relative has a problem. "The physical symptoms of Parkinsonism, such as lack of balance, may bring the patient to your office, but if it is accompanied by dementia, it is probably Parkinsonism rather than clinical PD," Dr. Reich said.
* Parkinsonism of "normal aging." "It's not clear what causes Parkinsonism of normal aging, but be careful about distinguishing it from idiopathic Parkinson's," Dr. Reich said. PD tends to peak at about 60 years of age, so be cautious about diagnosing it after age 75 years, he said. The last four pitfalls of PD diagnoses are false negatives. "These are patients who have PD, but because something about their presentation is atypical, the diagnosis may be missed," he said.
* Sensory or pain presentation of PD. Dr. Reich said he often sees patients who have recovered from a frozen shoulder, for example, but they still have trouble moving one hand. Foot pain, particularly in young-onset PD patients, as well as tingling or numbness, fibromyalgia, or restless legs syndrome, can be symptoms of PD.
* Young-onset PD. PD is often not recognized in patients in their 30s and 40s. "You can be too old for PD but not too young," he said. When you see someone who is 35-40 years old who has a tremor, PD might not even be part of most physicians' differential diagnosis. But physicians should not discount young-onset PD. "It is uncommon, but it is out there."
* Unilateral lower extremity presentation. "When a patient presents with one lower-extremity symptom, even if he or she complains of pain or weakness, don't discount PD," Dr. Reich said. Patients with PD might complain of muscular weakness when their problems are really the stiffness, slowness, dystonia, and pain of PD. Patients can have a tremor in one foot, for example, and might report that it is tougher to slide the affected foot into a shoe.
* Atremulous PD. When a patient does not have a tremor, the physician can miss a case of PD. Patients with atremulous PD are most often misdiagnosed with stroke, but the fact that only half the body is affected by stiffness or balance problems is a tip-off that the problem might be PD, Dr. Reich said. Also, these patients do not give the typical stroke history of sudden onset, he added.
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|Title Annotation:||Clinical Rounds|
|Publication:||Family Practice News|
|Date:||Apr 15, 2006|
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