Parkinsons disease, especially in its early stages when symptoms are mild, is not an easy disease to diagnose. The non-specific, and easily overlooked nature of the signs of Parkinsons make it difficult to spot, and unlike many illnesses, there is no one laboratory test or radiological exam that will provide a definitive diagnosis of Parkinsons disease.
Patients exhibiting Parkinsons-like symptoms may undergo blood and urine tests, or CT or MRI scans to exclude other conditions, but none of these will provide a diagnosis of Parkinsons disease.
The best way to test for Parkinsons disease is to conduct a systemic neurological examination that includes tests to gauge a patients reflexes, muscle strength, coordination, balance, gait, and overall movement. Even so, according to information presented on The Michael J. Fox Foundation for Parkinsons Research, up to 25 percent of Parkinsons disease diagnoses are incorrect.
So, why is there confusion about diagnosing Parkinsons disease? The simple answer is that symptoms of Parkinsons disease are not clear cut, and therefore, it is easy to mistake them for other conditions, or to classify them as parkinsonian when they are not.
Here is a brief overview of the top ten conditions mistaken for Parkinsons disease:
Multiple System Atrophy (Shy-Drager Syndrome): a rapidly progressing disease that first features autonomic nervous system insufficiencies (dizziness, lack of bladder control, impotence, etc), and then takes on Parkinsons disease-type symptoms such as rigidity, tremor, bradykinesia, postural instability, and difficulty walking. Some neurological specialists have speculated Shy-Drager Syndrome may be a form of Parkinsons disease rather than a separate condition, but for now, it remains its own entity.
Supranuclear Palsy: results in rapid paralysis of eye movements, rigidity, difficulty speaking, and subtle mental shifts. Supranuclear palsy is a disorder of a different part of the brain than Parkinsons disease, and patients with this condition do not respond to standard antiparkinsonian drugs such as levodopa. The speed at which the disease progresses also sets it apart from Parkinsons disease.
Benign Essential Tremor (familial tremor): a gradually progressing condition that shows as tremors in the hands and arms on both sides of a patients body, and occasionally the head. Unlike with Parkinsons familial tremor does not affect the legs, and the two illnesses respond to different drugs.
Beyond those top three, there are other conditions that are often confused with Parkinsons disease, including:
Amyotrophic Lateral Sclerosis (Lou Gehrigs disease)
Normal Pressure Hydrocephalus
Striato-Nigral Degeneration- form of multiple system atrophy involving the loss of connections between two areas of the brain, the striatum and the substantia nigra, which work together to ensure smooth movement and maintain balance.
Pseudobulbar Palsy: a bilateral impairment of the function of the lower cranial nerves 9, 10, 11 and 12 due to upper motor neuron lesion of the bulbar muscles from lesions of the corticobulbar pathways in the pyramidal tract.
Hallervorden Spatz Disease: a degenerative movement disorder that is genetic
Plus a couple more-
- Olivopontocerebellar Degeneration (OPCD)
- Huntingtons Disease
With such a variety of illnesses sharing many of the same symptoms and characteristics, its not surprising Parkinsons disease is often misdiagnosed. People who have mild symptoms, or who would like a second opinion, should certainly ask their doctor about having the diagnosis confirmed by another physician.
With early diagnosis being the key to maintaining longer-term independence and a high quality of life, it is important to have an accurate diagnosis so that appropriate treatment therapies can begin immediately.
William J. Weiner MD, Lisa M. Shulman MD, Anthony E. Lang MD FRCP
Parkinson’s Disease: A Complete Guide for Patients and Families
Johns Hopkins University Press; 2013, ISBN-13: 978-1421410760