How to Tell Essential Tremor from Parkinson’s Disease

Essential tremor (ET) is a functional movement disorder. The word “functional” means that the tremor’s source is how the nervous system is functioning (or rather, malfunctioning) instead of the result of a disease.

Disease or functional problem?

For a person with ET, it’s not much comfort to call tremors a functional problem. When tremors are severe and incapacitating, it feels like a disease condition. However, in medical terms, a disease is an organic or pathological state with cellular changes that can usually (but not always) be identified or diagnosed by physical tests. Such tests include blood and tissue analysis that may reveal distinct cellular changes or biomarkers, and various types of imaging for abnormalities (changes in anatomy, unusual masses, etc.). Also, many diseases lead to death if left untreated, or if there is no known cure. Thus, ET does not qualify as a disease—but this is of little comfort if tremors become so severe that life is no longer normal.

However, ET is sometimes incorrectly diagnosed as Parkinson’s disease (PD). One of the main symptoms of PD is tremors, usually starting in the fingers or hands, but which can also affect other parts of the body as the disease progresses. In addition, PD brings stiffness and rigidity, slowness of voluntary movements, facial and postural drooping, balance and gait problems, skin abnormalities, cognitive and emotional difficulties, and eventually near-total disability. Thus, a diagnosis of PD is devastating.

On the other hand, being diagnosed with a functional movement disorder like ET is not as dire, though it can be quite disheartening since “the shakes” can progress to a very disabling and isolating condition. The problem is how to tell one from the other, and so far there is no definitive physical test (e.g. blood work, brain scan, etc.) for either. How do doctors know if it’s one or the other?

How to tell the difference

While a primary care physician or internist may be the first doctor to see a patient with tremors, he or she is generally not the most qualified person to issue a diagnosis. Instead, a referral is made to a specialist called a neurologist who is trained and experienced in movement disorders. Since there are many things that can cause uncontrollable shakiness, the neurologist’s initial concern is ruling out a disease, especially PD. Since there are no lab tests that can confirm the diagnosis, the initial consultation usually consists of the following:

• Personal medical history, including any past or current medications
• Family history (almost half of ET cases include a family history of the tremors, whereas 20% or fewer PD cases have a hereditary component)
• Observation of physical symptoms, e.g. tremor, facial expression, walking, balance (rule out PD)
• Testing reflexes, motor coordination, and muscle rigidity (rule out PD)
• Writing tasks (handwriting sample, tracing a spiral shape
• Also ruling out PD based on pre-symptom experience, e.g. loss of sense of smell within the previous 10 years is a tell-tale sign of PD though it doesn’t occur in every patient)

If there is any doubt, there is a new type of CT scan called SPECT, which can detect the level of dopamine uptake in the brain. Dopamine is a neurotransmitter that helps connect brain signals with muscle movements. In PD, unlike ET, the cells that manufacture dopamine in the brain are no longer able to function, which is the source of the tremors and muscle problems that occur in PD. This is not the case with ET, so if the diagnosis is too close to call, the brain scan may be the deciding factor.

Importance of early diagnosis

It’s important to diagnose the cause of tremor symptoms early because each requires a different treatment approach. For instance, there are particular medications for PD that offset the loss of dopamine in the brain, and while they benefit almost every PD patient in the early stages, they are useless for ET. There are many interventions that are appropriate for either ET or PD that can ease symptoms, slow progression, and improve quality of life. An early diagnosis also helps the doctor, patient and family members to develop a “go forward” treatment strategy, set up an appointment schedule, find support, identify potential future needs, and plan accordingly.

A great asset of early and accurate diagnosis is that it enables patients and family empowerment to offset the discouragement, worry and fear that can accompany diagnosis. There is a saying that knowledge is power, and at Sperling Neurosurgery Associates we also believe knowledge is hope.

We are proud to offer an outpatient procedure called MRI-guided Focused Ultrasound (MRgFUS) to manage essential tremors, which is FDA approved to treat ET. MRgFUS does not require medication, there is no incision or drilling into the skull, and no exposure to radiation. Not only is it proven safe and effective for ET, it is currently in clinical trial for PD-related tremors, and we know that this is good reason for optimism about improved quality of life for those with tremors.

For more information contact Sperling Neurosurgery Associates