The Parkinson’s Institute Director of Clinical Studies and Movement Disorders Specialist Dr. Rohit Dhall, and neurosurgeon Dr. Jaimie Henderson, Director of Stereotactic and Functional Neurosurgery at Stanford Hospital and Clinics spoke about treatment for Essential Tremor (ET) in a seminar titled “Refuse to Surrender” in San Jose on June 11, 2016. Their discussion included a comparison between ET and Parkinson’s disease (PD) and how the tremor in both diseases can be lessened with Deep Brain Stimulation (DBS).
Their presentation touched on a question that tremor-predominant people with PD may have, “Did they get my diagnosis right?”
The ongoing uncertainty of whether a diagnosis is correct is bothersome for some Parkinson’s disease (PD) patients, even after getting a second opinion. ET looms along side PD as a possible reason for tremor.
25% wrong diagnosis
Research suggests that approximately 25 percent of Parkinson’s diagnoses are incorrect. Some of these diagnoses are not made by specialists. However, new disease symptoms develop over time in ET and PD, and even movement disorder specialists may not get it right the first time. Tremor patients should see a movement disorder specialist regularly to make sure that diagnosis and treatment are compatible.
Essential Tremor, the most common but quiet disorder
Essential tremor is considered to be the most common movement disorder. It affects 10 million people over the age of 65. By comparison, PD affects approximately 1.5 million people in the US. ET is said to be 8 times more common than PD.
In spite of the huge difference in numbers, ET has been described as the ‘quiet disease’ and it attracts less media coverage than PD.
Tremor In use with ET versus at rest with PD
ET is commonly described as an action tremor (when you’re actively using the affected muscles) or postural tremor (when you hold a muscle tone) rather than a resting tremor, or an intention tremor (when you intent to move) such as is seen in Parkinson’s.
ET is a progressive neurological condition that involves your hands, head and voice. PD may start in your hands, but it can affect other parts of your body such as legs, and chin, and it is also associated with stooped posture, slow movement, stiffness and shuffling gait.
The current thought on general differences include:
• Head tremor is uncommon in early Parkinson’s disease.
• Unlike the tremor of PD, essential tremor does not improve in response to levodopa. But it may be relieved with other medicines such as primidone and propranolol.
• In PD, the tremor usually starts on one side of the body and progresses to the other side, and it usually remains asymmetrical. In ET, both sides of the body are initially affected, and symmetrical.
DBS Treatment Similarities
The tremor in both ET and PD can be greatly reduced with Deep Brain Stimulation (DBS). In his presentation, Dr. Dhall said that DBS is “massively underutilized” by people with ET. Dr. Henderson described the hundreds of DBS surgeries he has done as being highly successful outcomes for his patients.
Overlapping clinical features?
Signs and symptoms can vary. People with ET and PD can have overlapping clinical features, and some patients may meet criteria for both diseases.
Clinical features challenged
To make it more confusing, the National Institute of Health (NIH) published a study that calls exception to current assumptions about ET. For instance, according to the study, rest tremor may be seen in 20–30% of patients with ET. It tends to occur in patients with more severe disease and disease of longer duration.
The NIH study also includes that action tremor can been seen in patients with PD; bilateral tremor can be found in PD, and that head tremor can been seen in PD. Such differences in research emphasis that a diagnosis may need to be altered as clinical features evolve.
Future diagnosis help: dopamine transporter imaging
In his presentation, Dr. Dhall explained dopamine transporter imaging, as a future diagnostic tool for ET. It is a brain scan that measures the uptake of dopamine called DaTscan, and it can help to differentiate between ET and parkinsonian tremor. Dopamine is depleted in patients with parkinsonism but not in patients with ET; therefore scans showing depletion in dopamine are likely parkinsonism, whereas a normal scan suggests a diagnosis of ET.
How can PD patients bring treatment and clarity about ET and PD to light? As with other Parkinson’s research, volunteers for clinical studies, time, and patience are needed.
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