Determining whether hand tremors are due to Parkinson’s disease or essential tremor can be challenging, even for doctors. The tremors in each condition can look quite similar, and some people may even have both Parkinson’s and essential tremor. While a neurological exam and careful evaluation of symptoms is required for diagnosis, there are some key differences that can help distinguish between the two conditions.
What are the differences between Parkinson’s tremors and essential tremor?
Parkinson’s disease and essential tremor have some overlapping symptoms but also differ in several ways:
| Parkinson’s Tremor | Essential Tremor |
|---|---|
| Usually starts on one side of the body first, like a hand or foot | Usually affects both hands, although often asymmetric |
| Occurs when the limb is at rest | Occurs during movement or when holding a position against gravity |
| Tremor slows and stops briefly upon intentional movement | Tremor occurs and persists during movement |
| Associated with other Parkinson’s symptoms like slow movements, rigidity, balance problems | Not associated with other neurological symptoms |
| Tremor frequency is generally slower, around 4-6 Hz | Tremor frequency is faster, around 8-10 Hz |
In Parkinson’s disease, the resting tremor typically starts in a hand, presenting as a “pill-rolling” tremor of the fingers and hand. The tremor lessens with intentional movement. In essential tremor, the tremor is induced by movement and sustaining a position against gravity. The tremor usually affects both hands in a more symmetric fashion compared to Parkinson’s.
What causes essential tremor vs. Parkinson’s tremor?
The tremors in Parkinson’s and essential tremor arise from different origins in the brain:
- Parkinson’s tremor is caused by degeneration of dopamine-producing neurons in an area of the brain called the substantia nigra. This leads to reduced dopamine signaling in another brain region called the basal ganglia, resulting in the motor symptoms of Parkinson’s.
- Essential tremor is thought to arise from abnormal oscillations in the cerebellum and its connections, although the exact cause is unclear. Unlike Parkinson’s, there is no neurodegeneration.
In both conditions, the abnormal brain activity leads to tremors, but via different mechanisms. Parkinson’s tremor is directly tied to the neurodegeneration underlying the disease, while essential tremor is not a neurodegenerative condition.
What are some other characteristics of Parkinson’s disease?
Beyond tremor, Parkinson’s disease involves other primary motor symptoms:
- Bradykinesia – Slowed movement and loss of spontaneous movement
- Rigidity – Stiffness and increased muscle tone
- Postural instability – Impaired balance control and coordination
In addition to the motor symptoms, Parkinson’s disease can cause various non-motor symptoms even in early stages, such as:
- Loss of smell (anosmia)
- Mood disorders – depression, anxiety
- REM sleep behavior disorder
- Cognitive impairment
- Autonomic dysfunction – constipation, orthostatic hypotension
The combination of motor and non-motor symptoms reflects the neurodegenerative process underlying Parkinson’s that involves both dopamine deficiency and more widespread neuropathology.
What features help distinguish essential tremor?
In contrast to Parkinson’s, essential tremor:
- Does not cause other motor symptoms besides tremor
- Does not involve cognitive, mood, or sleep disorders
- Does not reflect any neurodegenerative changes in the brain
- Can be asymmetric but often involves both hands
- Is not associated with lack of movement or rigidity
- Mainly occurs during intentional movement, sustaining a position, or certain postures
Although essential tremor may affect hands and arms, it typically does not impair normal motor function aside from tremor itself. Activities such as writing, drinking, and eating may be affected by hand tremor.
Are there any tests to distinguish Parkinson’s vs. essential tremor?
Currently there are no definitive diagnostic tests that can clearly distinguish Parkinson’s from essential tremor. However, doctors may perform several examinations and tests to help evaluate the symptoms:
- Neurological exam – Assesses motor function, coordination, reflexes, nerve function
- Observation of tremor – Notes characteristics at rest and with motion
- Brain imaging – CT or MRI to rule out other conditions
- DaTscan – SPECT imaging of dopamine transporters in Parkinson’s
Additional tests may include blood tests and electrophysiological tests. A classic “pill-rolling” resting tremor points to Parkinson’s, while a symmetric postural tremor suggests essential tremor. But many cases are not so clear-cut. A definitive diagnosis may only come over time as more symptoms emerge.
Can you have Parkinson’s and essential tremor together?
It’s estimated up to half of people with Parkinson’s may also have essential tremor. The conditions can coincide for several reasons:
- Their prevalence increases with age, and they both occur more commonly in older populations
- They may share some genetic risks
- Medications used for Parkinson’s symptoms may induce an enhanced postural tremor
When Parkinson’s and essential tremor co-occur, the resting tremor of Parkinson’s may be more prominent on one side of the body, while the postural tremor of essential tremor affects both hands more symmetrically. Each condition may respond differently to treatments.
How is essential tremor treated?
Essential tremor is typically treated with medications such as:
- Non-selective beta blockers like propranolol or nadolol
- Anti-seizure medications such as primidone
- Benzodiazepines like alprazolam or clonazepam
These medications help reduce tremor severity in about 50-70% of people. For medication-resistant tremor, procedures such as deep brain stimulation may be an option.
What medications are used for Parkinson’s tremor?
Parkinson’s tremor may improve with medications such as:
- Carbidopa/levodopa – Replaces lost dopamine
- Dopamine agonists – Mimic dopamine action
- MAO-B inhibitors – Prevent dopamine breakdown
- Amantadine – Enhances dopamine signaling
In advanced Parkinson’s, deep brain stimulation of the subthalamic nucleus or globus pallidus may help tremor. Other therapies like occupational therapy, exercise, and physical therapy may also help manage tremor.
What is the prognosis for Parkinson’s vs. essential tremor?
Parkinson’s disease is a progressive neurodegenerative disorder in which symptoms worsen over 5-10 years on average. Life expectancy is slightly reduced. Tremor may become severe and disabling.
Essential tremor does not shorten life span and may plateau or even improve in advanced age. It can cause disability due to tremor but does not progress to cause other major neurological deficits.
When to see a doctor
See a doctor promptly if you develop any of the following:
- Tremor that occurs at rest in the hands, arms, legs, jaw, or head
- Shaky tremor when holding the arms outstretched
- Tremor that interferes with daily activities
- Other neurological symptoms like slow movements, rigid muscles, balance problems
Early diagnosis allows more optimal treatment to minimize disability from tremor. A neurologist may perform a full evaluation and discuss treatment options to improve your tremor symptoms.
Conclusion
Parkinson’s disease and essential tremor can both cause hand tremors, but key differences exist. Parkinson’s tremor is a resting tremor that starts unilaterally, along with other motor symptoms. Essential tremor is an action and postural tremor often affecting both hands, without other deficits. There are no definitive tests to distinguish the two, so doctors must carefully assess the set of symptoms. Treatment and prognosis differ, making accurate diagnosis important. If you develop troublesome tremors, see a neurologist for proper evaluation and management.