Parkinson’s or Essential Tremor? How to Tell Them Apart

The first time you notice a tremor in your hand, a natural and often immediate fear is that it could be a sign of Parkinson’s disease. This is a common concern, but it is important to know that not all tremors are Parkinson’s. In fact, the most common type of tremor is a separate and distinct neurological condition known as Essential Tremor (ET). While both conditions cause a person to experience involuntary shaking, the characteristics of the tremor itself and the presence of other associated symptoms are the key differentiators that allow a doctor to make an accurate diagnosis. This guide will compare and contrast Essential Tremor and the tremor of Parkinson’s disease, explaining the specific features a neurologist looks for and outlining the diagnostic process used to tell the two apart.

A tremor is a type of involuntary, rhythmic, and oscillatory movement of a body part. Tremors are categorized based on when they occur:

• Resting Tremor: This type of tremor occurs when the body part is at rest, fully supported, and not actively being used. The tremor often subsides or disappears with purposeful movement.
• Action Tremor: This tremor occurs during voluntary, purposeful movement. It can be further divided into:
  • Postural Tremor: Occurs when holding a limb against gravity (e.g., holding your arms outstretched).
  • Kinetic Tremor: Occurs during movement (e.g., moving your hand to your mouth).
  • Intention Tremor: A kinetic tremor that worsens as the person gets closer to their target (e.g., trying to press a button).

The hallmark difference between Essential Tremor and Parkinson’s disease is the type of tremor that each condition presents.

• The Key Characteristic: An Action Tremor: The most prominent feature of Essential Tremor is a kinetic, postural, or intention tremor ^[1]. This means the tremor is most noticeable when a person is actively trying to do something. For example, the tremor may become pronounced when you lift a spoon to your mouth, try to write a sentence, or hold a cup of coffee. The tremor often lessens or disappears when the hands are at complete rest, such as when they are resting on your lap.
• Location: The tremor most commonly affects the hands, but it can also affect the head (leading to a “no-no” or “yes-yes” shaking motion), the voice (causing a quivering sound), and, less frequently, the legs or trunk. The tremor is usually symmetrical, affecting both sides of the body, though one side may be slightly worse than the other.
• Progression and Associated Symptoms: ET is a slowly progressive condition, but it is not life-threatening. The tremor may worsen over time, but it does not cause the other motor symptoms seen in Parkinson’s disease. ET is also often a familial condition, with a significant number of cases having a genetic link. ^[2]

• The Key Characteristic: A Resting Tremor: The classic tremor associated with Parkinson’s disease is a resting tremor. This means the tremor is most noticeable when the person is at rest, for example, sitting in a chair with their hands in their lap. The tremor often subsides or completely disappears when the person performs a purposeful movement, such as reaching for an object. The classic example is the “pill-rolling” motion of the thumb and forefinger. ^[3]
• Location and Asymmetry: The tremor of Parkinson’s disease almost always begins on one side of the body. It may eventually spread to the other side, but it typically remains asymmetrical, with one side being more affected than the other.
• Associated Symptoms: A PD tremor is just one of four cardinal motor symptoms of Parkinson’s disease. The others are crucial for a diagnosis and are not present in Essential Tremor. These include:
  • Bradykinesia: Slowness of movement. This can manifest as difficulty initiating a movement or a general slowing down of everyday tasks like walking or getting dressed.
  • Rigidity: Stiffness in the limbs and trunk.
  • Postural Instability: Impaired balance and coordination, leading to a tendency to fall. ^[4]

The diagnosis of a tremor is primarily clinical, meaning a neurologist makes the diagnosis based on a detailed medical history and a comprehensive physical and neurological examination.

1. The Neurological Exam:

   The neurologist will ask detailed questions about the tremor’s onset, frequency, and triggers. They will then observe the tremor and ask you to perform a series of tasks to see if the tremor is a resting or action tremor. These tasks may include:

   • Drawing a spiral: A person with ET will often have a shaky, wobbly spiral, while a person with PD will have a small, rigid, or constricted spiral (a symptom called micrographia).
   • Standing with arms outstretched: A person with ET will likely have a pronounced tremor in this position.
   • Walking and swinging your arms: The absence of a normal arm swing is a key indicator of bradykinesia in PD. ^[5]

2. Looking for Associated Symptoms:

   The neurologist will be looking for the other cardinal symptoms of PD. The presence of bradykinesia, rigidity, or postural instability in addition to the tremor is a strong indicator of Parkinson’s disease. The absence of these symptoms makes a diagnosis of Essential Tremor much more likely.

3. Advanced Diagnostic Tools:

   In some cases, where the diagnosis is unclear, a doctor may order additional tests.

   • DaTscan: This is a specialized imaging test that can visualize the dopamine system in the brain.²³ It can show a loss of dopamine-producing neurons in PD but will be normal in a person with ET. ^[6]
   • MRI or CT Scans: These are usually ordered to rule out other possible causes of tremor, such as a brain tumor or stroke, but they cannot diagnose or differentiate between ET and PD. ^[7]

The treatments for Essential Tremor and Parkinson’s disease are very different, which is why an accurate diagnosis is so important.

• Essential Tremor: The treatment for ET is focused on symptom management. First-line treatments often include beta-blockers or anti-seizure medications.
• Parkinson’s Disease: Because PD is a progressive disease caused by a lack of dopamine, the treatment is focused on replacing or mimicking the effects of dopamine. The gold standard treatment is a medication called levodopa. ^[8]

A tremor is a symptom, not a single condition. The distinguishing features of the tremor (resting vs. action), its location, and the presence of other associated symptoms are the key differentiators that allow doctors to make an accurate diagnosis. By working closely with a neurologist, you can get the right diagnosis and find a treatment plan that will help you manage your symptoms and maintain a high quality of life.