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When Tremors Are Not Parkinson’s

Involuntary trembling of the hands is a common symptom among middle-aged and older adults. However, many people immediately associate hand tremors with Parkinson’s disease, which can lead to unnecessary anxiety. In reality, Essential Tremor (ET) is the most prevalent movement disorder encountered in clinical practice, with a prevalence approximately 20 times higher than that of Parkinson’s disease.

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This article will examine the differences between these two conditions from several perspectives, including tremor characteristics, associated symptoms, disease progression, and treatment strategies. It also aims to provide readers with practical methods for self-observation and guidance on when to seek medical evaluation.

Hand Reaching Out

Resting Tremor vs Essential Tremor

Tremors can be broadly categorised into two groups based on when they occur, and this distinction provides an important clue in differentiating between underlying conditions:
 

Resting Tremor

This type typically appears when the limb is completely relaxed and not exerting any force — for example, when both hands are resting on the thighs or hanging naturally at the sides. In Parkinson’s disease, the tremor often manifests as a characteristic “pill-rolling” movement (a rhythmic rubbing between the thumb and index finger), with a frequency of around 4 to 6 cycles per second. Such tremors tend to diminish during voluntary movements (e.g., holding a cup), but re-emerge once the action ceases. The underlying mechanism involves degeneration of dopaminergic neurons in the basal ganglia, leading to abnormalities in motor control circuits.

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Essential Tremor

Essential Tremor (ET) can be classified into three main subtypes:

  • Postural Tremor – Tremors that become pronounced when maintaining a fixed posture, such as holding the arms outstretched.

  • Kinetic Tremor – Tremors that intensify during goal-directed movements, such as drinking from a cup or writing.

  • Intention Tremor – Tremors that increase in amplitude as the hand approaches a target, often associated with cerebellar dysfunction.

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The frequency of ET usually ranges from 4 to 12 cycles per second, which is higher compared with Parkinsonian tremors. In over 90% of cases, hand tremors are the initial symptom, later progressing to involve the head (seen as nodding or shaking movements) and laryngeal muscles (resulting in voice tremor). Only rarely does ET present first with lower limb involvement.

Doctor Wearing Surgical Gloves

Accurate diagnosis and timely treatment can help patients with tremor maintain a good quality of life. If related symptoms are present, it is advisable to consult a neurologist or neurosurgeon in order to establish an individualised treatment plan.

Essential Tremor (ET) vs Parkinson’s Disease (PD): Key Differences

  • Tremor Type

    • ET: Action tremor (postural/kinetic)

    • PD: Resting tremor (“pill-rolling”)

  • Initial Site of Onset

    • ET: Usually both hands (≈90%)

    • PD: Often one hand/foot (≈70%)

  • Frequency

    • ET: 4–12 times per second

    • PD: 4–6 times per second

  • Alcohol Effect

    • ET: Temporary improvement (seen in 50–70% of patients)

    • PD: No obvious effect

  • Associated Symptoms

    • ET: May include gait instability

    • PD: Rigidity, bradykinesia, postural instability

Treatment Options for the Two Conditions

Essential Tremor (ET) – Treatment Options
First-line medications include Propranolol (a β-blocker), which is effective in approximately 50% of patients, and Primidone (an antiepileptic), with symptom improvement reported in around 70% of cases. Second-line agents include benzodiazepines (e.g., clonazepam) and gabapentin.

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For severe cases, patients may benefit from Deep Brain Stimulation (DBS) targeting the ventral intermediate nucleus (VIM) of the thalamus, or from Magnetic Resonance-guided Focused Ultrasound (MRgFUS). The latter is a non-invasive thermal ablation technique that uses MRI guidance to precisely target and ablate abnormal tissue through thermal effects. In addition, patients are advised to minimise caffeine intake, manage stress effectively, and use weighted utensils to reduce the functional impact of tremors on daily life.

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Parkinson’s Disease (PD) – Treatment Options
Therapy primarily involves dopamine replacement, with Levodopa being the most effective option. However, long-term use may lead to motor complications. Dopamine agonists (e.g., pramipexole) are also commonly prescribed as alternatives or adjuncts.

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Surgical treatment options include Deep Brain Stimulation (DBS) targeting either the subthalamic nucleus (STN) or the globus pallidus internus (GPi). Careful patient selection is required, and the best results are typically seen in patients whose predominant symptom is tremor. In terms of rehabilitation, therapies such as Tai Chi and rhythmic auditory stimulation can help improve gait function.

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Although hand tremor is a hallmark feature of Parkinson’s disease, Essential Tremor (ET) remains the most common cause. A useful mnemonic is: “Resting tremor – Parkinson’s; Action tremor – Essential Tremor.” This can assist in differentiating the two conditions. With continuing advances in medical technology, newer non-invasive treatment options such as MR-guided focused ultrasound (MRgFUS) have become available. Patients are encouraged to seek early medical evaluation for accurate diagnosis. Initial management typically involves medication, but if symptoms fail to respond adequately, surgical approaches such as MRgFUS may be considered. Regular follow-up is essential to monitor disease progression and treatment outcomes.

Image by A. C.

Patients with Parkinson’s disease who also present with essential tremor often exhibit a poorer therapeutic response. Recent studies have shown that Parkinson’s patients carrying LRRK2 gene mutations are more likely to develop pronounced tremor symptoms.

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