Tremor is the most common form of involuntary movement disorder, characterized by a rhythmic and oscillating movement of a body part. These movements are often caused by the alternating contraction of opposing muscle groups and vary significantly in their rate and visibility. Understanding the specific type of tremor is the first step toward understanding the underlying cause and determining the appropriate course of action.
Defining Postural Tremor
A postural tremor is an involuntary, rhythmic muscle oscillation that manifests when a person actively attempts to maintain a limb or body part against the force of gravity. This type of tremor does not occur when the muscles are fully relaxed or supported, but appears when a person holds a sustained position. Common examples include holding the arms outstretched in front of the body or attempting to hold a cup of water steady.
The characteristics of this tremor involve a relatively high frequency, typically ranging from 4 to 12 Hertz (Hz). In the context of the most common cause, Essential Tremor, the frequency usually settles between 6 and 12 Hz. The amplitude, or size of the movement, tends to be variable, often starting small and potentially increasing as the posture is maintained.
Common Underlying Causes
The most frequent neurological cause of a persistent postural tremor is Essential Tremor (ET), estimated to affect up to five percent of the global population. This condition is progressive, and a family history is present in nearly half of all cases, suggesting a strong hereditary component. Essential Tremor is often characterized by a tremor that affects both sides of the body symmetrically, most noticeably in the hands and arms.
A postural tremor can also manifest as an enhanced physiological tremor, which is an exaggeration of the fine, high-frequency tremor present in all healthy individuals. This enhancement is not a disease itself but a temporary response to various systemic factors. Common non-pathological triggers include high anxiety, emotional stress, or physical fatigue.
Certain external substances and medications can also induce or worsen a postural tremor. Excessive consumption of caffeine, alcohol withdrawal, or the use of specific prescription drugs can increase the tremor’s amplitude. Examples of implicated medications include bronchodilators, corticosteroids, and some anti-seizure drugs like valproate, which can disrupt the body’s normal physiological balance.
Differentiating Tremor Types
Tremors are generally classified based on when they occur, which is a significant factor in determining the underlying condition. Postural tremor must be distinguished from the two other main categories: resting and intention tremors. The timing and manifestation of the movement provide distinct diagnostic clues.
A resting tremor occurs when the affected body part is completely relaxed and fully supported, such as when the hands are resting in a person’s lap. This type of tremor is often associated with Parkinson’s disease and presents with a slower frequency, typically between 3 and 6 Hz. The movement often disappears once the person initiates a voluntary action.
In contrast, an intention or kinetic tremor becomes pronounced during a goal-directed movement, such as attempting to touch a target. The tremor’s severity increases as the limb gets closer to its final destination, like when trying to bring a fork to the mouth. Intention tremors are frequently linked to damage within the cerebellum, which coordinates voluntary movements and balance.
Diagnosis and Management Approaches
The diagnostic process for a postural tremor begins with a detailed neurological examination. The goal is to accurately classify the tremor based on its activation condition, frequency, and distribution across the body. Physicians test for postural tremor by having the patient hold their arms outstretched and may ask the patient to perform tasks like drawing a spiral to assess the tremor’s characteristics.
A comprehensive review of the patient’s medical history, including all current medications and family history of movement disorders, is performed to rule out secondary causes. Blood tests may be necessary to exclude metabolic conditions that can enhance physiological tremor, such as hyperthyroidism or hypoglycemia.
For a diagnosis of Essential Tremor, management often involves a combination of medication and lifestyle adjustments. First-line pharmacological options include beta-blockers, such as propranolol, and the anti-seizure drug primidone, both of which are effective in reducing tremor severity. Lifestyle modifications focus on avoiding known triggers like excessive caffeine intake, managing stress, and ensuring adequate rest to minimize the enhancement of the tremor.