What is Postural Tremor
Postural tremor is an involuntary, rhythmic oscillation of a body part that occurs when maintaining a position against gravity, such as holding the arms outstretched or in a wing-beat position. 1, 2
Definition and Clinical Characteristics
Postural tremor represents one of the three main categories of tremor based on activation conditions, distinct from resting tremor (occurring when the body part is completely relaxed and supported) and kinetic tremor (occurring during voluntary movement). 1, 2
Key Features:
- Activation: Occurs specifically when maintaining a posture against gravity, such as extending the arms forward or holding them in a wing-beat position 1, 2
- Frequency: Typically ranges from 4-8 Hz depending on the underlying etiology 1
- Distribution: Most commonly affects the upper extremities and head 1
Clinical Assessment
Postural tremor is best elicited by having the patient hold their arms in two positions: the outstretched position (arms extended forward) and the wing-beat position (arms flexed at elbows with hands at shoulder level). 3 The wing-beat position typically reveals more severe tremor than the outstretched position in essential tremor cases, making it a more sensitive examination maneuver. 3
Important Distinction - Re-emergent Tremor:
In Parkinson's disease, a specific subtype called "re-emergent tremor" occurs after a latency period of several seconds to minutes when assuming a new posture. 4 This differs from essential tremor, which appears immediately without latency, and helps differentiate parkinsonian postural tremor from other causes. 4
Common Etiologies
The most common pathologic cause of postural tremor is essential tremor, affecting 0.4-6% of the population. 1, 2
Other Important Causes:
- Physiological tremor: Low-amplitude, high-frequency tremor present in all individuals, typically not symptomatic 2
- Drug-induced: Lithium, valproic acid, lamotrigine, antidepressants, and neuroleptics commonly cause postural tremor in psychiatric patients 5
- Parkinson's disease: Postural tremor with characteristic latency (re-emergent tremor) 4
- Metabolic conditions: Thyrotoxicosis, hypoglycemia 2
- Cerebellar disorders: Typically associated with intention tremor but can have postural component 2
Clinical Significance
Postural tremor is the most common movement disorder encountered in clinical practice and often causes more functional disability than resting tremor because it interferes with holding objects and performing activities of daily living. 1, 4 In Parkinson's disease patients, the postural (re-emergent) tremor is typically more troublesome than rest tremor because it results in spilling liquids and difficulty holding items like newspapers against gravity. 4
Common Diagnostic Pitfall:
Postural tremor in Parkinson's disease is frequently misdiagnosed as essential tremor, particularly when both conditions coexist. 4 The key distinguishing feature is the latency period before tremor emergence in parkinsonian patients versus immediate onset in essential tremor. 4