What are perpendicular, postural tension, and rest tremors?

From the Guidelines

Perpendicular, postural tension, and rest tremors are distinct concepts where rest tremor is specifically associated with Parkinson's disease, characterized by an involuntary 4-6 Hz rhythmic motion, typically in the fingers and thumb, which is most pronounced at rest and diminishes with voluntary movement 1.

Definitions and Associations

• Perpendicular refers to a 90-degree angle between lines or surfaces, relevant in medical contexts for describing anatomical orientations or positioning.
• Postural tension involves muscle contraction to maintain posture against gravity, crucial for balance but potentially contributing to conditions like tension headaches when excessive.
• Rest tremor, a key feature of Parkinson's disease, is an involuntary oscillation occurring in a body part that is completely supported against gravity and not engaged in voluntary movement, typically presenting as a "pill-rolling" motion of the fingers and thumb.

Clinical Significance

The distinction between these concepts is vital in neurological assessments for diagnosing and managing movement disorders. Rest tremor, in particular, is a significant diagnostic criterion for Parkinson's disease, as discussed in the context of Parkinsonian syndromes 1. Understanding the characteristics of rest tremor, such as its frequency and the conditions under which it occurs or diminishes, is essential for differentiating it from other types of tremors, like action or postural tremors, which have different pathophysiologies and treatment approaches.

Diagnostic Considerations

In the evaluation of Parkinsonian symptoms, correctly identifying the type of tremor present can guide further diagnostic steps and treatment plans. Given the complexity and variability of Parkinsonian syndromes, including Parkinson's disease, multiple system atrophy (MSA), progressive supranuclear palsy (PSP), and corticobasal degeneration (CBD), a thorough clinical assessment is critical 1. Each of these conditions has a distinct set of clinical features, and while rest tremor is most commonly associated with Parkinson's disease, other symptoms such as bradykinesia, rigidity, postural instability, and specific non-motor symptoms can help in making a diagnosis.

From the FDA Drug Label

CLINICAL PHARMACOLOGY Mechanism of Action Parkinson’s disease is a progressive, neurodegenerative disorder of the extrapyramidal nervous system affecting the mobility and control of the skeletal muscular system. Its characteristic features include resting tremor, rigidity, and bradykinetic movements.

The FDA drug label does not answer the question about perpendicular, postural tension, and rest tremors, as it only mentions resting tremor as a characteristic feature of Parkinson's disease, without providing information on the other two terms. 2

From the Research

Types of Tremors

• Perpendicular tremors are not explicitly defined in the provided studies, however, the studies discuss various types of tremors, including:
  • Rest tremors: occur when the body part is in repose 3, 4, 5, 6, 7
  • Postural tremors: occur with maintained posture 3, 4, 6, 7
  • Action tremors: occur with voluntary contraction of a muscle and can be further subdivided into postural, isometric, and kinetic tremors 4
• Postural tension and rest tremors are discussed in the context of various pathological conditions, including:
  • Essential tremor: characterized primarily by postural and action tremors 3, 4, 7
  • Parkinson's disease: causes a resting tremor in the arms and legs 3, 4, 5, 6, 7

Characteristics of Tremors

• Tremors can vary in frequency and amplitude and are influenced by physiologic and psychological factors and drugs 3
• The diagnosis of tremor is based on clinical information obtained from a thorough history and physical examination 4, 6, 7
• The approach and diagnosis of patients with tremor may be challenging for clinicians, and the differentiation between action, resting, and other task- and position-specific tremors is crucial 6