Parkinsonian Tremor

Parkinsonian tremor is a characteristic tremor associated with Parkinson’s disease (PD) and other parkinsonian syndromes. It is typically described as a resting tremor that occurs when the affected body part is at rest and diminishes with voluntary movement.

Definition of Parkinsonian Tremor

Parkinsonian tremor is defined as a rhythmic, oscillatory movement that primarily affects the hands, arms, legs, and sometimes the jaw or head. Key features include:

1. Resting Tremor: The tremor is most prominent when the affected body part is at rest and usually diminishes or disappears during voluntary movement.
2. Frequency: The tremor typically has a frequency of 4 to 6 Hz.
3. Asymmetry: It often presents asymmetrically, affecting one side of the body more than the other, especially in the early stages of Parkinson’s disease.

Mechanisms of Parkinsonian Tremor

The underlying mechanisms of parkinsonian tremor are primarily related to dysfunction in the basal ganglia, a group of nuclei in the brain that play a crucial role in motor control:

1. Basal Ganglia Dysfunction: In Parkinson’s disease, there is a loss of dopaminergic neurons in the substantia nigra, leading to an imbalance in the activity of the direct and indirect pathways of the basal ganglia. This imbalance contributes to the generation of tremors.
2. Increased Oscillatory Activity: The loss of dopamine leads to increased oscillatory activity in the basal ganglia circuits, particularly in the subthalamic nucleus and globus pallidus. This abnormal activity can manifest as tremors.
3. Sensory Feedback Mechanisms: The tremor may also be influenced by sensory feedback mechanisms that are disrupted in Parkinson’s disease, leading to abnormal motor output.

Clinical Significance of Parkinsonian Tremor

1. Diagnostic Indicator: The presence of a resting tremor is one of the cardinal features of Parkinson’s disease and can aid in the diagnosis of the condition.
2. Impact on Daily Functioning: Tremors can significantly affect a person’s ability to perform daily activities, such as writing, eating, and dressing, leading to increased dependence on caregivers.
3. Assessment of Disease Progression: The severity and frequency of tremors can help assess the progression of Parkinson’s disease and guide treatment decisions.

Assessment of Parkinsonian Tremor

1. Ask the patient to rest the hand in a pillow 
2. Observe Asymmetrical tremor
3. If you can’t elicit the tremor give the patient an arithmetic stress like subtracting serials of 7 from 100 or telling counts of 5 like 5..10..15
4. This will bring out the masked tremor in some patients

References

• Adams, R. D., Victor, M., & Rpper, A. H. (2014). Principles of Neurology (10th ed.). McGraw-Hill.
• Kandel, E. R., Schwartz, J. H., & Jessell, T. M. (2013). Principles of Neural Science. McGraw-Hill.
• Jankovic, J. (2008). Parkinson’s Disease: Clinical Features and Diagnosis. Journal of Neurology, 255(Suppl 5), 1-6.
• Louis, E. D., & Ferreira, J. J. (2010). Tremor: A History of the Disorder and Its Treatment. Movement Disorders, 25(1), 1-10.