- Resting Tremor: Occurs when muscle is fully supported against gravity and relaxed; decreases or disappears with voluntary movement.
- Primarily due to dysfunction in the basal ganglia, specifically the substantia nigra, leading to disturbances in the neural circuits that control movement initiation. This is often related to dopamine depletion.
- Parkinson Disease
- Midbrain Tremor
- Wilson Disease
- Progressive supranuclear palsy
- Multiple System Atrophy
- Drug-Induced Parkinsonism
- Action Tremor: Occurs During Voluntary Muscle Movement
- This is the classic sign of cerebellar dysfunction. The cerebellum is crucial for error correction and coordinating the timing and force of movements. Damage disrupts this feed-forward control, causing overshooting and corrective “jerks” that manifest as a tremor, which amplifies as the movement requires more precision near the target.
- Postural Tremor:
- Occurs while maintaining a position against gravity (e.g., arms extended forward).
- Key Causes: Essential Tremor (ET), Enhanced Physiologic Tremor, Wilson disease.
- Kinetic Tremor:
- Occurs during any voluntary movement.
- Intention Tremor (Target-directed): Amplitude increases as target is approached (dysmetria on finger-to-nose testing).
- Key Causes: Cerebellar disease (e.g., stroke, MS, chronic EtOH cerebellar degeneration, spinocerebellar ataxia).
- Simple Kinetic: Tremor remains constant throughout trajectory (not worsening near target).
- Isometric Tremor:
- Occurs during muscle contraction against a stationary object (e.g., squeezing an examiner’s hand, making a fist).
- Task-Specific Tremor:
- Isolated to specific complex motor activities (e.g., primary writing tremor).