Tremor classification

Tremor may be classified into resting or action tremor. Action tremor includes postural, kinetic (simple or intentional), isometric and task-specific tremor.

Tremor may be classified into two main groups: ^[1][2]

• Resting tremor: Occurs when the body is not moving and is at rest, the muscle is relaxed and supported against gravity. It could occur in hands, legs, or arms. Resting tremor decreases in intensity with targeted movement. Parkinson’s disease and drug-induced parkinsonism exhibit resting tremors. Other causes of resting tremor are Wilson’s disease, dystonia, rubral tremor (brainstem lesion), and progressive supranuclear palsy.
• Action Tremor: Could occur with any voluntary movement. It is further classified into:
  • Postural Tremor: Increases with voluntary movement. Physiologic tremor, essential tremor, drug or alcohol withdrawal and metabolic changes in thyroid, kidney, liver may result in postural tremor.
  • Kinetic Tremor:
    • Simple kinetic: Not affected by targeted movement. Occurs with normal limb movement.
    • Intentional tremor: Increases in intensity by targeted movement. Observed in cerebellar lesion caused by stroke, multiple sclerosis or tumor, spinocerebellar ataxia, vitamin E deficiency and lithium or alcohol toxicity.
  • Isometric tremor: Voluntary contraction of muscle against a heavy/rigid/stationary object. For instance, making a fist, using one hand to hold a heavy object, or pushing against a wall.
  • Task-induced tremor: Occurs when performing a highly skilled task, handwriting tremor, or musicians tremor.