Tremor
A tremor is an involuntary, rhythmic oscillation of a body part. It can occur at rest, during movement, or while holding a posture.
Essential tremor: A common movement disorder marked by action tremor, often affecting the hands and sometimes the head or voice. Its rhythmic shaking typically becomes most evident during movement or posture-holding.
Rest tremor: A tremor occurring when a body part is relaxed and supported against gravity. This pattern is a key clinical clue, especially in parkinsonian disorders.
Tremor assessment: The clinical evaluation of tremor through its history, triggers, distribution, examination, and possible causes. Classifying when and where shaking occurs is the starting point for evaluating it.
Physiological tremor: A fine, usually imperceptible oscillation present in healthy people that can become more visible under certain conditions. Enhanced physiological tremor can follow factors such as anxiety, fatigue, or stimulant use.
Parkinsonian tremor: A tremor associated with Parkinson’s disease, often prominent at rest and reduced during voluntary movement. Its resting pattern contrasts with tremors that mainly appear during action.
Action tremor: A tremor occurring during voluntary muscle contraction, including movement or posture-holding. Many tremors are classified by the task or posture that brings them out.
Electromyography: A technique that records the electrical activity produced by skeletal muscles. Muscle recordings can characterize tremor frequency and the timing of muscle activation.
Functional tremor: A tremor arising within functional neurological disorder, diagnosed by characteristic positive examination signs. Its variability and changes with attention or competing movement can distinguish it from other tremors.
Cerebellum: A brain structure involved in coordinating movement, balance, and motor learning. Cerebellar circuit disruption can produce intention tremor as movement approaches a target.
Intention tremor: An action tremor that grows stronger as a voluntary movement approaches its target. Its worsening near a target points toward impaired cerebellar coordination.