Tremor refers to involuntary rhythmic twitching of muscle groups. It often affects the hands, but it can also affect the whole body. Tremor is classified clinically by:
- Activation condition (rest, action, holding, undirected movement, target movement).
- Frequency (low frequency: 2-4 Hz, medium frequency: 4-7 Hz, high frequency: > 7 Hz).
- Intensity or amplitude
- Fine-beat tremor
- Medium-beat tremor
- Coarse-beat tremor
In the context of a tremor analysis, the following tremor forms are distinguished:
- Action tremor
- Holding tremor – tremor that occurs during holding work exerted against gravity; the upper extremity is usually affected; when the arm is held out, a tremor of medium frequency (5-8 Hz) sets in without delay; disease progression over many years is typical; family history positive in about 60%.
- Intention tremor – tremor of the limbs during a purposeful movement; the most common cause is multiple sclerosis (MS).
- Isometric tremor – tremor that occurs during isometric muscle work; triggered by a rigid voluntary movement.
- Kinetic termor (motion tremor).
- Motion tremor
- Dystonic tremor (moderate-frequency holding and movement tremor around 5-8 Hz) – tremor in the context of dystonia (presence of sustained or intermittent involuntary muscle tension); tremor is characterized by a dysfunction in the control of movement
- Essential tremor (moderate-frequency holding and action tremor/movement tremor around 5-8 Hz) – occurs without an identifiable underlying neurological disorder; considered a multi-etiologic syndrome whose causes, with the exception of some associated risk genes, have not yet been elucidated; most common form of tremor
- Note: A proportion of patients present with additional symptoms of unclear significance, such as ataxia (gait disturbance), dystonia (disturbance of muscle tension state), or resting tremor.
- Holmes tremor (synonyms: rubral tremor, midbrain tremor, myorhythmia, Bendict syndrome) (low frequency (2-5 Hz) and coarse-beat amplitude) – usually unilateral rest, holding and intention tremor.
- Neuropathic tremor (4-8 Hz and coarse-beat amplitude).
- Orthostatic tremor (OT; tremor in standing; non-visible, high-frequency tremor (12-20 Hz) – leads to a marked insecurity in standing when the leg muscles are tensed; patients complain of a feeling of weakness in the legs after standing up, rubber legs, insecurity in standing and balance problems; walking is usually hardly affected by this
- Parkinsonian tremor (mid-frequency: 4 – 7 Hz); occurs primarily at rest (resting tremor) and is unilateral; typical movement pattern (“pill-pulling tremor”) and slower than essential tremor; tremor in PD is historically divided into three types:
- Type I: resting tremor or resting and holding/moving tremor of the same frequency.
- Type II: resting and holding/movement tremor of different frequency.
- Type III: pure holding/movement tremor.
- Pathological tremor
- Physiological (without pathological value) tremor (fine-beat, high-frequency (7-12 Hz) – tremor with frequency reduction under weight load; is not or only minimally visible; is usually not perceived as disturbing; can be triggered by an active holding forward of the extremities.
- Psychogenic tremor
- Resting tremor
- Increased (intensified) physiological tremor – in contrast to physiological tremor usually visible and disturbing; fine to moderate tremor.
- Cerebellar tremor (slow frequency (2-5 Hz) and large amplitude) – is a cerebellar tremor of movement and intention; manifests as trunk or limb tremor
Warning signs (red flags)
- Anamnestic information:
- Chronic alcohol consumption
- Drug use
- Intention tremor (trembling of the limbs during a purposeful movement) + nystagmus (uncontrollable, rhythmic movements of the eyes) or dysarthria (impairment of speech) → think of: Cerebellar disorder
