Rest tremor
- Tremor in a body part that is not voluntarily activated.
- It should be assessed when the patient is attempting to relax and is given adequate opportunity to relax the affected body part.
- This may require complete support of the body part (e.g., the head) against gravity.
- Increase while
- Walking or
- When performing movements of another body part
- Also occur in advanced ET,
- But rest tremor does not subside during voluntary movements in ET and in dystonic tremor
- The re-emergent tremor of PD should be regarded as an action tremor irrespective of the waveform similarities with rest tremor.
Action tremor
- Occurs while
- Voluntarily maintaining a position against gravity (postural tremor and orthostatic tremor) OR
- During any voluntary movement (kinetic tremor).
- Kinetic tremor
- Subdivided into
- Simple kinetic tremor in which tremor is roughly the same throughout a movement (e.g., waiving with the hands at a slow speed), and
- Intention tremor in which a crescendo increase in tremor occurs as the affected body part approaches its visual target
- Task-specific kinetic tremor in which a specific task such as writing.
- Position-specific postural tremor
- Occurs when maintaining a specific position or posture
- Isometric tremor
- Occurs when a muscle contraction against a rigid stationary object
- Eg: when making a fist or squeezing an examiner’s fingers.
Isolated rest tremor syndromes
- Most commonly occur in an upper or lower limb or as a hemitremor, but may occur elsewhere (e.g., lips, jaw, or tongue). It is crucial to determine, using Axis 1 characteristics, whether the rest tremor is isolated or combined with other clinical features.
Isolated voice tremor
- Is a visible and/or audible tremor of the vocal apparatus.
Isolated head tremor
- Is a shaking of the head in yes-yes, no-no, or variable directions.
Palatal tremor
- Is characterized by rhythmic movement of the soft palate at 0.5 to 5 Hz.
Primary orthostatic tremor
- Is a generalized high- frequency (13-18 Hz) isolated tremor syndrome that occurs when standing.
- Confirmation of the tremor frequency is needed, typically with an electromyography (EMG).
Dystonic tremor syndromes
- Tremor syndromes combining tremor and dystonia as the leading neurological signs.
- Different syndromes are separated on clinical grounds.
- Tremor combined with parkinsonism (bradykinesia and rigidity)
- Typically a 4- to 7-Hz rest tremor of the hand (“pill-rolling” tremor), lower limb, jaw, tongue, or foot. This is called classic parkinsonian tremor.
- Other types of tremor may coexist in patients with parkinsonism, such as postural or kinetic tremor with the same or different frequency as the rest tremor.
- Intention tremor syndromes
- Consist of intention tremor at <5 Hz, with or without other localizing signs.
- Holmes tremor
- Is a syndrome of rest, postural, and intention tremor that usually emerges from proximal and distal rhythmic muscle contraction at low frequency (<5 Hz).
Myorhythmia
- Very rare rhythmic movement disorder of cranial or limb muscles at rest or during action and is classified here as a tremor.
- The frequency is 1 to 4 Hz. It is usually associated with localizing brainstem signs and usually with a diagnosable aetiology.
Functional (a.k.a., psychogenic) tremor
- Characterized by distractibility, frequency entrainment, or antagonistic muscle coactivation.
Indeterminate tremor syndrome
- Is reserved for a patient who does not fit into an established syndrome or who needs further observation to clarify the tremor syndrome.