There are various causes for tremor. The diagnosis of various kinds of tremors is based on the clinical spectrum and radiological imaging.
- Essential tremor
- Enhanced physiological tremor
- Parkinson’s disease tremor
- Drug-Induced action tremor
- Multiple Sclerosis
- Peripheral neuropathy-related
Midbrain or rubral
Essential tremor (ET) is one of the most common tremor disorders.
- Frequency being 4 – 12 Hz
- Most pronounced during purposeful movement.
- Often hereditary and is transmitted in an autosomal dominant mode.
- Mainly involves the upper limb and spares the lower limb.
- At its worst they can be a severe functional handicap preventing the patient from the use of upper extremities.
- Rest tremor in upper limb, fingers and hand which are pill rolling type with a frequency of around 5Hz.
- Usually asymmetrical
- Eliminates by movement but may recur in new posture (Re-emergent tremors)
- Lip, leg, tongue and jaw may also be involved
- Exacerbation by emotional stress
- Response to anti-parkinsonian drugs
Tremors of multiple sclerosis are much coarser and have larger amplitudes. The post stroke tremors and tremors due to other cerebral insults are less frequent and hence require specialist evaluation
Pathophysiology of Tremors
- 4 different mechanisms have been proposed
- Mechanical oscillations of the extremity.
- Reflexes eliciting and sustaining oscillations
- Essential oscillators to guarantee several normal physiologic functions (Central oscillators working abnormally are believed to produce tremor.)
- Tremulous central motor command because central feed-forward or feedback loops are altered
- None perceived
- Slight (barely noticeable)
- Moderate, noticeable, probably not
- Disabling (<2cm excursions)
- Marked, probably partially disabling
- (2-4cm excursions)
- Severe, coarse, disabling
- (> 4 cm excursions)