Essential tremor
Description
- Isolated bilateral action tremor of the upper limbs, present for >=3 years, without other neurological signs
- Action tremor = postural (arms outstretched) + kinetic (finger-nose, pouring, drawing spiral)
- 4-12 Hz, typically 6-8 Hz
- Essential tremor plus - the same tremor with soft additional signs (impaired tandem gait, questionable dystonic posturing, mild memory impairment, rest tremor)
Distribution
- Hands ~95% (bilateral, may be mildly asymmetric)
- Head ~30-40% ("no-no" or "yes-yes") - far more common than in Parkinson disease
- Voice ~20% - quavering, worse on sustained vowel
- Legs, trunk, jaw less common
Essential tremor vs Parkinson disease - the core discrimination
| Essential tremor | Parkinson disease | |
|---|---|---|
| Tremor type | Postural + kinetic | Rest ('pill-rolling'), re-emergent on posture |
| Frequency | 6-12 Hz | 4-6 Hz |
| Symmetry | Bilateral, roughly symmetric | Asymmetric |
| Head tremor | Common | Rare (jaw and chin instead) |
| Handwriting | Large, tremulous | Micrographia |
| Effect of alcohol | Improves | No effect |
| Family history | ~50-70% | ~15% |
| Other signs | None | Bradykinesia, rigidity, hypomimia, hyposmia, RBD |
| Course | Slowly progressive over decades | Progressive over years |
| Levodopa | No response | Responds |
- *Bradykinesia is what makes it Parkinson disease* - test repetitive finger tapping for decrement in amplitude, not just speed
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