Aids to the differential diagnosis of essential tremor
| Diagnostic aid | Caveat | Essential tremor versus Parkinson’s disease or essential tremor versus dystonia? |
| Patients with essential tremor do not have rigidity | Cogwheeling (without rigidity) may occur in patients with essential tremor | Essential tremor versus Parkinson’s disease |
| Patients with essential tremor do not have hypomimia | Essential tremor versus Parkinson’s disease | |
| Patients with essential tremor do not have bradykinesia accompanied by decrement | As many essential tremor patients are elderly, rapid alternating movements may be slow; however, true decrement should not be present nor should it be lateralising (ie, present on one side only) unless the patient is developing essential tremor–Parkinson’s disease | Essential tremor versus Parkinson’s disease |
| Isolated rest tremor is not a feature of essential tremor | Essential tremor versus Parkinson’s disease | |
| Isolated postural tremor is not a feature of essential tremor | Essential tremor versus Parkinson’s disease | |
| Postural tremor predominantly involving the metacarpophalangeal joints rather than the wrist is not a feature of essential tremor | Essential tremor versus Parkinson’s disease | |
| Postural tremor characterised by greater wrist rotation than wrist flexion and extension is not a feature of essential tremor | Essential tremor versus Parkinson’s disease | |
| Re-emergent tremor (ie, tremor emerging after a latency) is not a feature of essential tremor; it is a feature of Parkinson’s disease | Postural tremor of essential tremor may vary from moment to moment, which means that it may be absent or of low amplitude initially and then emerge after some time | Essential tremor versus Parkinson’s disease |
| Aside from a mild dystonic posture in patients with severe and longstanding essential tremor, dystonic postures, movements or tremor are not currently accepted as features of essential tremor | Essential tremor versus dystonia | |
| Dystonic tremor itself is often neither rhythmic nor oscillatory | Essential tremor versus dystonia | |
| The presence of moderate or marked head tremor in the absence of limb tremor is highly suggestive of an underlying diagnosis of dystonia | Essential tremor versus dystonia | |
| Unless it is particularly severe, the neck tremor of essential tremor, which is a postural tremor, should resolve while the patient lies on their back with their head fully at rest; in contrast, persistence of such tremor is often a sign of an underlying diagnosis of dystonia | Essential tremor versus dystonia | |
| Patients with neck tremor and underlying diagnoses of dystonia may have signs of dystonia, including head tilt or rotation, hypertrophy of the sternocleidomastoid or other neck muscles, the presence of a tremor null-point, or a sensory trick by history (ie, a manoeuvre such as touching the chin or back of the head that lessens the tremor) | Essential tremor versus dystonia |