Origin
Tardive tremor is a unique variant of a drug-induced tremor that has been associated with long-term use of agents with dopamine receptor blocking properties, such as neuroleptics and metoclopramide.
Clinical Features
Disabling tremor with coarse amplitude and frequencies ranging from 2.5 to 6 Hz. The tremor is most severe with posture holding, but also occurs at rest and during active movements. Onset of the tremor occurred between 2 and 20 years after initial drug exposure, typically developing on withdrawal of the medication, and persisting long after the removal of the offending agent. Patients usually have other coexistent tardive syndrome movements (eg, orofacial dyskinesia) with minimal or no parkinsonian features.
Age of onset
The risk factors for developing this tremor are not known, but as with other forms of tardive dyskinesia, patients of older age and female gender have a higher risk.
Distribution
Involving the upper limbs as well as the lower limb, head, face, jaw and lips in some cases.
Differential Diagnosis
When presented with a patient with a drug-induced tremor, the features that assist in distinguishing tardive from parkinsonian tremor include:
- Persistence or worsening of the tremor after removal of dopamine blocking agents.
- Predominantly action tremor.
- Improvement with agents that antagonise the effects of dopamine, for example, tetrabenazine, increasing or reintroducing the neuroleptic.