Читать книгу Current Concepts in Movement Disorder Management - Группа авторов - Страница 51

Physiologic tremor is present in all people to varying degrees, but infrequently leads to medical evaluation. It may be enhanced by states of high anxiety or fatigue. Drugs may cause or exacerbate underlying tremor. Drug-induced tremor is very common and usually manifests as a symmetric postural kinetic tremor, although asymmetric resting tremor can be seen in DIP from dopamine blocking agents. The list of tremor-genic medications is extensive and includes caffeine, stimulants, steroids, beta-agonists, antidepressants such as SSRIs and TCAs, lithium, valproate, and amiodarone. Temporal association with drug initiation is key, but may not be easy to extract from the history. Drug-induced tremor does not typically progress, although it may be dose dependent and thus appear to worsen when the drug is increased. Risk factors for drug-induced tremor include older age and polypharmacy (additive effect with multiple tremor-genic drugs). When the tremor becomes disruptive, the typical course involves switching to an alternative agent. If this is not feasible, a symptomatic medication such as propranolol or primidone may be tried.

Metabolic disturbances comprise another large category of tremor causes. Most commonly associated conditions include hyperthyroidism, hypoglycemia, liver dysfunction, and renal failure. The tremor tends to be a bilateral, symmetric postural kinetic tremor that resolves with correction of the metabolic abnormality. Action tremor may be part of another neurologic disorder, such as dystonia, Wilson’s disease, Fragile X-associated tremor-ataxia syndrome, and disorders affecting cerebellar function. Dystonic tremor is typically jerky and position-dependent, and sometimes task-specific. Cerebellar lesions often produce intention tremor, which involves occurrence or worsening of the tremor upon approaching a target.