Tremor, defined as a rhythmic involuntary oscillatory movement of a body part around an axis, is the most common of all movement disorders. It can be a symptom, a sign, a syndrome and an etiological diagnosis.
Tremors may be isolated (primary) or combined (Tremor-Plus) with other conditions. Classification methods include anatomic distribution and presence at rest or with movement.
What you can do
Every patient with tremor should be screened for thyrotoxicosis and Wilson’s disease. Red flags include: tremors of sudden onset with associated focal neurological signs (e.g. diplopia). Structural neuroimaging is not necessary unless clinically indicated such as in tremors, which are progressive and associated with other neurological signs.
Potential provocative and aggravating factors should be identified and if possible, addressed. Drugs are a common cause of tremor and can also aggravate primary tremor disorders. A thorough drug history should be undertaken in every patient presenting with tremor. Combined postural and rest tremors should suggest neuroleptic use. Caffeine and other stimulants are a common aggravating factor for postural tremors.
Often only reassurance is required. Some patients need treatment (medication or surgery) because of emotional upset or functional disability.
Therapy is most often required for postural and kinetic tremors, which are more likely to interfere with function. Rest tremors if severe, can cause considerable annoyance, embarrassment and sleep disturbance.
Drug therapy
Drug therapy for tremors is mainly symptomatic and empirical as the neurotransmitter systems involved in pathological tremors are largely unknown as are the mechanisms of action of most tremorlytic drugs.
Some 70-80% of patients with Parkinsons and essential tremor improve with adequate drug therapy. The most effective drugs for Parkinsonian tremor are dopaminergic agents (levodopa and dopamine agonists) and anticholinergics. In essential tremor, beta-blockers and primidone, alone or in combination is first line.
Benzodiazepines can be helpful in primary kinetic tremors. Botulinum toxin injections are effective in focal dystonic tremors, especially of the head. Cerebellar tremors are usually refractory to medical therapy, though there are anecdotal reports of response to 5-HTP, clonazepam and carbamazepine. Orthostatic tremor may respond to clonazepam, or gabapentin.
Deep brain stimulation
In severe (functionally significant) drug unresponsive tremors stereotactic deep brain stimulation (DBS) is an option. The venterolateral thalamus (VIM-nucleus) is the surgical target of choice for most tremors, though the posterior subthalamic region may be even more effective. The procedure may be performed unilaterally or bilaterally. Bilateral thalamic stimulation may result in gait ataxia and dysarthria, at stimulation levels necessary to control tremor. In patients with Parkinsonian tremor, the subthalamic nucleus or the posterior subthalamic region are the targets. This has a similar effect as VIM stimulation and also alleviates akinesia.
Key Points
- Tremor is common and usually benign.
- Reassurance and addressing provocative factors is often all that is required.
- Treat where quality of life or function are impaired.
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