Essential tremor: Choosing the right management plan for your patient
ABSTRACTEssential tremor is a common neurologic problem seen widely at all levels of patient care. It should be differentiated from secondary causes of tremor and Parkinson disease. It can be managed with commonly used drugs. However, severe, resistant, or atypical cases should be referred to a specialist for evaluation and the possible use of botulinum toxin or deep brain stimulation.
KEY POINTS
- In addition to motor dysfunction, the tremor can also have a significant psychological impact on the patient, especially since it usually gets worse in social situations.
- Essential tremor is a clinical diagnosis. After a thorough review of the medical history and medication exposures, laboratory and imaging tests may be ordered to rule out a secondary cause.
- The two first-line agents in drug therapy for essential tremor are the nonselective beta-blocker propranolol (Inderal) and the antiepileptic primidone (Mysoline). They can be used alone or in combination.
- Botulinum toxin injection and deep brain stimulation are reserved for resistant tremor or for patients who do not tolerate drug therapy.
SPECIALTY-LEVEL CARE
When essential tremor does not respond to drug therapy or the patient cannot tolerate drug therapy, the patient should be referred to a center specializing in movement disorders for more advanced treatment options, ie, botulinum toxin injection and deep brain stimulation surgery.
Botulinum toxin
Botulinum toxin type A has been studied for the treatment of essential tremor with variable degrees of success. It has been effective in reducing hand tremor in essential tremor, but without a concomitant improvement in functional disability.44 This limited functional improvement has been attributed to the development of muscle weakness after injection of the neurotoxin. This has also raised questions about unintentional unblinding when interpreting study results. Therefore, most clinicians restrict its use to focal forms of tremor such as voice tremor,45 head tremor, and task-specific tremor.
Side effects are limited and temporary and include muscle weakness, pain at the injection site, dysphagia (when injected for head or voice tremor), and a breathy vocal quality (when injected for voice tremor). Botulinum toxin injection is the treatment of choice for focal dystonia, and therefore would be a good option for dystonic tremor.
Thalamic deep brain stimulation
This technique involves stereotactic implantation of a stimulation lead in the ventral intermediate nucleus of the thalamus. The lead connects via a subcutaneous wire to an intermittent pulse generator, implanted subcutaneously in the infraclavicular region. The stimulation lead produces continuous stimulation of the ventralis intermedius nucleus that is functionally equal to lesional surgery, thus antagonizing the relay of tremor signals at the thalamus.
The battery of the pulse generator must be replaced every 4 to 7 years depending on usage and stimulation parameters. Battery replacement can be performed with minor surgery at the infraclavicular region.
Thalamic deep brain stimulation is indicated for patients with severe, disabling essential tremor who have tremor resistant to drug therapy or who cannot tolerate drug therapy.
The procedure has been shown to provide benefit in 90% of patients, with more than an 80% improvement in tremor severity and functional impact.46–49 Deep brain stimulation is effective against tremor affecting parts of the body other than the limbs, including the head; an exception to this is voice tremor, which usually does not improve dramatically. The procedure can be done unilaterally or bilaterally, depending on symptoms. Patients with asymmetrical tremor and those at risk of side effects can undergo unilateral surgery. Bilateral treatment is recommended for patients with symmetric tremor or significant head tremor, or who are young and healthy.
Surgical risks include brain hemorrhage and infection. Side effects of the stimulation include paresthesias, paresis, imbalance, dysarthria, and, in rare cases, dysphagia.
CHOOSING THE BEST MANAGEMENT PLAN FOR YOUR PATIENT
The choice of treatment may be challenging, given the multiple treatment options and the variability of tremor severity from one patient to another. The following guidelines can be used to help make this decision.
All patients should be advised to reduce caffeine intake, to have sufficient hours of sleep, and to avoid stressful situations.
Patients with minor, nondisabling tremor can be left untreated if the tremors are not bothersome or if the patient prefers not to pursue active treatment.
In patients who have bothersome tremor only when anxious or in certain social situations, give propranolol or alprazolam (or both) to be taken as needed. Relaxation techniques and meditation are also useful for these patients.
Patients with constant bothersome tremor should be started on either propranolol or primidone based on the patient’s profile and propensity to develop side effects from each of these drugs. The dosing should be optimized gradually according to the patient’s response and the drug’s tolerability.
If essential tremor is not sufficiently controlled with one first-line agent (propranolol or primidone), try combining the two first-line agents if the patient finds it tolerable.
A second-line agent can be added to either of the first-line agents or to the combination of both if tremor control is not yet sufficient. A second-line or third-line agent can also be used as the primary treatment if both first-line agents are contraindicated or intolerable. Combining two or more second- and third-line agents is another option. The choice of second- or third-line agent should be guided by the patient’s characteristics and comorbidities in relation to the agent’s side effects and contraindications as detailed in the above section.
Patients should be referred to a movement disorders specialist in cases of resistant tremor, intolerance to oral medications, severe disability, and atypical presentation. Types of tremor known to be poorly responsive to oral medications (eg, head tremor, voice tremor) deserve a specialist evaluation if they contribute significantly to the patient’s morbidity.
The usual specialist treatment of severe voice tremor and head tremor is botulinum toxin injection. Patients with resistant and disabling hand tremor are evaluated for thalamic deep brain stimulation.
Patients with residual disability despite medical and surgical treatment should be referred for occupational therapy. Occupational therapy can improve quality of life through the use of special utensils, pens, computer gadgets, and arm weights, among other devices.
