Essential tremor (ET) is the most common movement disorder. It is a progressive, often inherited disorder that usually begins in later adulthood. Patients with ET typically experience tremors when the hands are being used for activities like eating, drinking, writing or holding a magazine. The tremors also may affect the head, voice, tongue and legs and worsen with stress, fatigue and stimulants such as caffeine.
Essential tremor is thought to be caused by abnormal rhythmic electrical activity in the brain that send abnormal signals being sent out to the muscles. Several areas of the brain have been implicated in generating these abnormal signals. These regions include the cerebellum, red nucleus, globus pallidus, thalamus and cortex.
Patients with significant functional impairment usually opt for some form of treatment. Less impaired patients may choose to forgo treatment all together. Some patients that are not functionally impaired desire treatment because their tremor is a significant source of embarrassment. Once a patient desires therapy, there are several options:
Non-Medical Therapy – In some patients, tremors can be reduced by weighting the limb, usually by applying wrist weights. In a small proportion of patients, this can dampen down the tremor enough to provide some relief or improve functioning.
Since anxiety and stress classically make the tremor worse, non-medical relaxation techniques and biofeedback can be effective in some patients.
Medications known to make tremors worse should be eliminated or minimized when possible. These include lithium, several antipsychotics, valproic acid, corticosteroids, some anti-depressants and a class of drugs called adrenergic agonists. People with tremor also may benefit from avoiding dietary stimulants, such as caffeine. They should also be evaluated for hyperthyroidism, which can produce tremors that mimic ET.
Medication – The decision to treat with medications is made when the degree of impairment or discomfort outweighs the side effects of treatment. The mainstay medications include beta adrenergic blockers, such as propranolol (Inderal), and the anti-seizure medication primidone (Mysoline).
Surgery – When patients do not achieve satisfactory control of their tremor with non-medical or medical therapies and there is significant functional impairment, surgical options should be considered.
- Preoperative Assessment – All patients considering DBS to treat their symptoms are evaluated by a neurologist on our team. During this evaluation, the physician decides whether the medications the patient is taking are appropriate and optimal, and performs a cognitive evaluation to determine whether the patient can accurately and actively participate during the surgery and during brain stimulator programming. Medical clearance is also obtained through the patient’s internist prior to scheduling surgery. A neurosurgeon from our team then evaluates the risks and benefits of the surgery in the context of each patient’s needs. There is no guarantee that the tremor will be completely relieved with DBS.
- The Implanted System – The system consists of an electrode that goes into the brain, a connecting cable, and the “neurostimulator” which contains electronic circuitry as well as a battery.
- Programming of the Deep Brain Stimulator – Immediately following the surgery, there may be some benefit without the stimulator even being turned on. This is thought to be due to swelling around the tip of the implanted electrode. This effect can diminish over the following weeks to months. Usually, the initial programming is done three to four weeks after the surgery. During the first session, which lasts a few hours, the implanted device is checked to ensure it is functioning correctly. At this time, various parameters of stimulation (voltage, frequency of stimulator and which of the four electrodes are used) are programmed. This requires continuous feedback from the patient to determine if there are any side effects and to determine the best settings for tremor relief. Patients typically return several times over the next few months until the stimulator is programmed optimally. The trial and error of this can be frustrating, but most patients (80-90%) get very significant reduction in their tremor by the end of the process.
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