This is the most common movement disorder. It has been reported to affect 3% of the population. It is an inherited condition and the trait for this tremor can be passed from generation to generation. Fifty percent of children of an affected parent will inherit the tendency to get the tremor (autosomal dominant inheritance). The tremor will usually affect both sides of the body but may be asymmetric. The tremor severity slowly worsens with age (frequency slows, amplitude increases) with some stable phases occasionally lasting years.
This type of tremor may be very disabling, with 15% of patients having to retire prematurely due to the tremor.
The tremor most often affects the hands, but may affect arms, legs (~30%), voice, jaw and/or head. This tremor typically stops with rest or relaxation of the arms. It is more apparent when the patient holds their arms out straight (posturing) or when they are performing activities (intention), such as drinking soup with a spoon, holding up a cup, or writing.
It is worse when triggered by anxiety, fever, hyperthyroidism, physical exhaustion or low blood sugar. Some medications and some chemicals (e.g. theophylline, caffeine, alcohol withdrawal) will accentuate essential tremor.
Often no treatment is necessary other than reassurance once the diagnosis is made. Some counseling may be required in younger patients regarding career choices. Triggering factors should be removed (eg. reduce caffeine intake). If severe enough medications can be prescribed to help suppress the tremor.
The 3 options proven to be more effective than placebo include propranolol (Inderal), primidone (Mysoline), and topiramate (Topamax).
- Propranolol can be taken on an as needed basis, such as prior to stressful events (works within a half hour and usually lasts 2-5 hrs).
- Propranolol also comes in a long-acting formulation, which gives all day tremor relief. Note that this is not a safe option in asthmatics.
- Primidone is taken as a daily medication, and is considered to be as effective as propranolol.
- Propranolol and primidone combined can work in a synergistic manner, such that smaller dose of each together work better than large doses of either medication alone.
- Topiramate is almost as effective, but can have a less tolerable side effect profile in some patients.
- If the above are ineffective, then 2nd line agents such as gabapentin, acetazolamide (Diamox), pregabalin (Lyrica), clonidine, amantidine, and clonazepam although not proven in controlled trials to be effective in comparison to placebo can, in some individuals, produce significant benefit.
Once medical therapy as outlined above fails then surgical intervention in the form of thalamotomy or deep brain stimulation of the thalamus could be considered. Please refer to the following review article for the most current treatment algorithm.
1 – Deep Brain Stimulation
The standard surgical treatment is to implant a deep brain stimulator (DBS), which is a small electrode implanted into the thalamus that is connected to a programmable transmitter under the chest wall, like a pacemaker. By electrically interfering with the natural firing pattern of the brain cells in this area, the tremor is electrically suppressed. The goal is to not cause any permanent lesion in the brain. This, if successful, will stop the tremor on the opposite side of the body. There are, as with any surgical procedures, possible side effects that need to be discussed and considered. Risks increase with bilateral procedures, but these remain safer than techniques that lesion the brain.
2 – Steriotactic radio frequency thalamotomy
This is a procedure that surgically lesions (destroys) a very small area deep within the brain that causes the tremor (the thalamus). This, if successful, will stop the tremor on the opposite side of the body. There are, as with any surgical procedures, possible side effects that need to be discussed and considered. This will only target the tremor on the opposite side of the body … doing this procedure on both sides can risk significant speech impairment.
3 – High intensity focussed ultrasound (HIFU) thalmotomy
This is a more recent technique to non-surgically destroy brain pathways in an attempt to improve function of the basal ganglia and associated structures. This is a technique that is still undergoing investigation. MRI scanning prior to the procedure helps identify the correct location of the target in the patient’s brain. Although bilateral procedures in the past directed at the VIM nucleus of the thalamus were associated with a risk of increased side effects, there are newer targets being identified (cerebellothalamic tract) that may make bilateral treatments safer. Long term outcomes > 1 year are not yet published (as of 2017). Side effects reported in the NEJM in 2016 included 36% incidence of gait disturbance and 38% risk of sensory changes on the treated side. The procedure was approved by the FDA in July 2006. See the following review article to learn more about this procedure.
4 – Gamma knife (radio surgery) thalmotomy
Another procedure which also destroys a very localized area in the brain by applying many low energy radiation beams into one focussed spot. This procedure can be done without the need of any incisions. It also doesn’t take as long to complete. The experience with this technique is more limited and remains under investigation.