Advances in the treatment of essential tremor

March 11, 2019 Pravin Khemani, MD

A tremor is best described as a rhythmic to and fro movement of the limbs, head or torso, or a quivering of the voice. We have all had a transient tremor in our arms or legs or a ‘shaky’ feeling at some point in our lives from a variety of reasons- anxiety, nervousness, illness, fatigue, weakness, ‘teeth’ chattering cold etc.  Not unlike a headache, temporary tremors are very common, do not always warrant medical attention, and are not necessarily a harbinger of neurological disease. Transient tremors come and go, are situation-dependent and do not interfere with day-to-day activities. However, a persistent or progressive tremor of any part of the body is reason to seek your doctor’s advice. 

Essential tremor (ET) is a tremor of the limbs, which can cause significant disability as it progresses. Although it is most commonly noticed in the hands, it can affect the head, torso and voice. In its mildest form it is an annoyance and in its severest state it can make everyday tasks such as writing, holding a cup, eating, performing housework, or using tools impossible. Not everyone with ET comes to a doctor’s attention since the age of onset, rate of progression, severity, and the disability caused by ET varies. The exact prevalence of the disease is not precisely known, but it is estimated that in the US about 7 million people suffer from ET at any given time. The incidence of ET increases with age. 

As ET progresses, it can force individuals to give up daily tasks which those of us without tremor take for granted. Some individuals may even retire early due to tremor interfering with their occupation. Being aware of the various treatments for ET and seeking timely medical assistance can improve quality of life, which may otherwise be compromised due to tremor. Drugs such as propranolol or primidone are always the first-line treatment for ET, and although quite good at suppressing tremor when administered appropriately, they are not equally or permanently effective in everyone especially as tremor progresses in severity.  

When medications do not suppress tremor to effectively improve function, surgical treatments for ET are an option. Deep brain stimulation (DBS) is a surgical procedure which involves disruption of the abnormal tremor-generating circuit in the brain by precisely implanting an electrode in a part of the brain called the thalamus. The electrode is connected by a wire which is tunneled under the skin and attached to a small battery implanted in the chest. Selection of a candidate for DBS requires a well-orchestrated multidisciplinary collaboration between the movement disorders specialist treating the patient and the neurosurgery team performing the operation in order to ensure appropriate candidate selection and optimum treatment results. DBS surgery is performed in stages, with either one or both sides of the brain being treated, depending on the patient’s needs. Starting a few weeks after the surgery, the electrode is “programmed” by the neurologist at regular intervals to reduce tremor severity. 

Although DBS has been around since the early 90s and has been safely used to treat tens of thousands of people with severe ET, significant technological improvements have been made since its invention to improve the surgery and programming results. For instance, the latest DBS systems allow electricity to be directed or ‘steered’ in order to minimize side effects from programming while enhancing tremor suppression. Rechargeable batteries that last for a decade are available which eliminate the need to get battery replacements every 3-4 years. Brain MRIs performed for strokes and other neurological disorders, which were previously not permitted after DBS surgery, are now allowed albeit conditionally. Future developments in DBS surgery for ET are poised to finesse and customize treatments for patients with the objectives of further improving the durability and efficacy of tremor treatment. 

One of the most exciting developments in the field of ET treatment has been the advent of MRI guided Focused Ultrasound (MRgFUS) technology. MRgFUS treats tremor on either the left or right side of the body, depending on the patient’s needs Without any surgical incision, ultrasound waves are strategically transduced and ‘focused’ on the thalamus causing a small lesion that suppresses tremor. An MRI provides real time anatomical feedback to the neurosurgeon performing the procedure. The results are almost immediate, there is no hardware implanted in the system, and the patient can go home the same day. However, like DBS treatment, the neurosurgery team who performs the procedure works closely with the movement disorders team for appropriate patient selection to ensure optimum results. While the MRgFus is currently approved to treat ET on only one side of the body, research is underway to determine its safety in treating patients who need relief from tremor on both sides. 

A noninvasive, recently FDA-approved device to treat ET, is the CALA ONETM electronic band, which delivers low-intensity electricity at the wrist to disrupt brain circuits causing tremor. CALA TWO, TM an updated version of the older device, is currently being investigated for ET in a research study.

The marriage of medicine and innovative scientific technology have shifted the paradigm of ET treatment from complacency to one which has the potential to significantly improve the quality of life of individuals suffering from tremor. The first step in exploring treatment options for ET is a comprehensive evaluation by a neurologist who is experienced and knowledgeable the diagnosis of ET and its treatment and who works collaboratively with the neurosurgery team.

Pravin Khemani, MD, is a board-certified neurologist at Swedish Neuroscience Institute (SNI).

SNI is one of the few centers in the country offering a complete and comprehensive suite of ET treatment options. For additional information on treatment of ET at SNI, please visit: 

 https://www.swedish.org/services/neuroscience-institute/our-services/movement-disorders

https://www.swedish.org/services/neuroscience-institute/our-services/neuro-restoration

https://www.swedish.org/services/neuroscience-institute/our-services/focused-ultrasound

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