Essential Tremor Ultrasound Treatment
Essential tremor (ET) is the most common adult movement disorder, and as much as 20 times more prevalent than Parkinson's disease. Millions of people suffer from the syndrome for many years.
Essential tremor is not curable. All available treatments today seek to lower the severity of the condition.
ExAblate Neuro, using MR guided Focused Ultrasound (MRgFUS) is a non-invasive procedure which is being researched for the treatment of essential tremor.
A clinical trial conducted at the University of Virginia (UVA), USA, shows impressive results. Patients’ functional activities scores improved by 92 percent, as measured in the ‘Disability’ subsection of the Clinical Rating Scale for Tremor (CRST).
ABC World News with Diane Sawyer introduced its viewers to Phyllis Walker, a woman with essential tremor. Following her focused ultrasound treatment, her hand became steady enough to resume everyday activities.
As can be seen below, patients who could barely hold a pencil before the treatment can write clearly after treatment.
Before treatment After treatment
Drawing tests by a patient with essential tremor before and after MRgFUS treatment.
Courtesy of Elias J, M.D., University of Virginia, USA.
How does ExAblate Neuro Focused Ultrasound Treatment Work for Essential Tremor?
During treatment the patient lies in the MRI scanner with a novel helmet-like, multi-channel high power phased array transducer, used to destroy targeted tissue. The patient is awake the entire time and interacts with the treatment team.
The physician plans and conducts the procedure from a computer screen in the adjacent MRI control room. MRI scans are used to determine the targeted regions and continuous real time MRI images are obtained throughout the treatment to monitor efficacy by continuous temperature monitoring with the sub-degree accuracy, and ensure safety. Immediately at the end of the treatment, the clinical effect of the MRgFUS lesioning can be evaluated. The ability to provide pinpoint precision treatment at the planned target, without causing damage to any of the normal surrounding tissue, offers many potential advantages. It is non-invasive, incisionless, and bloodless, without bur holes or penetrating electrodes, reducing the risks of hemorrhage and infections. Since the skull remains intact there is no shifting of any tissues or neural structures within the brain during the procedure. Also, as no hardware is implanted, there is no electromagnetic noise interference, no need for programming follow-up or battery replacement or device management. MRgFUS does not use ionizing radiation, so treatment may be repeated, may be staged as the disease progresses, and has no risks of toxicity and accumulated dose effects. Several clinical trials have been initiated. In functional neurosurgery the goal is to ameliorate symptoms by targeting specific neural pathways in patients with movement disorders such as epilepsy, neuropathic pain, essential tremor and Parkinson’s(2). Similarly MRgFUS is being investigated to thermally destroy brain tumors.
Potential Advantages of MRgFUS Thalamotomy as a Treatment for Essential Tremor
- The treatment can be monitored in real-time with MRI for precision visualization and mapping of the brain. MR thermometry provides real time - feedback on the temperature rise and allows for immediate confirmation of the targeting process and the need for changing parameters during treatment.
- Thermal lesioning can be performed discreetly and accurately and can be evaluated immediately.
- Because the MRgFUS procedure is non-invasive, there is no scalp incision, no bur hole, and no electrode penetrating the brain. The risk of hemorrhagic complication should be reduced, and this noninvasive procedure should eliminate the risk of infectious complications.
- Unlike stereotactic radiosurgery, MRgFUS does not use ionizing radiation and does not carry a risk of radiation-induced tumorigenesis.
- Unlike DBS treatment, there is no implanted hardware, no concern of interference with external sources of electromagnetic noise, no need for extensive follow-up for programming, and no need for periodic battery replacement.
This represents a much simpler treatment plan for a patient suffering from ET. There will be hours of clinic time that is saved from DBS device management and replacement. Additionally, health care costs will be greatly reduced.
As with other surgical treatments, it will be possible to re-treat a patient who may develop a recurrence of the tremor
Other Treatment Options for Essential Tremor
The first line of treatment for essential tremor is medication. However, none of the medications available completely treat essential tremor, and may cause side effects. Also not everyone is a candidate for these medications.
There are also surgical procedures for treating essential tremor, these include:
Thalamotomy: A surgical intervention for the tremor is a procedure that severs nerve fibers from the thalamus. The thalamus is a group of cells deep in the brain involved in relaying motor and sensory signals from different portions of the brain. Thalamotomy involves creating a lesion or destroying a portion of the ventralis intermedius (VIM) nucleus of the thalamus It is conducted with several techniques including:
- Radiofrequency: The classical surgical method of dealing with tremor has been to destroy this small group of cells (thalamotomy) by passing an especially designed needle into the area and then heating the needle tip with radiofrequency electrical current.
- Deep Brain Stimulation (DBS): Uses a surgically implanted, battery-operated medical device called a neurostimulator—similar to a heart pacemaker and approximately the size of a stopwatch—to deliver electrical stimulation to targeted areas in the brain that control movement, blocking the abnormal nerve signals that cause tremor and PD symptoms. The lead (also called an electrode)—a thin, insulated wire—is inserted through a small opening in the skull and implanted in the brain. The tip of the electrode is positioned within the targeted brain area. The extension is an insulated wire that is passed under the skin of the head, neck, and shoulder, connectIng the lead to the neurostimulator. The neurostimulator (the "battery pack") is the third component and is usually implanted under the skin near the collarbone. In some cases it may be implanted lower in the chest or under the skin over the abdomen.
Once the system is in place, electrical impulses are sent from the neurostimulator up along the extension wire and the lead and into the brain. These impulses interfere with and block the electrical signals that cause tremor and PD symptoms.
- Stereotactic radiosurgery: Stereotactic radiosurgery is a form of radiation therapy that focuses high-powered x-rays on a small area of the body. Stereotactic radiosurgery better targets the abnormal area.
- Gamma Knife Thalamotomy: Gamma knife radiosurgical thalamotomy is a technique in which a thalamotomy is performed with beams of radiation rather than a surgical incision and use of electrodes.
What is Essential Tremor?
Essential tremor is a syndrome characterized by a slowly progressive postural and/or kinetic tremor, usually affecting both upper extremities. ET is a chronic condition characterized by involuntary, rhythmic tremor of a body part, most typically the hands and arms. In most patients, ET is considered a slowly progressive disorder and, in some patients, may eventually involve the head, voice, tongue (with associated dysarthria), legs, and trunk. However, in many people, the disease may be relatively non-progressive and the tremor may be mild throughout life.
The prevalence of essential tremor is estimated at 0.3-5.6% of the general population. It increases with age and is approximately 4% in persons aged 40 and older and considerably higher among persons in their 60s, 70s, 80s, and 90s.
Types of tremors
Rest tremor occurs when muscle is not voluntarily activated While action tremor is present with voluntary contraction of muscle.
Subtypes include postural, kinetic, and isometric tremor. Postural tremor is present while voluntarily maintaining a position against gravity. Kinetic tremor may occur during any form of voluntary movement. Intention or terminal tremor refers to exacerbation of kinetic tremor toward the end of a goal-directed movement.
Impact of essential tumor
As the disease progresses, individuals with essential tremor experience varying degrees of functional disability and resultant handicap. Affected individuals may have difficulty performing everyday tasks requiring fine motor manipulation skills. Holding or manipulating small objects, such as small tools or utensils, may be difficult. Hand tremor may cause difficulties with writing, drinking fluids from a glass or cup, eating, sewing, applying makeup, shaving, or dressing, for example.
While tremor is not medically dangerous, it is very disabling and affects mental status as well as functioning at home and in the work place.
Disability from essential tremor is common. Of individuals with essential tremor, 85% report significant changes in their livelihood and socializing and 15% report being seriously disabled by essential tremor.
Decreased quality of life results from both loss of function and embarrassment. In a study of hereditary essential tremor, 60% of affected individuals did not seek employment; 25% changed jobs or took early retirement; 65% did not dine out; 30% did not attend parties, shop alone, partake of a favorite hobby or sport, or use public transportation; and 20% stopped driving.
International Essential Tremor Foundation
Tremor Action Network
WE MOVE (Worldwide Education & Awareness for Movement Disorders)