Essential tremor (ET) is the most common movement disorder, affecting an estimated 3% of the population, or approximately 10 million people in the US. While ET is commonly viewed as a relatively benign disease, its associated disabling aspects – such as significant tremor of the hands – can impair a patient’s ability to eat, shave, write, perform household activities, and function in the workplace.
The underlying cause of ET is unclear, but cases often run in families (familial tremor). It has been estimated that approximately 50% of all cases are due to a genetic mutation, and the pattern of inheritance is most consistent with autosomal dominant transmission (i.e., dominant trait).
Until focused ultrasound (FUS) was available, traditional treatment options for ET included:
1) medication (often the first line therapy, but up to 30% of patients do not respond and may therefore be candidates for surgery);
2) thalamotomy procedures, in which a predefined small volume of brain tissue containing nerve cells causing the tremor is destroyed using stereotactic radiosurgery or radiofrequency (RF) ablation; and,
3) deep brain stimulation (DBS), in which a stimulator (i.e., “pacemaker”) generates mild electrical currents through an electrode implanted in the brain via a burr hole created in the skull.
Focused Ultrasound – A New Approach
FUS is a completely non-invasive method of thalamotomy (as described above) approved by the FDA in July 2016 that may be an effective option for certain patients. FUS is performed while the patient is awake and involves no anesthesia, no incisions in the scalp, and no burr holes through the skull or insertion of electrodes into the brain. During FUS therapy, target cells in a central part of the brain called the thalamus are visualized in real time using MR imaging. The highly precise treatment focuses beams of acoustic energy to heat and destroy target cells without harming adjacent tissue. At this time, the procedure can only be performed on one side of the brain, and patients usually have their dominant side treated.
FUS may offer the following benefits over other treatments:
- It is a non-invasive, single treatment so patients recover rapidly and return to activities of normal life quickly (usually the next day).
- It offers reduced risk of infection, damage to the non-targeted area, and blood clot formation.
- There is no exposure to radiation and its related side effects.
About Exablate Neuro
The Exablate Neuro system was developed by Insightec, an Israeli company. With Exablate Neuro, high intensity FUS waves are delivered through the skull – without incision or craniotomy – to precisely target a focal point in the ventral intermediate (VIM) nucleus of the thalamus, a tiny part of the brain thought to be responsible for causing tremors. The Exablate Neuro ultrasound transducer focuses 1,024 beams of sound that generate enough heat to ablate the targeted tissue during treatment. The result is an immediate and significant reduction of tremor for patients. During planning and treatment, the patient is fully conscious and lying on the treatment bed in an MRI scanner. MRI provides high-resolution visualization, patient-specific treatment planning, and continuous monitoring of the procedure. Real-time thermal feedback allows the physician to control and adjust the treatment, ensuring that the targeted tissue is completely ablated without impacting adjacent healthy tissue. This revolutionary, non-invasive treatment offers a life changing treatment to patients with essential tremor.
Risks associated with thalamotomy and/or FUS/Exablate Neuro can include transient and/or permanent sensory paresthesia, numbness, imbalance, gait disturbance, sonication-related pain, sonication-related dizziness or nausea, and the potential for deep vein thrombosis (associated with lying on the treatment bed for up to four hours while undergoing treatment).