Treatment of drug-resistant tremor using high-intensity focused ultrasound (HIFU)

Essential tremor is the most common movement disorder. It affects almost 3% of the population, about 1.4 million people in Spain. Although essential tremor is seen as a relatively benign disease, it can worsen patients' quality of life by limiting their ability to eat, dress and groom themselves, write, and carry out routine domestic and professional activities. Patients suffering from essential tremor may also find their social life impacted because of the visibility of the problem.  

The cause of essential tremor 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., the dominant trait). 

What is focused ultrasound treatment?

When the tremor is not controlled with medication, the most effective treatment option is to act directly on the brain circuit of the tremor, in the structure called the thalamus. The target is a region of the thalamus called the ventral intermediate nucleus (Vim). 

It is possible to act on the thalamus either by thalamotomy or by deep brain stimulation (DBS). Deep brain stimulation consists of surgically implanting electrodes in the thalamus to stop the tremor by means of electrical impulses from a neuro-stimulator.  

Thalamotomy consists of interrupting the tremor circuit through therapeutic ablation (controlled tissue damage). Therapeutic ablation can be obtained by various methods, such as the application of radiofrequency through an electrode surgically inserted into the thalamus, using transcranial gamma radiation (stereotactic radiosurgery), or by magnetic resonance-guided focused ultrasound (MRgFUS or HIFU).

Transcranial focused ultrasound (tFUS) makes it possible to perform a thalamotomy in a minimally invasive way, and with constant monitoring by magnetic resonance imaging (MRgFUS). This technology focuses beams of ultrasound energy with great precision on targeted tissue deep in the brain without damaging surrounding normal tissue. When the beams converge, ultrasound produces a focal increase in tissue temperature, which allows the disease to be treated without surgery.  

MRgFUS thalamotomy is performed with the patient conscious, and does not require scalp incisions, cranial openings, or insertion of prosthetic material. Thanks to personal interaction and magnetic resonance imaging, it is possible to monitor the patient's condition and their brain throughout the procedure. 

In selected cases, it is possible to carry out bilateral Vim treatments (of both hands) in two stages, with an interval of approximately nine months between the two treatments.


 

 

 

 

Benefits of MRgFUS thalamotomy

MRgFUS thalamotomy offers the following potential benefits for treatment of essential tremor: 

 

  • It is a single non-invasive treatment that allows patients to recover quickly and quickly return to normal activities of life (usually within a few days). 
  • It does not require any incision, cranial opening, or insertion of instruments into the brain. Therefore, it has a lower risk of infection and cerebral hemorrhage. 
  • It offers a quick resolution of symptoms. 
  • Unlike thalamotomy performed with stereotactic radiosurgery, MRgFUS thalamotomy does not use ionizing radiation, thus avoiding potential side effects of radiation exposure. 
  • It provides a non-invasive treatment option for patients with drug resistant essential tremor who do not wish to undergo surgery, or who, due to their age or health status, are not candidates for surgical treatment. 

Recovery and rehabilitation 

The MRgFUS technique may also improve quality of life and lower the cost of care for those patients with tremor caused by Parkinson's who cannot be treated by deep brain stimulation because of their age or for other reasons. 

The hospital stay after HIFU thalamotomy is one night, and the patient can be discharged the next day in most cases.  

After receiving HIFU, it is fairly common for the patient to notice that their balance is affected, but this is a short-term symptom, lasting from a few days to several weeks, depending on the age of the patient and how their balance was prior to the treatment. In some less frequent cases, the patient may notice short-term changes in the sensitivity of the fingers of the hand that was treated. 

More serious side effects or complications, such as hemorrhages or infections, are extremely unlikely because the procedure does not involve opening the skull or inserting instruments into the brain.  

Who are the doctors at Instituto Clavel who perform HIFU?

The treatment is performed by a team consisting of Dr. J. Rumià (specialist in functional neurosurgery), Dr. G. Salazar (neurologist expert in movement disorders), Dr. J. Tercero (neuro-anesthesiologist), and Ms. M. Azanuy (magnetic resonance technician with specific training in HIFU).

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