Tremor and
MRI-Guided Focussed Ultrasound

About Tremor

The most common cause of tremor is known as “essential tremor” and is closely related to another condition called dystonic tremor.

Essential and dystonic tremor usually cause shaking in the hands but can also cause shaking in the legs, the head and the voice.

Essential and dystonic tremor are thought to affect around 800,000 Australians.

Essential and dystonic tremor can run in families, are often heightened by stress and with movement, and can often be reduced by consuming alcohol. Dystonic tremor tends to be irregularly jerky and is associated with a feature called position specificity which means that it tends to be much more pronounced with certain postures of the hands and arms. In addition dystonic tremor can be associated with other features such as abnormal pulling and posturing of other muscle groups.

Essential (and dystonic) tremor can worsen over time, but are not related to Parkinson’s Disease. A movement disorder specialist can help confirm the diagnosis, but one of the common differences with a tremor caused by Parkinson’s disease is that it tends to be worst when not moving and decreases when actively doing something with the arms (whereas the reverse is true in essential and dystonic tremor).

Other causes of tremor can include thyroid problems, certain medications, and multiple sclerosis.

Essential and dystonic tremor tremor can occur at any age, even in childhood.

Medications are sometimes effective for tremor but only around half of people obtain significant benefit.

Essential and dystonic tremor often gradually worsen over the years.

Tremors can affect quality of life and can impede people from eating, drinking and looking after themselves. In addition they can be embarrassing and in some cases can lead to social isolation which in turn can lead to depression. One of the messages we hear time and again from patients with tremor is that whilst others (including well meaning doctors) can sometimes say “it’s just a tremor”,  for the person experiencing the tremor it can be associated with a major reduction in quality of life.

Treatments

Treatments for tremor range from no treatment for very mild cases, through to medications and certain neurosurgical procedures such as deep brain stimulation or MRI-guided focussed ultrasound thalamotomy

Medication

Medications such as beta-blockers, some anti-seizure medications and some anti-anxiety drugs can be trialled. The side effects vary depending on the medication but can include fatigue or drowsiness. About 50% of people will get some reduction in tremor though the side effects can be limiting.

Thalamotomy (open)

Thalamotomy is a neurosurgery procedure where a small hole is drilled into the skull and a tiny probe inserted into a part of the thalamus which is containing cells that cause or drive the tremor. These cells can then be destroyed leading to alleviation or complete resolution of the tremor. As with all neurosurgery procedures it carries some risks including bleeding and infection, and a small risk of paralysis or other neurological problems as well as the possibility of other rare problems.

Deep brain stimulation

Deep brain stimulation involves drilling a small hole in the head and inserting a permanent electrode into the thalamus or other region causing tremor. This is then connected via a wire to a pacemaker box located in the chest region. It carries some of the same risks as open thalamotomy but also carries risks related to the hardware such as hardware infection. The pacemaker box can be rechargeable or fixed cell and generally will need replacement sometime between 3 and 15 years depending on which model is used.

MRI-Guided Focussed Ultrasound (MRgFUS) thalamotomy

This is a new way of performing thalamotomy that does not require incisions, any holes to be drilled in the head, or any probes to be inserted. Side-effects have been reported (including numbness in the face or hand and gait disturbance) but are mostly mild and temporary.

Testing Handwriting during MRgFUS treatment

The team tests tremor during the MRgFUS treatment

The MRgFUS Thalamotomy Procedure

The MRgFUS thalamotomy involves no incisions and the patient is fully conscious throughout. A stereotactic head frame is placed on the head with local anaesthetic and the patient lies in the MR scanner. If required some sedation can be given to help maximise comfort and relaxation during the MRI and procedure.

The focussed ultrasound sends 1024 individual ultrasound beams through the brain that intersect at a single point in the thalamus and can destroy the tremor causing cells. This can all be monitored on the MRI and by repeatedly checking the patient and their tremor until the tremor has been adequately treated.

When it is over there is an immediate and significant reduction in tremor.

Insightec Exablate Neuro, used for the Neuravive Focussed Ultrasound treatment

Can I be assessed for suitability for this treatment?

Patients with tremor, Parkinson’s Disease, or dystonia may be assessed for suitability for treatment.

In general the assessment will include:

  • confirmation of the nature of the movement disorder
  • assessment with standardised rating scales
  • consideration of skull density on CT
  • consideration of the suitability of patient specific anatomy on a dedicated movement disorder stereotactic MRI, performed at St Vincent’s Hospital.
  • consideration of the effect of the movement disorder on quality of life
  • other relevant health issues

The assessment team comprises a neurologist, neurosurgeon, movement disorder nurse, and potentially psychologist and other allied health members.

  FAQ for Patient’s Undergoing MRI-Guided Focussed Ultrasound
  St Vincent’s Hospital Focussed Ultrasound website
  In the Media: Essential tremor treatment – Sydney nun first in southern hemisphere to undergo breakthrough procedure
  In the Media: ‘Brain surgery without surgery’ – Incisionless procedure helping fix uncontrollable tremors
  Surgical News May/June 2019 – Sydney team with new treatment for essential tremor

Research

MRgFUS has been the subject of intense research interest. For tremor this culminated in publication in the New England Journal of Medicine of the pivotal randomised controlled trial of MRgFUS thalamotomy.

Other current research projects active at various sites worldwide include:

  • MRgFUS pallidotomy for Parkinson’s Disease
  • MRgFUS for hypothalamic hamartoma causing epilepsy
  • other MRgFUS tremor targets

In addition there is significant interest in whether modulation of the blood brain barrier using MRgFUS may provide the possibility of treatment delivery of compounds to the central nervous system for Alzheimer’s Disease and for brain tumours.

 Nature.com: Blood–brain barrier opening in Alzheimer’s disease using MR-guided focused ultrasound
  NIH: Focused ultrasound disruption of the blood brain barrier: a new frontier for therapeutic delivery in molecular neuro-oncology

 

Please find a list of some relevant research publications:

  1. Krishna V, Sammartino F, Agrawal P, Changizi BK, Bourekas E, Knopp MV, Rezai A. Prospective Tractography-Based Targeting for Improved Safety of Focused Ultrasound Thalamotomy. Neurosurgery. 2018 Mar 21. doi: 10.1093/neuros/nyy020.
  2. Jung NY, Park CK, Chang WS, Jung HH, Chang JW. Effects on cognition and quality of life with unilateral magnetic resonance-guided focused ultrasound thalamotomy for essential tremor. Neurosurg Focus. 2018 Feb;44(2):E8. doi: 10.3171/2017.11.FOCUS17625.
  3. Chazen JL, Sarva H, Stieg PE, et al. Clinical improvement associated with targeted interruption of the cerebellothalamic tract following MR-guided focused ultrasound for essential tremor. J Neurosurg. October 2017:1-9. doi:10.3171/2017.4.JNS162803.
  4. Kim M, Jung NY, Park CK, Chang WS, Jung HH, Chang JW. Comparative Evaluation of Magnetic Resonance-Guided Focused Ultrasound Surgery for Essential Tremor. Stereotact Funct Neurosurg. 2017 Aug 16;95(4):279-286. doi: 10.1159/000478866.
  5. Niranjan A, Raju SS, Monaco EA 3rd, Flickinger JC, Lunsford LD. Is staged bilateral thalamic radiosurgery an option for otherwise surgically ineligible patients with medically refractory bilateral tremor? J Neurosurg. 2017 Apr 7:1-10. doi: 10.3171/2016.11.JNS162044.
  6. Ravikumar VK, Parker JJ, Hornbeck TS, Santini VE, Pauly KB, Wintermark M, Ghanouni P, Stein SC, Halpern CH. Cost-effectiveness of focused ultrasound, radiosurgery, and DBS for essential tremor. Mov Disord. 2017 Apr 3. doi: 10.1002/mds.26997.
  7. Schlesinger D, Lee M, Ter Haar G, Sela B, Eames M, Snell J, Kassell N, Sheehan J, Larner J, Aubry JF. Equivalence of cell survival data for radiation dose and thermal dose in ablative treatments: analysis applied to essential tremor thalamotomy by focused ultrasound and gamma knife. Int J Hyperthermia. 2017 Jan 3:1-27. doi: 10.1080/02656736.2016.1278281. 
  8. Hughes A, Huang Y, Pulkkinen A, Schwartz ML, Lozano AM, Hynynen K. A numerical study on the oblique focus in MR-guided transcranial focused ultrasound. Phys Med Biol. 2016 Nov 21;61(22):8025-8043.
  9. Jang C, Park HJ, Chang WS, Pae C, Chang JW. Immediate and Longitudinal Alterations of Functional Networks after Thalamotomy in Essential Tremor. Front Neurol. 2016 Oct 24;7:184.
  10. Elias WJ, Lipsman N, Ondo WG, Ghanouni P, Kim YG, Lee W, Schwartz M, Hynynen K, Lozano AM, Shah BB, Huss D, Dallapiazza RF, Gwinn R, Witt J, Ro S, Eisenberg HM, Fishman PS, Gandhi D, Halpern CH, Chuang R, Butts Pauly K, Tierney TS, Hayes MT, Cosgrove GR, Yamaguchi T, Abe K, Taira T, Chang JW. A Randomized Trial of Focused Ultrasound Thalamotomy for Essential Tremor. N Engl J Med. 2016 Aug 25;375(8):730-9. doi: 10.1056/NEJMoa1600159.
  11. Bond AE, Dallapiazza R, Huss D, Warren AL, Sperling S, Gwinn R, Shah BB, Elias WJ. A Randomized, Sham-Controlled Trial of Transcranial Magnetic Resonance-GuidedFocused Ultrasound Thalamotomy Trial for the Treatment of Tremor-Dominant, Idiopathic Parkinson Disease. Neurosurgery. 2016 Aug;63 Suppl 1:154. doi: 10.1227/01.neu.0000489702.18785.5f.
  12. Gallay MN, Moser D, Rossi F, Pourtehrani P, Magara AE, Kowalski M, Arnold A, Jeanmonod D. Incisionless transcranial MR-guided focused ultrasound in essential tremor: cerebellothalamic tractotomy. J Ther Ultrasound. 2016 Feb 13;4:5. doi: 10.1186/s40349-016-0049-8. eCollection 2016.

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