What’s on your mind? If you have essential tremor (ET) you probably have a lot of things on your mind:

• Medications like propranolol and primidone – should I take drugs? What about side effects?
• Progression – will my tremors get worse?
• Embarrassment – I can’t drink water or eat soup in a restaurant without splashing and spilling.
• Self-confidence – I flunked the interview because they thought I was nervous.
• Financial concerns – If I can’t do my data entry job, they’ll fire me.
• Loneliness – I quit playing mahjongg with my friends since I can’t manage the tiles

Life with tremors is complicated on every level: physical, emotional, psychological and mental. The daily stress of living with tremors absorbs energy and attention that would be otherwise devoted to more normal uses. To put it bluntly, people with ET have a lot of extra stuff on their mind.

Risk of cognitive effects of Deep Brain Stimulation

Drugs prescribed to control tremors are the first line of defense when “the shakes” begin to interfere with personal and professional activities. Unfortunately, they do not prove effective for about half of those with ET. Even when they help, dosages must be increased as tremors progress. If side effects become unpleasant, people simply discard the drugs and try other solutions, including neurosurgery.

Until recently, the preferred neurosurgery has been Deep Brain Stimulation, on one or both sides of the thalamus. However, there are possible cognitive risks. “Although neurosurgical procedures are effective treatments for controlling involuntary tremor in patients with essential tremor (ET), they can cause cognitive decline, which can affect quality of life (QOL).”ⁱ

In general, DBS implantation has been found to be safe and effective, though Koller et al. (2001) report that may come with “… loss of efficacy in some patients and device complications which increase the risk of additional surgical procedures.”ⁱⁱ But how great is the risk of cognitive impairment? Reports vary dramatically. A 2013 study found no change in cognition at 1 and 6 years after DBS surgery.ⁱⁱⁱ A 2007 article stated that after DBS, there were very low rates of cognitive effects, but discovered a slight increased risk of psychiatric adverse events—even a fractional risk of suicide.^iv

Another study suggests that certain factors may predispose a patient to adverse effects on the mind. Woods et al. (2003) note that patients who were older than 37 at the onset of ET were at greater risk; in addition, the higher DBS pulse-width settings brought good tremor control but were among the “strongest predictors of post-surgical cognitive decline” in their sample.^v They caution that patients considering DBS for ET control should weigh the corresponding risk of mild cognitive side effects.

Finally, as with any surgical procedure requiring significant time under anesthesia, a 2017 presentation at the 21st Congress of the International Parkinson and Movement Disorder Society linked the type and duration of anesthesia during DBS surgery to the odds of post-DBS cognitive impairment. Besides identifying the two anesthetic drugs (sevoflurane and dexmedetomidine) the presenter proposed that a two-stage surgery (one for implanted electrodes, one for implanted power pack) would minimize the impact on the brain by shortening time under anesthesia.^vi

Focused Ultrasound for ET is safe for cognitive function

A new neurosurgical treatment for ET called Neuravive (MRI-guided Focused Ultrasound, MRgFUS) is rapidly gaining favor as a completely noninvasive alternative to DBS. The procedure uses “rays” of ultrasound focused on a tiny area of the thalamus. A thousand rays aimed from all different directions pass harmlessly through brain tissue until they meet at their target. There, they create enough heat to ablate (destroy) the part of the brain that forwards abnormal tremor signals. When this is complete, the abnormal signals literally hit a “dead end” and never make it to the hand. Tremors stop. But how safe is it for cognitive and psychiatric functions that can impact quality of life?

To answer that question, Jung et al. (2018) performed an analysis of 20 patients who had MRgFUS at their center. According to their paper, “Patients were regularly evaluated with the Clinical Rating Scale for Tremor (CRST), neuroimaging, and cognition and QOL measures. The Seoul Neuropsychological Screening Battery was used to assess cognitive function, and the Quality of Life in Essential Tremor Questionnaire (QUEST) was used to evaluate the postoperative change in QOL.”^vii What Jung’s team concluded is great news for tremor patients considering between DBS, a complex surgery into the skull, brain, and chest wall with a brief hospital stay, or Neuravive, an outpatient, noninvasive procedure: “MRgFUS thalamotomy had beneficial effects in terms of not only tremor control but also safety for cognitive function and QOL.” In short, MRgFUS offers the best-case scenario: durable tremor control without changing your mind.

Find out more about MRI-guided Focused Ultrasound to control ET on our website.

ⁱJung 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.

ⁱⁱKoller WC, Lyons KE, Wilkinson SB, Troster AL, Pahwa R. Long-term safety and efficacy of unilateral deep brain stimulation of the thalamus in essential tremor. Mov Disord. 2001 May;16(3):464-8.

ⁱⁱⁱHeber IA, Coenen VA, Reetz K, Schulz JB et al. Cognitive effects of deep brain stimulation for essential tremor: evaluation at 1 and 6 years. J Neural Transm (Vienna). 2013 Nov;120(11):1569-77.

^ivAppleby BS, Duggan PS, Regenberg A, Rabins PV. Psychiatric and neuropsychiatric adverse events associated with deep brain stimulation: A meta-analysis of ten years’ experience. Mov Disord. 2007 Sep 15;22(12):1722-8.

^vWoods SP, Fields JA, Lyons KE, Pahwa R, Tröster AI. Pulse width is associated with cognitive decline after thalamic stimulation for essential tremor. Parkinsonism Relat Disord. 2003 Jun;9(5):295-300.

^viWhyte-Rayson A, Hickey P, Berger M. Postoperative Cognitive Impairment Following Deep Brain Stimulation Surgery. Abstract 380. Presented June 5, 2017 at the International Parkinson and Movement Disorder Society 21st International Congress (Vancouver, BC), June 4-8, 2017. http://www.mdsabstracts.org/abstract/postoperative-cognitive-impairment-following-deep-brain-stimulation-surgery/

^viiJung et al, ibid.