Surgery and Tremor

Surgical treatment

Surgical intervention in ET has been used for over 50 years, and is reserved for those patients who have particularly severe/disabling tremor which does not respond to medication. About 50% of severely affected ET patients have medication-resistant symptoms or are intolerant to medication, so that brain surgery is a valuable option for this relatively small proportion of ET individuals. In order to alleviate tremor in a patient’s right arm, surgery is performed on the left side of the brain and vice versa for the left arm. Consequently in order to alleviate tremor in both arms surgery is required on both sides of the brain (bilateral surgery).

Two areas deep within the brain can be targeted by surgeons to alleviate essential tremor:

1. the Thalamus, or
2. the Zona Incerta.

Surgeons can then use either a small burn (a lesion) to destroy one of these areas, for example in the thalamus this is called a thalamotomy,  or chronically stimulate the target area through implanted electrodes that remain in the patient’s brain permanently (deep brain stimulation).   The main risks of this type of surgery, when performed in a neurosurgical centre by a specialist functional neurosurgeon, are a 1/1000 risk of death, a 3% risk of a bleed within the skull and a 1% risk of a stroke (which may cause paralysis or numbness down one side of the body or speech impairments).

Evidence based surgical treatment of essential tremor

There is no level A evidence concerning the surgical treatment of essential tremor.

There is level B evidence to support the view that:

1. Deep brain stimulation has fewer adverse effects than thalamotomy.

There is level C evidence to support the views that:

1. Deep brain stimulation of the thalamus (thalamic stimulation) is an effective treatment for ET.

2. Unilateral thalamotomy is an effective treatment for ET.

3. Bilateral thalamotomy is not recommended because of the risks of worsening the patient’s speech.

There is weak evidence Level U (unproven) to support the views that:

1. Deep brain stimulation can also improve head and voice tremor.

2. It is not known whether the benefit to risk ratio favours thalamic stimulation for ET being performed on one side of the brain or both sides. The advantage of the former is that the risk is reduced but the disadvantage is that the tremor remains on one side of the body.

Long-term studies have shown that tremor control can be maintained for up to six years after deep brain stimulation. The effects of DBS on the patient’s thought processes, mood state and Quality of Life have been assessed up to 6 years after DBS and have generally been found to be positive. There were only mild effects on cognition, a small decline in verbal fluency, being found after DBS in some cases.