October 27, 2003
News Author: Laurie Barclay, MD
CME Author: Désirée Lie, MD, MSEd
Unilateral thalamic stimulation is safe and persistently effective for the treatment of refractory essential tremor, according to the results of a six-year follow-up study published in the October issue of the Journal of Neurology, Neurosurgery and Psychiatry. The editorialist agrees, despite the greater costs and need for more intensive follow-up.
"In short term follow up studies, thalamic stimulation was shown to cause a dramatic reduction in symptoms in essential tremor, with less adverse effects than thalamic lesioning by coagulation," write O. Sydow, from Karolinska Hospital in Stockholm, Sweden, and colleagues. "However, very few long term studies of thalamic stimulation in essential tremor have been published. One long term follow up showed a reduction in tremor suppression in some patients, and a rather high rate of surgical and device related complications, necessitating additional surgical interventions."
Of 37 patients implanted unilaterally or bilaterally with a thalamic stimulator for essential tremor, 19 patients were available for six-year follow-up. In most patients, the very good results with stimulation seen at one year were maintained after a mean follow-up of 6.5 years. Compared with baseline and with stimulation turned off, the reduction in scores on the essential tremor rating scale and improvement in activities of daily living were highly significant.
Although minor adverse effects of stimulation were common, there were few serious adverse events, and device-related complications were observed rarely and most could be resolved. The authors note the need for frequent follow-up with adjustment of the pulse generator parameters, surgical procedures for lead fractures and erosions, and eventual replacement of the pulse generator in all cases because of limited battery life.
"The total cost will be considerable but may be justified in these severely handicapped patients who cannot achieve adequate tremor control with the presently available drug treatments," the authors write. "Although to our knowledge no formal health economy studies have been done, it is likely that the cost-benefit ratio would be favourable in, for example, patients who cannot feed themselves or write.... The surgery and follow up should be carried out in relatively few centres that have good knowledge of stereotactic surgery and movement disorders."
Medtronic financed this study and supported three of its investigators.
"Unilateral deep brain stimulation is as effective as unilateral thalamotomy in the management of severe essential tremor and it may be that bilateral deep brain stimulation is better than unilateral deep brain stimulation, particularly for those with a generalised tremor syndrome," writes J. P. R. Dick, from Hope Hospital in Salford, UK, in an accompanying editorial.
"Had there been poor durability of long term deep brain stimulation, the marginal superiority of stimulation over thalamotomy would have been lost, especially considering the cost and the more intense follow up regime required for deep brain stimulation," Dr. Dick added.
Medtronic sponsored Dr. Dick to attend a two-day workshop on deep brain stimulation in Keil, Germany.
J Neurol, Neurosurg Psychiatry. 2003;74:1361-1362, 1387-1391
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In the Feb. 16, 1991, issue of The Lancet, Benabid and colleagues first showed the benefit of deep thalamic stimulation compared with thalamotomy for the short-term treatment of tremor refractory to medical therapy. There were fewer adverse effects and a dramatic reduction in tremor. Schuurman and colleagues, in a multicenter trial published in the Feb. 17, 2000, issue of the New England Journal of Medicine, found bilateral thalamic stimulation to be superior to thalamotomy, with better outcomes for patients with essential tremor than for patients with Parkinson's disease or multiple sclerosis. Compared with unilateral stimulation, Deuschl and colleagues also summarized in a review in the August 2000 issue of Current Opinions in Neurology that bilateral stimulation may have additional benefit for tremor associated with midline structures.
Most studies of thalamic stimulation have described effects at one year or less and some have suggested that the benefits diminish over time in patients with non-Parkinsonian tremor because of tolerance. Other longer-term studies of 17 months to 3.5 years suggest persistent benefits.
Thalamic stimulation is more costly than thalamatomy because of the need for follow-up, adjustment of pulses, battery replacement, and erosions and fractures of leads.
This descriptive study of prognosis conducted in a cohort of elderly patients who received mainly unilateral thalamic stimulation six years earlier compares the long-term benefits with preoperative baseline symptoms with stimulation on and off. There was no control group (ie, those who received no treatment or who received thalamotomy) in this study.
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