Multiple sclerosis patients with severe, treatment–resistant tremors may gain marked improvement from deep brain stimulation surgery, or DBS, in which two DBS leads are implanted in the side of the brain opposite the tremor, according to a new study by University of Florida researchers published in the latest edition of The Lancet Neurology journal.

The research team from the Evelyn F. and William L. McKnight Brain Institute of the University of Florida found that eight of the 12 patients in the study experienced a significant reduction in tremors for at least six months after the deep brain stimulation leads were turned on.

Tremor is a common symptom of multiple sclerosis, with up to half of MS patients developing severe or debilitating tremors, typically in the upper extremities.

“Traditionally, MS tremor hasn’t responded as well to deep brain stimulation as other types of tremor, such as in Parkinson’s disease or essential tremor, which respond really well to DBS,” said Seth Oliveria, MD, PhD, an assistant professor in UF’s Lillian S. Wells department of neurosurgery and lead author on the paper. “There have been a lot of trials over the years and in general, multiple sclerosis tremor hasn’t responded at all to deep brain stimulation or it has responded only temporarily and then come back.”

The need to find treatments for MS tremor cannot be overstated.

The new UF study is significant in two ways: first, the focus on MS tremor, and second, that surgeons implanted two – rather than one as is customary – DBS leads in the same side of the brain. The two leads, with four electrode contacts on each, were implanted parallel to one another in neighboring parts of the thalamus.

UF neurosurgery professor Kelly Foote, MD, along with his neurology partner Michael Okun, MD, chair of neurology, developed the new, patented technique for implanting and securing two DBS leads in the same side of the brain in order to modulate multiple nodes in a malfunctioning brain network.

In pioneering the use of the new technique, “we thought MS tremor would be a good test bed for the new dual–lead DBS strategy because it is severely debilitating and it tends to respond poorly to all existing therapies including traditional single–lead thalamic DBS,” said Foote, the senior author of the paper. “By implanting two DBS leads in the thalamus on the same side of the brain, we were able to stimulate a larger volume of tremor–causing brain tissue, including both cerebellar and pallidal circuits known to be involved in the generation of severe tremor. With dual–lead thalamic DBS, we managed to provide most of these severely affected patients with significant tremor suppression for at least six months.”

In the randomized controlled trial, each patient had two leads implanted during surgery, but only one of the two was initially activated. Both leads then were turned on for the second part of the study.

The promising results of this study in severe MS tremor provide hope that dual–lead DBS might be effective for other difficult–to–control tremor disorders, such as in severe Parkinson’s tremor or severe essential tremor, Oliveria said.

The study is titled, “Safety and efficacy of dual lead thalamic deep brain stimulation for treatment–refractory multiple sclerosis tremor: a randomized, single–center pilot trial.”