A Novel Way to Steady a Tremor

t age 78, keen and lively Blanche Matthai, who lives alone in her Baltimore apartment, found last year that an increasing trembling in her hands was affecting her fine motor control. Within months, she was no longer able to write, drive or even eat with ease.

“People who don’t have a movement disorder like essential tremor just can’t appreciate how it interferes with everyday life,” attests neurosurgeon Fred Lenz, M.D., Ph.D. “Medications don’t help much, so patients compensate by putting their arms through their belts to control shaking, or even sitting on their hands. Needless to say, they’re frequently embarrassed.”

Lenz, an expert in such conditions, was able to help Matthai get rid of the shaking in her right hand by performing what’s called a thalamotomy, a stereotactic procedure in which he actually destroys the precise portion of the thalamus that’s generating the problem. Matthai’s left hand, however, maintained its tremor, and in this case, Lenz opted not to make an additional lesion on the other side of the brain. The risk of affecting speech with two such procedures is too great.

But the neurologist had at his fingertips another approach—an implantable neuron-blocking system known as Activa Tremor Control Therapy that’s the first FDA-approved treatment for essential tremor in 30 years, specifically meant for disorders like the one plaguing Matthai. It’s a variation on a pain-control method that Lenz has employed for years. Metal contacts are implanted at key sites in a patient’s brain. Then, a current directed to the plates is able to interrupt unwanted brain activity.

With the Activa system, Lenz first must locate—with the help of CT and MRI scans—the approximate site in the ventral thalamus that’s linked with tremor. Then, he guides a microelectrode through a small burr-hole in the skull toward the suspected target. As he works, he looks for characteristic tremor readings, given off by a group of cells only 2 or 3 millimeters wide, that help him finally home in on the vital spot.

When he’s pinpointed his mark, Lenz permanently implants a flexible plastic tube (a millimeter in diameter). This houses a wire connected to metal contacts that lead under the skin to a battery-powered pulse generator implanted near the collarbone. By passing a hand-held magnet over the generator, patients trigger the mild electrical stimulation that blocks the tremor. “We can fine-tune the generator,” Lenz explains, “with a specially made, laptop computer. If there’s over- or under-stimulation, it’s correctable.”

Lenz can offer the alternative of a power source outside the body to patients who prefer that method by attaching a battery encased in a programmable housing on the patient’s belt (“It looks like a pager”). This connects, via a wire, to a plastic-coated coil that serves as an antenna on the skin above an implanted receiver. “The value of the new system over the lesion technique is that it isn’t permanent,” Lenz explains. “If the tremor returns or the patient develops side effects, we can make adjustments with relative ease.”

With either implantable system, the results are remarkable. There’s about an 80 percent absence of tremor on the contralateral side. “You see a patient shaking terribly, then you turn it on, and the shaking stops.”

—Marjorie Centofanti