IMPLANT EASES TREMOR

An electrode implanted deep in the brain alleviates or halts trembling in many of those suffering from a condition called essential tremor, which affects an estimated 2 million people in the US. The constant shaking, often affecting the hands, head and voice, can make basic tasks, such as eating, dressing and writing next to impossible. Drugs that control the tremors often lose their potency after a period of time.

The Activa Tremor Control device, manufactured by Medtronics Corp. of Minneapolis, was approved by the FDA just over a year ago. It is also effective for some Parkinson's patients whose only symptom is tremors, according to neurosurgeon Richard Lehman. The associate professor of surgery at UMDNJ-Robert Wood Johnson Medical School has implanted the electrode in four patients to date.

Lehman says the device stimulates the already overactive cells of the thalamus, which are compensating for injured or damaged cells in other parts of the brain. The high frequency of electricity emitted by the electrode seems to block neural circuits, inhibiting the tremors. The thalamus serves as a kind of hub in the brain for signals from the spinal cord, cortex and cerebellum.

Patients are awake for the two- to two-and-a-half hour procedure, which includes placing a pulse generator with battery in the chest and a connecting wire under the skin, which runs from the top of the head through the neck. The patient turns on the generator with a hand-held magnet, sending electrical impulses through the wire.The generator and battery have a life of five years.

The implant was tested on 113 Parkinson's patients and 83 with essential tremor during clinical trials. According to Lehman, all the patients were severely affected with trembling. Significant reduction of tremors was achieved in 75 percent of Parkinson's patients and 85 percent of those with essential tremor, but almost everyone experienced some relief, says the surgeon.