More than three decades ago, neurosurgeons first investigated the use of deep brain stimulation (DBS) to relieve severe body tremors in patients battling the neurological disorder Parkinson’s disease.
In 1997, the Food and Drug Administration officially approved DBS for tremors. Fifteen years later, its effects are still not completely understood.
For Diana Sidtis, Steinhardt School of Culture, Education, and Human Development professor of communicative sciences and disorders, and her husband, John J. Sidtis, research professor in the Department of Psychiatry at the NYU School of Medicine, the mystery of how DBS affects the “low, soft, and breathy” speech of those living with the illness remains a driving force behind their research. Thanks to a $2.2 million grant from the National Institutes of Health, they can continue their search for answers.
“Parkinson’s patients have movement disorders, tremors, or slowness of movement that result in speech problems,” Diana Sidtis explains. “Through previous studies, we found that Parkinson’s disease is characterized by greater difficulty speaking in spontaneous ‘normal’ conversation, with poorer voice quality and fluency. Yet in repetition, where patients are repeating the statements and words of another, voice quality and fluency are improved. DBS improves voice quality to the same extent that repetition does, but fluency is sometimes reduced. So what remains is how and why this is possible. This is what we are hoping to find out.”
Research studies in the first five years by John Sidtis found that DBS increases blood flow in the entire brain, not just the basal ganglia, the area of the brain directly related to the cause of Parkinson’s due to a deficiency of the neurotransmitter, dopamine. The lack of dopamine results in a movement disorder and thus the impaired speech. This finding may have significant implications for understanding the effects of the new DBS treatment.
According to the Parkinson’s Disease Foundation, some 90 percent of the nearly one million people with the ailment experience changes in their speech. In a collaborative effort, Sidtis and Sidtis will spend the next five years continuing to look closely at speech patterns of Parkinson’s patients undergoing DBS treatment. Their work thus far has shown that DBS does not have an adverse effect on speech, a common concern among Parkinson’s patients considering this treatment.
“We need a better estimate of how often DBS results in greater speech impairment, when it occurs, and how it can be characterized,” John Sidtis explains.