Speech problems are common in patients with Parkinson's disease. At an early stage, patients may find it hard to project their voice. As the disease progresses, patients start to have difficulty starting their speech even though they know the words they want to say. They experience freezing of the jaw, tongue and lips. When they eventually get their speech started, they have a hard time moving it forward. They keep on saying the same words or phrases over and over again while their voice gets softer and softer. Many words also run together or are slurred.
These symptoms make patients' speech hard to understand and directly affect their care and quality of life. Unfortunately, these symptoms have not responded to medication or surgery as other non-speech motor symptoms do. In fact, some surgical treatments could even make speech worse while other motor function such as walking improves. Traditional behavior therapy for these speech symptoms has not been successful either because these symptoms cannot be controlled voluntarily.
Recently, we have tested an in-the-ear therapeutic device that provides altered auditory feedback in eight patients with PD and moderate to severe speech impairment. The device is housed in a hearing aid shell, and it is programmable. Patients wore the device in one ear and heard their own speech through it after a short time delay and with a shift in pitch while they spoke. The delay ranged from 50-220 ms and their pitch shifted up or down from 500-2,000 Hz. For each patient, a specific combination of the time-delay and pitch-shift was found.
Our preliminary results were encouraging. Seven of the eight PD patients made significant improvement in their speech, and they were much easier to understand when they used the device.
The current project will systematically examine the therapeutic effect of altered auditory feedback provided by the in-the-ear device on the speech impairments in PD. We will study 20 patients with PD and moderate to severe speech impairment over a one-year period while they use the device routinely to provide the altered auditory feedback as they speak. Both short-term and long-term benefits of altered auditory feedback on speech will be monitored.
Based on the results of our preliminary study, we expect the patients' speech will improve. We hypothesize that the use of altered auditory feedback provides salient sensory information that triggers ancillary loops to allow PD patients to initiate their speech more easily and to maintain a constant speaking rate, thus making their speech more intelligible. This project has the potential to significantly impact the quality of life for patients with PD. When PD patients can express their wants and needs and can communicate effectively with their families, caretakers and physicians, their quality of life improves.