Parkinson's disease

Parkinson disease is a chronic, progressive disease affecting 1% of the population older than 60 years of age. The disease course varies considerably, with those diagnosed early in adulthood living longer with the disease than those diagnosed later in life. Loss of dopamine-secreting neurons within the substantia nigra and presence of Lewy bodies are the major pathological findings in Parkinson disease. Early in the disease course, dopamine deficiency is the predominant neurochemical abnormality. As the disease progresses, involvement of nondopaminergic brain regions results in levodopa-resistant motor and nonmotor symptoms. Although Parkinson disease is incurable, therapies can improve quality of life for many years. (From Connolly and Lang, (2014) JAMA, Vol. 311, 1670-83.)

It is estimated that between 60% and 80% of individuals with Parkinson's disease (IWPD) will develop speech symptoms as the disease progresses. In the early stages of PD, many individuals complain of a reduction in speech intensity, or “hypophonia.” Individuals with hypophonia can become extremely frustrated by the increasingly frequent requests that they receive to speak louder and repeat themselves. In addition to reduced speech intensity, it is also observed that individuals with PD will demonstrate reduced stress and intonation patterns, abnormal voice quality, distorted consonantal sounds, and abnormally rapid or slow speaking rate. As a result of these speech symptoms, the individual with PD can become increasingly difficult to understand (reduced intelligibility). This can become a major problem for conversations in social situations with only moderate levels of background noise (i.e. family gatherings, restaurants, etc.).

The following tables present information on the epidemiology and major symptoms of Parkinson’s disease.