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Speech Disorders in Parkinson’s Disease

Dr. Yael Manor

Ph.D., CCC – SLP

Speech is our most basic method of communication. We learn to talk as toddlers and, generally, never stop. It is hard to imagine a world in which we express our thoughts, feelings, and emotions without using speech.

With Parkinson’s Disease (PD), many neural functions are impaired, including patients’ ability to speak and communicate easily and effectively. Since most visible PD symptoms involve motor difficulties such as tremor and rigidity, speech disorders don’t always come to mind when we think about the effects of PD. Yet given the importance of effective verbal communication to patients’ quality of life, this little-known complication may take a heavy toll on PD patients’ everyday lives.

Nearly 80% of all PD patients may, at some point during the course of their disease, develop a speech disorder known as Hypokinetic Dysarthria. Dysarthria may affect speech in one or more ways, such as:

  • Voice loudness and quality disturbances – such as a weak or hoarse voice, a monotonous voice, a strained, breathy, or nasal voice, and even partial or complete loss of voice.
  •  Speech rate disturbances – such as stalled or hesitant speech, irregular speech, or quick, hasty speech.
  •  Pronunciation disturbances – such as omitted, blended, or improperly pronounced sounds.

Several processes contribute to the development of hypokinetic dysarthria in PD patients. The muscles involved in the speech apparatus – tongue, lips, cheeks, and jaw – weaken, and their range of motion, tone, and rate of movement all deteriorate. The muscles involved in voice production, notably those controlling breathing and the vocal cords, are also impaired.

Cognitive issues also contribute to speech deterioration in people living with PD. Studies have shown that PD patients often aren’t aware of their weak voice due to a decline in hearing feedback. Patients fail to correctly evaluate the volume of their speech, thinking that when they speak without any special effort, their voice is loud enough, when in fact sometimes it isn’t.

Of all the speech disturbances described above, voice impairments – notably a weak voice – are the first to appear, and may even be one of the first symptoms of Parkinson’s Disease to be noticed. Other disturbances, such as speech rate, fluency, and pronunciation, tend to appear at a later stage.

Once a person living with PD experiences difficulties speaking clearly and being understood easily, they may tend to avoid entering into conversations with others. Their insecurity regarding their own speech may cause them to be withdrawn, which, in turn, may adversely impact their quality of life as their condition progresses.

Diagnosis

If speech disturbances are suspected, the patient should consult with a Speech-Language Pathologist (SLP) experienced in treating people with PD, for a diagnosis. The clinician will take the patient’s medical history and complaints, and identify the specific type of speech and voice disturbance. The patient’s occupation, daily activities, and social background will also be discussed as they relate to how the patient uses their voice in their daily life.

Next, the clinician will proceed to evaluate the patient’s quality of speech. This is done both with the help of devices, such as a Sound Level Meter to measure speech loudness, as well as by using the clinician’s subjective judgement of specific measures. The patient will be asked to carry out simple speech-related tasks, such as producing specific consonants and vowels, and reading out words, phrases, and a short text. The clinician will also assess the patient’s spontaneous speech.

Another method used to identify speech disturbances in PD patients involves the use of acoustic analysis. This methods provides objective, reliable, highly-sensitive information by recording the patient as they perform various speech tasks. These recordings are then analyzed to assess voice loudness, tonality, speech rate, and other acoustic characteristics.

The clinician will also examine the different parts of the speech apparatus by evaluating the range of motion, muscle tone, and movement of the tongue, lips, cheeks, and jaw. In some cases, the patient may be referred to an Ear, Nose, and Throat (ENT) specialist for further evaluation.

Treating Voice and Speech Disorders

The treatment goal here is to help the patient speak comprehensibly, to increase their awareness of the loudness of their voice, and to get into the habit of making a conscious effort to speak clearly.
There are two main approaches to improving PD-related speech disorders. Below is a brief description of each.

Lee Silverman Voice Treatment (LSVT)

The Lee Silverman Voice Treatment, or LSVT for short, aims to teach the patient to speak more comprehensibly by increasing the loudness of their voice. The patient carries out strenuous speech exercises to bring their vocal cords together. This, in turn, enhances the respiratory support needed to make speech sound louder and clearer. This method is based on the motor learning theory, which stipulates that practice should be strenuous, repetitive, intensive, simple, and accompanied by a sensory awareness of the practice itself.


LSVT is based on five important aspects:

  • Loud voice – A loud voice improves vocal cord closure and respiratory support. In people with PD, the vocal cords do not fully close, causing speech to sound breathy and weak. This simple step has been shown to improve speech comprehensibility, rate of speech, and even posture.
  • Effort – Making an effort while speaking, helps increase voice loudness and clear pronunciation.
  •  Intensive treatment – The treatment plan typically includes four sessions per week during four consecutive weeks, or two sessions per week over an 8-week period.
  •  Volume calibration – Parkinson’s Disease makes it difficult for patients to correctly assess the volume of their own voice. Patients typically say that they are speaking too loudly when in fact they are speaking at a normal volume. Treatment aims to teach patients the correct amount of effort needed to produce clear speech.
  • Objective measures – During the course of treatment the patient’s speech is measured using instruments such as a decibel meter and timer. This helps motivate patients as they see a measurable improvement in their speech over time.
    In addition to more comprehensible speech, studies have found this treatment approach to improve other, non-speech aspects such as swallowing, facial expressions, brain functions, and emotional state. LSVT is suitable for patients in various stages of PD as it can be tailored to the specific needs of each patient.

Speak Out

When we speak, we usually do so automatically, without giving it much thought. Yet people with PD may develop deficiencies in the automatic mechanisms involved in speech. By increasing the patient’s awareness of the way they speak, they may be able to compensate for deficiencies that make their speech less clear.
This is accomplished by providing patients with external cues which turn their attention to the way they speak. This newly-acquired awareness, in turn, improves the accuracy with which they speak. Over time, "this positive feedback loop helps patients reach their speech goals, until their new way of speaking becomes natural.

Cues may include instructions such as: say it purposefully; speak deliberately; speak out!
A typical Speak Out treatment includes 12 individual sessions 2-3 times per week. Before the end of the individual-session series, patients join a Loud Crowd therapy group, as regular practice is essential to preserve progress. The patient’s family and friends participate in the final Speak Out session.

Conclusion

The sooner patients begin treatment for speech disorders, the more effective and beneficial treatment can be. Seeking treatment sooner rather than later enables patients to acquire and implement compensating techniques more easily.

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