Primary progressive apraxia of speech (PPAOS)

Overview

Primary progressive apraxia of speech (PPAOS) is a neurodegenerative disease that slowly affects a person's ability to speak clearly. It is not caused by weakness of the mouth muscles. In people with PPAOS, it is hard for the brain to plan and coordinate the movements needed for speech. Talking may become more difficult over time. Eventually, some people may slowly lose the ability to speak. PPAOS is a condition that develops in adulthood. It is not seen in children.

Symptoms

People with PPAOS often know exactly what they want to say, but their speech becomes slow. Words may be difficult to form and hard for others to understand. The signals between the brain and the mouth muscles are not sent correctly. The brain struggles to make the lips, jaw and tongue move as they typically do.

The symptoms of primary progressive apraxia of speech usually begin gradually and change slowly over time. The early symptoms of primary progressive apraxia of speech may include:

• Speaking more slowly than usual.
• Pausing between words, especially those that have more than one syllable.
• Difficulty expressing emotion through the voice.
• Difficulty forming words, especially those that are longer and more complex.

Later symptoms:

• Dysarthria. Speech becomes weak or imprecise.
• Aphasia. Language issues, such as putting words in the correct order or difficulty understanding what you hear and thinking of the words you want to say.
• Dysphagia. Issues with swallowing.
• Spasticity. PPAOS may overlap with other conditions, which may cause stiffness to spread to other areas of the body, such as the arms, legs and torso.
• Apraxia in other parts of the body. This may include not being able to use a common object, such as a brush or comb. It also may include not being able to do a familiar task, such as tie a shoe or write a note. This is because the brain has trouble planning.

Causes

Primary progressive apraxia of speech (PPAOS) is caused by gradual damage to cells in the front parts of the brain. These areas control speech planning and help organize speech timing and movements.

PPAOS happens when communication between nerve cells does not work as it should. In most people with PPAOS, the condition is linked to diseases that involve the buildup of a protein called tau. Many people with this condition also may have one of two diseases that cause symptoms. These are the two most common conditions linked to PPAOS:

• Corticobasal degeneration (CBD). This is a rare condition in which areas of the brain shrink, causing nerve cells to stop working and die. CBD also may cause clinical changes called corticobasal syndrome (CBS). These changes may include poor coordination and stiffness. And they may include difficulty with thinking, speech, language and other issues.
• Progressive supranuclear palsy (PSP). PSP is a rare condition that damages brain cells. The damaged cells are in areas that control body movement, coordination, thinking and other important functions. PSP can cause serious issues with balance and walking. It also can cause issues with eye movement and trouble swallowing.

While these are the two most common conditions, not everyone with PPAOS has the same underlying disease. Sometimes other proteins are involved.

Risk factors

No environmental or lifestyle risk factors have been clearly linked to PPAOS. Most people with PPAOS do not have a family history of the condition. In rare cases, genetic changes have been found. In some families, there may be more than one family member with a neurodegenerative disease. PPAOS typically begins after the age of 40 and most commonly after the age of 65.