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Causes of speech problems

MS can cause speech difficulties in different ways. It can affect the physical actions involved in producing speech and how your voice sounds. It may also change your understanding of language and the thought processes needed in deciding what to say.

What is dysarthria?

Dysarthria is the most common kind of speech problem for people with MS. It’s caused by MS damage in parts of the brain that control the muscles involved in speech. As a result, these muscles don’t work as well.  

For example, MS can:

  • affect how your tongue and lips move, making it difficult to pronounce precise sounds

  • weaken your diaphragm (the sheet of muscle under your rib cage), making it difficult to control the volume of your voice with your breath.

Dysarthria can lead to problems like slow or slurred speech, and difficulty pronouncing words.

What is dysphonia?

Dysphonia is when your voice is changed by the effects of MS on your voice box (larynx). This happens if MS activity affects the areas of your brain that control the voice box muscles. Dysphonia can affect how well you can control volume and pitch (how high or low your voice is). It can change how your voice sounds too – it might sound hoarse, or raspy. Dysphonia often overlaps with dysarthria because MS activity in the brain can affect the messages to all those muscles at the same time.

How do cognitive difficulties affect speech in MS?

MS can also cause changes in memory and thinking, known as cognitive difficulties. These could how you speak and use language. For example, you may find it hard to remember particular words and to join in with conversations. These kind of cognitive changes don’t affect everyone with MS. When they do they’re often mild.

What is dysphasia or aphasia?

Dysphasia (also known as aphasia), means difficulties with language. It’s caused by MS activity in areas of the brain responsible for understanding and communicating language. Dysphasia is rare in people with MS.

Dysphasia can affect you in two ways. It can make it:

  • difficult to find the right way to say something (‘expressive dysphasia’)  

  • hard to understand what someone’s saying (‘receptive dysphasia’)

Can MS medications cause speech problems?  

Some drug treatments, including some used to treat bladder problems, can cause a dry mouth as a side effect. This can contribute to dysarthria, making speaking more difficult. If this is an issue for you, tell your doctor. They may be able to adjust your medication to lessen this side effect. A dentist or speech and language therapist might also suggest ways to avoid having a dry mouth.  

Find out more about dry mouth and oral health