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Dysarthria and Dysphasia

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Definitions

Speech

How we say sounds and words:

  • The process of articulation and pronunciation using muscles in the head and neck. It describes the physical ability to form words

Language

The words we use and how we use them to share thoughts including what words mean, how to put words together, and when to say what.

  • The process of communicating feelings and thoughts by selecting words to speak and forming sentences using them

Fluency

The ability to speak without stuttering/removal of syllables etc. with good flow

  • The continuity, speed, and effort in speech production
  • Disorders in fluency include interruptions in flow, rate, and rhythm

Comprehension

Making sense of what is said

  • Requires executive function skills such as using prior knowledge/making inferences to make sense of what is said

Dysarthria

Dysarthria is a disorder of speech. This can be due to weakness, slowness, or impaired coordination and timing of the muscles needed for speech including the jaws, lips, tongue, palate, and respiratory muscles.

  • The presence of dysarthria means producing speech is difficult. Understanding and choosing the right words are preserved.

Dysphasia and aphasia

Dysphasia is a disorder of language. In general, the ‘dys-’ prefix means a partial loss and the ‘a-’ prefix means a total loss (e.g. dyspraxia is the partial loss of the ability to coordinate and perform skilled tasks, apraxia describes a complete loss of this ability.

Although technically speaking, aphasia is a complete loss of language function, it is used interchangeably with dysphasia, possibly due to ‘dysphasia’ sounding similar to ‘dysphagia’ (difficulty swallowing).

How we sound words (speech) may not necessarily be impaired (i.e. patients can still say full words), however, comprehension and language (understanding and choosing the right words and when to say what) are impaired in dysphasia/aphasia.

Dysphasia can be classified according to speech and comprehension, and according to fluency.

Apraxia of speech

This describes impairment in motor coordination of the muscles involved in speech that is not due to dysarthria. Overall, it means there are problems with impulses and the coordination of impulses being sent to the muscles of speech. Apraxia of speech is due to brain damage rather than muscle weakness.

Dominant Hemispheres

Overview

Wernicke’s and Broca’s areas, the speech areas of the brain, are in the left cerebral hemisphere in most left– and right–handed people (~70%). This hemisphere is called the dominant hemisphere. The right hemisphere is only dominant in around 30% of people.

This is useful because if a patient has a stroke with speech impairment, it is likely that the left side of the brain has been affected, and since most corticospinal fibres decussate in the pyramids of the medulla, the right side is affected. Therefore, left-sided weakness is less common.

Wernicke’s and Broca’s Areas

Wernicke’s area

Wernicke’s area is found in the superior temporal gyrus of the dominant hemisphere. It is one of the two areas in the cerebral cortex linked with speech. It is involved in the comprehension of written and spoken language.

Broca’s area

Broca’s area is found in the inferior frontal gyrus of the dominant hemisphere and is the other area in the cerebral cortex linked with speech. It is involved in the production of speech.

It may be helpful to think of Wernicke’s area as the area that ‘forms speech’ before ‘sending’ it to Broca’s area

Causes of Aphasia

Types of Aphasia: Differential Diagnoses

Approach

Questions to ask are:

  • Is the speech fluent?
    • If yes, then it is either Wernicke’s (receptive) aphasia or conduction aphasia depending on comprehension:
      • Comprehension impaired – Wernicke’s aphasia
      • Comprehension intact – conduction aphasia
    • If no, then it is either global aphasia or Broca’s (expressive) aphasia depending on comprehension
      • Comprehension impaired – global aphasia
      • Comprehension intact – Broca’s aphasia

Aphasia with fluent speech

Is comprehension intact?

  • If yes, (comprehension intact), then it is likely to be conduction aphasia:
    • Lesion site: arcuate fasciculus (connects Wernicke’s and Broca’s areas)
    • Presentation:
      • Fluent speech that makes sense (comprehension intact)
      • Repetition impaired
      • Make frequent errors during speech, but aware of the errors being made and have difficulties correcting them
    • Example:
      • Examiner: “Could you say sixty-eight?
      • Person with conduction aphasia: “Eighty-six. No wait, tixty-sight. No, eighty-tix”.
  • If no (comprehension impaired), then it is likely to be Wernicke’s (receptive) aphasia
    • Lesion site: superior temporal gyrus
    • Blood supply: inferior division of the left middle cerebral artery
    • Presentation:
      • Speech fluent but does not make sense (comprehension impaired)
      • Repetition impaired
      • New words or substitutions may be present
      • The person may respond with random words that sound fluent but do not make sense, including substituting words, creating new words, or rearranging sounds.

Aphasia with non-fluent speech

Is comprehension intact?

  • If yes (comprehension intact), then it is likely to be Broca’s (expressive) aphasia:
    • Lesion site: inferior frontal gyrus
    • Blood supply: superior division of the left middle cerebral artery
    • Presentation:
      • Speech is not fluent but comprehension is intact
      • Repetition is impaired
      • Speech may be agrammatic (missing conjunctions and articles e.g. ‘but’) and may sound effortful
    • Example:
      • Examiner: “What do you do for work?”
      • Person with Broca’s aphasia: “Well um worked um office um no longer working um there”
  • If no (comprehension impaired), then it is likely to be global aphasia
    • Lesion site: all 3 of Wernicke’s area, Broca’s area, and the arcuate fasciculus
    • Presentation:
      • No speech fluency or comprehension
      • Patients may be able to communicate with gestures

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