Makindo Medical Notes

Introduction

Aphasia is the most common early cognitive deficit after stroke, found in 20%-38% of patients. Speech and particularly language is an integral part of what makes us human. The loss of speech following a stroke can often be devastating. Almost a third of stroke patients develop difficulty with language. Persisting Aphasia/Dysphasia in particular affects mood, future employment, and the difficulty in being able to make use of any medium that is language-based. It is important that language issues are identified early and given appropriate therapy. Aphasia can have a serious impact on the communication aspects of patients' lives and on their carers, and it is important to ensure that families and carers understand how to support the patient.

Background

Difficulties with speech can be broadly grouped into difficulties with articulation and difficulties with the content of language. Language is a very localising neurology to the dominant cerebral cortex involving the dominant frontal lobe (Broca's area) and the temporal/parietal lobe (Wernicke's area). It is a key symptom to recognise in stroke most commonly as part of a left MCA arterial syndrome. Dysarthria is far less localising and can be non-specific. Language issues can affect speech, oral comprehension, reading, and writing. For those interested in language, I highly recommend the Language Instinct by Stephen Pinker to gain a basic understanding of language and related fascinating issues in language production.

Terminology

Neologisms: Newly coined terms, words, or phrases. Paraphasia: Speech disturbance from brain damage in which words are jumbled and sentences meaningless. Literal/phonemic: Shooshbruss/toothbrush; tevilision/television. Verbal/semantic: Table for chair, cranberry for teapot. Verbal paraphasia: Confusions of words or the replacement of one word by another real word. Malapropism: The use of an incorrect word in place of a word with a similar sound.

Aetiology

Traditional neurolinguistic models involve classical brain areas involved in language. This has generally included structures in the left cerebral hemisphere known as Broca's area, Wernicke's area, and the bundle of fibres connecting the two structures, the arcuate fasciculus. More recent studies indicate that the recognition of speech sounds is carried out in the superior temporal lobe bilaterally, which is also involved in phonological-level aspects of this process. The frontal/motor system is not central to speech recognition but may modulate auditory perception of speech, with conceptual access mechanisms likely located in the lateral posterior temporal lobe (middle and inferior temporal gyri).

Speech production involves sensory-related systems in the posterior superior temporal lobe in the left hemisphere. The interface between perceptual and motor systems is supported by a sensory-motor circuit for vocal tract actions (not dedicated to speech) that is similar to sensory-motor circuits found in the primate parietal lobe. Verbal short-term memory can be understood as an emergent property of this sensory-motor circuit. There is a dual-stream model of speech processing in which one pathway supports speech comprehension and the other supports sensory-motor integration. Damage to these areas and underlying neural networks is thought to be responsible for specific language deficits, or aphasias. Models based on this with a clinical-pathological basis have helped, though newer neuroimaging may suggest that this model does not fully explain language impairment, traditional models serve us for now.

Key Anatomical Structures

Paths Involved in Repeating a Read or Heard Word

Key Questions for Examining Speech

Distinguish it from other related conditions:

• Motor speech disorders
• Cognitive-communication disorders

Definition of Aphasia

Disturbance of language caused by brain damage affecting:

• Comprehension: Auditory and/or Reading.
• Expression: Speaking, Writing, Signing.

Important Distinctions to Determine by Assessment

• Language: Vocabulary, grammar.
• Speech: Movement, tongue, lips.
• Cognition: Attention, memory, problem-solving.

Language Input: How the Brain Processes the Comprehension of Speech

• Auditory Language (Hearing): Ears to Auditory Cortices to Wernicke's area.
• Visual Language (Reading): Eyes to Visual Cortices to Wernicke's area.
• Meaning Construction: Overall meaning, word relationships.
• Context Evaluation: Literal vs figurative meaning.

Language Output: Spontaneous Spoken Language

• Wernicke's area: Retrieves words, sentence structure.
• Arcuate fasciculus: Transmits it to Broca's area.
• Broca's area: Formulates an action plan.
• Primary Motor Cortex: Refines and sends to speech muscles.

Repetition (Tests the Entire Language Circuit)

• Primary Auditory Cortex: Speech or Visual Cortex for reading.
• Wernicke's area
• Arcuate fasciculus
• Broca's area: Forms articulatory plan.
• Primary Motor Cortex
• Pyramidal System: Sends to cranial nerves for articulation.

Bedside Assessment

• Observe Introductions: Gives clues about language issues.
• Fluency and Volume: Assess speech characteristics.
• Language Comprehension: Test with non-verbal tasks, e.g., 'Touch your chin, then your nose, then your ear.'
• Articulation: Repetition: 'no ifs, ands, or buts' and 'British constitution'.

The evaluation of a patient with suspected motor speech disorder should also include assessment of hearing.

Assessment of Speech

• Initial Talk: Ask 'Tell me where you are?' or 'Describe X for me'.
• Confabulation: Check for fabricated content, often in amnesia cases.

Dyspraxic Speech

Apraxia of speech is seen when a patient has trouble saying what he or she wants to say correctly and consistently. Speech is often slow, deliberate, effortful, and may have impaired prosody. It is not caused by weakness or paralysis of the speech muscles or aphasia, though these can coexist. Apraxia of speech strongly associates with lesions of the left inferior frontal gyrus and the left anterior insular. Diagnosis and management involve one-on-one speech-language therapy sessions.

Prognosis

Many patients experience spontaneous recovery in the first two weeks after stroke. Most return within the first three months, after which recovery is slow. Women recover better than men in oral production and auditory perception. A higher IQ and a higher level of education increase the likelihood of speech recovery, which may also be better and faster in left-handed and ambidextrous patients. Early and intensive therapy is needed.

Management

• Early Recognition: Involve Speech and Language Therapy (SLT) for tailored intervention.
• Educate Family: Use gestures, drawings, and patience to improve communication with patients.
• Therapy Timeline: Evidence shows enhanced therapy effectiveness within the first 4 months.

Links and References

• Basics of Speech Neuroscience
• National Aphasia Association
• Effectiveness of Enhanced Communication Therapy in the First Four Months after Stroke for Aphasia and Dysarthria: BMJ 2012