Understanding Types and Causes of Aphasia

Nov 10, 2024

Lecture Notes: Types of Aphasia

What is Aphasia?

  • Definition: Acquired cognitive condition affecting the ability to speak.
  • Causes: Injury to brain's language areas or surrounding areas.
    • Trauma (head injury)
    • Stroke (ischemic or hemorrhagic)
    • Brain mass (cancer)
    • Neurodegenerative diseases (Alzheimer's, vascular dementia, frontotemporal dementia)
    • Encephalitis (often infectious inflammation of the brain)
  • Epidemiology:
    • 90-95% of aphasia cases involve damage to the left hemisphere.
    • A third of cases are due to cerebrovascular accidents.
    • Increases with age due to increasing prevalence of causes like stroke and dementia.

Anatomy of Language Areas

  • Association with Handedness:
    • Right-handed individuals: Language centers in left hemisphere (>99%).
    • Left-handed individuals:
      • 70% in right hemisphere
      • 15% in left hemisphere
      • 15% bilateral
  • Key Areas:
    • Broca's Area: Posterior inferior frontal lobe; involved in speech initiation and motor control.
    • Wernicke's Area: Posterior superior temporal lobe; involved in language comprehension.
    • Angular Gyrus: Near Wernicke's area; involved in understanding written language.
    • Arcuate Fasciculus: Connects Broca's and Wernicke's areas.

Types of Aphasia

  • Non-Fluent Aphasia (Broca's/Expressive Aphasia): Lesion in Broca's area.

    • Good comprehension, poor speech initiation.
    • Poor grammatical speech and writing.
    • Paraphasias are uncommon.

  • Fluent Aphasia (Wernicke's/Receptive Aphasia): Lesion in Wernicke's area.

    • Meaningless speech, poor comprehension.
    • Common use of neologisms and paraphasias.
    • Unaware of mistakes.

  • Global Aphasia: Affects both Broca's and Wernicke's areas.

    • Poor speech and comprehension.
    • Severe type; poor repetition and naming.

  • Conduction Aphasia: Lesion in arcuate fasciculus.

    • Good spontaneous speech and comprehension.
    • Difficulty repeating phrases.

  • Transcortical Aphasias:

    • Sensory: Lesion around Wernicke's area; poor comprehension, good repetition.
    • Motor: Lesion around Broca's area; non-fluent but can repeat sentences.
    • Mixed: Lesions around both Broca's and Wernicke's areas; poor speech and comprehension but good repetition.

  • Anomic Aphasia (Anomia): Lesion at angular gyrus.

    • Good speech, comprehension, and repetition but poor naming.

Clinical Features

  • Non-Fluent Aphasia: Broken speech, good comprehension.
  • Fluent Aphasia: Good spontaneous speech, poor meaning.
  • Global Aphasia: Severe speech and comprehension deficits.
  • Conduction Aphasia: Difficulty with repetition.
  • Transcortical Aphasias: Variable speech and comprehension abilities, often with intact repetition.
  • Anomic Aphasia: Difficulty in finding words.

Diagnosis and Treatment

  • Diagnosis: Clinical assessment, imaging (CT, MRI), and blood work.
  • Treatment:
    • Speech and language therapy.
    • Addressing underlying causes: stroke treatment, surgery, antivirals, etc.
    • Better outcomes if younger, healthier, and possibly left-handed due to potential bilateral language centers.

Exclusions

  • Not aphasia: Developmental disorders, motor speech disorders, psychiatric condition-related language problems.

This lecture provided an in-depth overview of the various types of aphasia, their causes, associated brain areas, and clinical features, as well as diagnostic and treatment approaches.