Understanding Aphasia: Types, Characteristics, and Language Alterations
Aphasia
Aphasia is a speech impediment caused by cerebral disturbance. It can be defined as a disorder of the ability to use or decode the significant elements of speech, words, or phonemes. To be diagnosed with aphasia, the following criteria must be met:
- Lesion in the language areas of the brain
- Prior acquisition of language
- Altered expression and/or comprehension of language
Types of Aphasia
Central Aphasia
- Broca’s Aphasia
- Wernicke’s Aphasia
- Conduction Aphasia
- Global Aphasia
- Anomic Aphasia
Aphasia Syndromes of Pure Instrumental or Areas
- Pure Anarthria
- Pure Agraphia
- Pure Verbal Deafness
- Pure Alexia
Aphasia Syndromes of Associative Areas
- Transcortical Sensory (ATS)
- Transcortical Motor (ATM)
- Transcortical Mixed (ATMx)
Subcortical Aphasia Syndromes
- Caudate Nucleus Dependent Aphasia
- Thalamic Aphasia
Unclassifiable Aphasias
There are some aphasias that do not fit neatly into the above categories.
Common Features of Aphasia
A common feature of all aphasias is impaired understanding. However, certain types of aphasia (Wernicke’s, Global, and Transcortical Sensory) exhibit more severe comprehension deficits. Understanding is never completely lost in post-aphasia. All aphasias involving Wernicke’s area, conduction, Broca’s, and Global aphasia experience difficulty with repetition. Reading and writing are also affected in most aphasias. Broca’s and Wernicke’s aphasia are the most prevalent types.
Characteristic Aphasias
Wernicke’s Aphasia
Wernicke’s aphasia is characterized by a significant disorder of understanding. For example, a patient might respond to the command “Give me your hand” with “It’s sunny.” Verbal expression is abnormal, with many problems in articulation. There is an inability to understand words or to arrange sounds consistently. Speech in Wernicke’s aphasia is fluent and melodic, but individuals may struggle to find the right words. They may repeat certain words and phrases poorly due to impaired comprehension. Reading and writing are also impaired in most cases. Notably, individuals with Wernicke’s aphasia are often aware of their language deficits.
Broca’s Aphasia
Broca’s aphasia results from damage to Broca’s area and its connections. This area is responsible for the motor planning of speech. There are flaws in articulation, but comprehension remains relatively intact while language production is severely impaired. Repetition, reading, and language are impaired. Writing is often reduced to signing or copying. Associated disorders may include right-sided facial paralysis and vision loss.
Global Aphasia
Global aphasia occurs when the entire perisylvian speech area is affected, often due to damage to the middle cerebral artery or internal carotid artery. It involves severe deterioration in language comprehension and expression, essentially combining the most severe aspects of Broca’s and Wernicke’s aphasia. There is massive destruction of the language areas. Repetition is impossible or reduced to syllabic fragments. Understanding is limited to very simple, short, and predictable commands. Reading is impossible, and writing is limited to signing or copying.
Conduction Aphasia
Conduction aphasia is characterized by fluent spontaneous speech and good comprehension but poor repetition with the presence of literal paraphasias. Understanding is almost normal. Conduction aphasia often includes: defects in naming, changes in reading (comprehension is significantly higher than reading aloud), changes in writing (from minor spelling errors to severe agraphia), ideomotor apraxia, and neurological abnormalities (such as right hemiparesis and cortical sensory loss).
Anomia
Anomia is the inability to find nouns, verbs, and other content words, both orally and in writing. There are difficulties with masculine and feminine endings.
Aphasia Syndromes of Associative Areas
Transcortical Motor Aphasia (MTA)
MTA can result from damage to the supplementary motor cortex and white matter pathways beneath it. Another possible location is in front of and below Broca’s area. Spontaneous speech is very limited, with slurred and poor articulation, generally composed of short sentences. Repetition is much better than spontaneous language, with the ability to replicate relatively long sentences. Comprehension of spoken language is relatively preserved. Individuals retain the ability to name but often need articulatory support. In many cases, they can read aloud with some difficulty. Writing is impaired.
Transcortical Sensory Aphasia (ATS)
ATS is caused by large lesions in the parieto-temporo-occipital areas, disrupting the connection between these areas and Wernicke’s area. Spontaneous speech is fluent but includes verbal paraphasias and anomia. Speech characteristics are very similar to Wernicke’s aphasia. Understanding of spoken language is very limited. Repetition is almost normal, sometimes exhibiting echolalia. Reading comprehension is severely impaired, and reading aloud is also deficient. Writing is unintelligible. ATS is one of the most common forms of aphasia seen in Alzheimer’s disease, possibly due to its association with bilateral lesions.
Mixed Transcortical Aphasia (MTA)
MTA involves destruction of the entire border zone (almost global). Spontaneous speech is severely impaired and limited, with the use of stereotyped phrases and short words. Repetition is possible. Understanding is impaired, with little comprehension of spoken language and almost no ability to name. Reading and writing are virtually impossible.
Language
Language is the primary means of communication among humans. It is a phylogenetically acquired activity involving audio-verbal associations, visual-verbal associations, correspondence between words and experiences, learning sociolinguistic procedures, and verbal representation of experiences. Language development requires normal hearing, psychological and neurological development, and normal articulatory organs. Language is a tool and a manifestation of thought. The word is the proper function of the self.
Language is based on an arbitrary code. We must consider the following elements of language:
- Stroke: A simple unit that does not convey meaning on its own.
- Phoneme: The smallest sound unit that can produce a change in meaning.
- Moneme: A word or combination of phonemes with meaning, representing the development of a thought.
- Phrase: A combination of monemes.
- Sentence: A combination of phrases.
General Functional System of Speech
- Receptor System: Visual, auditory, etc.
- Affector System: Somatosensory
- Central Integrator System: Subcortical, cortical, telencephalic, diencephalic
- Effector System:
Organization of Language
- Cortical: Brodmann area 44 (Broca’s area), Brodmann area 3 (foot of the articulatory cortex), Brodmann area 22 (Wernicke’s area), Brodmann areas 41 and 42 (auditory cortex), Brodmann area 39 (angular gyrus), Brodmann area 40 (supramarginal gyrus), prefrontal cortex
- Subcortical: Polisub, leucosub
- Diencephalic: Dorsomedial pulvinar thalamus
- Brainstem: Cerebellum, midbrain reticular formation
Alterations of Language
- Before Language Acquisition: Specific language impairments
- After Language Acquisition: Aphasia, dysphasia, reading and writing disorders