Aphasia is abnormal language. Aphasia is not limited to speech, but may also include text or sign language. Aphasia is usually detected during the interview, but subtle language deficits may only be found with testing on examination. For the language examination, the patient is asked to produce spontaneous sentences, repeat sentences, and follow commands (without physical demonstration by the examiner). Each of these may progress from simple to complex to quantify the severity of aphasia. This testing is usually done verbally, but may be done with text or sign language as well. Dysphasia is a proper term for a partial deficit of language, but is rarely used because it sounds similar to dysphagia (abnormal swallowing). Paraphasia refers to a word error, which is common with aphasia. A paraphasia may have a similar sound, such as “block” instead of “clock”; a similar meaning, such as “watch” instead of “clock”; or may be nonsense, such as “brop”.
There are several types of aphasia. Anomia is abnormal naming, which may be limited to only parts of objects. For example, a patient may be able to name a hand but not knuckles. The mildest aphasia may be isolated anomia, which may occur with dysfunction of either language cortex. Fluency refers to the rate of word production, which is helping for locating dysfunction in aphasia, but in this context does not refer to correct or incorrect words (paraphasias).
Expressive aphasia involves abnormal language production, which is also called nonfluent or motor aphasia. With expressive aphasia, there is diminished fluency (decreased rate of word production) and simplification of words and grammar. Patients are often frustrated, probably because comprehension is normal, and they are aware of their limited ability to express themselves. Most patients with expressive aphasia specifically have Broca’s aphasia, which also includes impaired repetition, and which is usually caused by dysfunction of Broca’s area. A less common type of expressive aphasia is transcortical motor aphasia, where, unlike Broca’s aphasia, there is normal repetition. This is usually caused by dysfunction around, but not in, Broca’s area, which spares Broca’s area and the arcuate fasciculus, but disconnects Broca’s area from other cortical areas.
Receptive aphasia involves abnormal comprehension, which is also called fluent or sensory aphasia. With receptive aphasia, there is normal fluency (normal or even increased rate of word production), but the phrases may be nonsensical due to frequent paraphasias (“word salad”). Patients with receptive aphasia usually are not frustrated, and are often unaware of their deficits, perhaps due to impaired comprehension. Some of these patients may think they are normal and everyone around them has abnormal language. Most patients with receptive aphasia specifically have Wernicke’s aphasia, which also includes impaired repetition, and which is usually caused by dysfunction of Wernicke’s area. A less common type of receptive aphasia is transcortical sensory aphasia, where, unlike Wernicke’s aphasia, there is normal repetition. This is usually caused by dysfunction around, but not in, Wernicke’s area, which spares Wernicke’s area and the arcuate fasciculus, but disconnects Wernicke’s area from other cortical areas.
Mixed aphasia has features of both expressive and receptive aphasias, and is usually caused by dysfunction of both Broca’s and Wernicke’s areas. Mixed aphasia is often called global aphasia, but this term is not used consistently as many clinicians also use it for total aphasia, where there is an absence of all language function. Conduction aphasia is an isolated deficit of repetition, which is usually from dysfunction of the arcuate fasciculus.