Approach to aphasia: Clinical sciences

Aphasia refers to an acquired communication disorder that can affect the patient’s ability to speak, understand speech, read, and write. Lesions anywhere along the language circuitry can result in this communication impairment. Now, based on the part of the brain that's affected, we can further subdivide aphasia into several main types! Broca and transcortical motor aphasia are characterized by impairment in language production or expression, while Wernicke and transcortical sensory aphasia are associated with a loss of language comprehension or reception. Finally, conduction aphasia is characterized by a loss of repetition, and global aphasia is associated with a severe loss of language production and comprehension.

Now, if your patient presents with a chief concern suggestive of aphasia, first, obtain a focused history and physical exam. Friends and family members will typically report that the patient has trouble communicating. Additionally, the physical exam will usually reveal limited verbal or written language output, nonsensical speech, impaired comprehension of verbal or written language, or impaired repetition. With any of these findings, you can diagnose aphasia, so your next step is to assess the type.

First, let’s focus on expressive aphasia! These patients are speaking in short, poorly-formed sentences. Also, they will have difficulties coming up with words and they will have trouble with writing. The physical exam is notable for non-fluent speech, meaning speech that is not smooth, with word-finding difficulty, loss of grammar, and abnormal rate and cadence. The patient is sometimes described as having telegraphic speech, with improper grammar and using mainly nouns and verbs. Something similar to the early days when telegrams were a mode of long-distance communication, and the sender was charged by the word. You will also find impaired written language with mostly intact reading and hearing comprehension. In this case, diagnose an expressive aphasia. Of note, patients with expressive aphasia are usually aware of their language impairment, so they will appear very frustrated during attempts to communicate.

Now, there are two main types of expressive aphasia. In order to differentiate between the two, you will need to assess the patient’s ability to repeat words or phrases. If your patient is unable to repeat, the brain injury is in the Broca area, which is in the dominant posterior inferior frontal lobe. In this case, diagnose Broca aphasia. On the other hand, if repetition is intact, the lesion is anterior and superior to the Broca area in the dominant frontal lobe, so be sure to diagnose transcortical motor aphasia.

Next, let’s take a look at receptive aphasia! These patients are speaking effortlessly but what they are saying makes no sense. Also, they will have trouble understanding others and reading. The physical exam will show that speech is fluent but nonsensical, meaning that the patient may speak at a relatively normal rate and cadence, but the content doesn’t make sense. This is often described as a word salad. They might use a word that sounds similar or is similar in meaning, to the word they’re trying to say. These errors are known as paraphasic errors. Also, you will notice that the comprehension of written and spoken language is significantly impaired. In this case, diagnose receptive aphasia. In contrast to expressive aphasia, individuals with receptive aphasia often do not have insight into their loss of language, so they are often frustrated that people can’t understand their speech.

Once you diagnose receptive aphasia, again, assess the patient’s ability to repeat words or phrases. If the patient can't repeat what you are saying, the lesion is in the dominant posterior superior temporal lobe, at the Wernicke area, where language comprehension is processed. In this case, diagnose Wernicke aphasia. On the flip side, if your patient can repeat, the lesion is not in the Wernicke area, but close to it, so diagnose transcortical sensory aphasia.

Now, let’s move on to conduction aphasia. Conduction aphasia is associated with lesions of the arcuate fasciculus, which is a pathway that connects Wernicke and Broca areas. These individuals usually make minor errors in otherwise pretty normal speech. Also, they will have some mild trouble with understanding others and with reading. Finally, the physical exam will show mostly fluent speech and mildly impaired comprehension, but with severe inability to repeat words and phrases. With these findings, diagnose conduction aphasia!

Finally, let’s discuss global aphasia, which is the most severe type of aphasia that’s usually associated with a large lesion affecting both the Broca and Wernicke areas and the region between them. In this case, close friends and family members will report that the patient is not speaking or that they have minimal speech. Also, they will report that the patient doesn’t understand any spoken language. The exam will reveal no speech output or minimal nonfluent speech output. Additionally, the patient will be unable to write, comprehend spoken and written language, and repeat any phrases. With these findings, diagnose global aphasia!

Now, once you diagnose a specific type of aphasia, it’s time to figure out the underlying cause. Start by assessing the timing of symptom onset. If the aphasia appears suddenly, you should consider stroke or traumatic brain injury. In both cases, the injury involves more than just language areas, so the patient will present with additional focal neurologic deficits, such as contralateral weakness and visual field loss. Next, obtain a CT or MRI of the brain. If imaging reveals infarction or hemorrhage, diagnose stroke as the underlying etiology.