Disorders of Speech and Language : Aphasia / Dysphasia

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Disturbed speech and language are important symptoms of the neurological disease. The two are not synonymous. Speech is the ability to clearly and verbally communicate messages or information to others. Whereas, language allows the communication of thoughts and experiences by linking them to arbitrary symbols known as words. Deep understanding of difference between speech and language disorders are essential as patients with language disorders are labelled confused as a consequence of superficial evaluation.

Language is a function of dominant cerebral hemisphere and may be divided into :

• emotional (the instinctive expression of the feelings representing the earliest forms of language acquired in the infancy)
• symbolic or prepositional (conveying thoughts, opinion and concepts, which are acquired over a period and is dependent upon culture, education and normal cerebral development). 

The language network shows a left hemisphere dominance pattern in majority of the population. Brain areas involved in language function includes :

1. Wernicke's area : Includes the posterior third of the superior temporal gyrus and a surrounding rim of the inferior parietal lobule. The essential function of Wernicke's area is to transform sensory inputs into their neural word representation that give the word its meaning.
2. Broca's area : includes the posterior part of the inferior frontal gyrus. The essential function of this area is to transform neural word representations into their articulatory sequences so that the words can be uttered in the form of spoken language.
3. Arcuate fasciculus : Includes perisylvian fibers which connect Wernicke's area and Broca's area. These fibers are responsible mainly for repetition.

Aphasia / Dysphasia is an acquired loss of production or comprehension of spoken and/or written language secondary to brain damage. Aphasia should be diagnosed only when there are deficits in the formal aspect of language such as naming, word choice, comprehension, spelling and syntax. 

The clinical examination of language should include the assessment of : 

• Naming : The ability to name the object is one of the earliest acquired and most basic function.
• It is tested by asking to name the objects, object parts, body part and colors. Word finding difficulty, error in naming is noted.

• Spontaneous speech : There is verbal fluency  in speech without undue word finding pauses or failure in word searching.
• It can be tested while taking history from patient and look for error in content of speech, pauses and word output. 
• Normally word output is 50-200 words/minute. If word output is less than 50 words/minute or is unable to speak 5 letter word in a single breath then the condition is labeled as non-fluent speech. If word output is fast and more than 200 words per minute then the condition is called as logorrhea. 

• Comprehension : Most common error while testing for comprehension is asking general  or open ended questions like show your tongue, close your eyes, etc.
• Pointing commands test : Observe whether patient can follow single or multiple steps commands. For example: 
• patient is asked to point single objects or body parts, 
• patient can be asked to perform the procedure of making a simple snack dish by reading or by following spoken commands, 
• ask about simple and basic steps of gardening or tea making after reading the procedure, etc.
• "Yes" / "No" response test : A series of simple and complex questions requiring only yes or no answers is asked to the patient. It is important to ask at least 7 questions because correct responses can occur by chance alone 50% of times with either yes or no answers. Example : "Is this a hotel"?, "Is is sunny outside"?, "Is August the 8th month of the year"?

• Repetition : Patient is asked to repeat the word or sentence after the examiner. Paraphasias, grammatic errors, omissions or additions etc are noted. Normally person can repeat a sentence of 19 syllables. For example : no-if-and-or-buts, 1-2-3.... 1-2-3... etc.

• Reading : Reading ability is directly related to educational status of the patient. Both reading aloud and reading comprehension is tested.

• Writing : Patient is asked to write letters to dictation. Patient can be asked to write names of common objects or body parts. Once patient is able to write single words successfully, then ask him to write sentence describing the weather, his job, procedure of making any dish, etc. It is important to note that questions which are asked to patients should not be very easy or familiar or frequently asked. For example : asking patients to write his/her name is not meaningful, as name writing is preserved even in severe agraphia.

Fig :  Different types of Aphasia

Different types of Aphasia : 

1) Wernicke's Aphasia : 

• Also called as Receptive aphasia: affectation in Wernicke's area (temporal lobe). Some patients with Wernicke's Aphasia due to intracerebral hemorrhage or head trauma may recover and improve as haemorrhage or injury heals.
• Comprehension is impaired for spoken and written language. Patient is unable to follow commands. 
• Spontaneous speech is fluent, but highly paraphasic. Paraphasic errors leads to strings of neologisms, which form the basis of what is known as "jargon aphasia". Gestures and pantomime do not improve communication.
• Repetition, naming, reading and writing are also impaired.

2) Broca's Aphasia : 

• Also called as Expressive aphasia : affectations in Broca's area (frontal lobe). 
• Spontaneous speech is non-fluent, labored, interrupted by many word-finding pauses, and usually dysarthric. Output may be reduced to a grunt or single word ("yes" or "no"), which is emitted with different intonations in an attempt to express approval or disapproval.
• Comprehension is intact. Reading comprehension is also preserved.
• In addition to fluency, naming and repetition are also impaired.
• Insight into their condition is preserved, in contrast to Wernicke's aphasia. Even when spontaneous speech is severely dysarthric, the patient may be able to display a relatively normal articulation of words when singing. This dissociation has been used to develop specific therapeutic approaches (melodic intonation therapy) for Broca's aphasia.

3) Global Aphasia :

• Speech output is nonfluent, and comprehension of spoken language is severely impaired.
• Naming, repetition, and writing are also impaired.
• This syndrome represents the combined dysfunction of the Broca's and Wernicke's areas and usually results from strokes that involve the entire middle cerebral artery distribution in the left hemisphere.

4) Conduction Aphasia : 

• Speech output is fluent, comprehension of spoken language is intact.
• Repetition is severely impaired as perisylvian arcuate fasciculus are only damaged. Affectation in Arcuate fasciculus, which connects two speech areas. Patient is unable to repeat.
• Naming and writing may be also impaired.

5) Nonfluent transcortical aphasia (Transcortical motor aphasia) :

• The features are similar to Broca's aphasia, but repetition is intact.
• The lesion site disconnects the intact language network from prefrontal areas of the brain and usually involves the anterior watershed zone between anterior and middle cerebral artery territories.

6) Fluent Transcortical Aphasia (Transcortical sensory aphasia) : 

• Clinical features are similar to Wernicke's aphasia, but repetition is intact.
• The lesion site disconnects the intact core of the language network from other temporoparietal association areas. 
• Cerebrovascular lesions (e.g., infarctions in the posterior watershed zone) or neoplasms that involve the temporoparietal cortex posterior to Wernicke's area are most common causes.

7) Anomic Aphasia :

• Articulation, comprehension, and repetition are intact, but naming, word finding, and spelling are impaired.
• The lesion site can be anywhere within the left hemisphere language network, including the middle and inferior temporal gyri. According to physiology textbook lesion of left angular gyrus is responsible for anomic aphasia.
• Anomic aphasia is the single most common language disturbance seen in head trauma, metabolic encephalopathy and Alzheimer's disease.

Fig : Characteristics of various Aphasia

Fig : Affected brain areas causing Aphasia

Thankyou for reading !!!

Dr.Ashwini Sangar, Dr.Sheetal Dhande-Tatar, Dr. Pallavi Kolhe-Khadse