Aphasia is the loss or impairment of language function caused by braindamage  that is typically associated with lesions in the language-dominant hemisphere (the left hemisphere for 96% of right-handed and 70% of left-handed individuals ).
This term comes from the Ancient Greek word ἀφασία which means “speechlessness” . However, this disorder can also compromise—in many different ways and to many different degrees—both language production and comprehension in any of its modalities: oral expression, auditory comprehension, reading or writing [4,5]. Therefore, depending on the linguistic abilities that are impaired—and which can also coexist with other cognitive deficits—aphasic syndromes can be very heterogeneous.
Aphasia, Speech Disorders and Communication Disorders
Since aphasia (as a disorder of language) also involves a deterioration of communication skills, it is important to discriminate between this disorder and other types of communication disorders that can result from acquired brain injury such as speech disorders and neuropsychological disorders such as apraxia of speech or cognitive-communication disorders .
Aphasia vs. Speech Disorders
Speech disorders such as dysphonia, dysphasia, dysglossia, dyslalia, or dysarthria are alterations of different origins (buccophonatory or neurological) that affect various parameters of speech such as the acoustic characteristics of voice (intensity, tone, and timbre), fluency, pronunciation, and the articulation of phonemes and words, but in which language is preserved .
Aphasia, on the other hand, is characterized by an alteration in the structure of language affecting its semantic, grammatical, phonological and/or syntactic level, which deteriorates its symbolic nature , that is, the capacity of language to represent ideas or thoughts.
Therefore, while this disorder is a specific impairment of language that affects its oral modality and the ability to communicate, speech disorders affect communication but not language.
In certain cases, aphasia may co-occur with apraxia of speech, which is, like aphasia, an acquired disorder resulting from brain injury. Apraxia of speech is characterized by an impaired ability to execute voluntarily the appropriate movements for articulation of speech due to a lesion in motor association areas of the cerebral cortex responsible for the programming of voluntary movements of the musculature of the mouth, tongue and larynx [2, 5]. Although some aphasic syndromes such as non-fluent aphasia may include apraxia of speech as a symptom, apraxia of speech itselfis an alteration of kinetic planning.