Dysphasia - One in a group of speech disorders in which there is impairment of the
power of expression by speech, writing, or signs, or impairment of the power of comprehension
of spoken or written language. More severe forms of dysphasia are known as aphasia.
The term dysphasia is more frequently used by European health professionals, whereas
in North American the term, aphasia is more commonly used. The two terms, however,
can be and are used interchangeably. They both refer to the full or partial loss
of verbal communication skills due to damage or degeneration within the brain's language
centres.
Verbal communication is derived from several regions located in the language-dominant
hemisphere of the brain.
These include:
The adjacent inferior parietal lobe.
The inferolateral lobe.
The posterosuperior temporal lobe.
The subcortical connection between these areas.
Disease, direct trauma, lesions, or infarction involving one or more of these regions
can disrupt or prevent proper language function.
Dysphasia does not necessarily prevent proper cognitive function. The person can
think and feel with perfect clarity. This can become extremely frustrating as they
cannot express their thoughts and feelings to others.
Dysphasia can occur in a variety of forms, depending on how the communicative disruption
manifests, affecting one or more of the basic language functions:
Comprehension - understanding spoken language.
Naming - identifying items with words.
Repetition - repeating words or phrases.
Speech.
Although there are several subtypes of dysphasias, they most commonly manifest in
one of three syndromes:
Expressive dysphasia.
Receptive dysphasia.
Global dysphasia.
Expressive dysphasia, also known as motor dysphasia, produces a conscious and recognizable
disruption of a patient's speech production and language output. This includes the
impairment of speech initiation, proper grammatical sequencing, and proper word forming
and articulation. Although people can perfectly understand what is said to them,
they have great difficulty communicating their thoughts.
Broca's dysphasia is the most common type of expressive dysphasia. It is caused by
damage to the lower area of the premotor cortex, located just in front of the primary
motor cortex. This region is most commonly referred to as the Broca's area. Speech
for people suffering from Broca's dysphasia may be completely impossible. Others
may be able to form single words or full sentences, but only through great effort.
Transcortical dysphasia also known as isolation syndrome is caused by damage to the
language-dominant brain that separates all or parts of the central region from the
rest of the brain. There are three sub-classes of transcortical dysphasia, which
define the impairments to a patient's ability to repeat words, sentences, and phrases:
transcortical motor dysphasia, transcortical sensory dysphasia, and mixed transcortical
dysphasia. Additional impairments may occur depending on the extent and location
of the damage.
Receptive dysphasia, also known as sensory dysphasia, impairs the patient's comprehension
and meaning of language. The person can speak fluently and articulately, but will
utilize meaningless words, nonsensical grammar, and unnecessary phrases to the point
of becoming incomprehensible. However, they will be completely unaware of their mistakes.
Additionally, they will find it difficult to comprehend spoken language and / or
word-object relation.
Wernicke's dysphasia is the most common of the receptive dysphasia. It is caused
by damage to the Wernicke's area, located in the posterior superior temporal lobe
of the language-dominant hemisphere. Although the person can speak clearly and at
length, many of their words, phases, and sentences will be nonsensical in nature.
Also they will experience difficulty in understanding spoken language, and may suffer
a complete lack of comprehension. Semantic distinctions between words may become
mixed up and jumbled, increasing confusion.
Anomic dysphasia, is caused by damage to the temporal parietal area and / or the
angular gyrus region. Although very similar to Wernicke's dysphasia, anomic dysphasia
is distinguished by its disruption of a person's word-retrieval skills. They will
be unable to correctly name people or objects, causing them to pause or substitute
generalized words.
Conduction dysphasia is a relatively uncommon disease. Damage to the upper temporal
lobe, lower parietal, or connection between the Wernicke's and Broca's areas can
result in the inability to repeat words, phrases, or sentences. The person may also
suffer the inability to describe people or objects in the proper terms.
Global dysphasia, the third most common form of dysphasia, results from damage to
both the anterior and posterior regions of the language-dominant hemisphere. In global
dysphasia, all of the person's language skills are disrupted; however, some may be
disrupted more severely than others.
Symptoms will present in accordance to the particular type of dysphasia suffered.
Due to the proximity to areas of the brain that control motor function, expressive
dysphasias may be accompanied by noticeable motor impairment.
The majority of symptoms will be language related. Such as:
Difficulty remembering words.
Difficulty naming objects and/or people.
Difficulty speaking in complete and/or meaningful sentences.
