This chapter focuses on the impairments to speech and language that occur after brain injury. These impairments can be grouped into four main categories:
- •
Aphasia
- •
Dysarthria
- •
Apraxia of speech
- •
Cognitive communication disorders.
It is common for these language impairments to occur together, but they can occur separately as well.
Aphasia
Aphasia is the impairment in the ability to produce and/or comprehend spoken or written language caused by damage affecting one or more areas of the brain responsible for language. Aphasia can develop suddenly after a stroke or head injury or slowly secondary to a brain tumor or a progressive neurologic disease such as Alzheimer’s disease. It may include impairments in auditory comprehension, verbal expression, reading comprehension, and/or written expression and may cooccur with other speech disorders, such as dysarthria or apraxia of speech.
- •
Types of aphasia can be categorized based on three main aspects of communication ( Table 32.1 , Fig. 32.1 ):
- •
Fluency
- •
Comprehension
- •
Repetition
TABLE 32.1
Types of Aphasia
Adapted from Braddom’s Physical Medicine and Rehabilitation and Principles of Rehabilitation Medicine .
Type of Aphasia
Fluency
Comprehension
Repetition
Area of Injury
Global
−
−
−
Left middle cerebral artery stroke
Mixed transcortical
−
−
+
Border zones between parietal, temporal, and frontal lobes
Broca’s
−
+
−
Left posterior inferior frontal lobe
Transcortical motor
−
+
+
Frontal lobe, anterior or superior to Broca’s area
Wernicke’s
+
−
−
Left superior temporal gyrus
Transcortical sensory
+
−
+
Posterior temporal lobe
Conduction
+
+
−
Arcuate fasciculus
Anomia
+
+
+
Angular gyrus
Crossed
+/−
+/−
+/−
Rare occurrence when lesion in the right hemisphere mirrors those seen in the left hemisphere
• Fig. 32.1
Aphasia Tree Diagram
(Adapted with permission from the National Aphasia Association.
- •
Epidemiology
- •
Stroke is the most common cause of aphasia, affecting up to 40% to 60% of stroke patients.
- •
About 1 million people in the United States currently live with aphasia, with 180,000 Americans developing aphasia annually.
- •
Poststroke aphasia can significantly affect a person’s quality of life and has been shown to have a greater negative effect than common conditions such as cancer and Alzheimer’s and Parkinson’s diseases.
Functional neuroanatomy
- •
The language center of the brain is located in the dominant hemisphere—the left hemisphere in the vast majority of individuals. Even in left-handed individuals, approximately 70% have left hemispheric dominance.
- •
Broca’s aphasia is named after the French scientist Paul Broca who first related deficits associated with this type of aphasia to localized brain damage in 1861. Individuals have difficulty accurately forming the words they want to say. Although they may understand speech and know what they want to say, they frequently speak in short phrases with halting, effortful speech, with imprecise articulation and paraphasia. The lesion is localized to the lateral frontal/suprasylvian area of the frontal lobe, commonly known as Broca’s area ( Fig. 32.2 ). Those with Broca’s aphasia often have right-sided weakness or paralysis because the frontal lobe also plays a role in motor control.
• Fig. 32.2
Basic neuroanatomy of the language centers of the brain.
(Reprinted with permission from Hall J. Guyton and Hall Textbook of Medical Physiology. 12th ed. Philadelphia, PA: Saunders Elsevier; 2011.)
- •
In Wernicke’s—or fluent—aphasia, individuals often speak in long, complete phrases that have no meaning. They have a fluent jargon speech with normal prosody, poor auditory comprehension and repetition, and difficulty understanding speech. The lesion localizes to damage to the posterior third of the superior gyrus in the temporal lobe (see Fig. 32.2 ).
- •
The arcuate fasciculus—a bundle of axons that connects Wernicke’s area to the motor and premotor cortex (including Broca’s area)—allows for speech repetition. Damage to this group of neurons results in a conduction aphasia, where speech is fluent (although there may be word-finding pauses) and repetition is impaired. Damage to Broca’s area, Wernicke’s area, or arcuate fasciculus will result in impaired repetition because the connection between the areas has been affected.
- •
Lesions affecting the anterior frontal paramedian area anterosuperior to Broca’s area will result in impaired initiation of verbal output in a condition known as t ranscortical motor aphasia .
- •
Lesions located in the posterior parietotemporal area sparing Wernicke’s area will lead to anomia with poor auditory comprehension, with intact repetition resulting in a condition called transcortical sensory aphasia .
- •
Damage to both the motor and comprehension centers of the brain, such as after a large left middle cerebral artery stroke, will result in a global deficit in language. Patients will have profound anomia with very poor auditory comprehension with stereotypic utterances.
- •
Damage to the right hemisphere may lead to cognitive communication disorders such as neglect, affecting reading and writing ability, impairments in memory, attention, perception, and learning.
Treatment
Speech pathologists are experts at assessing and treating the areas and severity of language deficit, including auditory comprehension, fluency, reading, and writing.
- •
Diagnostic evaluation tools: Western Aphasia Battery and Boston Diagnostic Evaluation of Aphasia
- •
Studies have shown that intense speech therapy leads to better improvement than intermittent or less structured therapy and that early intense therapy may promote cortical reorganization leading to persistent improvements in language.
- •
Constraint-induced aphasia therapy (CIAT) focuses on overcoming learned nonuse of language deficits and has been shown to improve aphasia when used in intensive therapy. This form of therapy prohibits the patient from communicating nonverbally to encourage the use of verbal communication.
- •
Melodic intonation therapy also has been shown to have some benefit in patients with Broca’s aphasia in the acute setting after stroke.
- •
Another strategy to improve communication is augmentative and alternative communication (AAC). These focus on restorative and compensatory strategies, which range in complexity from the use of basic pictures and word boards to computerized communication devices.
Pharmacologic treatment
Brain injury, whether from trauma or stroke, causes disruptions in the noradrenergic, cholinergic, serotonergic, and dopaminergic pathways from the brainstem to the language cortex. Pharmacologic treatment of aphasia has been studied, but the quality of these studies varies, the patient populations are small, and the results have been inconclusive.
- •
Catecholaminergic drugs such as bromocriptine, levodopa, dextroamphetamine, and amantadine have been studied but have not shown clear and lasting benefits in improving aphasia.
- •
Cholinergic drugs such as ameridin, donepezil, bifemelane, aniracetam, galantamine, and physostigmine have also been studied, with donepezil showing some short-term benefit in treating chronic poststroke aphasia.
- •
Memantine, an NMDA receptor antagonist, may have some lasting benefit when combined with CIAT.
- •
Piracetam, a nutritional supplement derived from gamma-aminobutyric acid (GABA), may have some short-term benefit in the acute phase when combined with speech therapy.
Noninvasive brain stimulation
A range of nonpharmacologic treatments for aphasia exists as an adjunct to speech therapy. These include the use of use of electrical current to modify brain activity, a phenomenon first mentioned more than 200 years ago. ,
Two such methods include:
- •
Transcranial direct current stimulation (tDCS)
- •
Transcranial magnetic stimulation (TMS)
- •
tDCS: electrodes are placed on the scalp to produce a static electrical field in the underlying brain structures. This has been shown to produce prolonged and sustainable shifts in cortical excitability and functioning when studied in conjunction with functional magnetic resonance imaging (fMRI), positron emission tomography (PET), and electroencephalogram (EEG). ,
- •
TMS: an electrical coil is placed over the patient’s scalp to induce a fluctuating magnetic wave that creates a dynamic electrical field in the underlying brain.
- •
Both methods have shown promising results in treating chronic aphasia and are safe procedures with very few side effects.
- •
Contraindications to TMS are the presence of metallic or cochlear implants, increased risk of seizures, and unstable medical conditions.
- •
Increased risk of seizures and presence of implants are also considered relative contraindications in tDCS, but studies have not actually shown increased seizure frequency in patients with epilepsy who receive tDCS.
- •
Despite promising results, the studies investigating the efficacy of these techniques have lacked large sample sizes, and these practices are still not used widely. , ,
- •
Recovery
Those with aphasia will have the greatest recovery within the first 3 months poststroke. If the symptoms of aphasia last longer than 2 or 3 months after a stroke, a complete recovery is unlikely, although some continue to improve over years or even decades. ,
Dysarthria
Dysarthria is an acquired motor speech disorder after a neurologic injury leading to muscle weakness or incoordination, resulting in impaired phonation, articulation, respiration, and resonance. Dysarthria can be caused by both upper and motor neuron injuries, which include stroke, traumatic brain injury (TBI), amyotrophic lateral sclerosis, Parkinson’s disease, and multiple sclerosis.
- •
Dysarthria can be categorized into types according to the area of deficit ( Table 32.2 ):
- •
Flaccid
- •
Spastic
- •
Ataxic
- •
Hypokinetic
- •
Hyperkinetic
- •
Mixed
TABLE 32.2Related posts:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
- •
