Speech disorders

Speech

Anatomy & Physiology of Speech

Disorders of Speech

By Dr.Vitrag Shah

Dr.Vitrag Shah - www.medicalgeek.com

Communication Process

Communication symbols

Communication signals






Dominant Vs Non-Dominant Hemisphere

The concept of "cerebral dominance" and a dominant and nondominant hemisphere has been replaced by a concept of complementary specialization of the hemispheres, one for sequential-analytic processes (the categorical hemisphere) and one for visuospatial relations (the representational hemisphere).

The categorical hemisphere is concerned with language functions.


Speech & Hemispherical Dominance Hemispheric specialization is related to handedness. Handedness appears to be genetically determined. In 96% of

right-handed individuals, who constitute 91% of the human population, the left hemisphere is the dominant or categorical hemisphere, and in the remaining 4%, the right hemisphere is dominant. In approximately 15% of left-handed individuals, the right hemisphere is the categorical hemisphere and in 15%, there is no clear lateralization. However, in the remaining 70% of left-handers, the left hemisphere is the categorical hemisphere.

It is interesting that learning disabilities such as dyslexia , an impaired ability to learn to read, are 12 times as common in left-handers as they are in right-handers, possibly because some fundamental abnormality in the left hemisphere led to a switch in handedness early in development.

However, the spatial talents of left-handers may be well above average; a disproportionately large number of artists, musicians, and mathematicians are left-handed. For unknown reasons, left-handers have slightly but significantly shorter life spans than right-handers.


It is interesting that in individuals who learn a second language in adulthood, fMRI reveals that the portion of Broca's area concerned with it is adjacent to but separate from the area concerned with the native language.

However, in children who learn two languages early in life, only a single area is involved with both. It is well known, of course, that children acquire fluency in a second language more easily than adults.

The speech area of the adult cortex is larger on the left than on the right. It is believed that the two hemispheres of the newborn have equipotentialcapabilities. During childhood, one hemisphere slowly comes to dominate the other, and it is only after the first decade that the dominance becomes fixed. This would explain why a 5-year-old child with damage to the dominant hemisphere can easily learn to become left-handed and speak well, whereas in the adult this is almost impossible.


NEUROANATOMY The cerebral cortex of the human brain contains

approximately 20 billion neurons spread over an area of 2.5 m2.

Five anatomically defined large-scale networks are most relevant to clinical practice: (1) a perisylviannetwork for language, (2) a parietofrontal network for spatial cognition, (3) an occipitotemporalnetwork for face and object recognition, (4) a limbic network for retentive memory, and (5) a prefrontal network for cognitive and behavioral control.

The primary brain areas concerned with language are arrayed along and near the sylvian fissure (lateral cerebral sulcus) of the categorical hemisphere.




Broca’s Area or Brodmann areas 44 & 45

The motor speech area of Broca is located in the posterior inferior frontal gyrus (between the anterior and ascending rami and the ascending and posterior rami of the lateral fissure)(Brodmann areas 44 and 45).

The Broca speech area brings about the formation of words by its connections with the adjacent primary motor areas; the muscles of the larynx, mouth, tongue, soft palate, and the respiratory muscles are appropriately stimulated & controls the output of spoken language.

The sequencing function of Broca's area also appears to involve the ordering of words into sentences that contain a meaning-appropriate syntax (grammar).



Wernicke's area or Brodmann's area 22 The sensory speech area of Wernicke is localized in

the left dominant hemisphere, mainly in the superior temporal gyrus, with extensions around the posterior end of the lateral sulcus into the parietal region.

The Wernicke area is connected to the Broca area by a bundle of nerve fibers called the arcuatefasciculus.

It receives fibers from the visual cortex in the occipital lobe and the auditory cortex in the superior temporal gyrus.

The Wernicke area permits the understanding of the written and spoken language and enables a person to read a sentence, understand it, and say it out loud





Angular gyrus

The angular gyrus in the inferior parietal lobule is adjacent to visual receptive areas and subserves the perception of written language, as well as other language processing functions.

Destructive lesions in the angular gyrus in the posterior parietal lobe (often considered a part of the Wernicke area) divide the pathway between the visual association area and the anterior part of the Wernicke area. This results in the patient being unable to read (alexia) or write (agraphia).


Insula

The insula is an area of the cortex that is buried within the lateral sulcus and forms its floor.It can be examined only when the lips of the lateral sulcus are separated widely.

It is believed that this area is important for planning or coordinating the articulatorymovements necessary for speech.

Patients who have lesions involving the insula have difficulty in pronouncing phonemes in their proper order and usually produce sounds that are close to the target word but are not exactly correct.


Physiology of Speech & Language A region at the posterior end of the superior temporal gyrus

called Wernicke's area is concerned with comprehension of auditory and visual information. It projects via the arcuatefasciculus to Broca's area (area 44) in the frontal lobe immediately in front of the inferior end of the motor cortex.

Broca's area processes the information received from Wernicke's area into a detailed and coordinated pattern for vocalization and then projects the pattern via a speech articulation area in the insula to the motor cortex, which initiates the appropriate movements of the lips, tongue, and larynx to produce speech.

The probable sequence of events that occurs when a subject names a visual object is shown in Figure 19–8. The angular gyrus behind Wernicke's area appears to process information from words that are read in such a way that they can be converted into the auditory forms of the words in Wernicke'sarea.









Word deafness: Difficulty in understanding the meaning of words heard.Word blindness: Difficulty in understanding the meaning of words seen.Bradylalia: Slowness of speech e.g. in Hypothyroidism, Depression,

ParkinsonismEcholalia: Repetition of examiner’s words by patient.Palilalia: Repetition of terminal words of own speech.Paraphasia: Simple syllabic words are missing and replaced by

substitutions so that desired response is only approximated.

Literal : Incorrect letters (Grass is green) Verbal : Incorrect words (Grass is blue) Neologisms: Nonsense words (Grass is grumps)


Prerequisites before testing speech

Level of consciousness

Handedness

Mother language

Intelligence level

Deaf of not

Vision

Mutism is inability to speak while Aphonia is inability to produce sounds.


Aphasia



APHASIA

Nonfluent

Poor Repetition

PC

Global

GC

Broca

Good Repetition

PC

Mixed TC

GC

TC motor

Fluent

Poor Repetition

PC

Wernicke

GCConduction

Good Repetition

PC

TC Sensory

GC

Anomic

TC – TranscorticalPC – Poor comprehensionGC – Good comprehension

Algorithm for approach to Aphasia





When asked to name a common object (pencil or wristwatch), the patient may fail to come up with the appropriate word, may provide a circumlocutious description of the object ("the thing for writing"), or may come up with the wrong word (paraphasia).

If the patient offers an incorrect but related word ("pen" for "pencil"), the naming error is known as a semantic paraphasia; if the word approximates the correct answer but is phonetically inaccurate ("plentil" for "pencil"), it is known as a phonemic paraphasia.




Ony-way vs Two-way naming deficit

In most anomias, the patient cannot retrieve the appropriate name when shown an object but can point to the appropriate object when the name is provided by the examiner. This is known as a one-way (or retrieval-based) naming deficit. A two-way naming deficit exists if the patient can neither provide nor recognize the correct name, indicating the likely presence of a comprehension impairment for the word.





Broca's aphasia is not just an "expressive" or "motor" disorder and that it also may involve a comprehension deficit for function words and syntax.

Patients with Broca's aphasia can be tearful, easily frustrated, and profoundly depressed. 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'saphasia.

Additional neurologic deficits usually include right facial weakness, hemiparesis or hemiplegia, and a buccofacial apraxiacharacterized by an inability to carry out motor commands involving oropharyngeal and facial musculature (e.g., patients are unable to demonstrate how to blow out a match or suck through a straw). Visual fields are intact.

The cause is most often infarction of Broca's area and surrounding anterior perisylvian and insular cortex due to occlusion of the superior division of the middle cerebral artery

When the cause of Broca's aphasia is stroke, recovery of language function generally peaks within 2 to 6 months, after which time further progress is limited.


(Jargon Aphasia)


The patient does not seem to realize that his or her language is incomprehensible and may appear angry and impatient when the examiner fails to decipher the meaning of a severely paraphasic statement. In some patients this type of aphasia can be associated with severe agitation and paranoid behaviors.

One area of comprehension that may be preserved is the ability to follow commands aimed at axial musculature. The dissociation between the failure to understand simple questions ("What is your name?") in a patient who rapidly closes his or her eyes, sits up, or rolls over when asked to do so is characteristic of Wernicke's aphasia and helps differentiate it from deafness, psychiatric disease, or malingering.

An embolus to the inferior division of the middle cerebral artery, to the posterior temporal or angular branches in particular, is the most common etiology .

Some patients with Wernicke's aphasia due to intracerebral hemorrhage or head trauma may improve as the hemorrhage or the injury heals. In most other patients, prognosis for recovery of language function is guarded.



Reading aloud is impaired, but reading comprehension is preserved.

The lesion sites spare Broca's and Wernicke's areas but may induce a functional disconnection between the two so that neural word representations formed in Wernicke's area and adjacent regions cannot be conveyed to Broca'sarea for assembly into corresponding articulatory patterns.


Anomic aphasia is the single most common language disturbance seen in head trauma, metabolic encephalopathy, and Alzheimer's disease. Dr.Vitrag Shah - www.medicalgeek.com


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 or the supplementary motor cortex in the territory of the anterior cerebral artery.



Isolation Aphasia This rare syndrome represents a combination of the two

transcortical aphasias. Comprehension is severely impaired, and there is no purposeful speech output.

The patient may parrot fragments of heard conversations (echolalia), indicating that the neural mechanisms for repetition are at least partially intact.

This condition represents the pathologic function of the language network when it is isolated from other regions of the brain. Broca's and Wernicke's areas tend to be spared, but there is damage to the surrounding frontal, parietal, and temporal cortex.

Lesions are patchy and can be associated with anoxia, carbon monoxide poisoning, or complete watershed zone infarctions.


Pure Word Deafness The most common causes are either bilateral or

left-sided middle cerebral artery (MCA) strokes affecting the superior temporal gyrus.

The net effect of the underlying lesion is to interrupt the flow of information from the auditory association cortex to Wernicke's area.

Since auditory information cannot be conveyed to the language network, however, it cannot be decoded into neural word representations, and the patient reacts to speech as if it were in an alien tongue that cannot be deciphered.

Patients cannot repeat spoken language but have no difficulty naming objects. In time, patients with pure word deafness teach themselves lipreading and may appear to have improved.


Pure Alexia Without Agraphia

This is the visual equivalent of pure word deafness. The lesions interrupt the flow of visual input into the language network. There is usually a right hemianopia, but the core language network remains unaffected.

Patients with this syndrome also may lose the ability to name colors, although they can match colors. This is known as a coloranomia.

The most common etiology of pure alexia is a vascular lesion in the territory of the posterior cerebral artery or an infiltrating neoplasm in the left occipital cortex


Aphemia (Pure word mutism)

There is an acute onset of severely impaired fluency (often mutism), which cannot be accounted for by corticobulbar, cerebellar, or extrapyramidal dysfunction. Recovery is the rule and involves an intermediate stage of hoarse whispering.

Writing, reading, and comprehension are intact, and so this is not a true aphasic syndrome.


Aprosodia

Variations of melodic stress and intonation influence the meaning and impact of spoken language. For example, the two statements "He isclever." and "He is clever?" contain an identical word choice and syntax but convey vastly different messages because of differences in the intonation and stress with which the statements are uttered. This aspect of language is known as prosody.

Damage to perisylvian areas in the right hemisphere can interfere with speech prosody and can lead to syndromes of aprosodia.


Subcortical Aphasia

Damage to subcortical components of the language network (e.g., the striatum and thalamus of the left hemisphere) also can lead to aphasia.

In a patient with a CVA, an anomic aphasia accompanied by dysarthria or a fluent aphasia with hemiparesis should raise the suspicion of a subcortical lesion site.


Progressive Aphasias Aphasias caused by cerebrovascular accidents start suddenly

and display maximal deficits at the onset.These are the "classic" aphasias described above.

Aphasias caused by neurodegenerative diseases have an insidious onset and a relentless progression so that the symptomatology changes over time.

The single most common sign of primary progressive aphasia is an inability to come up with the right word during conversation and/or an inability to name objects shown by the examiner (anomia).

The impairments of syntax, comprehension, naming, or writing in PPA form slightly different patterns from those seen in CVA-caused aphasias.

Three subtypes of PPA can be recognized: an agrammaticvariant characterized by poor fluency and impaired grammar, a semantic variant characterized by preserved fluency and syntax but poor single word comprehension, and a logopenic variant characterized by preserved syntax and comprehension but frequent word-finding pauses during spontaneous speech.




Wernicke-Lichtheim Model



Case : Aphasia A 49-year-old man with hypertrophic cardiomyopathy

has three episodes of difficulty speaking over the course of a day. The episodes are brief, each lasting less than 30 seconds. He is fully aware of the events. He is able to understand what is being said to him at the time. The following day he loses consciousness and is taken to the local hospital, where he is found to have an irregular cardiac rhythm. He attempts to speak but is unable to produce any words or sounds. He is able to follow both written and verbal commands. Brain MRI reveals an acute infarct in the left inferior frontal lobe. The patient is diagnosed with Broca’s aphasia secondary to a stroke caused by a cardiac embolism. Over the course of several weeks, he gradually regains the ability to speak; however, his fluency and ability to repeat phrases spoken to him remain impaired.



Gerstmann's Syndrome

The combination of acalculia (impairment of simple arithmetic), dysgraphia (impaired writing), finger anomia (an inability to name individual fingers such as the index and thumb), and right-left confusion .

In making this diagnosis it is important to establish that the finger and left-right naming deficits are not part of a more generalized anomiaand that the patient is not otherwise aphasic.

When Gerstmann's syndrome is seen in isolation, it is commonly associated with damage to the inferior parietal lobule (especially the angular gyrus) in the left hemisphere.



DysarthriaCerebellar Dysarthria:

Patient speaks slowly and deliberately, syllable by syllable as if scanning a line of poetry and the normal prosodic rhythm is lost (Scanning speech).

When the speech has explosive character & slurring of consonants, it’s called Staccato speech.

Cortical Dysarthria:

Irregular hesitancy in word production associated with difficulty in abstract, volitional movements of the lips and tongue (Orofacialapraxia). Usually associated with aphasia.

Rigid Dysarthria:

Due to extra-pyramidal involvement – low volume, monotonous speech of parkinsonism.

Pseudobulbar (Spastic) Dysarthria:

Individual syllables are slurred and the precision of consonant pronounciation is lost.Due to leisons in corticospinal fibres supplying muscles of face, larynx, tongue & respiration. Difficulty in pronouncing b, p, t.

Bulbar (Flaccid) dysarthria:

LMN palsy affects the muscles of articulation. Non specific slurring of speech present.


Bibilography

Harrison’s principles of internal medicine 18th Edition

Bedsideclinics in medicine by Dr.Arupkumar kundu

Manual of Practical Medicine – B Alagappan

Bickerstaff's Neurological Examination in Clinical Practice

Slides by Dr.Aswini Kumar



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Date post:	07-May-2015
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Speech disorders

Health & Medicine