Speech Disorder

 

Speech disorder

PKGhatak, MD

Speech is defined as the ability to express thoughts and feelings by articulated sounds. Language is in the same domain as speech but not the same. Language is the medium of communication with said words and symbols. 

1. Speech disorder in children is primarily developmental and congenital, after that comes others.

2. Developmental delay presents as uncoordinated brain function manifest as Stuttering. 

3. The next group comprises Autism, dyslexia and cerebral palsy.

4. Birth defects such as tongue-tie, defects of the floor of the mouth, hare-lip and cleft palate and occiput occipito-facial abnormality. Many of them are surgically correctable.

 5. Apraxia and dysarthria are apparently similar defects but in apraxia, the brain fails to formulate a motor plan to supply nerve impulses to muscles of the larynx and vocal cords; in Dysarthria the muscles of the mouth and tongue fail to move properly due to mechanical and /or coordination abnormalities and fails to produce a normal speech.

 6. Congenital deafness or onset of early childhood deafness, leads to absent speech known as muteness. However, the mute babies did cry at the time of birth proving that absent speech in these babies comes from deafness.

Speech disorder in adults.

Speech problems in adults are always acquired after having normal speech for years.

There are three categories of this disorder - I. Transient and reversible. II. Secondary. III. Primary.

 I. Transient:

Alcohol intoxication is the most common cause of stuttering, fumbling for words and inappropriate answers. Opioid addiction and use of recreational drugs, tranquilizers, sleeping pills are additional causes.

II. Secondary:

Multiple sclerosis (MS) produces various neurological deficits including speech. One special feature of MS is the exacerbation and remission of symptoms. ALS, Ascending paralysis, Myasthenia gravis, and myopathy of various types. and diseases involving the larynx, vocal cords and paralysis of the recurrent laryngeal nerve are further examples of speech defects.

III. Primary:

The brain is the center for speech formation (ideation), generation of motor signals and transmission of information to muscles involved in the execution and articulation of spoken words. Any disruption of the flow of information to the effector organ/tissues will adversely affect speech. Some of the pathological causes are interruption of blood supply, pressure from space occupying lesions, inflammation and infection of the brain, and traumatic injury to speech centers.

Ideation:   One can easily recall teachers telling “engage your brain before you blurred out words”. That is the ideation – the speaker has instant knowledge of what he is going to say in a conversation or at the podium before a lecture. Ideation is the result of coordinated activities of many brain centers, including visual, auditory, and memory centers which are located in the different areas of the cerebral cortex.

Motor function:   Cerebral motor center is located in the Pyramidal cortex of the brain. The axons from pyramidal neurons make synaptic connections to the lower motor neuron of the motor nuclei of cranial nerves and anterior horn cells of the spinal cord. Nerve impulses are carried to the muscles of the larynx, vocal cords, throat, lips, mouth, tongue, diaphragm and respiratory muscles of the chest wall transmitted by the axons of the lower motor neurons.

Monitoring and modification of speech are active processes and require communication via synaptic relays between various brain centers.

Localization of lesion:

At an earlier time, every speech abnormality was documented by neurological examination and then verified by autopsy. The medical practice of that time required memorizing named syndromes to identify each speech defect. Now neuroimaging by functional MRI and CT, with and without contrast, have made the diagnosis more refined and accurate at the same time names attached to lesions are not required to be remembered.

Types of speech abnormalities in adults.

 1. Broca's Aphasia.

Broca's aphasia is both a language and word disorder due to damage to Broca's area of the brain. Broca's area is a special speech center located in the left frontal lobe of the cerebral cortex. It is situated in the depth of the main horizontal fissure dividing the cortex into frontal and middle lobes and partially covered by the tip of the left temporal lobe. Anatomically, it is located in the inferior frontal gyrus. Blood supply of the Broca's area comes from the branch of the middle cerebral artery. Interruption of the blood supply produces a language and speech disorder known as Broca's Aphasia.

In Broca's Aphasia, the patient retains the capacity of Ideation but loses languages due to partial loss of capacity to construct either the spoken or written language. Broca's aphasia has two components – Expressive aphasia and Receptive aphasia. In expressive aphasia, the patient is able to say important words but leaves out prepositions, pronouns and functional words. Speech becomes piecemeal, comes out in sprats and stops, says wrong words, missing the word orders. This type of speech is known as Telegraphic speech (at one time the telegram was the fastest mode of communication but expensive and the charges were based on the number of words to be transmitted. That leads to cutting out words). In Broca's aphasia, the patient is cognizant of his disability and becomes visibly frustrated in his attempt to find his speech back.

In Receptive aphasia, the patient is able to speak in grammatical sentences but lacks semantic significance and exhibits trouble in comprehension.

Thrombosis or emboli obstruction of the Left middle cerebral artery produces Right sided paralysis including the right lower half of the face and loss of sensation from the right side of the body and loss of right visual field and Broca's aphasia.

 2. Wernicke's area. Werneck's area is located in the parietal cortex next to the lateral sulcus at the junction of the parietal and occipital lobes. In this area, the visual and auditory words are comprehended and an area for selecting words and phrases to construct a meaningful sentence. Patients with damaged Wernicke's area, from alcoholism and other diseases, produce articulated sentences but many lack any meaning. And some patients may speak fluently and are not aware they are uttering meaningless words. Alcoholism may lead to Korsakoff psychosis. During an episode of Korsakoff psychosis, the speaks freely but confabulates and tells amazing stories.

3. Aphonia:

A lack of ability to produce any sound is known as aphonia. Direct injury to vocal cords, tracheostomy and bilateral recurrent laryngeal nerve damage can produce aphonia. And in addition, there are instances when a person is about to give an important talk and gets up to the podium and then is unable to make any sound. Some psychological or emotional neuronal activities overwhelm the natural order of speech making process.

4. Apraxia and Dysarthria are common in stroke and other lesions of the brain involving speech forming areas.

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