Disorders of Speech and Language : Dysarthria and Articulation disturbances

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Disturbed speech and language are important symptoms of the neurological disease. The two are not synonymous. Speech is the ability to clearly and verbally communicate messages or information to others. Whereas, language allows the communication of thoughts and experiences by linking them to arbitrary symbols known as words. Deep understanding of difference between speech and language disorders are essential as patients with language disorders are labelled confused as a consequence of superficial evaluation.

Speech production results from a sequence of oro-motor controlled muscular activities for voice production. It includes producing airflow out of lungs (exhaling), a vibration of the muscles of the voice box (vocal cords) and regulating the amount of resonating air allowed to escape through mouth or/and nose. The air escaping the mouth can be manipulated by the lips (labial control), teeth, tongue (lingual control), laryngeal and pharyngeal/palatal function).

Language is a function of the dominant cerebral hemisphere and may be divided into: a) emotional (the instinctive expression of the feelings representing the earliest forms of language acquired in the infancy and b) symbolic or prepositional (conveying thoughts, opinion and concepts, which are acquired over a period and is dependent upon culture, education and normal cerebral development. 

Components of Speech disorders :

A) Aphasia / Dysphasia : Dysphasia is an acquired loss of production or comprehension of spoken and/or written language secondary to brain damage. Aphasia should be diagnosed only when there are deficits in the formal aspect of language such as naming, word choice, comprehension, spelling and syntax. It includes :

• Receptive aphasia/ Wernicke's aphasia: affectation in Wernicke's area (temporal lobe). Patient is unable to follow commands.
• Conductive aphasia : affectation in Arcuate fasciculus, which connects two speech areas. Patient is unable to repeat.
• Expressive aphasia/ Broca's aphasia: affectations in Broca's area (frontal lobe). Patient has non-fluent speech.
• Nominal aphasia: affectation in the angular gyrus. Patient is unable to name objects.

B) Articulation/ Dysarthria : Dysarthria is a disturbance of articulation in which the content of speech (language) is unaffected. These speech disorders results from disturbances in muscular control of articulation weakness, slowness, or incoordination, due to damage to the central or peripheral nervous system or both. It includes :

• Cerebellar cause leading to ataxic dysarthria, scanning or staccato speech. The characteristic speech appears to be slow, slurred and explosive.
• Bulbar cause leading to flaccidity (lack of  normal muscle tone) of muscles controlling tongue movements. The characteristic speech appears to have nasal intonation.
• Pseudobulbar cause leading to spastic dysarthric speech. The characteristic speech appears to be slow, laborious, harsh voice.
• Extrapyramidal cause leading to hypokinetic or hyperkinetic dysarthric speech. 

C) Dysphonia : Sound is produced by the passage of air over the vocal cords. Respiratory disease or vocal cord paralysis results in a disturbances of this facility leading to dysphonia. A complete inability to produce sound is referred to aphonia. Dysarthria often co-exists.

In today's blog we will focus on different speech disorders due to dysarthria/ articulation disturbances and their diagnostic approach.

DYSARTHRIA / ARTICULATION DISTURBANCES :

Types of dysarthria :

1) Flaccid Dysarthria :

• Site of lesion is peripheral nervous system or lower motor neuron system (bulbar area impaired)
• Neuromuscular symptoms includes weakness, lack of normal muscle tone.
• Characteristic voice and speech appears: hypernasality, imprecise consonant production, breathing of voice, nasal emission.

2) Spastic Dysarthria :

• Site of lesion is pyramidal system (pseudobulbar impairments).
• Neuromuscular symptoms includes muscular weakness, increased muscle tone.
• Characteristic voice and speech appears: imprecise consonants, harsh voice quality, strained-strangled voice quality.

3) Ataxic Dysarthria :

• Site of lesion is cerebellum or its connections.
• Neuromuscular symptoms includes imbalance while walking and clumsiness of movements.
• Characteristic voice and speech appears: imprecise consonants, irregular articulatory breakdowns, intermittent explosive consonants, prolonged phonemes, prolonged intervals, slow rate.

4) Hypokinetic Dysarthria :

• Site of lesion is subcortical structures involving basal ganglia (extrapyramidal impairments).
• Neuromuscular symptoms includes slow movements, rigidity and tremors features.
• Characteristic voice and speech appears: articulatory mechanism impaired because of reduced range of motion involving the lips, tongue, and jaw. Disturbances may range from mildly imprecise, monotonous speech to total unintelligibility.

5) Hyperkinetic Dysarthria :

• Site of lesion is subcortical structures involving basal ganglia (extrapyramidal impairments).
• Neuromuscular symptoms includes quick, unsustained, involuntary movements, jerky or irregular movements and at times dystonic features with sustained contractions.
• Products of involuntary movements that interfere with speech. It gives impression that normal speech is being executed but interfered with abnormal involuntary movement that distort, slow or interrupt it. 
• It can be divided into :
• Hyperkinetic dysarthria of Chorea, myoclonus and tics shows quick involuntary movements.
• Hyperkinetic dysarthria of athetosis and dystonia shows slow involuntary movements.
• Gilles de la Tourette's syndrome (hyperkinetic dysarthria of tics) includes 
• Emission of grunts as a result is spontaneous contractions of the respiratory and phonatory muscles
• Barking noises
• Echolalia
• Coprolalia: Obscene language without provocation or reason.

Diagnostic approach for disorders of speech :

• Initiate  evaluation by listening to spontaneous speech and then ask the patient to read aloud.
• Observe for :
• Lingual consonants - 'ta ta ta' (made with tongue)
• Labial consonants - 'mm mm mm' (made with lips)
• Guttural consonants - 'ga ga ga' (laryngeal and pharyngeal/palatal)
• If any difficulty is observed with articulation then patient is having dysarthria.
• Spastic Dysarthria (cortical origin) : Speech hoarse and strained; labial consonants especially affected. Associated contralateral hemiparesis or dysphagia present. Causative disease e.g. middle cerebral artery occlusion, neoplasm.
• Spastic Dysarthria (corticalbulbar origin) : Other signs of pseudobulbar palsy (impaired chewing, swallowing) observed. Causative disease e.g. motor neuron diseases, bilateral small vessel occlusion.
• Ataxic Dysarthria (lesion in cerebellar vermis and paravermis) : Speech slow and monotonous with abnormal separation of syllables - 'scanning speech'; at times may sound explosive. Also associated signs of cerebellar disease present. Causative disease e.g. Multiple Sclerosis, Hereditary Ataxia.
• Flaccid Dysarthria (involvement of X and XII nuclei or emergent nerves to muscles of articulation) : Labial consonants first affected, later gutturals. Nasal speech and progression to total loss of articulation (anarthria). Associated signs of LMN weakness of X and XII nerve present. Causative disease e.g. Motor neuron disease, Bulbar poliomyelitis, Cranial polyneuritis.

• In Hypokinetic (slow) or hyperkinetic (fast) dysarthria the lesion is present in extrapyramidal system. Associated signs of extrapyramidal disease is observed.
• In Hypokinetic Dysarthria, the speech is slow and monotonous with poor volume and little inflection - and short rushes of speech. Example : Parkinson's disease, progressive supranuclear plasy.
• In Hyperkinetic dysarthria, the prosodic speech features might be excess (prolonged interval, excess and equal stress, variable rate of speech), insufficient (monopitch, monoloudness, reduced stress, inappropriate silence), imprecise consonants, phonation (harsh voice quality, voice stoppage, excess loudness variation, strained-strangled voice quality).

Thankyou for reading !!!

Dr. Ashwini Sangar, Dr.Sheetal Tatar-Dhande, Dr.Pallavi Khadse-Kolhe.