115 Chapter 10: Motor Speech Disorders

Dysarthia

A speech disorder resulting from weakness, paralysis, or incoordination of speech production muscles

Spastic Dysarthria

Damage to bilateral upper motor neuron (direct and indirect pathways)

Causes of spastic dysarthria

Stroke, traumatic brain injury, neurodegenerative diseases

Distinctive features of spastic dysarthria

Slow speaking rate, monopitch and monoloudness, short phrases, low pitch, and strained/strangled voice quality

Flaccid Dysarthria

Damage to lower motor neuron (cranial and/or spinal nerves)

Causes of flaccid dysarthria

Stroke, TBI, neurodegenerative diseases (Guillan-Barre, Myasthenia Gravis, Muscular Dystrophy)

Distinctive features of flaccid dysarthria

Hypernasality, nasal emission, short phrases, consistent breathiness, and audible inspiration

Unilateral UMN Dysarthria

Unilateral UMN lesion to the facial nerve (CN VII) which causes weakness and incoordination of face and tongue contralateral to lesion

Distinctive features of unilateral UMN dysarthria

Imprecise articulation and slow speech rate

Hypokinetic Dysarthria

Damage to basal ganglia control circuit (decreased direct pathway activation and increased indirect pathway activation)

Cause of hypokinetic dysarthria

Parkinson’s Disease

Distinctive features of hypokinetic dysarthria

Short rushes of speech, monopitch and monoloudness, inapropriate pausing, reduced loudness, and breathiness

Hyperkinetic Dysarthria

Damage to basal ganglia control circuit (decreased indirect pathway activation)

Cause of hyperkinetic dysarthria

Huntington’s Disease

Distinctive features of hyperkinetic dysarthria

Prolonged intervals between syllables/words with inappropriate silences, variable rate, prolonged phonemes, excess loudness variations, voice stoppages, and transient breathiness

Ataxic Dysarthria

Damage to the cerebellum control circuit

Causes of ataxic dysarthria

Stroke, TBI, neurodegenerative diseases

Distinctive features of ataxic dysarthria

Slurred/scanning speech, irregular articulatory breakdowns, distorted vowels, excess and equal stress, and prolonged phonemes

Mixed Dysarthria

Damage to unilateral motor neuron (direct and indirect pathways) and lower motor neuron

Example of mixed dysarthria

ALS (spastic-flaccid dysarthria)

Distinctive features of mixed dysarthria

Slow speaking rate (s), harsh, strained-strangled voice (s), monopitch and monoloudness (s), hypernasality (f), and short phrases (both)

Pediatric Dysarthria

Congenital or acquired; symptoms may change with age because speech is developing on an impaired system

Causes of pediatric dysarthria

CVA, TBI, developmental disorders (cerebral palsy, down syndrome, drowning, fever, seizure, poison, etc.)

Direct activation pathway (pyramidal tract)

One synapse between UMN and LMN

Indirect activation pathway (extrapyramidal tract)

Multiple synapses between UMN and LMN

Parts of basal ganglia

Direct and indirect activation pathways

Cerebellum

Aides in timing and force of movement

Direct activation pathway

Facilitates motor programs (starts movement)

Indirect activation pathway

Inhibits motor programs (stops movement)

Trigeminal (cranial nerve V)

Pain and touch sensation of the face and anterior 2/3rd tongue; motor to muscles of mastication

Which cranial nerves are both motor and sensory?

Trigeminal (v), facial (vii), glossopharyngeal (ix), and vagus (x)

Facial (cranial nerve VII)

Motor to muscles of facial expression; taste in anterior 2/3rd tongue

Glossopharyngeal (cranial nerve IX)

Sensation from palate, posterior 1/3rd tongue, oral pharynx; taste posterior 1/3rd tongue; motor to stylopharyngeus muscle

Vagus (cranial nerve X)

Sensation from pharynx, larynx; taste from epiglottis and pharynx; motor to larynx, pharynx, soft palate

Spinal Accessory (cranial nerve XI)

Motor to strap muscles of the neck

Hypoglossal

Motor to tongue

Which cranial nerves are just motor?

Spinal accessory (xi) and hypoglossal

Apraxia

A speech disorder which results from an impairment in motor programming for speech

Causes of apraxia

May be comorbid with aphasia, can also result from degenerative disease, TBI, anoxia, and tumors

Characteristics of apraxia

Errors tend to be inconsistent to target, increase with complexity and on infrequent sounds, increased errors in the word initial position/difficulty initiating speech, and reduced speaking rate and distorted prosody

Childhood Apraxia of Speech

Deficit in planning and programming speech movements; may occur with language and/or phonological impairments

Characteristics of CAS

Distorted vowels and consonants, inconsistent voicing errors, inconsistent prosody with pausing and stress errors, and articulatory groping