CODI 555 Motor Speech Disorders
Lecture 5: Cerebellar Disorders: Ataxic Dysarthria

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 Cerebellar Control Circuits

•  Receives sensory input form extensive areas of the body
•  Auditory feedback
•  Proprioceptive feedback from speech muscles, joints, etc.
•  Connections with IAP
•  Connections with basal ganglia control circuits
•  Pathways include
•  Projections from motor and motor cortex to pontine nuclei to cerebellum to thalamus and back to cortex
•  Fibers from descending corticobulbar and corticospinal tracts to cerebellum and then back to cortex by way of deep cerebellar nuclei and thalamus

 Functions of Cerebellar Control Circuits

•  Receives various input & organizes, modifies and sends information back to cortical structures
•  Planning and programing learned movements
•  Thought to be responsible for automatic nature of movements & performance of motor movements as a whole instead of individual parts
•  Allows CNS to make on-line adjustments

 Effects of Lesions to Cerebellar Circuits

•  Incoordination in contraction of muscles for smooth movements -ataxia
•  Hypotonia (variable)
•  Nystagmus
•  Intention tremor

 Ataxic Dysarthria:  Common Etiologies

•  Those affecting speech are usually bilateral & due to generalized cerebellar disease rather than a focal lesion
•  Vascular lesions - aneurysms, AVMs, hemorrhage in brainstem or midbrain
•  Tumors - acoustic neuromas
•  Trauma
•  Degenerative diseases - MS, Friedrich’s ataxia, OPCA
•  Toxic/metabolic diseases
•  Hypothyroidism & normal pressure hydrocephalus

 Ataxic Dysarthria: Neuromotor Deficits

•  Hypotonia and reduced resistance to passive movement
•  Broad-based gait & truncal instability
•  Intention tremors
•  Nystagmus
•  Dysmetria, dysrhythmia & dysdiadochokinesis - ataxia

 Ataxic Dysarthria: Nonspeech Oral Mechanism Deficits

•  Often normal with respect to structures at rest and in sustained postures
•  Nonspeech AMRs may be irregular though speech AMRs are more relevant to speech diagnosis
•  Direction of movements is inaccurate, rhythm is irregular, rate is slow, range is excessive to normal ; force is normal to excessive and tone is reduced

 Ataxic Dysarthria: Patient Perceptions & Complaints

•  “drunken” quality to speech
•  Rapid deterioration of speech with limited alcohol intake
•  Problems coordinating breathing and speaking
•  Bite cheek and tongue while talking
•  Do not report fatigue or increased effort or complaints with swallowing
•  Slowing down improves intelligibility greatly

 Ataxic Dysarthria: Deviant Speech characteristics

•  Hoarse-breathy, coarse voice, tremor,monopitch, monoloudness
•  Normal resonance
•  Intermittant articulatory breakdowns
•  Explosive syllable stress, loudness and pitch outbursts, abnormal prolongations of phonemes & intervals between sounds & words
•  Shallow inhalations, reduced exhalation control, rapid breaths, irregular and sudden-forced patterns
•  Ataxic Dysarthria

 Distinguishing Clusters

•  Articulatory inaccuracy - imprecise consonants, irregular articulatory breakdowns, distorted vowels
•  Prosodic excess - Excess & equal stress, prolonged phonemes, prolonged intervals, slow rate
•  Phonatory -prosodic insufficiency - Harshness, monopitch, monoloudness

 Ataxic Dysarthria: Most Distinctive Speech Deviations

•  Excess and equal stress
•  Phoneme and interval prolongation,
•  Dysrhythmia of speech and syllable repetition
•  Irregular articulatory breakdown
•  Distorted vowels
•  Excess loudness variations