Motor Speech Disorders - Other Disorders

Acquired Neurogenic Mutism

Mutism is the absence of speech, which can be deliberate or reflect psychiatric disturbances.
Neurogenic mutism can stem from dysarthria, apraxia of speech, aphasia, or non-aphasic cognitive and affective conditions.
It can occur post-seizures or after surgical sectioning of the corpus callosum.
Distinguishing between the forms of mutism aids in differential diagnosis, localization, and treatment.

Motor Speech Disorders and Anarthria

Anarthria is speechlessness resulting from severe loss of neuromuscular control over the speech system, referring to dysarthria in its most severe form.
Language and cognitive abilities may remain intact.
It's difficult to determine the type of dysarthria unless seen earlier in the disease process.
Often, it represents the end stage of dysarthria in neurodegenerative conditions.

Neurological Substrates and Etiologies of Anarthria

Bilateral lower motor neuron (LMN) involvement of speech and respiratory cranial nerves.
Bilateral damage to direct/indirect activation pathways.
Bilateral control circuit pathology
Etiologies include: ALS, other neurodegenerative diseases, brainstem strokes, multiple bilateral strokes, demyelinating disease, closed head injuries, severe/end-stage Parkinson's disease, Wilson's disease, Alzheimer's disease, encephalopathy, and cerebral palsy (CP).

Dysarthrias Leading to Anarthria

Flaccid dysarthria alone seldom leads to anarthria because it's unusual for multiple cranial nerves to be involved bilaterally.
However, flaccid dysarthria caused by Myasthenia Gravis (MG), Guillain-Barré syndrome, and brainstem tumors affecting many cranial nerves can result in mutism.
Ataxic and hyperkinetic dysarthrias rarely result in mutism.
Spastic and hypokinetic dysarthrias can result in anarthria, with spastic dysarthria being more causative.
Mixed dysarthrias account for more cases than any single form, often being the end-stage of dysarthria in various neurodegenerative diseases.
Table 12.1 in Duffy (2020) provides a summary of neuro substrates and distinguishing clinical features.

Locked-In Syndrome (LIS)

Characterized by anarthria plus quadriplegia, total body immobility except for vertical eye movements and/or eye blinking.
Patients are conscious with sufficient cognition to communicate via eye movements.
An "incomplete" syndrome may present with horizontal gaze or facial movement.
Ventilatory support and suctioning of secretions are often required, potentially necessitating a tracheotomy.
Typically, voluntary movement of the jaw, face, tongue, velopharynx, or vocal folds is impossible, leading to severe dysphagia.
Pulmonary complications are the most common cause of death.

Neurological Substrates and Etiologies of Locked-In Syndrome

Brainstem stroke carries a high risk of death in the initial days to months, with variable but usually limited recovery.
Other causes include trauma, tumor, infection, multiple sclerosis (MS), and drug toxicity or abuse.

Anarthria Associated with Locked-In Syndrome

Severe spastic or mixed spastic-flaccid dysarthria.
Voluntary movement of jaw, face, tongue, velopharynx, or vocal folds is typically impossible.
Dysphagia is severe.
Stereotyped chewing, sucking, or facial grimacing may be elicited with noxious or perioral stimuli.
Incomplete LIS can present with limited movement of structures.

Associated Symptoms with Locked-In Syndrome

Cognitive deficits early post-onset.
Edema.
Near-complete loss of volitional motor functions or sensation, perception, and cognition if additional lesions are present.
Cognition can be relatively intact if lesions are confined to the brainstem.
Speech improves later than limb movement with dramatic improvement over several years.

Biopercular Syndrome

A rare disorder associated with varying degrees of dysarthria, including mutism; also known as Foix-Chavany-Marie syndrome or anterior opercular syndrome or flaccid facial diplegia.
Severely reduced voluntary orofacial mobility, hypotonic face, jaw, tongue, and palate weakness bilaterally.
The upper face is often affected, impairing the ability to voluntarily close the eyes or frown.
Reflexive cough, yawn, and automatic/emotional facial and jaw movements (laughing and crying) are preserved.
Severe oral phase dysphagia, with the pharyngeal phase potentially remaining normal.
Absent gag reflex.
Gastrostomy is often needed due to high risk of aspiration pneumonia.

Neurologic Substrates and Etiologies of Biopercular Syndrome

Bilateral damage to the rolandic operculum - lower part of the precentral and postcentral gyri of the cerebral hemispheres.
Typically follows a unilateral stroke, succeeded by a second one.
Some cases develop with a unilateral stroke, but experts believe a second lesion or more diffuse process is involved.
Acute onset of anarthria with preserved spoken and written language comprehension and writing, and in the absence of limb weakness indicates anterior opercular strokes.
Trauma, tumors, and infectious diseases are also possible causes, as well as a variant of primary lateral sclerosis, PPA/PPAOS.
Congenital etiology is also possible.

Anarthria/Dysarthria of Biopercular Syndrome

Dysarthria resembles spastic dysarthria.
BUT: absence of confirmatory signs of pseudobulbar affect, hyperactive gag reflex, and pathological oral reflexes, with preserved emotional laughter and crying (atypical for spastic dysarthria).
Conclusion: Underlying dysarthria type is unclear, most likely spastic, in which AOS/NVOA may also be present.
Recognition of the syndrome assists in identifying the site of the lesion.
Poor prognosis for recovery of speech if vascular etiology.

Cerebellar Mutism

Occurs primarily in children, most often after posterior fossa surgery involving tumors in the 4th ventricle, cerebellar vermis or perivermal areas, either or both cerebellar hemispheres, and/or pons.
Onset is often delayed post-op.
Mutism is nearly always transient.
No clear anatomic or physiologic basis is understood.
Incidence is 11% to 39% due to individual variations of tumors/location/etc.
Uncommon in adults.

Neurologic Substrates and Etiologies of Cerebellar Mutism

No single explanation exists, but may involve
- Damage to the cerebellum and other posterior fossa structures.
- Remote effects on cortical functioning.
- Loss of function of cortical areas through remote metabolic effects or diaschesis (loss of function in an area of the brain connected to a damaged area).

Associated Symptoms of Cerebellar Mutism

Preoperative dysarthria in some cases.
Mutism occurs 1-7 days post-op, lasting on average 4-8 weeks, but can persist for up to 12 months.
Cranial nerve deficits are not usually apparent.
Poor oral intake, emotional lability, apathy, irritability, impulsivity, decreased initiation of voluntary movements, and difficulty performing complex, non-speech oromotor movements have occurred.
Ataxic dysarthria usually develops as anarthria improves and may last 1-12 years post-onset.
Persisting associated language and cognitive deficits can occur.

Clinical Manifestations of Anarthria with Traumatic Midbrain Injuries

Typically mute for days to months after regaining consciousness.
Mobility of the jaw, lips, and tongue severely limited.
Speech reemerges slowly, often initially breathy-whispered or with high-pitched dysphonia.
Poor articulation and respiratory control.
Often described as mixed spastic-hypokinetic dysarthria.

Apraxia of Speech (AOS) and Mutism

Mutism is not unusual with the onset of AOS but seldom lasts longer than a few days if caused by a stroke.
It can last long past the acute phase, even without aphasia or dysarthria.
Patients tend to have associated nonverbal oral apraxia (NVOA).
Some are unable to phonate or whisper, but some can produce lip movements without voicing, implying apraxia of phonation.
Traumatic Brain Injury (TBI) patients (3%) can evidence mutism, linked to left basal ganglia lesions.
It is crucial to ascertain the presence/extent of dysarthria, as mutism may be due to severe dysarthria/anarthria.
Can occur with degenerative neurologic disease due to AOS alone or combined effects of AOS, dysarthria, language, and/or cognitive deficits.

Aphasia and Mutism

Mutism after stroke/trauma-induced aphasia isn't unusual, but persistent mutism is uncommon, even with severe aphasia.
Mutism with subcortical lesions leading to aphasia may be more common than with cortical lesions, possibly caused by exacerbations of/results of AOS and/or dysarthria.
Lesions of the left superior premotor area can cause muteness, evolving to transcortical motor aphasia (limited speech, but repetition, naming, and oral reading are relatively more preserved).
Evolution: may mouth or whisper words without phonation, flat prosody, and flat affect secondary to frontal lobe deficit.
Non-aphasic cognitive issues may explain mutism more than aphasia.

Disorders of Arousal, Responsiveness, and Diffuse Cortical Functions and Mutism

Coma results from diffuse bilateral cerebral hemisphere damage, brainstem injury, or both, leading to unresponsiveness.
Vegetative state: a condition of wakeful unawareness after coma from TBI, with severe, bilateral cerebral hemisphere pathology and relative preservation of brainstem function.
Minimally Conscious State: a degree of awareness and responsiveness where the patient can track visually, reach for objects, follow simple commands, and respond YES/NO, and may have occasional intelligible words.

Akinetic Mutism (AM)

Abulia, or diminished motivation, is linked to pathology in anterior or mesial portions of the frontal lobes.
Characterized by a lack of initiative or spontaneity of thought, speech, physical action, and affective expression, appearing apathetic when mild, progressing to mutism when severe.
"Akinetic mutism" is the term for extreme abulia.
Apparent reluctance to perform simple motor activities despite preserved arousal/alertness, basic motor and sensory abilities, visual tracking ability, and basic cognitive abilities.
Lesions: mesial surface of one or both frontal lobes, including the supplementary motor area (SMA) and anterior cingulate gyrus, and potentially the basal ganglia and thalamus; massive bifrontal lobe damage, or brain stem damage affecting the reticular activating system (RAS), which influences alertness.

Characteristics of Muteness in Akinetic Mutism

Associated with an apparent reluctance to perform even simple motor activities despite preserved arousal, alertness, basic motor and sensory abilities, visual tracking ability, and at least some basic cognitive abilities.
Patients sit with eyes open, appearing alert and about to respond, but they are unresponsive and apathetic.
They don't react to movement, although they may follow movement.
May exhibit vegetative jaw and facial movements and may swallow food after it is placed in their mouth, often only after a significant delay.
Gradations of severity are possible as they recover from trauma, potentially beginning with brief aphonia or whispers.
Responses may be incomplete, e.g., when asked "Can you tell me the time?" they may only answer "yes".

Etiology-Specific Neurogenic Mutism

Speech arrest following partial seizures (ictal speech arrest).
Drug-induced mutism after immunosuppressive agents are used for liver and heart transplantation or cancer treatment, which can be improved or reversed if identified quickly and the dose is decreased or stopped.
Mutism after Corpus Callosotomy (to reduce seizures) is uncommon and rarely persists for more than several weeks; comprehension and writing can be spared during the mute period, and recovery can involve whispering, hoarseness, and NVOA.

Neurogenic Speech Deficits Table

Neurogenic Stuttering
- Anatomic Locus: Bilateral, Multifocal, diffuse / Left hemisphere / Basal Ganglia / Multiple lesion sites (right hemisphere, SMA, thalamus, midbrain, pons, cerebellum)
- Possible Nature of Deficit: Aphasia, AOS / Hypokinetic dysarthria/ Various dysarthria types / Dysequilibrium of a bilaterally innervated system
Palilalia
- Anatomic Locus: Basal ganglia, frontal lobes
- Possible Nature of Deficit: Damaged inhibitory motor circuits / Hypokinetic dysarthria
Echolalia
- Anatomic Locus: Left hemisphere, diffuse, multifocal, ?basal ganglia control circuit (Pick's disease, dementia, progressive ndd, tumor, trauma, etc.)
- Possible Nature of Deficit: Preserved input/output with lowered threshold for responding to external Stim; poor propositional language
Attenuated speech/hypophonia
- Anatomic Locus: Frontal lobe; limbic; thalamic; Basal ganglia
- Possible Nature of Deficit: Cognitive-affective / Hypokinetic dysarthria
Disinhibited vocalization
- Anatomic Locus: Diffuse, multifocal, basal ganglia
- Possible Nature of Deficit: Cognitive-affective, hyperkinesia (Tourette's)

Right Hemisphere Aprosodia

Deficit in the interpretation or production of distinctions in the frequency, duration, or amplitude variations in speech that convey emotional tone, emphasis, and certain linguistic information.
Etiology: Stroke, etc.
Possible issues: ?Dysarthria / ?Motor planning/programming / ?Cognitive-affective / ?other

Functional Speech Disorders (FSDs)

Can be difficult to distinguish from motor speech disorders (MSD) and can co-occur.
Specific speech characteristics can include depression, manic-depression, and schizophrenia.
Can manifest in changes in voice, fluency, or prosody (Voice > stuttering > articulation and prosodic deficits > infantile speech > mutism).
Can raise questions about neurologic disease, requiring careful history and diagnosis.
Symptomatic treatment sometimes results in rapid and dramatic improvement, suggesting a functional diagnosis; however, the absence of an immediate response doesn't rule out a functional etiology.
FSDs can co-occur with neurologic disease, so it is important to tease out and differentially diagnose MSD vs. FSD to contribute to an accurate medical diagnosis.

Distinguishing FSDs from Neurogenic Speech Disorders

Histories of those with FSDs vs. neurogenic speech disorders are helpful in distinguishing each.
History differences include non-neurologic illness or non-neurologic physical trauma at onset.
Prior history of unexplained speech or other physical deficits.
Ongoing psychological stress/conflict unrelated to speech or physical symptoms.
Evidence of primary or secondary gain.
Denial of the possibility that psychological factors may play a role.
Unexplained fluctuations in the presence and severity of symptoms or fluctuations as a function of situational emotional content.

Speech Characteristics of FSDs

Characteristics don't fit known patterns of neurogenic speech disorders.
Inconsistencies between speech and oral mech findings.
Variability in severity or specific speech characteristics as a function of task or emotional content.
Improvement or worsening of symptoms as a function of clinician suggestion.
Improved speech when distracted.
The pattern of speech fatigue is inconsistent with common patterns of speech changes with physical fatigue.
Significant, sometimes rapid improvement in speech with symptomatic therapy.

Torus Palatinus/Tori Palatini

Harmless and painless bony growth located on the hard palate.
Appears in the middle of the hard palate and can vary in size and shape.
Present in 20-30% of the population; occurs often in women, primarily of Asian descent.
Shape can be flat, nodular, spindle-shaped, or like a cluster of growths—like the brain.
Slow-growing, typically beginning in puberty and possibly not noticeable until middle age.
May shrink due to the body's natural resorption of bone as we age.
Generally not cancerous; cancerous growths more often occur in soft tissue.