Voice Resonance Week 5: Neurogenic Voice Disorders

What are neurogenic voice disorders?

Voice impairments caused by a lesion in the brain (CNS or PNS)

What is an upper motor neuron?

Comes from area 4 and takes the message to the neuron that is going to communicate with the muscle

Tracts of a UMN

Corticospinal and corticobulbar

UMN Lesions

Involve a broader range of muscles/areas

What is a lower motor neuron?

Comes from their various nuclei

Types of LMN

• CN with a motor component (LMN for the larynx is the Vagus)

• Spinal nerves (ALL since they have both motor and sensory components)

LMN Lesions

More specific

What is the larynx innervated by? 

Vagus nerve (CN 10) 

What are the 3 branches of the vagus nerve that are important for speech production?

• Superior Laryngeal Nerve (SLN)

• Recurrent Laryngeal Nerve (RLN)

• Pharyngeal Nerve 

Superior Laryngeal Nerve

• Internal Branch: sensory info from the larynx

• External Branch: motor innervation to the cricothyroid

Recurrent Laryngeal Nerve

Motor innervation to all other intrinsic laryngeal nerves (LCA, PCA, TA, IA) except the cricothyroid

What are most neurogenic voice disorders caused by? 

Impairments in the descending motor pathways

What are the 7 types of dysarthria?

Depends on where the lesion is!

• Spastic

• Flaccid

• Ataxic

• Hypokinetic

• Hyperkinetic

• Unilateral UMN

• Mixed

What is spastic dysarthria caused by?

Bilateral UMN lesions

What are the symptoms of spastic dysarthria?

• Spasticity of the muscles (increased muscle tone, stiffness, imprecise articulation) 

• Harsh/strangled voice quality 

What is flaccid dysarthria caused by?

Unilateral or bilateral LMN lesions (any lesions of the vagus nerve will cause flaccidity)

What are the symptoms of flaccid dysarthria?

Hypernasality and breathy voice quality; atrophy

What is ataxic dysarthria caused by?

Lesion on the cerebellum

What are the symptoms of ataxic dysarthria?

• Balance/coordination issues 

• Speech: irregular rhythm, long pauses, abnormal prolongation of sounds 

Why does ataxia cause incoordination?

The brain is not getting enough feedback or feedforward (preparatory instructions before an activity is performed) 

What is hypokinetic dysarthria caused by?

Lesion on the basal ganglia or substantia nigra, which secretes dopamine and sends input to the BG; Parkinson’s is the only known cause

What are the symptoms of hypokinetic dysarthria (Parkinson’s)?

• Rigid/spastic movements

• Rest tremor 

• Slow speech rate 

• Harsh voice 

What is hyperkinetic dysarthria caused by?

Primary problem is in the extrapyramidal system (UMN), but there are many causes; Huntington’s Disease

What are the symptoms of hyperkinetic dysarthria?

More movement than desired and tremors

Unilateral UMN Dysarthria

One half of the lower half of the face is impacted; does not impact voice

Mixed Dysarthria 

Combination of one or more types of dysarthria; ALS, Multiple Sclerosis

What are the different types of vocal fold paralysis?

• Adductor (bilateral or unilateral)

• Abductor (bilateral or unilateral)

What causes adductor paralysis? 

Lesion to the RLN (IA, LCA, TA)

Unilateral Adductor Paralysis

Severity is not as bad as bilateral because the other VF can compensate for the impaired one

Bilateral Adductor Paralysis

Both VF are open, meaning there is no sub-glottal pressure and no mucosal wave

What issues can bilateral adductor paralysis cause? 

Greater risk of aspiration from swallowing because the VF can not act as an extra layer of airway protection; a cough also can not be generated with poor sub-glottal pressure 

What causes abductor paralysis?

Lesion to the RLN (PCA)

Unilateral Abductor Paralysis 

Quality of voice is raspy since the mucosal wave is messed up and pitch is impacted; breathing is difficult 

Bilateral Abductor Paralysis

Voice can not really be produced (aphonia); breathing is the main concern

What is dystonia?

A movement disorder characterized by sustained or intermittent muscle contractions causing abnormal and repetitive movements

What is focal dystonia?

A sub-classification of dystonia where only 1 body region is affected

What is spasmodic dysphonia? 

A focal dystonia that affects all intrinsic laryngeal musculature; a type of hyperkinetic dysarthria that affects voice 

What is the treatment for SD?

Does not respond to voice therapy; botox is effective because it paralyzes the VF

What are the types of SD?

• Adductor (ADSD)

• Abductor (ABSD)

• Mixed

What is ADSD?

Most prevalent form of SD; intermittent voice breaks and effortful phonation caused by intermittent hyperadduction of VF (muscles are spasming while VF are adducting)

Impacts/symptoms of ADSD

• Strained/strangled voice quality 

• Vowel production 

• Speech related movements 

How do you determine ADSD?

Must get a speech sample, primarily vowels to see the spasms

What is ABSD?

Muscle spasming when VF are abducting; VF have prolonged involuntary opening

What happens when the VF can not close?

Excessive air is lost and many patients complain of shortness of breath

Impacts of ABSD

Voiceless consonants (breathy breaks during sustained consonant production)

How do you determine ABSD?

Have the patient read voiceless consonant sentences to the muscles spasming

What are the different types of evaluation for SD?

Laryngoscopy and auditory-perceptual evaluation