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Neurologic process of speech production involves (3):

1. Cognitive-Linguistic Process (Aphasia)
2. Motor Speech Programming (apraxia)
3. Neuromuscular Execution (dysarthria)


Cognitive-Linguistic Process –

the aspect of speech production involving an intention to communicate which is organized into the verbal symbols that follow the rules of language. (Aphasia)


Motor Speech Programming –

the intended communication has to be executed by the neuromuscular system. To do this the speaker selects and organizes the sensorimotor programs that cause the appropriate speech muscles to be activated at the right time. This is the speech programming process. (apraxia)


Neuromuscular Execution –

The CNS and PNS innervate the necessary muscles of respiration, phonation, articulation and resonance to produce desired words. (dysarthria)


Motor Speech Disorders:

Disorders of speech resulting from neurologic impairment affecting the motor programming or neuromuscular execution of speech (2):
-apraxia of speech
-the dysarthrias


Types of Motor Speech Disorders (2)

Dysarthria & Apraxia



Collective name for group of motor speech disorders resulting from disturbances in muscular control over the speech mechanism due to damage of the CNS or PNS.

Can result in paralysis, weakness, or incoordination of speech musculature.


Dysarthria can affect which speech subsystems (5)?

All speech subsystems:
1. Respiration
2. Phonation
3. Resonance
4. Articulation
5. Prosody


Site of lesion for Dysarthria:



Types of Dysarthria – developed by Darley, Aronson & Brown (6)

1. Flaccid
2. Spastic
3. Ataxic
4. Hypokinetic
5. Hyperkinetic
6. Mixed



Neurogenic speech disorder resulting from impairment of the capacity to program sensorimotor commands for the positioning and movement of muscles for volitional production of speech.

Occurs in the absence of weakness.


Can apraxia and dysarthria co-occur with aphasia?

Yes, both apraxia and dysarthria can co-occur with aphasia

BUT apraxia more commonly co-occurs with aphasia


Apraxia of speech can affect which subsystems of speech (2)?

1. Articulation – may be inconsistent errors (?), difficulty with initiating speech

2. Prosody – due to starting and stopping in self-correcting


Does the course of motor speech disorders depends on etiology?



Course of disease for motor speech disorders (5):

1. Transient – symptoms don’t last, they disappear completely

2. Improving – things are improving but some symptoms are still there – just not as severe.

3. Progressive – symptoms don’t get better, they continue to get worse or new symptoms appear.

4. Exacerbating-remitting – symptoms occur, then get better, then occur again; gets worse, then better, etc.

5. Stationary – symptoms remain unchanged after they have reached maximum severity.


Treatment of motor speech disorders...

varies depending on type of dysarthria

i.e. for progressive course goals will be different than for developmental or transient


How do symptoms develop for motor speech disorders?(3 types)

1. Acute – comes on quickly within minutes
2. Subacute – comes on within days
3. Chronic – comes on within months


Most motor speech disorders are associated with...

chronic disorders


The Central Nervous System includes:

1. Brain
-Brain stem
2. Spinal cord
*areas encased by bone


4 Lobes of the cerebrum:

Frontal lobe
Parietal lobe
Temporal lobe
Occipital lobe


The cerebrum is made up of:

Cortex – outer layer (bark)
Gyri – ridges
Sulci - valleys


The Cerebellum's job:

Modifing cortical activity


The 3 lobes of the cerebellum are:

1. anterior
2. posterior
3. flocculonodular

-Has 2 hemispheres, right and left
-Vermis – midportion


3 Parts of the brain stem:

Midbrain – links cerebrum to brain stem page 41
Pons – bridges to cerebellum
Medulla – controls respiration


Midbrain (place):

links cerebrum to brain stem


Pons (place):

bridges to cerebellum


Medulla (function):

controls respiration


Are the bones of the skull separated or fused?

Fused -protective device- also hampers at times when expansion needed


4 anatomic levels of the CNS:

1. Supratentorial
2. Posterior
3. Spinal
4. Peripheral


Supratentorial level of the CNS:

Made up of anterior & middle fossae

Contains the paired frontal, temporal, parietal & occipital lobes AND basal ganglia, thalamus, hypothalamus & cranial nerves I & II


Posterior level of the CNS:

Made up of posterior fossa

Contains brainstem, cerebellum & cranial nerves III-XII.


Fossae –

3 cavities in base of skull

Fossa – ditch



Holes in fossae where cranial nerves exit skull


Where do cranial nerves II-XII originate?

In brain stem at the posterior fossa level


Where do cranial nerves I + II originate?

In the supratentorial level
Cranial nerves important for speech originate at this level, but are part of the PNS.


Are cranial nerves part of the CNS or the PNS?


but, they originate at the supratentorial (I + II) or Posterior level (III-XII) of the CNS


Spinal level of the CNS:

Spinal cord begins at lower end of medulla, surrounded by bony vertebral column

Spinal cord ends at first lumbar vertebrae.


Peripheral level of the CNS:

12 pairs of cranial nerves
31 pairs of spinal nerves
exit skull through foramina.


Why is it important for speech to have pairs (left + right) of cranial nerves?



Where do cranial nerves emerge from?

base of brain (brainstem) and penetrate skull through foramina to reach sensory - motor targets


Meninges (covering of the CNS) consist of 3 layers:

1. Dura mater-outer membrane -2 layers fused together
2. Arachnoid mater - below dura, loosely covers brain
3. Pia mater-innermost layer, closely attached to surface of brain


Spaces around the meninges (3):

1. Epidural space-between dura and bone

2. Subdural space-beneath dura (infection can develop in these 2 spaces due to trauma, blood & pus pool here)

3. Subarachnoid space-beneath arachnoid –filled with CSF, connected to inner part of brain via ventricular system


Neurologic Systems (6):

1. Ventricular
2. Vascular
3. Neurochemical systems
4. Consciousness system
5. Motor system
6. Sensory system


Ventricular Neurologic System:

Also called Cerebrospinal system

Ventricles are cavities filled with CSF (cushions brain) produced by choroid plexuses (structures in each ventricle)

Consist mainly of - paired lateral ventricles in each hemisphere, third ventricle between the 2 thalami & 4th ventricle


Vascular Neurologic System:

Involves blood vessels-provides oxygen and nutrients to structures & removes waste.

Brain receives blood from 2 arterial systems, carotid and vertebral basilar system These join at Circle of Willis at base of brain. Vascular disturbances can cause motor speech disorders


Neurochemical systems:

Influences all anatomic levels of nervous system.

Includes amino acids, ACH, neuropeptides, etc.


Consciousness system:

Important for maintaining consciousness, attention & awareness of environment.

Structures involved in this level include those found at supratentorial & posterior fossae level.

Damage can result in motor speech disorders.


Motor system:

Responsible for all motor activity including that of speech.

Includes efferent connection to cortex, basal ganglia, cerebellum, CNS/PNS pathways.

Damage here can cause motor speech disorders.


Sensory system:

Includes peripheral receptor organs


Structural elements of Neurons

1. Dendrites
2. Axons
3. Cell body (soma)



Transmit sensory information toward the soma



Transmit information away from the soma

Axons end in synapses which release neurotransmitters

Axons = collection of many nerve fibers


Most important neurotranmitter for muscles contraction?

Release of AcH results in contraction of muscle fiber



Groups of fibers traveling together in PNS


Where are cell bodies located?

Cell bodies stay in CNS


Where do nerves travel?

Between cell bodies and peripheral end organ to be innervated


In CNS, groups of fibers are called:

pathways or tracts


Where are impulses carried to in the CNS?

pathways/tracts carry impulses to other neurons


Where are impulses carried to in the PNS?

impulse is carried to the end organs


Motor Unit:

Made up of the axon and the muscle fiber it innervates


Supporting (Glial) Cells (3):

1. Oligdendroglia cells-form myelin in CNS
2. Schwann cells – form myelin in PNS. (between myelin in both are spaces called Nodes of Ranvier.)
3. Astrocytes- found in CNS –help move substances between blood and neurons of CNS – part of blood-brain barrier that keeps toxins from brain.


Oligdendroglia cells (type of glial cell):

form myelin in CNS


Schwann cells (type of glial cell):

form myelin in PNS


Spaces between myelin in CNS and PNS:

Nodes of Ranvier


Astrocytes (type of glial cell):

found in CNS

help move substances between blood and neurons of CNS – part of blood-brain barrier that keeps toxins from brain


How can a neuron be damaged?

lack of oxygen (ischemia) caused by disruption in blood supply


When axons are separated from cell body it causes...

motor speech problems


If lower motor neuron innervation to muscle is lost...

muscle will atrophy


What are some pathological reactions to neurons, axons, myelin, and lower motor neurons (5)?

1. Neuron can be damaged due to lack of oxygen (ischemia) caused by disruption in blood supply.

2. Axons may be separated from cell body resulting in motor speech problems.
3. If lower motor neuron innervation to muscle is lost – muscle will atrophy.

4. Myelin can shrink due to injuries

5. Certain diseases attack myelin, i.e. multiple sclerosis & Guillain Barre dz. Causes demyelination



Paired structures deep inside brain

Acts as relay station

Helps to mediate speech, language & cognitive function

Also integral part of motor control system


Basal Ganglia:

Located deep inside cerebrum

Consists of # of related structures

Important part of motor speech system


Parts of the Basal Ganglia:

* Globus Pallidus
* Striatum
-Caudate Nucleus
* Lentiform nucleus – composed of globus pallidus & putamen


Substantia Nigra & Subthalamic Nuclei:

Important in motor control & work with basal ganglia.

Similar in structure & function to basal ganglia. (Sometimes substantia nigra may be considered part of basal ganglia.)

Located primarily in midbrain

Important in motor control – works with basal ganglia.


Reticular formation:

Part of brain stem

Important in motor control


Localization of Neurological Lesions:

Damage can be:

1. Focal – found in single area.

2. Multifocal – found in more than one area.

3. Diffuse – involve bilateral symmetric parts of nervous system, such as dementia, where there is generalized cerebral atrophy


Etiologies capable of producing Motor Speech Disorders (6):

1. Degenerative diseases-gradual decline in neuronal function.

2. Inflammatory diseases-Meningitis

3. Toxic-metabolic diseases-due to vitamin deficiencies, drug toxicity.

4. Neoplastic dz – tumors.

5. Traumatic injuries – gunshot, car accidents, falls, etc.

6. Vascular diseases – CVA most common. Neurons deprived of oxygen due to disruption in blood supply. CVA results in focal lesions and is acute.


Motor Unit:

Consist of motor neuron and muscle fibers innervated by the motor neuron.


Lower Motor Neurons:

Motor nuclei through which CNS sends impulses to muscles (and glands).

Motor neurons involved in motor movement & originate in brain stem or spinal cord from a cranial or spinal nerve

Axons of these neurons leave cell bodies & travel to specific muscles. Axons subdivide into branches that connect with muscles fibers


Inproper innervation of muscles can result in (2):

-muscle atrophies (withers)


How can an axon innervate several muscles fibers?

it splits into branches


Do muscles fibers receive information from just 1 motor neuron?


Each fiber may receive input from branches of different motor neurons


Upper Motor Neurons:

Cell bodies in motor cortex and their descending axonal processes that synapse on cranial and spinal motor neurons

Originate in upper brain levels


4 main parts to speech motor system:

1. Final Common Pathway
2. Direct Activation Pathway
3. Indirect Activation Pathway
4. Control Circuits

*The organization of the speech motor system emphasizes motor (efferent) pathways, however sensory (afferent) pathways are important also and problems in sensory pathways can impact motor function


Final Common Pathway of the Speech Motor System:

Also called Lower Motor Neuron system or PNS.

Called Final Common Pathway because it’s the last link in sequence of motor events that lead to motor movement & all other components have to go through it.

-12 paired cranial nerves
-31 paired spinal nerves


Muscles Innervation can be (4)

1. Bilateral
2. Unilateral

1. Contralateral
2. Ipsilateral


Bilateral Muscle Innervation:

Receives innervation from both sides

Protective function for most of cranial nerves

If one side is damaged, the other side may stay intact.

Provides protection for important functions.


Unilateral Muscle Innervation:

Receives innervation from only 1 side

Damage occurs more easily than with bilateral innervation


Contralateral Muscle Innervation:

Receives innervation from opposite side


Ipsilateral Muscle Innervation:

Receives innervation from same side


For most nerves equal innervation comes from...

opposite (both) sides of the cortex


Does Cranial Nerve VII (facial nerve) have bilateral or contralateral innervation?


-bilateral innervation for upper face
-contralateral, unilateral innervation for lower face


How is Cranial Nerve XII (hyproglassal) innervated?

-Bilateral to most tongue muscles
-Contralateral innervation to genioglossus


Where can lesions (damage) to nerves occur?

either UMN or LMN


Damage to LMN system results in:

1. weakness
2. atrophy
3. fasiculations


Cranial Nerve V (Trigeminal Nerve):

-Bilateral Innervation

-Largest of cranial nerves

-Sensory from face, mouth, jaw, tongue.

-Motor to muscles of mastication, tensor tympani (middle ear, tenses the tympanic membrane), tensor veli palatini (tenses soft palate), mylohyoid (extrinsic laryngeal muscle involved in moving larynx)


Bilateral lesions to Cranial Nerve V (Trigeminal Nerve) (a LMN) result in:

-Jaw may hang open at rest
-Can have profound effect on speech


Unilateral lesions to Cranial Nerve V (Trigeminal Nerve) (a LMN):

-Jaw deviates to weak side ALWAYS
- Does not affect speech too much


Cranial Nerve VII (Facial Nerve):

-Innervates muscles of facial expression

-Bilateral innervation – to upper face - so if patient can’t wrinkle forehead, there are probably 2 lesions.

-Contralateral– to lower part of face


Cranial Nerve IX (Glossopharyngeal Nerve):

-Innervates stylopharyngeus muscle of pharynx (elevates pharynx in speech & swallowing).

-Sends sensory information from pharynx, tongue and Eustachian tube.

-Lesions cause reduced pharyngeal sensation & decrease in gag reflex.

-Bilateral innervation


3 Branches of Cranial Nerve X (Vagus Nerve):

1. Pharyngeal branch

2. Superior laryngeal branch

3. Recurrent laryngeal nerve

*Bilateral innervation for all branches


Pharyngeal branch of the Vagus Nerve (CN X):

Innervates muscles of pharynx (except stylopharyngeus – IX) and soft palate (except tensor veli palatini-Vth) , also palatoglossus muscle of tongue

Responsible for elevating & pulling back the velum in VP closure in speech & swallowing. (Levator palatini – one of the main muscles which elevates soft palate.)
(Cranial nerve IX assists the pharyngeal branch in this.)


Superior laryngeal branch of the Vagus Nerve (CN X):

Innervates pharyngeal constrictor and cricothyroid (intrinsic laryngeal muscle – changes pitch through tensing vocal folds)


Recurrent Laryngeal Nerve branch of the Vagus Nerve (CN X):

Innervates other intrinsic laryngeal muscles
i.e. lateral cricoarytenoid, interarytenoids and posterior cricoarytenoid, thyroarytenoid


Cranial Nerve XI ((Spinal) Accessory Nerve):

-Head and neck movement

-Intermingles with Vagus and contributes to innervation of levator palatini (elevates soft palate) and somewhat to intrinsic laryngeal muscles

-Bilateral innervation


Cranial Nerve XII (Hypoglossal Nerve):

-Innervates all intrinsic tongue muscles and all extrinsic tongue muscles except palatoglossus (innervated by Xth)

-Innervation is bilateral to all tongue muscles, except genioglossus

-Damage can cause atrophy, weakness & fasiculations on tongue (LMN).
-UMN lesion – tongue deviates to side contralateral to lesion
-LMN lesion – tongue deviates to same side of lesion


When unilateral lesions occur, why does the structure (tongue, jaw, etc.) deviate to the side of weakness?

Because normal muscle contraction occurs on the strong (normal) side and no or little contraction occurs on the weak side
There is nothing to counteract the action of the muscle on the normal side
This results in the tongue, jaw, etc. being pushed to the weak side


If the unilateral lesion is UMN, the structure deviates...

contralateral to the side of the lesion


If the unilateral lesion is LMN, the structure deviates...

ipsilateral to the side of the lesion


If the lesion is bilateral, the result is...

decreased ROM and decreased strength


Spinal Nerves innervate...

muscles of respiration, including the phrenic nerve which innervates the diaphragm


Direct Activation Pathway (Pyramidal Tract):

-Directly connects and influences the FCP/LMN

-Along with the Indirect Activation Pathway, makes up the UMN system

-UMN system includes neurons that regulate the LMNs


2 tracts that make up part of the Upper Motor Neuron System and Direct Activation Pathway:

1. Coricobulbar
2. Corticospinal


Corticobulbar Tract:

-Most important for speech - involves the cranial nerves important for speech

-Originates in cortex (mainly at the primary motor cortex) and terminates in brainstem at the level of the cranial nerve nuclei involved with speech

-Called corticobulbar because “bulb” refers to brainstem, where the axons terminate


Corticospinal Tract:

-Originates in cortex and descends to lower medulla where it terminates at the level of the spinal nerve nuclei


Where do the Corticobulbar and Corticospinal tracts descend form?

Both tracts descend from cortex (primarily motor cortex of both hemispheres, also from premotor cortex and Supplemental Motor area) through corona radiata and internal capsule to brainstem.

The corticospinal tract continues on to the spinal cord.


The Direct Activation Pathway is important for...

controlled skilled, discrete and often rapid voluntary movements as is seen in speech


Do unilateral LMN lesions have a severe impact on speech?



Do unilateral UMN lesions have a severe impact on speech?

Because there is still innervation from the other side


Do bilateral UMN lesions have a severe impact on speech?



Where does weakness occur when UMN lesions is unilateral?

Typically on the opposite side of the body (contralateral)


Indirect Activation Pathway (Extrapyramidal Pathway):

-Part of the UMN system along with the Direct Activation Pathway.

-Is less understood and its function is difficult to separate from basal ganglia and cerebellum

-Does influence directly the LMN system whereas the basal ganglia and cerebellum do not

-Starts in motor cortex and has various synapses before arriving at brainstem

-The DAP is analogous to a direct or express train line with no stops. Whereas the IAP is like a local line stopping at various places

-The IAP is made up of several short paths and interconnected structures between the origin in the cortex and its final termination at the cranial nerve nuclei and spinal cord nuclei (corticorecticular, etc.)


Reticular formation:

Scattered cells in the brainstem that is important in sensorimotor integration


Control Circuits (function):

Integrate or help control the structures and pathways involved in motor movement

Have no direct contact with LMNs


Control Circuits (2):

1. Basal Ganglia
2. Cerebellum


Basal Ganglia Control Circuit:

-Depends on balance among several neurotransmitters (AcH, dopamine, and GABA (gamma-aminobutyric acid) for aiding motor activity.

-Provides input to cerebral cortex to coordinate motor movement.

-Involved in regulating muscle tone & maintaining normal posture.


Damage to the Basal Ganglia Control Circuit:

Can result in Hypokinetic dysarthria or Hyperkinetic dysarthria


Cerebellar Control Circuit:

Integrates and coordinates movements for speech, including timing, size of muscular action and sequences of movements to provide smoothly flowing well-timed, coordinated speech


Damage to the Cerebellar Control Circuit:

ataxic dysarthria