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A Look Inside Dysphagia
Transcript of A Look Inside Dysphagia
Problems Affecting the head and neck
Cancer in the throat, esophagus, or mouth
Injury or surgery involving the head and neck
Decayed or missing teeth
Amyotrophic Lateral Sclerosis
Damage to the nervous system
Spinal cord injury
How Do We Swallow?
Muscles and nerves work together to prepare and conduct the final action of swallowing
Three stages of swallowing:
Tongue collects food/liquid
mastification breaks down food
saliva softens the food
Structures of the mouth prepare bolus for swallow.
Tongue pushes food/liquid to back of mouth
This will trigger a swallowing response, and food will pass through the pharynx
The larynx will close tightly, and breathing will stop to prevent food/liquid from entering the lungs.
Food/liquid enters the esophagus
This transports the bolus from the mouth to the stomach via esophagus
Typically takes about 3 seconds depending on texture and consistency of bolus.
Gross Anatomy: Frontal Lobe
Primary motor cortex (BA 4)
Representation of homunculus which innervates muscles in the face used for mastification and tongue movement
Bioelectrical activity of nerve cells in the area are responsible for activating and controlling motor movements on the contralateral side of the body.
Premotor cortex (BA 6)
Regulates responsiveness to primary motor cortex
Motor movements in the oral cavity
Gross Anatomy: Parietal Lobe
Primary sensory cortex (BA 3, 1, 2)
Somatic sensation are perceived
You can sense if food taste bad, then you are going to spit it out
sensation of pain and temperature can be felt from the oral cavity, to the esophagus, and ending in the stomach.
How Does Dysphagia Occur?
Occurs when there is a problem with neural control or structures involved with the swallowing process
Weakening of the tongue or cheek muscles can make it hard to move food around
Stroke or nervous system disorders
Weak throat muscles make it difficult to move the food toward the stomach
Disorders of the esophagus
A Look Inside Dysphagia
California State University, Fullerton
Types of Dysphagia
Most common type (75-85% of dysphagia patients)
Difficulty moving liquid or the food bolus from the oral cavity to the top portion of the esophagus
There is a lack of voluntary movement to transfer food from the mouth to the pharynx
Sensation of food sticking in the oral cavity or neck
Dysfunction of esophageal sphincter
Lack of relaxation and coordination with pharyngeal contraction
Difficulty with the passage of solids or liquids through the esophagus, specifically between upper and lower esophageal sphincter.
Abnormal innervation of the esophagus or physical obstruction
Depends on etiology of esophageal disturbance
Disturbance will occur with solids and liquids
Abnormal innervation of esophagus disorders include:
Abnormalities in the number of contractions
Velocity and force of contractions
The coordination and timing of contractions
Physical obstructions include
swallowing difficulties for solids occur earlier and are more difficult than swallowing liquids.
When the esophageal lumen becomes narrowed to less than 12mm it will be difficult to swallow solids.
Impairment of passage of material from the lower esophageal sphincter to the gastric fundus because of motor or physical obstruction
Abnormalities of lower esophageal sphincter from tumors
Hypertenstion of the lower esophageal sphincter causes inadequate relaxation of sphincter from the bottom portion of the esophagus to the stomach.
Sensation of food sticking to lower end of the sternum
Physical impact of the esophageal wall and lumen or inadequate filtration of the esophageal wall leading to obstruction.
Esophageal pain or chest pain
Two Stages / Reflex Actions
Mastification and creation of bolus and using muscles and tongue to move food to the pharyngeal cavity
Tongue movement (up and backward) will lead the bolus to the back of the throat
Important for oral phase.
Reflexive stage is the bolus moving towards the stomach from the pharynx to the esophagus.
Sensory projections from the posterior palate will cause reticular swallowing center to take action, which is located in the lower pons and upper medulla.
Important for pharyngeal and esophageal phase.
Major Reflexive Action
Protects the upper respiratory tract by cleaning the nasopharynx and oral pharynx
Closes the nasopharynx and the larynx to prevent pulmonary aspiration of food particles
Upward movement of the palate to close the nasopharynx
Backward and downward movement of the epiglottis to close off the glottis.
Raising the larynx to close the airway
After the bolus passes the pharynx, the reticular respiratory center allows respiration to take action
Gross Anatomy: Brainstem
Gross Anatomy: Spinal Cord
Gross Anatomy: Limbic Lobe
Midbrain, pons, and medulla
Consists of CN nuclei
Maintains homeostatic state of the brain
Regulating visceral sensorimotor and neuroendocrine activities like movement
Regulation of breathing and swallowing
Integrates sensorimotor functions of the CN used for swallowing
Transmits motor impulses from the brain to the visceral organs and muscles
Transmits sensory information from the body to the to the brain
Contains all spinal nerve cells
Ascending and descending fibers
Receive sensory information from the body through the dorsal root fibers
Motor nerve cells that activate visceral and skeletal muscles
Surrounds the medial margins of the frontal, parietal, and temporal lobes.
Cingulate gyrus, hippocampal formation, parahippocampal gyrus, uncus, and subcallosal gyrus
All of these structures connect to the diencephalon and brainstem nuclei are important for visceral functions
Needing to feed for survival.
If you can’t swallow= you can’t eat/drink= YOU DIE!!!
Internal Anatomy: Medulla
Holds many CN nuclei
Decussation of sensory and motor fibers
Crossing of the corticolspinal fibers aids the motor cortex in conducting the appropriate function.
Spinal trigeminal tract
CN V: mediates sensation in the face
Fibers enter the brainstem and descend ipsilaterally in the medulla to end at spinal trigeminal nucleus.
Secondary fibers will then cross the midline and reach the thalamus where sensory information is processed through the primary sensory cortex in parietal lobe.
Hypoglossal (CN XII) nuclei is presented and is important for intrinsic and extrinsic tongue movement.
The region between the inferior cerebellar peduncle and reticular formation will contain glossopharyngeal (CN IX) and Vagus (CN X) nuclie
The nucleus ambigus
contains CN IX and CN X motor movement nuclei important for swallowing functions by controlling muscles of the soft palate, pharynx, larynx, and upper esophagus.
Internal Anatomy Cont'd.
The glossopharyngeal (CN IX) nerve appears
The medial lemniscus can be found.
Fine and discriminative touch
Spinal trigeminal tract will descend ipsilatarlly to synapse CN V to relay somatosensory sensation of the face.
Pontine tegmentum contains facial nerve (CN VII), and is important for facial movement for mastication for the preparation of swallowing a bolus
Modify motor activity to produce precise movement
The muscles used during the oral phase of swallowing consist of fine motor movement.
Over time, these learned motor movements become autonomic movements.
Internal Anatomy Cont'd.
Channels projections of sensory (pain, temperature, and taste) information entering the lower levels of the nervous system to specific cortical areas.
Relay information and project afferents from the basal ganglia, limbic system, and cerebellum to the primary and premotor cortex.
Ventral posterior medial nuclues
Thalmic sensory relay center for sensations of taste, pain, temperature, and discrimative touch for head and face.
Important for facial sensation
A part of the autonomic nervous system.
Efferent projections to the brainstem and spinal cord to control the ANS and its functions
Important for food and water intake for survival needs
Neurons & Phsyiology
Cranial nerves are a part of the CNS and are lower motor neurons
The type of neurons are unipolar and multipolar
The neurons are made up of the cell body, the axon, and dendrites
Lower motor neurons are classified into alpha, beta and gamma motor neurons
Damage to the nuclei of the Glossopharyngeal and Vagus nerves can result in dysphagia.
Damage to lower motor neurons cause muscle atrophy
Unipolar neurons have only one process.
The unipolar neurons are a sensory nerve component.
Multipolar neurons have many dendrites and one axon
Multipolar neurons are the neurons associated with motor movements
Cranial Nerves Relevant to Dysphagia
Trigeminal Nerve (CN V)
- has both sensory and motor functions. It is mainly a sensory nerve for the face, head and oral structures and motor nerve for jaw nerves.
Loss of trigeminal function is association with facial sensory loss and paralysis of the jaw, as related to dysphagia it would make it difficult to chew.
Facial Nerve (CN VII)
- has both sensory and motor functions. It controls all muscles of facial expression. It is responsible for taste from the anterior 2/3rds of the tongue. Damage to the facial nerve results in facial paralysis and loss of taste sensation
Glossopharyngeal Nerve (CN IX)
- has both sensory and motor functions. Sensory function is to process the sensation of touch and taste from the posterior 1/3rd of the tongue and oral pharynx. Motor function is to contribute to the process of swallowing.
Damage results in lost of taste in posterior 1/3rd of the tongue and mild dysphagia.
Vagus Nerve (X)
- both sensory and motor functions. Motor function to activate the muscles of the pharynx, larynx, and soft palate.
Damage results in decreased sensation from activation of visceral organs and paralysis of the larynx and pharynx.
Spinal Accessory Nerve (XI)
- motor function that innervates the sternocleidomastoid (head rotation) and trapezius (shoulder elevation).
Hypoglossal Nerve (CN XII)
- motor function that innervates the muscles of the tongue.
Damage can result in paralysis of half of the tongue.
Motor & Sensory System
Compares efferent commands against the intended movements with the sensory information received
Constantly monitors cortical output by receiving input from the motor cortex, brainstem reticular reflex networks, & spinal cord
Connect cerebellum to brainstem
All efferent and afferent fibers traveling to & from the cerebellum pass through these three bundles:
Superior Cerebellar Peduncle
Largely efferent fibers that arise from the dentate, emboliform, and globose (cerebellar nuclei)
Fibers decussate at level of inferior colliculus
Middle Cerebellar Peduncle
Largely afferent fibers
Forms the largest tract in the cerebellum
Massive afferents from the cerebral motor cortex that synapse in the ipsilateral pontine nuclei
Inferior Cerebellar Peduncle
Largely afferent fibers
Ascending inputs from distal limbs gain rapid entry to ipsilateral cerebellum
Motor System & Tracts
Carry sensory and motor information
Travel vertically to connect the cortices with the brainstem and spinal cord structures
Project through the corona radiata and coalesce as a large fiber bundle in the internal capsule
Contains all ascending and descending fibers as they pass between the basal ganglia and the thalamus
Consists of the:
The site where
fibers descend to innervate the CN nuclei and play an important role in motor speech processes
Arises from the UMNs in the lower third of the precentral cortex and adjacent areas
Contains approximately 70% of short motor fibers
Exclusively controls skeletal muscles of the head and face through activation of motor nuclei in the brainstem.
Includes the Trigeminal, Facial, Glossopharyngeal, Vagus, Spinal accessory, & Hypoglossal cranial nerve nuclei.
Crosses at multiple points before synapsing onto cranial nerves rather than at a single point at the midline
This causes some cranial nerves to be bilaterally innervated and others innervated unilaterally.
Bilateral or Unilateral Innervation
Implications for any of these cranial nerves would result in contralateral damage
CN VII Facial - lower facial muscles
CN XI Spinal Accessory
CN XII Hypoglossal
Implications for any of these cranial nerves would result in ipsilateral damage
CN V Trigeminal
CN VII Facial - upper facial muscles
CN IX Glossopharyngeal
CN X Vagus
Regulates muscle tone for limb extension and posture in support of the body against gravity
Important to have good posture and not be slouched over while eating to ensure efficient swallowing and avoid any possible dangers.
Fibers control the reflexive adjustment of the body and limbs to keep the head stable
A stable head is necessary for swallowing. One does not shake their head around or let their head wobble while eating/swallowing.
Regulates neck and body movement
All of these tracts receive input from the cerebellum
Sensory System & Tracts
The process of swallowing is organized with sensory input from receptors in:
the base of the tongue
the soft palate
posterior pharyngeal wall
This input is transmitted to the swallowing center, located within the pontine reticular system, through the facial (VII), glossopharyngeal (IX), and vagus (X) cranial nerves.
Oral Sensory Structures/Systems
responsible for taste of anterior 2/3 tongue
nerve endings where texture is sensed throughout the mouth
nerve that transduce information tastes are sensed by taste buds
brain structure responsible for the perception of taste
where odor is still experienced from food in mouth through the air that passes through the rear of the oral cavity into the nasal passages
Afferent Tracts Cont'd
receive input from virtually all ascending systems
1st order neurons:
collect sensory info from the periphery and transmit it to the second-order neurons in the CNS
2nd order neurons :
either in brainstem or spinal cord, consistently cross the midline & ascend to opposite thalamus
3rd order neurons :
project from the thalamus to the primary sensory cortex
Spinal Trigeminal Tract:
sensory nucleus which carries deep/crude touch, pain and temp info from the ipisilateral face
Sensory Order of Cranial Nerves
General Visceral Afferent
1st order = trigeminal ganglion
2nd order = descending spinal nucleus and primary sensory nucleus
Special Visceral Afferent
1st Order = geniculate ganglion
2nd Order = nucleus solitarus
General Visceral Afferent & Special Visceral Afferent
1st order = inferior ganglion
2nd order = nucleus solitarus
General Visceral Afferent & Special Visceral Afferent
1st order = inferior ganglion
2nd order = nucleus solitatus
– Trigeminal Sensory Fibers: carry input from maxillary & mandibular division into the trigeminal sensory nuclei. Sends sensory information about touch and pressure
– Afferent input related to swallowing travels via sensory fibers in the trigeminal nerve, the glossopharyngeal nerve, the internal branch of the superior laryngeal nerve, and other branches of the vagus nerve
– Sensory input from both the pharynx and the esophagus
Risks Unrelated to
As a result of Dysphagia, a person can experience:
can cause weight loss
which can lead to other serious illness such as pneumonia
self isolation in social situations involving eating
Bhatnagar, S. C. (2013). Neuroscience for the Study of Communicative Disorders-4th Edition. Philadelphia, PA: Lippincott, Williams, & Wilkins.