1 chapter 15: cranial nerves chris rorden university of south carolina norman j. arnold school of...
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Chapter 15: Cranial Nerves
Chris RordenUniversity of South CarolinaNorman J. Arnold School of Public HealthDepartment of Communication Sciences and DisordersUniversity of South Carolina
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Functional Classification of CN
Spinal Nerve classification– General Efferent or Afferent: serve general motor, sensory.
Cranial Nerves classification– Receptor type:
General - just like spinal nerves Special –Use special receptors and neurons to serve additional specialized
functions
– Signal type Efferent – Motoric Afferent Sensory
– Voluntary or reflexive? Somatic. Innervate somatic muscles (muscles that arise from the soma in the
embryological stage – voluntary muscle control) Visceral. Innervate visceral structures.
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7 Functional Types
1. General Somatic Efferent (GSE) Activates Muscles from Somites (Skeletal, Extraocular, Glossal)
2. General Visceral Efferent (GVE) Activates Visceral Organs3. Special Visceral Efferent (SVE) Activates Muscles of face, palate,
mouth, pharynx and larynx Excludes eye and tongue muscles4. Special Visceral Afferent (SVA) Mediates visceral sensation of
taste from tongue Olfaction from Nose5. General Visceral Afferent (GVA) Mediates sensory innervation
from visceral organs6. General Somatic Afferent (GSA) Mediates information from
muscles, skin, ligament and joints7. Special Somatic Afferent (SSA) Mediates special sensations of
vision from retina and audition and equilibrium from inner ear
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Peripheral Nervous System (PNS)
12 pairs of cranial nerves-– Sensory, motor, or mixed
“On Old Olympus Towering Top A Famous Vocal German Viewed Some Hops.”
“On Old Olympus Towering Top A Finn And German Viewed Some Hops.”
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Cranial Nerves (12 pair)
I. Olfactory: smell
II. Optic: vision
III. Oculomotor: eyelid and eyeball movement
IV. Trochlear: motor for vision (turns eye downward and laterally)
V. Trigeminal: chewing, face and mouth touch and painVI. Abducens: motor to lateral eye musclesVII. Facial: controls most facial expressions , taste, secretion of tears & salivaVIII. Vestibulocochlear: sensory for hearing and balance (aka Acoustic, Auditory)IX. Glossopharyngeal: sensory to tongue, pharynx, and soft palate; motor to muscles of the
the pharynx and stylopharyngeus
X. Vagus Nerve: sensory to ear, pharynx, larynx, and viscera; motor to pharynx, larynx, tongue, and smooth muscles of the viscera, 2 parts: superior laryngeal branch and recurrent laryngeal branch
XI. Spinal Accessory Nerve: motor to pharynx, larynx, soft palate and neck
XII. Hypoglossal Nerve: motor to strap muscles of the neck, intrinsic and extrinsic muscles of the tongue
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I: Olfactory
Special Sensory : smell-Injured by shearing (car accident) – unilateral loss
of smell
rad.usuhs.mil/cranial_nerves/timrad.html
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II: Optic
Special Sensory: Sight Optic nerve nuclei are located in the lateral
geniculate bodyPupil constricts for light to contralateral eye,
but not ipsilateral. Unilateral vision loss
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III: Oculomotor
Somatic Motor: Superior, Medial, Inferior Rectus, Inferior Oblique
Visceral Motor: Sphincter Pupillae
Pupil asymmetry, no pupil reflex – regardless of which eye observes light. Difficulty with eye movements.
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IV: Trochlear
(Latin for pulley) Somatic Motor:
Superior Oblique Injury leads to
diplopia (due to eye drifting upward), esp when looking down
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V: Trigeminal
Somatic Sensory: Face Somatic Motor: Mastication (chewing), Tensor
Tympani (reduced ossicle movement), Tensor Palati (soft palate – chewing and eustachion tubes)
light touch and pain on the forehead (V1), cheeks (V2) and chin (V3).
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VI: Abducens
Somatic Motor: Lateral Rectus
Damage to the nerve is seen with decreased ability to abduct the eye. (diplopia: affected eye is pulled medially)
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VII: Facial
Somatic sensory: Posterior External Ear Canal Special Sensory: Taste (Anterior 2/3 Tongue) Somatic Motor: Muscles Of Facial Expression Visceral Motor: Salivary Glands, Lacrimal Glands
Drooping corner of mouth while at rest. Asymmetry of expressions (wrinkle forehead, raise eyebrows, etc)
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VIII: Vestibulocochlear
Special Sensory: Auditory/Balance
Can patient hear finger rubbing near ear.
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IX: Glossopharyngeal
Somatic Sensory: Posterior 1/3 Tongue, Middle Ear
Visceral Sensory: Carotid Body/Sinus Special Sensory: Taste (Posterior 1/3
Tongue) Somatic Motor: Stylopharyngeus Visceral Motor: Parotid Gland
Asymmetric palate while saying ‘Aaah’, poor gag reflex (sensory = IX, motor = X)
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X: Vagus
Somatic Sensory: External Ear Visceral Sensory: Aortic Arch/Body Special sensory: Taste Over Epiglottis Somatic Motor: Soft Palate, Pharynx,
Larynx (Vocalization and Swallowing) Visceral Motor: Bronchoconstriction,
Peristalsis, Bradycardia, Vomitting
Asymmetric palate while saying ‘Aaah’, poor gag reflex (sensory = IX, motor = X)
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XI: Spinal Accessory
Somatic Motor: Trapezius, Sternocleidomastoid
Drooping shoulder. Weakness turning head in one direction, difficult to shrug shoulders against resistance.
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XII: Hypoglossal
Somatic Motor: Tongue
Observe tongue while on floor of mouth. Twitching can suggest XII injury.
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Branchial Origin of Speech-Related Muscles
Speech related muscles = visceral? Six branchial arches present in embryo One
disappears during development Some cranial nerves originate from 5 brachial
arches and are special visceral efferent nerves
Speech related nerves Include– Trigeminal (V)– Facial (VII)– Glossopharyngeal (IX)– Superior laryngeal and recurrent laryngeal
branches of Vagus (X)
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Cranial Nerve Nuclei
Midbrain (3)- Control Eye Muscles– Two Motor N. of Oculomotor– One Motor N. of Trochlear
Pons (6)– Three Sensory N. of Trigeminal
Mesencephalic N. Primary Sensory N. Spinal Trigeminal N.
– Motor N. of Trigeminal N.– Abducens N.– Facial Motor N.
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Cranial Nerve Nuclei: Medulla (9)
1. Cochlear N. (Hearing)2. Vestibular N. (Equilibrium)3. Salivary N. (Secretions)4. Dorsal Motor N. of Vagus (Visceral
Motor) 5. Hypoglossal N. (Tongue)6. Nucleus Solitarius (Visceral Sensory)
afferent swallowing7. Spinal Trigeminal N. (Sensory)8. Nucleus Ambiguus (Laryngeal &
Pharyngeal Motor) efferent swallowing9. Inferior Olivary N. (Info to Cerebellum)
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Pathways - Corticobulbar Motor
Corticobulbar tract– Fibers between cortex and brain stem
Cross midline at different levels– Upper and Lower Motor Neurons
Clinical Signs: – Lower Motor NeuronParalysisAbsent ReflexesFlaccid Muscle ToneFibrillationFasciculations (twitching) Atrophy
– Upper Motor NeuronSpasticityIncreased Tendon
ReflexesContralateral Paresis
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Pathways - Sensory
3 Major types of sensory pathways– 1st order - Outside brainstem– 2nd order Cell bodies in gray matter of brainstem– 3rd order - Cell bodies in ventral posterior medial
N. of Thalamus projecting to cortex in parietal lobeSmell, hearing and vision are exceptions to
rule three
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Olfactory Nerve (I)
Special visceral afferentParts
– Olfactory Bulb– Olfactory Tract– Temporal Cortex
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Olfactory Nerve (I)
Fibers pass through the foramina in the cribriform plate to olfactory bulb, olfactory tract to temporal cortex (uncus, amygdaloid N. and parahippocampal gyrus). Connects to limbic system and emotional brain.
Olfactory ability decreases with age Anosmia: impaired smell (ask patient to
identify odors)
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Optic Nerve (II)
Special somatic afferent Retina to Optic Nerve to Optic Chiasm To Lateral Geniculate Body To Optic Radiations To Visual Cortex in Occipital Lobe Clinically:
– Injury results in visual field loss– Common visual field losses in Chapter 8 (ask client to
closes one eye and fix gaze straight ahead. Determine when patient can see objects in parts of visual field)
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Oculomotor Nerve (III)
General somatic efferent– Innervate extrinsic muscles of eye
General visceral efferent– Provides parasympathetic projections to constrictor
fibers of iris and ciliary muscles– Provides motor innervation for iris to adjust to light
and lens to focus– Edinger-Westphal Nucleus
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Oculomotor Nerve (III)
OculomotorNerve
Edinger-WestphalNucleus
SuperiorColliculus
CiliaryGanglion
(Pupil size, lens shape)
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Left Oculomotor (III) Nerve Paralysis
Left eye isdeviated laterally Does not move
laterally
Diplopia
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Diplopia
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Clinical Info: Oculomotor Nerve (III)
Clinical Info: Oculomotor Nerve (III)Ptosis - eyelid droopOphthalmoplegia
– problems in adjusting to light– deviation of eye movements– diplopia (double vision)
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Trochlear IV
General somatic efferent Only CN to exit brainstem dorsally Only CN that exits contralaterally Anterior oblique muscle for eye
movement is only function Clinical
– Difficulty looking downward and outward when Trochlear is injured
– eye drifts upward relative to the normal eye
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Trochlear Nucleus
SuperiorObliqueMuscle
Trochlear (IV)Nerve
TrochlearNucleus
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Superior Oblique Muscle Function
Right Superior Oblique Muscle
Eye ball directed down and out
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Trigeminal (V)
General somatic afferent Principal sensory nerve for head, face, orbit and oral
cavity mediate sensations of pain, temperature,
proprioception and fine discriminative touch Sensations from anterior 2/3 of tongue Three sensory branches
– Ophthalmic– Maxillary– Mandibular
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Trigeminal (V)
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Trigeminal (V)
Special visceral efferent Motor for mastication muscles for chewing and
speaking– Internal and external pterygoid– Temporalis– Masseter– Mylohyoid– Anterior belly of digastric– Tensor veli palatini– Tensor tympani
Reflex for jaw jerk reflex (mandibular)
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Trigeminal (V)
Opthalmic
Mandibular
Maxillary
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Motor Branch of Trigeminal Nerve
Pterygoid musclesLateral (external)
Medial (internal)
Temporalis muscle
Masseter muscle
Mylohyoid
Anterior bellyOf digastric
Tensor palatine
Tensor tympani
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Clinical Info: Trigeminal (V)
Sensory– Test for touch discrimination in different facial zones– Check for sneeze and corneal reflexes– Tic of douloureux (trigeminal neuralgia) which is excruciating
pain Motor
– Check for paralysis or paresis of ipsilateral muscles of mastication
– Check for absent or exaggerated jaw reflex– Look for deviation of jaw toward side of injury– Unilateral lesion has mild effect on bite strength while bilateral
has severe effect
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Abducens (VI)
General somatic efferent Innervates only a single muscle:
lateral rectus muscle which moves eye laterally
Clinical Info: – When injured, medial rectus muscle is
unopposed – eye shifts medially– Susceptible to disruption– Check for medial strabismus
Turns in medially Double vision
Left Abducens (VI)Nerve ParalysisLeft eye is deviated medially
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Left Abducens (VI) Nerve Paralysis
Diplopia Disappears on Eye Movementto the Right
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Abducens (VI)
Abducens (VI) Nerve
Lateral RectusMuscle
Abducens (VI) Nucleus
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Facial Nerve (VII)
General visceral efferent– Parasympathetic innervation of lacrimal gland and
palatal saliva– Innervation of mucous membrane secretions in
mouth and pharynxSpecial visceral afferent
– Gustatory sensations from anterior 2/3 of tongue
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Facial Nerve (VII)
Special visceral efferent Primary motor nerve for facial
muscles Extrinsic Muscles of ear
– Cats can rotate outer ear Stapedius Muscle
– Contraction attenuates sound Swallowing
– Stylohyoid Muscle– Posterior Belly of Digastric Muscle
Lacrimal secretion - Tears
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Clinical Info: Facial Nerve (VII)
Upper Motor Neuron Disease– Why is it hard to only raise one eyebrow?– Unilateral paresis of muscles of lower half of face– Muscles above bilaterally innervated– Bilateral lesion can cause paralysis of upper and
lower muscles bilaterally Lower Motor Neuron Disease
– Injury near pons can cause lower motor neuron disease
– Unilateral Paralysis of all facial muscles, stapedial muscle and taste in 2/3 of tongue
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Clinical Examples: Facial Nerve
UMN LMN
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Clinical Examples: Facial Nerve
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Clinical Info: Facial Nerve (VII)
Bell’s Palsy– LMN syndrome with sudden onset of paralysis of
ipsilateral facial muscles– Inflammatory injury, infection or degenerative
disease
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Vestibulo-acoustic Nerve (VIII)
Special somatic afferentVestibular Nerve
– Gives feedback about position of head in space and balance
Acoustic Nerve– Hearing
Clinical Info– Tests for equilibrium, vertigo or dizziness,
nystagmus and hearing loss
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Glosso-pharyngeal Nerve (IX)
General visceral afferent– Mediates general visceral sensation from soft palate,
palatal arch, posterior 1/3 of tongue and carotid sinus General visceral efferent
– Secretion from parotid gland (salivary gland) Special visceral afferent
– Taste sensation form posterior 1/3 of tongue Special visceral efferent
– Contributes to swallowing through stylopharyngeus and upper pharyngeal constrictor fibers
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Clinical Info: Glosso-pharyngeal (IX)
May be evident in dysphagia or loss of taste to posterior 1/3 of tongue
Loss of gag reflexExcessive oral secretionsDry mouthNeed bilateral damage of nerve to have strong
clinical signs
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Vagus Nerve (X)
General visceral afferent– Sensation from pharynx, larynx, thorax, abdomen– Regulates nausea, oxygen intake, lung inflation
General visceral efferent– Innervates glands, cardiac muscles, trachea, bronchi,
esophagus, stomach and intestine Special visceral afferent
– Mediates taste sensation from posterior pharynx and epiglottis Special visceral efferent
– Controls muscles of larynx, pharynx, soft palate for phonation, swallowing and resonance
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Clinical Info: Vagus Nerve (X)
Bilateral lesion of the brainstem can be fatal due to respiratory involvement
Unilateral lesion can result in ipsilateral paresis or paralysis of soft palate, pharynx and larynx
Pharyngeal Branch– Pharynx and soft palate involvement– Uvula pulled to unaffected side, bilateral soft palate droops
Recurrent Laryngeal Branch– Unilateral: Paralysis of vocal folds– Bilateral: Inspiratory stridor and aphonia
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Clinical Info: Vagus Nerve (X)
Normal Soft Palate Unilateral Paralysis Bilateral Paralysis
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Clinical Info: Vagus Nerve (X)
Autonomic reflexes reducedAnesthesia of pharynx and larynx and loss of
tasteSuperior Laryngeal Branch
– Loss of ability to change pitch
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Spinal Accessory Nerve (XI)
General visceral efferent– Controls head position by controlling trapezius and
sternocleidomastoid musclesClinical Information
– Affects ability to control head movements– Ask patient to rotate head and note control
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Hypoglossal Nerve (XII)
General somatic efferent– Controls tongue movement– Controls extrinsic and intrinsic muscles of tongue
except palatoglossal (X)– Eating, sucking and chewing reflexes
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Clinical Info: Hypoglossal (XII)
LMN unilateral lesion can cause wrinkling and flaccidity of tone with atrophy over time
Dysarthria and DysphagiaUnilateral UMN lesions do not
have much affect as tongue is bilaterally innervated
Ask patient to complete oral motor movements
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Clinical Info: Hypoglossal (XII)
Unilateral
Tongue
Paralysis
Bilateral
Tongue
Paralysis
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Innervation of the tongue
Glosso-pharyngeal (IX) Nerve
Trigeminal (V)Nerve
General (tactile, etc.)
Special (taste)
Glosso-pharyngeal(IX) Nerve
Facial (VII)Nerve
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Cranial Nerve Combinations
More than one nerve involved with some structures
Eyes muscle controlSensory fibers to tongue
– Anterior 2/3 special and general sensation: Facial and Trigeminal,
– Posterior 1/3special and general sensation: Glossopharyngeal
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Cranial Nerve Combinations
Motor Nerve Supply to Soft Palate and Pharynx– Vagus, Trigeminal and Glossopharyngeal
Sensory Nerve Supply to Soft Palate and Pharynx– Glossopharyngeal, Vagus and Trigeminal
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Nerve Classifications
This division give rise to a classification based on whether a nerve is:
Afferent, efferent, or bothSomatic or visceral, or bothSpecial, general, or bothThe only combination that does not exist is:
Special, somatic, efferent.
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Case # 1
Setting: Neonatal intensive care unit (NICU) Patient: Pt. is a two-day old male. Delivery was complex
but completed with cesarean section, neurological exam suggests a right facial paralysis /s other prominent symptoms.
1. What cranial nerve(s) is/are involved?2. Discuss the probable cause of the right facial paralysis3. In what cases will the symptoms resolve?4. What are some possible current functional problems that
may be present?5. What are some possible future functional problems?
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Case # 2
Setting: Out-patient clinic Patient: 64 y.o. male. Pt. is 18 months post-stroke. Neurological
exam revealed: aphasia, dilated left pupil, left eye deviated downwards and lateral. Left eyelid droop.
1. What cranial nerve is involved?2. What kind of a visual problem would this patient have?3. What can the patient do to compensate for the visual problem?4. Will this condition persist?5. In the long run, how will the brain compensate for this problem?6. Is it probable that the same lesion resulted in the visual problem
and the aphasia?
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Case #3
Setting: Nursing home Patient: Pt. is a 78 y.o. female who has been residing at the nursing
home for the last 3 years. She was originally admitted to the nursing home following amputation of both legs below the knee. This was necessary secondary to diabetes that results in gradual neuropathy and loss of vascular circulation in the extremities. A recent visit by the primary care physician revealed loss of sensation in the face secondary to progressive neuropathy. Her jaw is slightly deviated to the left.
1. What cranial nerve is involved?
2. How can you determine which afferent part of this cranial nerve is affected?
3. What would cause the jaw to deviate to one side?
4. Is this an upper or lower motor neuron problem?
5. Will she improve? Why/why not?
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Case #4
Setting: ICU Patient: 42 y.o. female. Patient was brought to the ER following a motor
vehicle accident. She was comatose for 4 days but is now alert but not oriented. Pt. has multiple fractures including the: left tibia, left humerus and clavicle. Extensive facial bruising. MRI showed scattered bruising of the cortex and possible brain stem involvement. The neuro exam revealed severe aphonia, stridor, absent swallow reflex, drooping soft palate, no gag reflex.
1. What cranial nerve is most likely affected?
2. Is this an upper or lower motor problem?
3. What are some other neurological symptoms that could be present?
4. Would you recommend an oral diet for this patient? Why/why not?
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Case #5
Setting: Nursing home (SNF) Patient: Pt. is a 71 y.o. male who recently suffered a stroke.
The MRI revealed multiple infarctions at the level of the basal ganglia and perhaps the brain stem. The neuro report from the hospital suggested that the patient has right lower facial droop, poor movement of most facial muscles, exaggerated smile, and excessive laughter or crying.
1. Does this clinical picture agree with cranial nerve involvement? Why/why not?
2. Is this an upper or lower motor neuron problem?3. Poor movement of most facial muscles would implicate what
cranial nerve?
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VIII Injury: www.dizziness-and-hearing.com/testing/acoustic_reflexes.htm
Central case example: A 40 year old man was well until he was involved in an auto accident. Two days later he developed diplopia and a rotatory type vertigo. On physical examination he had clear spontaneous nystagmus and mildly decreased hearing on the left side. Audiometry documented mildly impaired hearing on the left, but acoustic reflexes were abnormal with very rapid decay on the left side. Brainstem auditory evoked responses were abnormal on the left (neural response times to sounds). An MRI scan documented a lesion resembling an MS placque in his left cerebellar peduncle area, just behind the 8th nerve (see figure to right). His symptoms resolved spontaneously and he has had not further neurological complaints in 5 years of followup.