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Lecture - Human Structure & Function > Cranial Nerves > Flashcards

Cranial Nerves Flashcards

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1
Q

Cranial Nerves

A
  • Peripheral nerves that exit / enter the central nervous system
  • 31 pairs of spinal nerves
  • Some: special sensory or parasympathetic component
  • CNs can be motor, sensory, or mixed
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2
Q

Cranial Nerves – Origin

A

12 pair of cranial nerves

  • CNs III - XII exit from the brain stem
  • CN I projects directly to the telencephalon
  • CN II is an outgrowth of the diencephalon
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3
Q

Spinal Nerves & CNs

A

Spinal Nerves

• Somatic sensory fibers conveying information from skin, muscle and joint on pain, temperature, and touch

• Visceral sensory information from blood vessels (for BP and chemistry) or visceral structures such as the digestive tract

**• Visceral motor ** autonomic motor to viscera (peristalis, secretion)

**• Somatic motor ** voluntary skeletal muscle

Cranial Nerves

  • CNs have somatic sensory, visceral sensory, visceral motor, somatic motor, and a special sensory component (ex: smell, taste, equilibrium).
  • Some CNs: parasympathetic function.
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4
Q

Cranial Nerve Nuclei

A
  • Nuclei = Brain of the nerve
  • Nuclei are a collection of neuronal cell bodies located within the central nervous system
  • Function: Sensory (afferent) axons enter and synapse onto neural cell bodies and motor (effernt) axons originate centrally at nuclei and project to peripheral structures
  • The bundles of effernt and afferent axons associated with CN nuclei are the cranial nerves
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5
Q

Cranial Nerve Composition

A

• Sensory – I, II, VIII • Motor – II, IV, VI, XI, XII • Mixed – V, VII, IX, X

Parasympathetic Function (calming) • CN III Occulomotor Nerve • CN VII Facial Nerve • CIX Glossopharyngeal • CN X Vagus

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6
Q

Functional Components

A

• Somatic Motor - Striated muscle of tongue and eze

**• Branchial Motor ** - Muscles of mastication, face, larynx, pharynx

**• Visceral Motor ** - Parasympathetic to smooth muscle and glands

**• Visceral Sensory ** - unconsious visceral sensations

• Somatic Sensory - General sensation may or may not be consious in nature

• Special Sensory - taste, smell, hearing, vision, and balance

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7
Q

Name all the Cranial Nerves.

A

• CN I Olfactory
• CN II Optic
• CN III Oculomotor
• CN IV Trochlear
• CN V Trigeminal
- CN V1 Opthalmic division
- CN V2 Maxillary division
- CN V3 Mandibular division
• CN VI Abducens
• CN VII Facial
• CN VIII Vestibulocochlear
• CN IX Glossopharyngeal
• CN X Vagus
• CN XI Accessory
• CN XII Hypoglossal

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8
Q

CN I Olfactory

A

Special sensory visceral afferent

Function: Smell

  • Communicates with the temporal lobe (Uncus and etorhinal cortex)
  • Olfaction: Sesation of odors that results from detection of odorous substances aerosolized in the environment
  • Olfactory epithelium: roof of nasal cavity, contains cells whose axons constitute the olfactor nerves (approx. 25 million neurosensory cells per side of nose).
  • Nerves pass through the cribiform plate of the ethmoid bone and synapse onto the olfactory bulb
  • Axons extend from the bulb to form the olfactory tract which communicates with the medial temporal lobe

• Exit: Foramen of cribiform plate

• Location of Nuclei: Telencephalon

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9
Q

CN I Olfactory – Injufry & Test

A
  • Resulst in Anosmia - loss of sense of smell
  • Facture of cribiform plate (CSF leakage)
  • Tumor of frontal lobe or anterior meninges may compress olfactory bulb or tract
  • Temporal lobe tumor
  • Viral or allergic rhinitis
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10
Q

CN I Olfactory – Test

A
  • Unilateral test that must be performed bilaterally
  • Block one nostril + place something pungent under the other nostril (coffee). Ask the patient when they smell it.
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11
Q

CN II Optic

A

• Special Sensory

  • *• Function:**
    • Visual acuity
    • Intactness of visual fields

• Surrounded by meninges and subarachnoid space (CSF)

• Optic Nerve: Formed by retinal ganglion cells that pierce the sclera dep tot he otpic disc

• Optic Chiasm:
Point where optic nerve axons from retinal ganglia cells int he nasal half of each retina decussate – for binocular vison

• Optic Tracts: Ipsilateral temporal retinal axon fibers and crossed contralateral nasal axon fibers

• Left and right tracts terminate in the corresponding lateral geniculate body of the thalamus and is relayed to visual cortices

• Enter: Optic Canal

• Location of Nuclei: Diencephalon

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12
Q

CN II Optic – Injury

A

Papilledema

  • Edema of Papilla (optic disc)
  • Caused by increased intracranial pressure (CSF pressure) surrounding optic nerve
  • Pressure is placed on vein and prevents return of venous blood form retina

Optic Neuritis

  • Inflammation due to exposure to toxic sustances
  • Degenration
  • De-myelinating Disorder
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13
Q

CN II Optic – Test

A

**Test: **

• with Snellen Chart • Placed 6 m away

• close one eye and read the smallest line they can make out
→ 1 miss is fine; 3-4 move up one line

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14
Q

CN III Occulomotor

A

• Motor

  • *• Function:**
    • Pupil constriction
    • Upward / Downward / Medial gaze
    • Eyelid elevation
  • Somatic and Visceral Efferent
  • Motor to 4 of 6 extra-occular eye striated muscles → Superior, medial, and inferiro rectus → Inferiror oblique

• Motor to upper eyelid (striated mm)
→ Levator palpebrae superioris

  • Motor to sphincter of pupil, the smooth muscle of the iris (parasympathetic, visceral) → Constriction of pupil (smooth mm)
  • Motor to ciliary muscles of lens → Produces accomodation of lens (smooth mm)

• Exit: Superior orbital fissure

• Location of Nuclei: brain stem

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15
Q

CN III Occulomotor – Eye Muscles

A
  • Superior rectus - elevate + add
  • Inferior rectus - depress + add
  • Medial rectus - add
  • Inferior obplique - elevate + add(no direct pull → coming from behind the eye, loops around → attaches to eye → elevates + add)
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16
Q

CN III Occulomotor – Injury

A

• Ptosis: drooping of upper eyelid

• No pupillary reflex

• Dialation of the pupil (interruption of Parasymp)

• Eyeball abducted and inferior

• Increased ICP (intercranial pressure) → Can compress CN III → Result: decreased / slow pupillary light reflex ipsilateral

• Aneurysm of PCA or SCA (post & sup cerebral arteries)

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17
Q

CN III Occulomotor – Test

A

Pupil constriction (direct & consensual)

• Shine a light in patients eye. Look to see if the pupil of the eye the light is shone in constricts; also look if the contralateral pupil constricts.

Eyelid elevation

  • Look for symmetry of the eyelids
  • Ptosis (droopy eyelid)
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18
Q

CN IV Trochlear

A

• Motor

• Function: ** ** Somatic Motor + proprioception to one extra-occular eye muscule → Superior Oblique (moves the eyeball inferiorly and laterally) → “Down + Out” (cute shoes)

  • Travels the longest distance intercranially (subarachnoid)
  • Smallest cranial nerve
  • Only nerve to emerge dorsally (posterior surface) from the midbrain
  • Exit: Superior Orbital Fissure
  • Location of nuclei: Midbrain - exit from brain stem
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19
Q

CN IV Trochlear – Injury

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A
  • Rarely paralyzed alone
  • Can be tron in severe head injuries
  • Diplopia (double vision) when looking inferiorly + medially
20
Q

CN V Trigemninal – Test

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A

• Test:
• Sensory component:
- Sensation to face (hot/cold, sharp/dull)
- Corneal reflex:touch cornea w/ a paper towel
–> blinking
• Motor component:
- Palpate masseter muscles

21
Q

CN V Trigeminal

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A

Mixed: Motor & Sensory • General Sensory w/ Somatic Afferents

  • *Function:** • Sensory:
    • face, cornea, nasal & oral cavity, upper & lower teeth
    • Ophthalmic, Maxillary, Mandibular division

• Motor:

   - Muscles of Mastication
   - Mandibular division

3 Divisions • Ophthalmic - Sensory • Macillary - Sensory • Mandibular - Sensory + Motor

• Location of Nuclei: Pons and Medulla

22
Q

CN V Trigemnial – Opthalmic Division

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A

Somatic Sensory for:

  • Cornea: transparent covering for the eyes
  • Forehead
  • Scalp
  • Eyelids
  • Nose
  • Nasal Mucosa

Exit: Superior Orbital Fissure

23
Q

CN V Trigeminal – Maxillary Division

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A

Somatic sensry for:

  • Skin over Maxilla
  • Upper Lip
  • Maxillary teeth

Exit: Foramen rotundum

24
Q

CN V Trigeminal – Mandibular Division

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A

Somatic sensory for:

  • Skin over Mandible, lower lip, side of head
  • Mandibular Teeth
  • Temporomandibular Joint (TMJ)
  • Somatic sensation anterior 2/3 of tongue

Motor for muscles of mastication:

  • Masseter
  • Pytegoids (Medial + Lateral)
  • Mylohyoid
  • Anterior Belly Digastric
  • Tensor Tympani

Exit: Foramen ovale

25
CN V Trigeminal -- Injury
**Injury:** * Tumors or lesions of pons and medulla * Aneurysms * Meningeal Infections ** Paralysis** to mm of mastication → loss of thermal/painful sensation to face, loss of corneal reflex
26
CN VI Abducens
**Motor** **Function:** Pure lateral eye movement • Somatic Motor ot one extra-occular eye muscle → Lateral Rectus: abducts / moves eye laterally **Exit:** Superior Orbital Fissure **Location of Nuclei:** Pons, Nerve emerges from bainstem between pons and medulla and runs alongside basilar artery then bends sharply over petrous part of temporal bone
27
CN VI Abducens -- Injury
Eye rests medially deviated b/c lateral rectus is pralyzed and can cause diplopia * Increased ICP stretches the nerve * Brain tumor may compress the nerve * Aneurysm of the Circle of Willis
28
CN VI Abducens -- Test
III, IV, VI tested together - Smooth pursuits: Check for smooth tracking ("follow my pen") - Saccades: Accuracies (no jumping or overshooting; "look at my nose, look at my pen")
29
CN VII Facial
**Mixed****:** Sensory + Motor **Sensory Function:** = special visceral and general somatic afferent * Taste: anterior 2/3rds of tongue, soft palate * Somatic sencory to external ear * Parasympathetic to several salivary glands, lacrimal glands **Motor Function:** = brachial/somatic & parasympathetic general visceral efferent • Muscles of facial expression, throat muscles, and auricular muscles (stapedius) **Exit:** Internal Acoustic Meatus (Stylomastoid Foramen) **Emergence:** Junction of pons and medulla **Location of Nuclei:** Pons
30
CN VII Facial -- Injury
Most frequently injured CN • **Sensory:** loss of tste ant 2/3rds of tongue **• Motor:** Facial muscle paralysis • **Location of injury** determines sequela with altered salivation and tear production, facial muscle paralysis and tst loss. Each being possible. **• Belly Palsy:** Unilateral paralysis of some or all facial muscles secondary to a lesion of facial nerve CN VII **• Idopathic**
31
CN VII Facial -- Test
• Sensory component: - Taste test: ID sweet or salty • Motor component: - Corneal reflex:touch cornea w/ a paper towel - -\> blinking - "Make faces"
32
CN VIII Vestibulocochlear
**Sensory** **Function:** • Special Sensory for hearing and equilibrium (balance issues) **2 Divisions** • Vestibular: Equilibrium and balance w/ 4 Nuclei at pons and medulla juncture • Cochlear: Hearing with 2 nuclei located in the medulla **Entrance:** Internal Acoustic Meatus ⇒ seperates into vestibular and cochlear Ns **Cochlear Nerve:** • Information Relay • Medial geniculate body of thalamus • Auditory aspect of cerebral cortex (superior region of temporal lobe near lateral sulcus) Cochlear function: Hearing acuity Vestibular function: position in space related to position & movement of head and balance
33
CN VIII Vestibulocochlear -- Injury
**MOI:** • Acoustic Neuroma • Trauma • Middle Ear Infection • Labyrinthine artery damage **Injury:** • Tinitus (ring, buzz) • Vertigo (diyyy, loss of balance • Altered hearing **Deafness** • conductive (external and / or middle ear) (oritis media) • sensorineural (disease of cochlea, or cochlea to brain) **Acoustic neuroma** (neurofibroma) * Slow growing B9 tumor Schwann cells (neurolemma, the outer most layer of Schwann cells) in cochlear nerve * Leads to loss of hearing, probable dysequilibrium and tinnitus in 70% of patients **Vertigo** (hallucinogenic movement) * Spinning vs. swaying back & forth * Meniere Syndrome - all ages, sually middle to older age
34
CN VIII Vestibulocochlear -- Test
• Hearing tests: - Rine Test (Air): tuning fork through air - Weber Test (Bone): tuning fork on bony promnence: mastoid process, cranium • Vestibular testing: - cold/warm stimulus - -\> SHOULD cause vertigo/nystagmus - -\> direction of nystagmus or eye beating - -\> COWS: cold opposite, warm same • Vestibulo-ocular reflex - Reflex test for III, VI & VIII - Eyes should stay on examiners nose while head thrust performed. - Conjugate horizontal gaze: coordinated eye movement
35
CN IX Glossopharyngeal
**Mixed:** Motor, Sensory & Parasympathetic • Gag reflex **Sensory Function:** • Taste on posterior 1/3rd of tongue, somatic sensaton on 1/3rd of tongue, auditory tube & middle ear, carotid bodies (on bifurcation of arteries) **Motor Function:** • Stylopharyngeus (elevates pharynx w/ swalloing) **Parasympathetic Function:** • Parotid Gland (Salivary gland arond the mandibular ramus **Exit:** Jugular Foramen **Location of Nuclei:** Medulla • 2 sensory • 2 motor • Share nuclei w/ CN X Vagus & CN XI Accessory
36
CN IX Glossopharyngeal Nerve -- Injury
Tumors * Loss of taste posterior 1/3rd of tongue * Absent gag reflex * Often includes involvement of CN X Vagus and CN XI Accessory
37
CN IX -- Glossopharyngeal Nerve -- Test
• Sensory component: - Taste test: Does it taste bitter? - Gag reflex: lightly stimulate back of throat • Motor component: - Have patient swallowing a liquid
38
CN X Vagus
**Mixed** **Sensory Function:** • General somatic, special cisceral (taste, carotid bodies/sinus), general visceral • Heart, lungs, trachea, pharynx, larynx, bronchi, GI tract, external ear **Motor Function:** • Visceral (parasympathetic) to thoracic and abdominal viscera • Somatic motor to soft palate, pharynx (post. Tongue, mouth), laryngeal muscles • Motor: heart, lungs, trachea, palate, pharynx, larynx, bronchi, GI tract (ex: constricts bronchioles, decreases HR, increases GI motility) **Parasympathetic Function:** • Thoracic and abdominal viscera, to level of left colic flexure **Exit:** Jugular Foramen **Emergence:** from a sercies of rootlets in Medulla * Travels through the neck in the carotid sheath with the internal carotid and internal jugular vein * Travel down the thorax in the esophageal hiatus of the diaphragm to the abdominal cavity **Location of Nuclei:** Medulla + Cranial Spinal Cord • 2 sensory • 2 motor
39
CN X Vagus -- Injury
**• Dysphagia:** Difficulty swallowing - Injury to pharyngeal branches - **• Dysphonie:** Difficulty speaking **• Aphonia:** Loss of voice **• Inspirator stridor:** high pitch harsh respiratory sound
40
CN X Vagus -- Test
• Say Ahhh - Test --\> examine symmetry of uvula If lesion --\> uvula deviates contralaterally (strong side is pulling) --\> listen for hoarsness - -\> If both severed --\> aphonia (unable to talk) - -\> if one severed --\> deviates from affected side
41
CN XI Accessory
Also called Spinal Accessory Nerve **Motor** **Function:** • Sternocleidomastoid (SCM) - somatic • Trapezius • Striated mm of soft palate, pharynx, and larynx via connections with CN X Vagus • Cranial and spinal nerve roots form the first 5 cranial levels **Exit:** Jugular foramen
42
CN XI Accessory Nerve -- Injury
* Lymph node biospy * Surgical procedures ot intenal carotid or internal jugular veins ⇒ Resultant weakness of SCM and Traps
43
CN XI Accessory -- Test
* Shoulder shrug test: Trapezius * Head turn test: Sternocleidomastoid
44
CN XII Hypoglossal
**Motor** **Function:** • Intrinsic + extrinsic muscles of tongue • Motor nerves carry proprioceptive info • Tongue movement, symmetry & shape **Exit:** through hypoglossal canal **Location of Nuclei:** Medulla • Branches off Medulla
45
CN XII Hypoglossal Nerve -- Injury
* Paralysis of ½ of tongue, ipsilateral to side of injury * Deviates toward side of paralysis (pushing)
46
CN XII Hypoglossal Nerve -- Test
• Let me see your tongue test: --\> examine resting tongue • Stick out your tongue test: --\> examine tongue movement, strength & coordination --\> if lesion --\> tongue deviates ipsilaterally (strong side pushing)
47
Anatomical Origin Summary
**Forebrain:** CN I + II **Midbrain:** CN III + IV **Brainstem:** * **Pons:** CN V * **Junction between Pons & Medulla:** CN VI + VII + VIII **• Medulla:** CN IX + X + XII **Superior Spinal Cord:** CN XI

Lecture - Human Structure & Function (4 decks)

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