Cranial Nerves

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Cranial Nerves

• Nathan Hales, M.D.
• Department of Otorhinolaryngology
• September 18, 2006

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Cranial Nerves
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Cranial Nerves
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Cranial Nerves

• Motor and sensory innervation of the head and
  neck
• Innervation of special sense organs

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Pneumonic

• Names
• On old Olympus towering top a fair vain German
  vends a hop.
• Function
• Some say marry money, but my brother says Big
  brains mean more.

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Parasympathetics
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Sympathetics
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Cranial Nerves - Origins
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Foramina of the Cranial Base
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Cranial Nerves
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Olfactory Nerve
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I- Olfactory

• Type- visceral sensory
• Function- smell
• CNS- extension of brain
• Exit - cribiform plate

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Cranial Nerves
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II- Optic

• Type- special sensory
• Function- vision
• CNS- occipital lobe
• Exit- optic canal

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Optic Nerve
Medial Fibers Cross
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Cranial Nerves
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Cranial Nerves 3,4, and 6

• Essential in eye movement.

SO4LR6
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Extraocular movement
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Cavernous Sinus
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III- Oculomotor

• Type
• Somatic motor
• Visceral motor (para/sympathetic)
• CNS- midbrain Exit- superior
  orbital fissure
• Function(motor)
• Extraocular muscles-medial, superior, and
  inferior rectus, inferior oblique muscle
• Levator palpebrae superioris - opens eyelid

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III- Oculomotor

• Function (para/symp)
• Ciliary muscle of lens and sphincter muscles of
  iris
• Parasympathetics cause constriction of pupil and
  lens accommodation (for near vision)
• Sympathetics cause pupillary dilation

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IV- Trochlear

• Type- somatic motor
• Function- superior oblique muscle of eye
• If damaged- trouble bringing eye medially and
  inferiorly
• CNS- brainstem
• Exit- superior orbital fissure

SO4
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VI- Abducens

• Type- somatic motor
• Function- lateral rectus
• If damaged- eye stays medial
• CNS- pons
• Exit- superior orbital fissure

LR6
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Cranial Nerves
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V- Trigeminal

• CNS- pons
• Exit
• V1- superior orbital fissure
• V2- foramen rotundum
• V3- foramen ovale

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Foramina of the Cranial Base
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Trigeminal Nerve
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V- Trigeminal

• Type
• Somatic motor
• Somatic sensory
• Function (motor)
• V3 innervates muscles of mastication (temporalis,
  masseter, medial and lateral pterygoids),
  mylohyoid and anterior digastric muscle
• Tensors tympani and palatini

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Trigeminal Nerve

• Function (sensory)
• V1- Supraorbital/ supratrochlear
• sensation to upper face/ forehead
• Innervates lacrimal gland (parasymp from CN
  7-greater sup petrosal), cornea (corneal reflex),
  tip of nose

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Trigeminal Nerve

• V2- Maxillary division
• Sensation to middle part of face- teeth, maxilla,
  max sinus, palate, nose, lower eyelid, upper lip

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Trigeminal Nerve

• V3- Mandibular division
• Sensation to teeth, mandible, chin, etc
• Lingual Nerve- sensation- ant 2/3 of tongue.
  Taste- ant 2/3 of tongue from chorda tympani.
  (Parasymps from chorda tympani (CN 7) to
  sublingual and submandibular gland)
• Auriculotemporal n.- sensory to EAC

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Trigeminal Nerve
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Cranial Nerve 7 and 8

• To be covered in subsequent lectures
• Nervus Intermedius
• Sensation to the posterior meatus of the EAC.
• Hetzelbergers Sign for Acoustic neuroma

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Foramina of the Cranial Base
9,10,11,12
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CN 9- Glossopharyngeal

• Type- somatic motor, visceral sensory, special
  sensory, autonomic
• CNS- medulla
• Exit- Jugular Foramen
• Function-
• Motor- stylopharyngeus muscle
• Sens- pharynx, tonsil, and middle ear/eustachian
  tube (Jacobsons nerve)

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Glossopharyngeal

• Parasympathetics
• Jacobsons nerve- lesser superficial petrosal-
  otic ganglion- auriculotemporal (V3) to parotid
  gland- stim secretion
• Special Sensory- taste from post. 1/3 of tongue
• Pressure and chemoreceptors from carotid
• Gag reflex

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Tympanic Plexis of IX
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CN 10- Vagus

• Type- motor, sensory, autonomic
• CNS- Medulla
• Exit- Jugular Foramen
• Function-
• Sensory- posterior end of tongue and epiglottis,
  larynx
• Superior laryngeal Nerve (internal branch)-
  sensation above vocal cords (supraglottis)
• Recurrent laryngeal Nerve- sens below VCs
• Arnolds Nerve- sensation to middle ear
• Sensation to post part of ext ear and EAC

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Vagus

• Motor
• Superior laryngeal (external branch)-
  cricothyroid
• Recurrent Laryngeal- laryngeal muscles
• Constrictor muscles of pharynx (superior, middle,
  and inferior)- combines with CN 9
• Soft Palate (levator veli palatini,
  palatopharyngeus, palatoglossus)

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Vagus

• Parasympathetics
• Heart- constricts arteries
• Lungs- bronchial constriction
• GI- Peristalsis- gut motility- esophagus down to
  duodenum

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CN 11- Spinal Accessory

• Type- Motor ONLY
• CNS- medulla and Cervical Spine
• Exit- Jugular Foramen
• Function Motor
• Sternocleidomastoid- turns head to same side
  muscle is on, Trapezius (shoulder movement-
  elevation)
• Contributions to Pharynx by CN 10

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XI
Voluntary motor nerve
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CN 12- Hypoglossal

• Type- Motor
• CNS- medulla
• Exit- hypoglossal canal
• Function- all tongue muscles
• intrinsic muscles, genioglossus, geniohyoid,
  styloglossus, hyoglossus (not palatoglossus)
• Tongue will deviate to side of lesion
• Lick your wounds

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CN 12- Hypoglossal
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Conclusion

• Know the names of the 12 nerves first, then
• Think about what each does
• Sensation vs motor
• Where it exits the skull base
• Clinically what deficit it causes
• If any doubt consult your local ORL surgeon!

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Thanks!
Nathan Hales, M.D. ORL Chief Resident nhales_at_ouhsc
.edu 405-271-5504