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Cranial nerves are useful in diagnosing whether someone has had a stroke.

CN5 – Trigeminal nerve

  • Largest nerve and one of the most important; divides into three major nerves
  • Mostly composed of somatosensory fibres (pain, temperature, touch and proprioception)
    • Supplies the skin and mucosa of the head
    • Cell bodies are mostly within the large trigeminal ganglion
  • Exception: proprioception
  • Ganglion is located beneath the dura on the front of the petrous temporal bone in the middle cranial fossa
  • From here, the sensory nuclei of the trigeminal nerve extend throughout the brainstem
  • Motor fibres supply the muscles of mastication at the temperomandibular joint
  • Emerges from the brainstem at the lateral side of the pons
    • Pierces the dura then divides into 3 branches: ophthalmic, maxillary and mandibular nerves just after synapsing in the trigeminal ganglion
  • Branches:
    • Ophthalmic nerve – purely sensory
      • Follows the lateral wall of the cavernous sinus, inferior to CN4
      • Enters the orbit through the superior orbital fissure
      • Branches supply the cornea, mucosa of the upper nasal cavity, skin of the upper eyelid and forehead
      • Controls the corneal reflex – the touch reflex of the eye
      • Gives off lacrimal nerve to cause crying
    • Maxillary nerve – purely sensory
      • Exits the cranial cavity by foramen rotundum
      • Enters the pterygopalatine fossa
      • Branches supply the mucosa of the nasal cavity, upper jaw and teeth, maxillary sinuses and

skin of the lower eyelid, nose, upper lip

      • Superior alveolar nerve supplies the upper jaw
      • Terminal branch is the infraorbital nerve that follows the floor of the orbit before passing through the maxillary sinus and emerging onto the cheek
    • Mandibular nerve – motor and sensory
      • Exits the cranial cavity by foramen ovale
      • Enters the infratemporal fossa medial to the temporomandibular joint
      • Branches to the muscles of mastication (temporalis, masseter, med/lat pterygoid), mucosa of the check and skin of the temporal region
        • Main branches:
          • Lingual – sensory to anterior part of the tongue
          • Inferior alveolar nerve – mucosa and teeth of the lower jaw, skin of chin
      • Supplies tensor tympani
  • Swelling is trigeminal ganglion (like a dorsal root ganglion). From the anterior surface of this ganglion arise the three branches listed above.
  • Pathology
    • Shingles (herpes)
  • Chickenpox that never disappears
  • Affects sensory neurons
  • Can cause blisters in a particular dermatome
  • Particularly bad in the trigeminal nerve
    • Neuralgia
  • Sensory fibres become hypersensitive
  • Often caused by pressure, ie: a BV crossing a nerve?
  • Particularly painful in CN5
  • Sensory:
    • pain, temperature, touch and pressure from skin of face, oral and nasal cavi>es, paranasal sinuses, dura mater
  • Note that the motor tuft is small while the sensory tuft is large


Pathway of trigeminal nerve

  • leaves anterior aspect of pons
  • In middle cranial fossa splits into three divisions
  • ophthalmic (sensory)
    • exits skull through superior orbital fissure
  • maxillary (sensory)
    • exits skull through foramen rotundum
  • mandibular (sensory and motor)
    • exits skull through foramen ovale
  • The trigeminal nerve divides into three branches:
    • Ophthalmic n. (V1) - superior orbital fissure
    • Maxillary n. (V2) - foramen rotundum
    • Mandibular n.(V3) - foramen ovale
  • See the diagram showing branching of the trigeminal nerve

Cavernous sinus & related nerve

  • Sits within two layers of dura mater. The cavernous sinus has lots of dural septae within it.
  • Within this sinus is the internal carotid artery (artery going within a vein). If the artery bursts, we get an AV fistula.
  • CN 3, 4, 5i and 5ii lie on the lateral wall of the cavernous sinus. CN 6 lies close to the internal carotid artery (medially).
  • Pituitary gland sits on the sella turcica. If a tumour of the pituitary gland starts expanding, it will compress the cavernous sinuses

CN7 - Facial nerve

  • Mixed nerve containing:
    • Motor fibres to the muscles of facial expression – within the skin (easily damaged); does so through its many branches that form after passing through the parotid gland
    • Taste fibres to the anterior 2/3 of the tongue
    • Parasympathetic fibres controlling mucous, salivary and lacrimal glands of the head (all except parotid gland; which it pierces)
      • Sensory fibres for the lacrimal gland are within the lacrimal nerve, a branch of the ophthalmic division (V1) of the trigeminal nerve
    • A few somatosensory fibres from the external ear
  • Emerges from brainstem at the pontomedullary junction
    • Enters the internal acoustic meatus
    • Travels towards the ear with CN8
      • At the inner ear it gives off a parasympathetic branch that synapses in a small ganglion (pterygopalatine ganglion) before travelling with the maxillary nerve branches to supply the nose and orbit glands (incl. lacrimal)
    • The main branch passes behind the ear in the facial canal and gives off the chorda tympani branch
      • This joins up with the lingual nerve and conveys taste fibres to the tongue and parasympathetic supply to the 2 large salivary glands. Chorda tympani hitchhikes on the lingual nerve and supplies taste to the tongue.
    • Sensory - a small area of skin of external ear
    • The main branch continues and exits the skull through the stylomastoid foramen and enters the parotid gland
      • Splits into branches that emerge on the face and supply muscles of facial expression
      • Also gives a branch to the stapedius muscle in the ear
        • Contracts the tympanic membrane when noise is too loud and stops excessive vibration
        • Pathology
          • Particularly vulnerable to injury in the:
      • Internal acoustic meatus (eg: benign tumour: acoustic neuroma)
        • Swelling can compression CN7 and 8 and maybe CN5
      • Facial canal (eg. middle ear infections, surgery)
        • Orbicularis oculi muscles closes the eyes – risk of corneal damage if reflex lost
        • Orbicularis oris closes the mouth
      • On the face (skin lacerations)
    • Bell’s palsy – paralysis of the facial nerve
      • Can be spontaneous/viral
      • Function can return over time

CN8 – Vestibulocochlear nerve

  • Carries information from hearing (cochlear) and balance (vestibular) receptors from the inner ear
    • Enters the cranial cavity via the internal acoustic meatus (in the petrous temporal bone), along with the facial nerve
    • Enters the brainstem at the pontomedullary junction lateral to CN7

CN9 – Glossopharyngeal nerve

  • A complex nerve containing:
    • Sensory fibres from the walls of the pharynx and posterior tongue (incl. taste)
    • Visceral sensory fibres from chemo (CO2) and baroreceptors (BP) in the carotid arteries
    • Motor fibres to the pharynx
    • Parasympathetic fibres to the parotid gland
  • Emerges from the medulla at the lateral side of the olive
    • Enters the jugular foramen (note all the other CNs that pass through the JF)
  • Rarely damaged in isolation
  • Carries taste from posterior 1/3 of the tongue, somatosensory (pharynx, external ear and tympanic membrane, posterior 1/3 of tongue (gag reflex), carotid sinus/bodies), motor (stylopharyngeus - the muscle that causes the pharynx to rise up), parasympathetic (parotid gland - salivary; NB: all facial glands are supplied by facial nerve except for the parotid gland, which it pierces)
  • Pathway: from upper medulla between olive and inferior cerebellar peduncle; exits skull through jugular foramen
  • Glossopharyngeal nerve joins with the vagus fibres, to supply all of the pharynx and larynx