Cranial nerves

• What are cranial nerves?


  Sensory and motor nerves that link face, head and neck to brain
• How many pairs of cranial nerves are there?


  12
• What are the primary categories of cranial nerves based on function?


  1. Sensory nerves carry sensory info (smell hear and taste)
  2. Motor nerves control voluntary muscle movements
  3. Autonomic nerves are involved in parasympathetic functions (activites occuring when body is at rest)
• nemonic to remember all 12 cranial nerves

  Oh

  Oh

  Oh

  To

  Touch

  And

  Feel

  Very

  Green

  Vegetables

  A

  H
• What cranial nerves enter and exit the brain?


  Enter = sensory

  Exit = motor and autonomic

  Both = mixed nerves
• 1. Olfactory Nerve

  • Composition: sensory
  • Pathway: Through cribriform plate to olfactory bulbs
  • Functions : sense of smell
  • Effects of Damage: can be ruptured by head injury = loss of smell (anosmia)
• 2. Optic Nerve


  Composition: sensory

  Pathway: Optic canal -> optic chiasm -> optic tract -> lateral geniculate nucleus.

  Function: vision

  Effects of damage: Lesions cause visual field losses
• what is a optic chiasm?


  Nasal half of retina for both eyes cross over

  right visual field info -> left side of brain

  left visual field info -> right side of brain

  Allows for binocular vision

  Temporal half of retina for both eyes doesn't cross

  
• How can Bi-Temporal Hemi-Anopsia lead to loss of visual fields?

  Pitutary.g (below optic chiasm) tumour grows upwards which ruptures the optic chiasm.

  Px will lose temporal side fields of both eyes
• 3. Oculomotor Nerve 


  Composition: Motor

  Pathway : Coming from superior orbital fissure

  Function: eye movements

  Effects of damage: causes abnormal position of eye in the orbit

  position varies upon what nerve has been damaged
• What Extraocular muscles are controlled by the Oculomotor nerve?


  4 / 6

  1. medial rectus
  2. inferior rectus
  3. superior rectus
  4. inferior oblique
• 4. Trochlear Nerve


  composition ; motor

  Pathway; coming from superior orbital fissure

  function ; Controls superior oblique muscle for downward eye movement

  Effects of damage ; diplopia (double vision)
• 5. Trigeminal Nerve (V)

  Compostion; mainly sensory, some motor

  Function: Sensory for face/head (3 Trigeminal division), motor for chewing.

  Clinical: Damage can impair facial sensation and chewing.
• 6. Abducent Nerve (VI):

  • Function: Controls lateral rectus muscle (outwards).
  • Clinical: Damage leads to medial strabismus.***
• What 3 cranial nerves enter the eye orbit through the suprior orbital fisssure?

  Oculomotor, Trochlear, Abducens
• What muscles in the eye movement the eye in what direction?

  Superior rectus = up

  Inferior rectus = down

  Medial rectus = in towards nose

  lateral rectus = out

  Superior oblique = down and in

  Inferior oblique = up and in
• How do you test extra ocular muscles?


  Ocular motility test

  1. examine position of the eye in straight ahead gaze
  2. examine direction that is defected
• state the symptoms of oculomotor nerve (3) palsy?

  1. Exo-Tropia (pupil facing out)
  2. Diplopia (double vision)
  3. MR is paralyzed, LR over-acts
  4. Ptosis - drooping eyelid
  5. pupil dilated
• what does the Ocuolomotor nerve (3) supply? 


  1. Levator palpebrae muscle (skeletal muscle which lifts the upper lid)
  2. Internal eye muscles ( E.g. pupil constrictor and ciliary muscles)
• state the symptoms of Trochlear nerve (4) palsy?



  1. Hyper-tropia (face up) + Eso-tropia (face in)
  2. SO is paralyzed + other 5 over-act
• state the symptoms of Abducent (6) nerve palsy?



  1. Eso-tropic (face in)
  2. LR paralyzed
  3. other muscles esp MR overacts
• What are the pathways are used by the Trigeminal (3) nerve divisions ?

  1. Opthalmic = superior orbital fissure
  2. Maxiallary = Formen rotundum
  3. Mandibular = Foramen ovale

  
• What sensation is each Trigeminal nerve division associated with?

  V1: Ophthalmic - Sensation to the forehead, upper eyelid, and cornea.

  V2: Maxillary - Sensation to the cheek, upper lip, and lower eyelid.

  V3: Mandibular - Sensation to the lower lip, lower teeth and jaw, + part of the ear.
• What are the 3 Trigeminal nerve divisons?


  1. V1 (ophthalmic)
  2. V2 (maxillary)
  3. V3 (mandibular)

  
• Pons location and function


  upper part of the brainstem

  Links brain to spinal cord

  contains several junction points for nerves that control muscles + carry information from senses in your head and face
• 7. Facial nerve


  Composition ; Sensory, motor + automatic

  Motor = supplies muscles in charge of facial expression inc. near eyes

  Sensory nerves = supply taste buds on anterior tongue

  Autonomic = supplies lacrimal gland (tear film) via pterygopalatine ganglion + submandibular and subingual salivary glands via Geniculate Ganglion

  Pathways = internal auditory meatus

  Effect of damage = Bell's Palsy
• What is the orbicularis oculi muscle?

  Supplied by sensory facial nerve + surrounds each eye orbit

  controls closing the eyelids

  spreads tear film over cornea when blinking
• What are the symptoms of Bell's Palsy?


  1. Facial paralysis
  2. Right nerve affected
  3. Left nerve in tact

  
• How can upper eyelid palsy be treated?


  Gold weight implant

  weight of implant + force of gracvity forces eyelid to close
• Everted lower eyelid symptoms and treatment?


  lower eyelid turns outward and droops away from the eye

  surgery to tighten lower lid
• Treatment for Dry eyes?


  lubricating drops or ointments