2. What are Cranial Nerves?
Definition: Nerves that emerge directly from the
brain
There are 12 of them
I.Olfactory II.Optic III.Oculomotor IV. Trochlear
V.Trigeminal VI.Abducens VII.Facial VIII.
Vestibulocochlear IX.Glossopharyngeal
X.Vagus XI.Spinal Accessory XII.Hypoglossal
3. Where do they come from?
1 & 2 from the cerebrum
3-12 from the brainstem
Olfactory – Telencephalon
Optic –Diencephalon
Oculomotor – Ant. Midbrain
Trochlear – Dorsal Midbrain
Trigeminal - Pons
Abducens – Pons (under
floor of the fourth ventricle)
Facial – Pons –
cerebellopontine angle
Vestibulo-cochlear –
cerebellopontine angle
(lat to CVII)
Glossopharyngeal -Medulla
Vagus –Medulla
Spinal Accessory –
cranial and spinal roots
Hypoglossal – Medulla
4. Efferent and Afferent Cranial Nerves
Some
Say
Money
Matters
But
My
Brother
Says
Big
….Brains
Matter
More
Olfactory
Optic
Oculomotor
Trochlear
Trigeminal
Abducens
Facial
Vestibulocochlear
Glossopharyngeal
Vagus
Spinal Accessory
Hypoglossal
5. I: Olfactory
Efferent or Afferent: Afferent (sensory)
Function: Smell
Examination: Block one nostril. Get patient
to smell strong distinctive smell (coffee, lemon, cinnamon).
Normal: If patient can smell/identify smell with both nostrils –
olfactory nerve intact
Palsy/Lesion: Unilateral loss of smell – lesion. Generally
from trauma, meningitis, tumour. WILL NOT AFFECT
SENSATION.
6. Optic Nerve
Efferent or Afferent: Afferent
Function: Visual transmission – eye to brain
Examination: 1. Visual Acuity: Read progressively smaller writing on the
snellen chart.
2. Visual fields – finger wiggle, fingers/ red hat pin in from the periphery (for
each eye)
3. Pupillary light reflex and Swinging light reflex
Normal: Consensual response to both pupillary light and swinging light reflex
Palsy: 1, visual acuity is reduced in one or both eyes 2. Peripheral vision is
reduced compared to yours 3. non –consensual pupillary light reflex, swinging
light reflex – pupil dilates when light shining on it – the consensual response is
stronger than the direct
7. Oculomotor
Efferent or Afferent: Efferent
Function: Innervates all but two muscles for eye movement.
Examination: 1. Look for ptosis, eye position and nystagmus,
inspect pupil for PERRLA
2. Test Ocular Movement ‘H’. Ask about diplopia
3. Accommodation reflex
Normal: Consensual pupil responses
No diplopia or nystagmus
Palsy: obvious ptosis, lateral rectus
And superior oblique acting unnopposed
8. Trochlear
Efferent or Afferent: Efferent
Function: Innervates Superior Oblique
Examination: Examination: 1. Look for ptosis, eye position
and nystagmus, inspect pupil for PERRLA
2. Test Ocular Movement ‘H’. Ask about diplopia
3. Accommodation reflex
Palsy: Intorsion
(same plane
as face). Eye points supero-
Medially
9. Abducens
Efferent or Afferent: Efferent
Function: Innervates Lateral Rectus
Examination: 1. Look for ptosis, eye position and nystagmus,
inspect pupil for PERRLA
2. Test Ocular Movement ‘H’. Ask about diplopia
3. Accommodation reflex
Palsy: lack of innervation of lateral
Rectus, eye cannot be abducted
10. Trigeminal: V1, 2, 3
Efferent or Afferent: Both
Function:
Sensory to the face: V1 – ophthalmic, V2- maxillary, V3 –
mandibular
Motor: Muscles of mastication
Examination: S: Point touch with cotton wool/tissue, pain using a sharp point,
temperature – cold tuning fork
Corneal reflex: rapid blinking of the eye lids from a sudden stimulus
Motor: Inspect. Palpate temporalis and masseter as patient clenches the jaw,
pterygoids – mouth open against resistance, jaw jerk
Normal: even feeling of sensation, both eyelids respond to corneal reflex, able to
clench jaw, no jaw jerk
Palsy: wasting of temporalis or masseter, unable to resist pressure to close mouth
11. Facial
Efferent or Afferent: Both
Function: Sensory - Taste (Anterior 2/3 of the tongue); Motor – Muscles
of facial expression
Examination:
Sensory: Test Taste of distinctive flavours (similar to the
smell test of olfactory).
Motor: 1) raise both eyebrows 2) screw eyes up, try to pull
open to test muscular strength 3) frown 4) smile 5) bare teeth (show
both upper and lower teeth) 6) puff out cheeks
Palsy: Bell’s Palsy (central/peripheral)
Ramsay-Hunt Syndrome
12. Vestibulo-cochlear
Efferent or Afferent: Afferent
Function: Hearing
Examination: 1) Whisper a number into patient’s ears. One at a time.
Ask the patient to repeat the numbers
2) Rinne Test 3) Weber Test
Normal: 1. Correct number 2. Air conduction louder than bone 3. Hear
the tuning fork in both ears equally
Palsy: Rinne normal (both ears). Weber lateralisation = contralateral
sensorineural hearing loss. Rinne – BC>AC in left, weber normal or left
lateralisation = conductive loss left. Rinne BC>AC left, weber lateralises
right = conductive and sensorineural loss left
13. Glossopharyngeal
Efferent or Afferent: Both
Function: Swallowing, Gag Reflex
Examination: Gag response :/, palatal articulation –
KA or guttural articulation GO
Palsy: Abnormal Cough on swallowing
14. Vagus
Efferent or Afferent: Both
Function: Swallowing, gag reflex
Examination: Test in the same way as the
glossopharyngeal
Palsy: Abnormal Cough on swallowing
15. Spinal Accessory
Efferent or Afferent: Efferent
Function: Innervation to SCM and Trapezius
Examination: Ask patient to turn head, shrug shoulders
(against resistance).
Normal: Symmetrical movements performed. Able to resist
pressure
Palsy: Muscle wasting, unable to resist pressure
16. Hypoglossal
Efferent or Afferent: Efferent
Function: innervation to genioglossus. NOT to palatoglossus
(innervated by vagus nerve)
Examination: Inspect for tongue fasciculations, asymmetry
or atrophy. Ask patient to poke out their tongue
Normal: No deviation of the tongue on protrusion
Palsy: Will deviate ipsilateral to the paralysis and
contralateral to the lesion