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Cranial Nerves

  1. 1. Cranial Nerve Examination Samantha Harrison MBBS 3 King’s College London
  2. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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
  17. 17. References  Crossman and Neary  Oxford Clinical Handbook

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