Examinationofthecranialnerves

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Examination of the cranial nerves

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Examinationofthecranialnerves

  1. 1. EXAMINATION OF THE CRANIAL NERVES
  2. 2. OLFACTORY NERVE (I) <ul><li>Test with alcowipes, coffee etc. </li></ul><ul><li>Unilateral anosmia may be significant </li></ul><ul><li>Bilateral anosmia: commonest cause viral </li></ul><ul><li>Classical pathology:olfactory groove meningioma </li></ul><ul><li>Basal skull fractures another potential cause (unilateral or bilateral) </li></ul>
  3. 3. OPTIC NERVE (II) <ul><li>Visual acuity </li></ul><ul><li>Visual fields to confrontation </li></ul><ul><li>Pupillary reflexes (II and III) </li></ul><ul><li>Fundoscopy (papilloedema, optic atrophy, retinitis pigmentosa) </li></ul>
  4. 4. VISUAL ACUITY <ul><li>CORRECTED (ie brain not lens) </li></ul><ul><li>Each eye separately </li></ul><ul><li>Snellen charts for distance and near vision reading charts for near vision </li></ul><ul><li>Best approximation: small print (or equivalent) at normal reading distance </li></ul><ul><li>If unable, finger counting, hand movements, perception of light </li></ul>
  5. 5. VISUAL FIELDS <ul><li>Often forgotten but very important </li></ul><ul><li>First do a bilateral screening test: will uncover the majority of significant visual field defects immediately </li></ul><ul><li>Go on to check each eye separately, ask about scotomata </li></ul><ul><li>Mention checking for blind spot enlargement </li></ul>
  6. 6. COMMON FIELD DEFECTS <ul><li>HOMONOMOUS HEMIANOPIA: lesion posterior to the optic chiasm (eg posterior cerebral artery territory infarction) </li></ul><ul><li>BITEMPORAL HEMIANOPIA: lesion at the optic chiasm (eg pituitary tumour) </li></ul><ul><li>BLINDNESS ONE EYE: lesion in eye, retina or optic nerve </li></ul>
  7. 7. PUPILLARY RESPONSES <ul><li>Light reflex is the clinically significant one </li></ul><ul><li>Afferent limb = II, efferent limb = III </li></ul><ul><li>Look at pupillary sizes </li></ul><ul><li>Direct and consensual response </li></ul><ul><li>Look for afferent pupillary defect (optic nerve lesion) </li></ul>
  8. 8. PUPILLARY ABNORMALITIES <ul><li>One large pupil: IIIrd nerve palsy, iris problem (eg traumatic midriasis), unilateral dilator eye drops </li></ul><ul><li>Small pupil: Horner’s syndrome, Argyll-Roberston pupil (small, irregular, reacts to accommodation but not to light) </li></ul><ul><li>Bilateral small pupils: drugs (opiates), pontine lesion (haemorrhage) </li></ul>
  9. 9. HORNER’S SYNDROME <ul><li>Oculosympathetic paralysis </li></ul><ul><li>A good lateralising sign but a poor localising sign </li></ul><ul><li>Ptosis, miosis and sometimes unilateral anhydrosis of face </li></ul><ul><li>Look especially at neck, supraclavicular fossa and hand (Pancoast’s tumour) </li></ul>
  10. 10. Eye movements (III, IV and VI) <ul><li>IV: TROCHLEAR NERVE (supplies superior oblique muscle) </li></ul><ul><li>VI: ABDUCENT NERVE (supplies lateral rectus muscle) </li></ul><ul><li>III: OCULOMOTOR NERVE: all other extraocular muscles, also carries parasympathetic (constrictor) fibres to pupil, and fibres to levator palpebrae superioris </li></ul>
  11. 11. EYE MOVEMENTS <ul><li>Look at eyes in primary position of gaze </li></ul><ul><li>IIIrd nerve palsy: eye often ‘down and out’ </li></ul><ul><li>VI nerve palsy: often eyes convergent (unopposed medial rectus) </li></ul><ul><li>Look at pupils </li></ul><ul><li>Look for ptosis </li></ul>
  12. 12. EYE MOVEMENTS <ul><li>Follow a moving object (finger, end of tendon hammer) and ask for any symptomatic diplopia </li></ul><ul><li>Determine position/s causing maximum diplopia </li></ul><ul><li>Ask about separation of images (horizontal or oblique) </li></ul><ul><li>Check diplopia is BINOCULAR </li></ul>
  13. 13. TYPICAL EXAM CASES <ul><li>IIIrd nerve palsy: ptosis, eye ‘down and out’, diplopia in all except one direction of gaze, may have dilated pupil ( a ‘surgical’ IIIrd nerve palsy </li></ul><ul><li>VI nerve palsy: eye convergent, diplopia on lateral gaze only, horizontally separated images </li></ul>
  14. 14. CAUSES OF COMPLEX OPTHALMOPLEGIA <ul><li>Dysthyroid eye disease </li></ul><ul><li>Myasthenia gravis (look for fatiguability of diplopia and ptosis) </li></ul><ul><li>Mitochondrial disorders </li></ul>
  15. 15. INTERNUCLEAR OPHTHALMOPLEGIA <ul><li>Nystagmus in the abducting eye </li></ul><ul><li>Failure of adduction of the other eye </li></ul><ul><li>Both eyes move normally when tested individually </li></ul><ul><li>Lesion in the MEDIAL LONGITUDINAL FASICULUS (on the side WITHOUT nystagmus </li></ul><ul><li>Can be bilateral </li></ul>
  16. 16. TRIGEMINAL NERVE (V) <ul><li>Most important function is sensory </li></ul><ul><li>Ophthalmic, maxillary and mandibular divisions </li></ul><ul><li>Test with light touch and pinprick in all 3 divisions, comparing each side </li></ul><ul><li>Corneal reflexes (afferent limb V, efferent limb VII) </li></ul><ul><li>Know something about trigeminal neuralgia (examination is normal in these cases) </li></ul>
  17. 17. FACIAL NERVE (VII) <ul><li>Supplies the muscles of the face </li></ul><ul><li>DIFFERENTIATE AN UPPER MOTOR NEURON FROM A LOWER MOTOR NEURON LESION </li></ul><ul><li>Upper motor neuron lesion: milder, spares the forehead, no Bell’s phenomenon </li></ul>
  18. 18. VESTIBULOCOCHLEAR NERVE (VIII) <ul><li>For clinical examination purposes, forget the vestibular element </li></ul><ul><li>Check hearing approximately in each ear </li></ul><ul><li>If reduced, determine whether conductive (BC >AC) or sensorineural (AC>BC) deafness </li></ul>
  19. 19. GLOSSOPHARYNGEAL (IX) AND VAGUS (X) <ul><li>Tested together </li></ul><ul><li>Speech, palate, cough, swallow, (gag reflex) </li></ul><ul><li>Bulbar palsy: bilateral LMN lesions of IX and X: poor palatal movement, nasal speech, nasal regurgitation of fluids </li></ul><ul><li>Pseudobulbar palsy: bilateral UMN lesions: ‘hot potato’ speech, no nasal regurgitation, additional frontal lobe signs </li></ul>
  20. 20. ACCESSORY NERVE (XI) <ul><li>Cranial and spinal roots </li></ul><ul><li>Cranial roots: sternocleidomastoid (note direction of head turn) </li></ul><ul><li>Spinal roots: trapezius (shoulder shrug) </li></ul>
  21. 21. HYPOGLOSSAL NERVE <ul><li>Movement of the tongue </li></ul><ul><li>Look for wasting and fasiculation of the tongue </li></ul><ul><li>Deviation of tongue on protrusion </li></ul><ul><li>Tongue movements including power </li></ul>

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