EXAMINATION OF THE CRANIAL NERVES

1
EXAMINATION OF THE CRANIAL NERVES
2
OLFACTORY NERVE (I)

• Test with alcowipes, coffee etc.
• Unilateral anosmia may be significant
• Bilateral anosmia commonest cause viral
• Classical pathologyolfactory groove meningioma
• Basal skull fractures another potential cause
  (unilateral or bilateral)

3
OPTIC NERVE (II)

• Visual acuity
• Visual fields to confrontation
• Pupillary reflexes (II and III)
• Fundoscopy (papilloedema, optic atrophy,
  retinitis pigmentosa)

4
VISUAL ACUITY

• CORRECTED (ie brain not lens)
• Each eye separately
• Snellen charts for distance and near vision
  reading charts for near vision
• Best approximation small print (or equivalent)
  at normal reading distance
• If unable, finger counting, hand movements,
  perception of light

5
VISUAL FIELDS

• Often forgotten but very important
• First do a bilateral screening test will uncover
  the majority of significant visual field defects
  immediately
• Go on to check each eye separately, ask about
  scotomata
• Mention checking for blind spot enlargement

6
COMMON FIELD DEFECTS

• HOMONOMOUS HEMIANOPIA lesion posterior to the
  optic chiasm (eg posterior cerebral artery
  territory infarction)
• BITEMPORAL HEMIANOPIA lesion at the optic chiasm
  (eg pituitary tumour)
• BLINDNESS ONE EYE lesion in eye, retina or optic
  nerve

7
PUPILLARY RESPONSES

• Light reflex is the clinically significant one
• Afferent limb II, efferent limb III
• Look at pupillary sizes
• Direct and consensual response
• Look for afferent pupillary defect (optic nerve
  lesion)

8
PUPILLARY ABNORMALITIES

• One large pupil IIIrd nerve palsy, iris problem
  (eg traumatic midriasis), unilateral dilator eye
  drops
• Small pupil Horners syndrome, Argyll-Roberston
  pupil (small, irregular, reacts to accommodation
  but not to light)
• Bilateral small pupils drugs (opiates), pontine
  lesion (haemorrhage)

9
HORNERS SYNDROME

• Oculosympathetic paralysis
• A good lateralising sign but a poor localising
  sign
• Ptosis, miosis and sometimes unilateral
  anhydrosis of face
• Look especially at neck, supraclavicular fossa
  and hand (Pancoasts tumour)

10
Eye movements (III, IV and VI)

• IV TROCHLEAR NERVE (supplies superior oblique
  muscle)
• VI ABDUCENT NERVE (supplies lateral rectus
  muscle)
• III OCULOMOTOR NERVE all other extraocular
  muscles, also carries parasympathetic
  (constrictor) fibres to pupil, and fibres to
  levator palpebrae superioris

11
EYE MOVEMENTS

• Look at eyes in primary position of gaze
• IIIrd nerve palsy eye often down and out
• VI nerve palsy often eyes convergent (unopposed
  medial rectus)
• Look at pupils
• Look for ptosis

12
EYE MOVEMENTS

• Follow a moving object (finger, end of tendon
  hammer) and ask for any symptomatic diplopia
• Determine position/s causing maximum diplopia
• Ask about separation of images (horizontal or
  oblique)
• Check diplopia is BINOCULAR

13
TYPICAL EXAM CASES

• 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
• VI nerve palsy eye convergent, diplopia on
  lateral gaze only, horizontally separated images

14
CAUSES OF COMPLEX OPTHALMOPLEGIA

• Dysthyroid eye disease
• Myasthenia gravis (look for fatiguability of
  diplopia and ptosis)
• Mitochondrial disorders

15
INTERNUCLEAR OPHTHALMOPLEGIA

• Nystagmus in the abducting eye
• Failure of adduction of the other eye
• Both eyes move normally when tested individually
• Lesion in the MEDIAL LONGITUDINAL FASICULUS (on
  the side WITHOUT nystagmus
• Can be bilateral

16
TRIGEMINAL NERVE (V)

• Most important function is sensory
• Ophthalmic, maxillary and mandibular divisions
• Test with light touch and pinprick in all 3
  divisions, comparing each side
• Corneal reflexes (afferent limb V, efferent limb
  VII)
• Know something about trigeminal neuralgia
  (examination is normal in these cases)

17
FACIAL NERVE (VII)

• Supplies the muscles of the face
• DIFFERENTIATE AN UPPER MOTOR NEURON FROM A LOWER
  MOTOR NEURON LESION
• Upper motor neuron lesion milder, spares the
  forehead, no Bells phenomenon

18
VESTIBULOCOCHLEAR NERVE (VIII)

• For clinical examination purposes, forget the
  vestibular element
• Check hearing approximately in each ear
• If reduced, determine whether conductive (BC gtAC)
  or sensorineural (ACgtBC) deafness

19
GLOSSOPHARYNGEAL (IX) AND VAGUS (X)

• Tested together
• Speech, palate, cough, swallow, (gag reflex)
• Bulbar palsy bilateral LMN lesions of IX and X
  poor palatal movement, nasal speech, nasal
  regurgitation of fluids
• Pseudobulbar palsy bilateral UMN lesions hot
  potato speech, no nasal regurgitation,
  additional frontal lobe signs

20
ACCESSORY NERVE (XI)

• Cranial and spinal roots
• Cranial roots sternocleidomastoid (note
  direction of head turn)
• Spinal roots trapezius (shoulder shrug)

21
HYPOGLOSSAL NERVE

• Movement of the tongue
• Look for wasting and fasiculation of the tongue
• Deviation of tongue on protrusion
• Tongue movements including power

22
(No Transcript)