Examination of Cranial Nerves

• systemic disease with CN pathology

  
  

  What is myasthenia gravis?

  Myasthenia gravis is a rare long-term condition that causes muscle weakness

  
  

  .• Acquired weakness - AChR antibodies

  • Variable weakness subject to variability

  • Limb, ocular, bulbar, respiratory involvement

  • Treatable

  
• systemic disease with CN pathology

  
  

  What is myotonic dystrophy?

  Myotonic dystrophy is a genetic condition that causes progressive muscle weakness and wasting

  
  

  • Most common muscular dystrophy of adult life

  (1 in 8000)

  • Subject to an<cipa<on

  • may feature malocclusion

  • Risk of anaesthe<c complica<ons

  
• multiple CN abnormalities:

  
  

  What are some peripheral causes of Horner's syndrome?

  Trauma

  Carotid dissection

  Aortic aneurysm(Pancoast)

  tumour
• multiple CN abnormalities:

  
  

  What are some central causes of Horner's syndrome?

  Stroke or demyelination
• multiple CN abnormalities:

  
  

  What is Horner's syndrome?


  Injury to the cervical sympathetic chain. (contains cranial nerves)

  
  

  Think MAP:

  - Miosis (small pupil)

  - Anhidrosis of ipsilateral face (absence of sweating)

  - Ptosis (drooping or falling of the upper eyelid)

  
  

  (sometimes enophthalmos (eyes sink deeper into eye socket) is present too)
• multiple CN abnormalities:

  
  

  Give some examples of syndromes with multiple cranial nerve abnormalities.

  - Cerebellopontine angle lesion (unilateral C.V, VII, VIII)

  - Cavernous sinus lesion (unilateral C.III, IV, V1, VI)

  - Horner syndrome (sympathetic trunk damage)
• single CN abnormalities:

  
  

  What is accessory nerve palsy?

  An abnormal shoulder condition that arises due to injury of the spinal accessory nerve (cranial nerve 11).

  - Can result in weakness of trapezius muscle, shoulder pain and "winging" of the shoulder blades

  
• single CN abnormalities:

  
  

  What is hypoglossal nerve palsy?

  Damage to the hypoglossal nerve (cranial nerve 12) which causes paralysis of the tongue

  
• single CN abnormalities:

  
  

  What is the most common cause of lingual nerve injuries?

  Third molar surgery
• CN examination

  
  

  How do you examine the mouth and tongue for CN V, CN VII, CN IX, CN X, CN XII?

  Ask about taste

  Listen to the voice

  Inspection

  Uvula

  Gag reflex (not routine)

  Tongue
• CN examination

  
  

  How do you assess the vestibulocochlear nerve (CN VIII)?

  -------Auditory:

  Rinne's test (for conductive hearing)

  Weber's test (for sensorineural hearing loss)

  
  

  -------Vestibular:

  Gait

  Nystagmus

  Hallpike

  manoeuvres
• single CN abnormalities:

  
  

  What is a common cause of unilateral upper motor neuron lesions?

  Cerebrovascular incidents
• single CN abnormalities:

  
  

  What are potential causes of uniIateral lower motor neuron lesions?

  Bell's palsy

  Herpetic infections
• single CN abnormalities:

  
  

  What is facial nerve palsy?


  -Complete destruction of the facial nucleus itself or its branchial efferent fibres (facial nerve proper)

  -Peripheral ipsilateral facial paralysis (absent forehead creases and drooping smile) with inability to close eye on involved side

  -Associated with Lyme disease, herpes simplex, and less commonly, herpes zoster (Ramsay-Hunt syndrome), sarcoidosis, tumours, diabetes

  
• CN examination

  
  

  How can you assess the facial nerve (CN 7)?


  Ask the patient to scrunch their eyes closed, wrinkle up their forehead, blow out their cheeks and smile

  
  

  - you can also test the corneal reflex (only on unconscious patients as it is quite unpleasant)
• single CN abnormalities:

  
  

  what can cause complete sensory loss in a R sided distinction of the face?

  - all sensory branches of the trigeminal nerve being damaged

  - frequently seen in patients with herpes zoster
• single CN abnormalities:

  
  

  what is inferior alveolar nerve damage?

  - pain or abnormal sensations in the chin, lower teeth, lower jaw, and lower lips.

  - Nerve damage may result in speech difficulties and/or affect chewing.

  
  

  due to damage of the sensory branch of the mandibular nerve (CN V3) (which is itself the third branch of the trigeminal nerve (CN V)).
• single CN abnormalities:

  
  

  How can inferior alveolar nerve damage take place?

  Implants, root treatments or third molar surgery are amongst the reasons
• single CN abnormalities:

  
  

  What is Frey's syndrome?

  Also known as auriculotemporal syndrome and it brings about increased sweating of the facial skin when eating, due to reinnervation of the divided sympathetic nerves to the facial skin by fibres of the secretomotor branch of the auriculotemporal nerve

  
  

  - due to trigeminal nerve damage

  
• CN examination

  
  

  What is another important test for testing function of the trigeminal nerve?

  Test the corneal reflex (only on unconscious patients as it is quite unpleasant)
• CN examination

  
  

  How do you assess motor function of the trigeminal nerve?

  Asking the patient to press with their jaw against your fingers (assessing strength of mastication muscles)
• CN examination

  
  

  How do you assess the sensory function of the trigeminal nerve?

  Touch the patient's face lightly with a cotton pad
• single CN abnormalities:

  
  

  What is external ophthalmoplegia?

  Condition characterised by weakness of the eye muscles

  
• single CN abnormalities:

  
  

  What are some features of double vision?

  It's maximal in direction of gaze of affected muscle and the false image is the outer image which arises in the affected eye
• single CN abnormalities:

  
  

  What are some causes of single palsies of C.III, IV and VI?

  Medical:

  e.g. diabetes, atherosclerosis

  
  

  Surgical:

  e.g. tumour, aneurysm, trauma
• single CN abnormalities:

  
  

  what is double vision?

  Double vision, which is also called diplopia, causes people to see two of the same image—whether horizontal, vertical or diagonal—instead of one.

  
  

  - normally due to damage of the 3rd, 4th or 6th cranial nerves
• single CN abnormalities:

  
  

  what is abducens nerve palsy?

  Causes problems with eye movement e.g. not being able to look to the left

  
  

  - due to damage from cranial nerve VI

  
• single CN abnormalities:

  
  

  What is trochlear nerve palsy?

  Condition which causes an ipsilateral higher eye and excyclotorsion

  
  

  - due to damage from cranial nerve IV

  
• single CN abnormalities:

  
  

  What is oculomotor nerve palsy?

  A condition known as "down n out syndrome" where the eye looks down and out when there is a problem with the oculomotor nerve. You can also get pupillary dilatation and your eyelid may be closed

  
  

  - due to damage from cranial nerve III

  
• single CN abnormalities:

  
  

  what is optic atrophy?

  damage to optic nerve (second cranial nerve (CN II))
• single CN abnormalities:

  
  

  what is papilloedema?


  swelling of optic disc due to elevated intracranial pressure
• single CN abnormalities:

  
  

  What might cause unilateral anosmia?

  Frontal lobe lesion
• single CN abnormalities:

  
  

  What might cause bilateral anosmia?

  Trauma

  Parkinson's disease

  Covid-19
• single CN abnormalities:

  
  

  what is anosmia?

  partial or full loss of smell

  
  

  - normally due to damage to CN I
• CN examination

  
  

  describe direct, consensual, and accomodation pupillary reactions


  - A direct pupillary reflex is pupillary response to light that enters the ipsilateral (same) eye.

  - A consensual pupillary reflex is response of a pupil to light that enters the contralateral (opposite) eye.

  - The accommodation reflex (or near response) is a three-part reflex that brings near objects into focus through lens thickening, pupillary constriction, and inward rotation of the eyes—eye convergence.
• CN examination

  
  

  how are the eyes examined?

  Inspection

  Pupillary reactions (direct, consensual, accomodation)

  Visual acuity (reading from a distance or assessing colour)

  Visual fields

  Eye movements

  Fundoscopy (ophthalmoscope is used to examine the eye)
• CN examination

  
  

  what is the sequence of CN examination?

  Smell (C.I)

  Eyes (C.II, III, IV, VI)

  Face (C.V, VII)

  Hearing & balance (C.VIII)

  Mouth (C.V, VII, IX, X, XII)

  Neck & shoulders (C.XI)
• which cranial nerves are for the neck and shoulders?

  11 - cranial accessory
• which cranial nerves are for the mouth?

  5 - lingual (sesnory branch of mandibular division of trigeminal)

  7 - facial

  9 - glossopharyngeal

  10 - vagus

  12 - hypoglossal
• which cranial nerves are for the face?

  5 - trigeminal

  7 - facial