4.1 Cranial Nerve Lesions

Question 1

How is CNI examined?

Answer 1

Sense of smell in each nostril with coffee/orange

Question 2

Describe what causes CNI lesions and what this can lead to.

Answer 2

Fractures of cribriform plate
Anosmia (temporary due to infection, permanent due to trauma or tumrous)
CSF rhinorrhoea - if dura mater is pierced, leakage of CSF into nasal cavity.

Question 3

How is CNII examined?

Answer 3

Visual acuity
Colour vision
Visual fields
Pupillary reflexes
Fundoscopy

Question 4

Describe causes of CNII lesion and what this causes.

Answer 4

Direct trauma to eye or orbit, fracture of optic canal or pressure on optic nerve
Loss of pupillary constriction and visual field defects.

Question 5

How is CNIII examined?

Answer 5

Movement of eye in H for extraocular muscles
Ptosis
Pupillary reflex (consensual)
Accommodation

Question 6

What can cause CNIII palsy?

Answer 6

Aneurysms
Increased intracranial pressure
Cavernous sinus infection/trauma

Question 7

How does CNIII palsy present?

Answer 7

Down and Out
(LR6 SO4)
Ptosis - denervation of legator palpebrae superioris
Dilated pupil - palsy of autonomic parasympathetics - denervationof sphincter pupillage

Question 8

Describe how the site of CNIII lesion can be determined.

Answer 8

Complete palsy - anywhere proximal to ciliary ganglion:
Down and out
Prosis
Mydraiasis
Loss of accommodation

Distal to ciliary ganglion
Down and out
ptosis
Pupils of eyes will be equal - pupil sparing - fibres controlling pupillary function are superficial and spared.

Question 9

How is CNIV assessed?

Answer 9

Test movement of eye H

Test diplopia

Question 10

Describe how CNIV lesion presents. Causes?

Answer 10

Inability to look down when eye is adducted.
Diplopia on looking down and in (e.g. going down stairs).

Cuases:
Stretching
Cavernous sinus thrombosis.

Question 11

Describe the corneal reflex and what nerve it is testing.

Answer 11

Involuntary blinking of eyelids stimulated by tactile, thermal or painful stimulation of cornea
Ophthalmic nerve if afferent
Facial nerve is efferent –> orbicularis oculi contraction

Absent = CNV1 or CNVII lesion

Question 12

How is CNV examined?

Answer 12

Sensory in 3 parts of face
Distribution of varicella zoster rash
Corneal reflex
Lacrimal/nasal secretions.

Question 13

What nerve does varicella zoster usually affect?

Answer 13

Ophthalmic

Question 14

How is CNVI tested?

Answer 14

Eye movement H

Question 15

Describe CNVI lesion. Causes?

Answer 15

Cannot abduct affected eye. Diplopia on lateral gaze

Fractures involving the cavernous sinus or orbit may lead to nerve lesions
Thrombosis of cavernous sinus,
Aneurysm to cerebral arterial ring.

Question 16

How is CNVII examined?

Answer 16

raise eyebrows
Wrinkle forehead
Close eyes tightly
Broad smile for muscles and symmetry
Puffing out cheeks
Change in taste
Dry eyes
Dry mouth

Question 17

Describe intracranial lesions of CNVII. Causes?

Answer 17

Proximal to sylomastoid foramen
Muscles of facial expression paralysed or weakened
Chorda tympani = reduced salivation and loss of taste on ipsilateral anterior 2/3 tongue
Nerve to stapedius = ipsilateral hyperacusis
Greater petrosal nerve
Ipsilateral reduced lacrimal fluid

Middle ear pathology is common cause
No cause - Bell’s palsy

Question 18

Describe extracranial lesions of CNVII. Causes?

Answer 18

Distal to sylomastoid foramen
Only motor function affected - paralysis/weakness of facial expression muscles
Eye remains open
Angle of mouth droops
Forehead does not wrinkle
Loss of naso-labial fold on ipsilateral side
Loss of lacrimation
Loss of secretomotor in oral/nasal mucosa
Loss of sphincter muscles
Ptosis and oral incompetence

Cuases
Parotid gland pathology/surgery/inflammation
Infection by herpes
Compression during forceps
Fracture of temporal bone

Question 19

What is Bell’s palsy

Answer 19

Facial paralysis resulting from facial nerve dysfunction

Usually temporary 6 weeks

Question 20

Why in a central CNVII lesion does the forehead wrinkle?

Answer 20

Bilateral innervation of frontalis.

Asymmetry = peripheral lesion

Question 21

How does CNVIII lesion present? Causes?

Answer 21

vertigo, nystagmus, loss of equilibrium, progressive unilateral hearing loss, tinnitus

Basillar skull fractures
Ear infections
acoustic neruoma

Question 22

What is the test for CNIX?

Answer 22

Gag reflex
Afferent - CNIX
Efferent CNX

Question 23

Lesion of CNIX? Causes?

Answer 23

Loss of taste to posterior 1/3 of tongue
Dysphagia
BP problems
Parotid problems

Deeplacerations of neck

Question 24

CNXI lesion?

Causes?

Answer 24

Wasting of SCM/trapexius
SCM - turn head against resistance (to opposite side)
Trapezius - shrug against resistance

Causes:
Surgery or laceration to the neck can cause lesions to the nerve

Question 25

CNXII lesion?

Causes?

Answer 25

Protrude tongue - deviates towards affected side
Fasciculations (bag of worms)
Neck laceration, tymour ICA dissection and basal skull fracture.

Question 26

CNX lesion - RLN?

Answer 26

Hoarseness of voice due to paralysis of vocal cord
LRLN - aortic arch aneuryms
Mitral stenosis, enlarged LA, pushed up left PA
Compress left RLN against Aortic Arch
Bronchial/oesophageal carcinoma

Question 27

CNX lesion presentation? causes?

Answer 27

Gag absent (efferent branch)
Uvula deviation away from affected side due to CNX innervation of palatopharyngeus and palatoglossus
Thyroidectomy damage SLN

Question 28

What is carotid sinus massage

Answer 28

Massaage compresses carotid sinusleading to perception of high BP
This causes CNX to increase firing and reduce activity in SAN and AVN
Overall decreased rate and strength of contraction.
Reduced tachycardia