4.1 Cranial Nerve Lesions Flashcards
How is CNI examined?
Sense of smell in each nostril with coffee/orange
Describe what causes CNI lesions and what this can lead to.
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.
How is CNII examined?
Visual acuity Colour vision Visual fields Pupillary reflexes Fundoscopy
Describe causes of CNII lesion and what this causes.
Direct trauma to eye or orbit, fracture of optic canal or pressure on optic nerve
Loss of pupillary constriction and visual field defects.
How is CNIII examined?
Movement of eye in H for extraocular muscles
Ptosis
Pupillary reflex (consensual)
Accommodation
What can cause CNIII palsy?
Aneurysms
Increased intracranial pressure
Cavernous sinus infection/trauma
How does CNIII palsy present?
Down and Out
(LR6 SO4)
Ptosis - denervation of legator palpebrae superioris
Dilated pupil - palsy of autonomic parasympathetics - denervationof sphincter pupillage
Describe how the site of CNIII lesion can be determined.
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.
How is CNIV assessed?
Test movement of eye H
Test diplopia
Describe how CNIV lesion presents. Causes?
Inability to look down when eye is adducted.
Diplopia on looking down and in (e.g. going down stairs).
Cuases:
Stretching
Cavernous sinus thrombosis.
Describe the corneal reflex and what nerve it is testing.
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
How is CNV examined?
Sensory in 3 parts of face
Distribution of varicella zoster rash
Corneal reflex
Lacrimal/nasal secretions.
What nerve does varicella zoster usually affect?
Ophthalmic
How is CNVI tested?
Eye movement H
Describe CNVI lesion. Causes?
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.
How is CNVII examined?
raise eyebrows Wrinkle forehead Close eyes tightly Broad smile for muscles and symmetry Puffing out cheeks Change in taste Dry eyes Dry mouth
Describe intracranial lesions of CNVII. Causes?
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
Describe extracranial lesions of CNVII. Causes?
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
What is Bell’s palsy
Facial paralysis resulting from facial nerve dysfunction
Usually temporary 6 weeks
Why in a central CNVII lesion does the forehead wrinkle?
Bilateral innervation of frontalis.
Asymmetry = peripheral lesion
How does CNVIII lesion present? Causes?
vertigo, nystagmus, loss of equilibrium, progressive unilateral hearing loss, tinnitus
Basillar skull fractures
Ear infections
acoustic neruoma
What is the test for CNIX?
Gag reflex
Afferent - CNIX
Efferent CNX
Lesion of CNIX? Causes?
Loss of taste to posterior 1/3 of tongue
Dysphagia
BP problems
Parotid problems
Deeplacerations of neck
CNXI lesion?
Causes?
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
CNXII lesion?
Causes?
Protrude tongue - deviates towards affected side
Fasciculations (bag of worms)
Neck laceration, tymour ICA dissection and basal skull fracture.
CNX lesion - RLN?
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
CNX lesion presentation? causes?
Gag absent (efferent branch)
Uvula deviation away from affected side due to CNX innervation of palatopharyngeus and palatoglossus
Thyroidectomy damage SLN
What is carotid sinus massage
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
