13. Cranial Nerve Lesions Flashcards
Give some general causes of cranial nerve damage.
Polio
Guillian barre
MS
Tumour
Vasculitis
Stroke
Lupus
Syphilis
TB/fungal meningitis
What is CN1?
Olfactory nerve
- For smelling!
How can the olfactory nerve be damaged?
Trauma to cribriform plate
What does CN1 palsy present as?
Anosmia
Give 2 causes of anosmia caused by an olfactory nerve palsy.
- Respiratory tract infection
- Olfactory groove tumour
- Meningitis
What is CN 2?
Optic nerve
- For sight
Optic nerve vs optic tract?
Optic nerve is from the eye to the optic chiasm.
Optic tract is from the chiasm to the lateral geniculate body.
The right pupil constricts in response to light shone in the left eye, but when you shine the light on the right eye, neither eyes constrict.
Where is the problem?
CN2 - the optic nerve
- As the pupil is not detecting the light.
A left parietal lesion of the optic radiation causes what kind of vision deficit?
Quadrantanopia
of inferior right quadrant
PITS - parietal lesion = inf loss, temporal lesion = superior loss)
What is CN3?
Oculomotor nerve
What does CN3 innervate?
CN3 is the occulomotor nerve.
Motor – Innervates the majority of the extraocular muscles:
1. Levator palpebrae superioris (muscle of the eyelid)
2. Superior rectus
3. Inferior rectus
4. Medial rectus
5. Inferior oblique
Parasympathetic – Supplies the:
1. Sphincter pupillae of the eye
2. Ciliary muscles of the eye
If 1 pupil is not constricting to direct or consensual light stimulation to the other eye, where is the problem?
CN3 - the pupil is not constricting
What are the 3 main signs of a lesion to CN3?
- Ptosis - dropping eyelids
- Outward deviation (‘down and out’) - as there is function of the lateral rectus to look out (CN6), but not inferior oblique (CN3) to counteract it
- Dilated fixed pupil
Also:
- Pupil does not accomodate to light
- Absent pupillary light reflex
What is CN4?
Trochlear nerve
What does CN4 innervate?
CN4 = trochlear nerve
Innervates superior oblique - looks in and down
What does damage to CN4 result in?
Defective downward gaze - vertical diplopia
(diplopia on looking down e.g. walking downstairs)
What kind of visual symptoms would you get with a trochlear nerve lesion?
Diplopia on looking down and in
What is CNV?
Trigeminal nerve
What are the 3 branches of the trigeminal nerve?
V1 - opthalmic - forehead sensation
V2 - maxillary - cheeks sensation
V3 - mandibular - chewing + sensation on anterior 2/3 tongue
What are the functions of the trigeminal nerve?
- Facial sensation
- Muscles of mastication
- Tensor tympani (muscle within the middle ear)
How can the trigeminal nerve be damaged?
- Trigeminal neuralgia (pain but no sensory loss)
- Herpes zoster
- Nasopharyngeal carcinoma
- Acoustic neuroma (a type of non-cancerous (benign) brain tumour)
How may lesions to the trigeminal nerve cause?
- Trigeminal neuralgia
- Loss of corneal reflex
- Loss of facial sensation
- Paralysis of mastication muscles
- Deviation of jaw to weak side
What is CNVI?
Abducens nerve
What does the CNVI innervate?
The lateral rectus muscle, thus the eyes will be adducted
What do lesions to CNVI result in?
Defective adduction
- Horizontal diplopia
Complete external opthalmoplegia is due to palsy of which nerves and what does it cause?
Palsy of the oculomotor, trochlear and abducens (III, IV and VI) nerves.
Causing complete paralysis of the eye.
What is CN7?
Facial nerve - facial expression
What are the functions of the facial nerve (CNVII)?
- Muscles of facial expression
- Taste - anterior 2/3 of the tongue
- Salivation + lacrimation
What are the parasympathetic functions of the facial nerve?
- Lacrimation
- Salivation
What are the causes of facial nerve dysfunction?
- Bells palsy
- Temporal bone fracture
- Herpes zoster
What do lesions to the facial nerve result in?
- Flaccid paralysis of upper + lower face
- Loss of corneal reflex
- Loss of taste
- Hyperacusis (AKA noise sensitivity - when everyday sounds seem much louder to you than they should)
What is CN8?
Vestibulocochlear - hearing and balance
What are the functions of CN8?
- Hearing
- Balance
Aminoglycosides cause damage to which nerve?
Vestibulocochlear CN 8
What do lesions to CN8 present as?
- Hearing impairment
- Vertigo and lack of balance
What is CN9?
Glossopharyngeal nerve
What are the functions of CN9?
- Taste - posterior 1/3 of tongue.
- Parasympathetic -> Provides parasympathetic innervation to the parotid salivary gland.
- Sensory -> Innervates the stylopharyngeus muscle of the pharynx.
- Swallowing.
Which cranial nerves innervate the tongue?
- CNVII Facial nerve -> for taste -> anterior 2/3 of tongue
- CNIX Glossopharyngeal nerve -> for taste -> posterior 1/3 of tongue
- CNV Trigeminal nerve -> sensation
- CNXII Hypoglossa nerve -> motor
- CNX Vagus nerve -> supplies the 1 muscle, the palatoglossus muscle
How do lesions in CNIX Glossopharyngeal nerve present?
- Gag reflex issues
- Swallowing issues
- Vocal issues
- Hypersensitive carotid sinus reflex
How can you test the CNIX Glossopharngeal nerve?
Gag reflex
What is CNX?
Vagus nerve
What are the functions of CNX Vagus nerve?
- Sensory and motor to pharynx and larynx
- Phonation - production and utterance of speech sounds
- Swallowing
- Parasympathetic to GI tract and viscera
How do lesions in CNX Vagus nerve present as?
- Uvual deviates from side of lesion
- Loss of gag reflex
What is CNXI?
Accessory nerve
Which cranial nerve innervates the accessory muscles?
CN 11 Accessory nerve
What is the function of the CNXI Accessory nerve?
Controls the movement of certain neck muscles
Which 2 muscles does the accessory nerve innervate?
- Sternocleidomastoid muscle
- Trapezius muscle
How can you test the accessory nerve?
Ask patient to shrug their shoulders or turn head
What is CNXII?
Hypoglossal nerve
What does CNXII innervate?
Intrinsic and extrinsic muscles of the tongue
What is the functions of CNXII?
Controls muscles that move the tongue
How do lesions in CNXII present as?
Tongue deviates towards side of lesion
How can you test CN12?
CN 12 is hypoglossal.
Ask patient to stick tongue out, it will deviate to weak side.
Why do lesions of the glossopharyngeal and vagus appear together?
They both leave the skull through the jugular foramen.
A patient is struggling to turn their head to the right - they think they have slept on it in a weird position.
What nerve could have been damaged?
Left hand side accessory nerve
You ask a patient to stick their tongue out and it immediately deviates to the right and is very stiff to move.
What do you suspect?
UMN lesion affecting the right hypoglossal nerve
