Cranial nerve disorders Flashcards
What are the twelve cranial nerves?
I – Olfactory (S)
II – Optic (S)
III – Oculomotor (M) IV – Trochlear (M)
V – Trigeminal (S/M) VI – Abducens (M)
VII – Facial (S/M)
VIII – Vestibulocochlear (S) IX – Glossopharyngeal (S/M) X – Vagus (S/M)
XI – Accessory (M)
XII – Hypoglossal (M)
What does cranial nerve 1 do?
- Smell perception.
- Olfactory receptor cells found in the mucous membrane of the nasal cavity
CN I passes through the cribiform plate of the ethmoid bone and continues to reach the cerebral cortex
Collateral fibres to amygdala and hippocampus
To be perceived as an odour an inhaled substance must be soluble in water
How do you test cranial nerve one?
Ask if any problems with smell
Use of an odorous object e.g. an orange, coffee to test each nostril
individually
Further investigation may involve CT/MRI brain or other appropriate neurological investigations
What pathology can occur with problems with CN1?
Anosmia ( loss of smell)
Dysosmia (smell alteration)
olfactory halucinations
What can cause anosmia?
Congenital absence of receptors – Kallman Syndrome, Albinism
Psychogenic (taste usually intact)
Nasal obstruction/rhinitis
Cribiform plate pathology – Head injury/skull fracture, Cranial surgery, SAH Central pathology – Tumours, Aneurysms, Meningitis, Sarcoidosis, MS
What can cause dysosmia?
Depression
Local nasopharyngeal conditions
What can cause olfactory halucinations?
Temporal lobe disease - Epilepsy (complex partial seizures)
Psychiatric disease – Depression, Schizophrenia
What can cause reduced odour recognition?
Alzeihmers
How does the visual pathway work?
Retinal nerve cells converge at the optic disc to form the optic nerve
At the optic chiasm lateral fibres continue in the ipsilateral optic tract, however medial fibres decussate (cross) into the contralateral optic tract
Fibres run to the visual cortex in the occipital lobe of the brain
What will occur with left optic nerve compression?
Defect on left side
1) What visual defects will occur with chiasm compressions from pituitory tumour?
2) What visual defects occur with a left cerbrovascular event?
1) bitemporal hemianopia
2) homonymous hemianopia
How do you test CN2?
Visual acuity – Snellen chart
Visual fields
Pupillary reflexes – (PERLA) (Note CN III involvement)
Light
Accommodation
Fundoscopy
What CN2 pathology is there?
Eye lesions – Cateracts, Glaucoma, Migraine, Vitreous haemorrhage, Infarction, Infection e.g. Choreoretinitis (CMV)
Optic nerve/chiasm/tract
Ischaemia – Giant cell arteritis, Thrombus /Embolism, Systemic hypotension, other
connective tissue disorders
Demyelination – MS (optic neuritis)
Pressure – Tumour –a pituitary adenoma in particular can cause pressure on the optic chiasm, Grave’s disease, Paget’s disease, Aneurysms
Raised intracranial pressure
Cranial nerves 3,4 6, what are their functions?
They are motor nerves that supply the extraocular muscles and elevators of the upper eyelid.
Muscle action is coordinated to give both rapid eye movements (saccades) and smooth pursuit eye movements. The cerebellum plays a role in this coordination.
What muscles move your eyes?
What muscles do CN3 (occulomotor) innervate?
All the muscles around the eye except Lateral rectus and superior oblique
What nerve supplies lateral rectus?
abducens
What nerve supplies superio oblique?
Trochlea nerve.
What pathology is associated with CN3,4,6?
Any pathology affecting the brainstem, cavernous sinus, superior orbital fissure
or orbit can cause dysfunction of these cranial nerves.
Nystagmus is a pattern of involuntary eye movement that can be physiological or pathological. Cerebellar and vestubular pathology often presents with nystagmus.
Ptosis is drooping of the upper eyelid. It may be seen in CN III lesions, stroke, myaesthenia gravis, muscular dystrophies and Horner’s syndrome.
Horner’s syndrome occurs when there is damage to the oculosympathetic pathway. It presents as unilateral ptosis, miosis and anhidrosis.
Most common presenting complaint is diplopia
What is cranial nerve5? What are the different branches and what do they innervate?
Trigeminal Nerve
Va) Opthalmic division- Innervates, scalp and forehead, cornea and nose (including corneal reflex)
Vb)Maxillary division
Sensation of skin over lower eyelid, cheek and upper jaw, midlateral nose and lateral part of
alar, upper lip, upper teeth and palate
Passes to the trigeminal ganglion via the foramen rotundum
Vc Mandibular division
Sensation of skin over temple, lower jaw (sparing the angle of the mandible C2/3 nerve roots),
lower lip, anterior tongue, lower teeth and floor of mouth
Motor supply to muscles of mastication
Enters/exits the skull via the foramen ovale
How can you test CN5 function?
To test the sensory element-
- Have the patient close their eyes and use cotton wool to touch the three sensory areas on both sides, asking the patient to say if/when they feel something
- Corneal reflex test – use a wisp of cotton wool to touch over the cornea (over the iris). Normal response is a blink on both sides.
How to test the motor element of CN5?
Feel the masseters and temporalis muscles with the teeth clenched. Ask the patient to open their mouth passively (jaw may deviate to the affected side) and then against resistance (looking for general weakness)
What are the signs of CNV pathology?
Unilateral sensory loss over the face/tongue/buccal mucosa
Absent corneal reflex
Jaw deviation on opening towards the affected side
Wasting of muscles of mastication
Trigeminal neuralgia
Sudden, severe, recurrent stabbing pains in the distribution of one or more branches of the Vth cranial nerve.
What CNV pathology can be present?
Brainstem lesions – MS, Infarction, Syringobulbia
Cerebellopontine angle lesions – Acoustic neuroma, Meningioma
Cavernous sinus lesions – Thrombosis, ICA aneurysm
Peripheral lesions – Orbital cellulitis/trauma, Maxillary or Mandibular infection or tumour, Skull fracture, Peripheral neuropathies.
Trigeminal neuralgia
What does Cranial nerve 7 supply
Intracranial branches:
Greater petrosal nerve Nerve to stapedius mm. Chorda tympani
Extracranial branches:
Posterior auricular nerve
Nerve to stylohyoid and posterior belly of digastric mm. 5 major facial branches
What are the 5 extra oral facial branches?
Temporal
Zygomatic
Buccal
Mandibular
Cervical
How to tes cranial nerve VII?
Ask patient to:
Scrunch up their eyes
Raise eyebrows
Blow out cheeks
Show teeth
Schirmer’s test to evaluate lacrimal function
What is CNVII main actions?
Motor supply to muscles of facial expression and stapedius muscle.
PSNS to salivary and lacrimal glands
Sensory from skin around the EAM
Taste from anterior 2/3rds of the tongue
What CNVII pathology can be present?
Cerebral cortex – Stroke, Tumour
Brainstem – Stroke, Tumour, MS
Cerebellopontine angle – Acoustic neuroma, Meningioma
Geniculate ganglion – Herpes zoster (Ramsey Hunt syndrome)
Facial canal – Bell’s palsy
Petrous temporal bone – Skull fracture
Facial nerve branches – Parotid tumour/infection, Facial trauma/lacerations
Facial mononeuropathy – Vasculitis, Sarcoidsis, Behcets’s syndrome, Sjogren’s syndrome, DM
What is an upper motor neurone?
UMN
A motor neurone that originates in the motor cortex or brainstem and carries motor information down to LMNs
What is a lower motor neurone?
Originate in the spinal cord or brainstem nuclei and carry motor information to effector organs
What facial weakness do you get with a) upper motor neurone pathology or B) lower motor neurone pathology
What is bells palsy?
A unilateral, lower motor neurone facial paralysis that is thought to be due to acute viral inflammatory demyelination of the facial nerve, causing swelling and secondary nerve ischaemia within the facial canal.
What are the clinical features of bells palsy?
How do you treat Bell’s palsy?
Can resolve fully without any treatment
Prednisolone 50mg PO for 5 days
Aciclovir
Avoidance of complications – eye patch, lubricating eye drops
What is the prognosis of bells palsy?
60-80% make a full recovery
Recovery usually begins within 8 weeks and is complete by 6-12 months
Residual defects may include facial weakness, ‘crocodile tears’ (gustatory crying) and synkinesias including ‘jaw winking’
Poor prognostic factors are
- Profound facial weakness Reduced tearing
Hyperacusis
Older age
Systemic hypertension, diabetes or psychiatric illness
What is ramsey hunt syndrome?
A reactivation of the herpes varicella zoster virus (shingles) affecting the facial nerve.
Symptoms/signs
Otalgia
Hearing loss
Vesicles in the external ear canal and
palate
Ipsilateral facial paralysis
Possible tinnitus or vertigo
Treatment: antiviral medication
WHAT IS CNVIII’s function?
Vestibular nerve – Sensory nerve involved with balance, carrying information from the vestibular apparatus
Cochlear nerve – Sensory nerve involved with hearing, carrying information from receptor hair cells in the organ of corti within the cochlear
What is the CNVIII pathology?
Brainstem - MS, Stroke, Tumour
Cerebello-pontine angle – Acoustic neuroma, meningioma
Base of skull – Paget’s disease, nasopharyngeal carcinoma, meningitis
Peripheral pathology
Ototoxins – Furosemide, Aminogylcoside antibiotics (gentamicin)
Benign Paroxysmal Positional Vertigo (BPPV) – episodic vertigo of brief duration induced by head movements. Usually due to cupulolithiasis of the semicircular canals. Treated with Epley head manoeuvres
Vestibular neuronitis- acute, usually non-recurrent vertigo without hearing loss or tinnitus
** Menieres disease** – recurrent severe vertigo with unilateral hearing loss and tinnitus
What are the clinical features of CNVIII pathology?
Deafness (sensorineural deafness) Tinnitus
Vertigo
Nystagmus – (rapid involuntary movement of the eyes) horizontal or rotatory nystagmus, fast beats away from the side of the lesion
How to test CNVIII?
Testing of hearing:
Vocal distraction testing - a general screen
Tuning fork testing (512Hz) – to distinguish sensorineural and conductive deafness
Weber – tuning fork held at midline forehead
Rinne – tuning fork held by each ear and then on the mastoid process.
Normal = Air conduction is louder than bone conduction
Testing of balance: Turning test
Function of glossopharyngeal nerve?
Sensation from middle ear, pharynx and posterior 2/3rds of the tongue Taste from posterior 2/3rds of the tongue
Motor to stylopharyngeus muscle
PSNS to the parotid gland (via the otic ganglion)
What is the function of the vagus nerve?
Sensation from larynx, pharynx, EAM, tympanic membrane
Visceral sensation from many body organs
Motor to muscles of the larynx, pharynx and soft palate
PSNS to various viscera
What pathology can occur with Vagus nerve pathology?
Ipsilateral palatal/pharyngeal weakness – nasal speech, regurgitation of food into nose, dysphagia, asymmetric palatal movement (uvula moves away from side of lesion)
Ipslateral vocal cord weakness – hoarseness, dysphonia, weak (bovine) cough, asymmetric vocal cord weakness
Loss of sensation over the EAM
Systemic issues such as cardiac arrhythmias, constipation, incontinence
What pathology can present with the glossopharyngeal nerve?
CN IX lesions present with ipsilateral loss of pharyngeal sensation.
How do glossophayngeal and vagus combined lesions present?
They have the symptoms of isolated gloospharyngeal and vagus in addition to loss of gag reflex
The recurrent laryngeal nerve is a branch of the Vagus, which side is more commonly assosciated with pathology? and what causes RLN pathology?
The left RLN loops under the aortic arch and is more commonly damaged than the right RLN.
How do you test the function of nerves 9 and 10?
Look at the uvula and ask the patient to say ‘ahh’. Deviation to one side suggests a CN X lesion on the opposite side
Assessment of cough and swallow
Gag reflex
What does the accesory nerve (CNXI) supply?
Spinal part- comes from C1-C5 anterior horns and supplys the trapeziusand sternocleidomastoid
cranial part- motor supply of muscles to larynx,pharynx and soft palate.
How to test the accesory nerve?
Shrug their shoulders (Trapezius)
Turn their head to each side against resistance (SCM)
What does the hypoglossal nerve supply?
Motor supply to the muscles of the tongue.
It contributes to speech and swallowing
How do you test CN12 function?
Assess the tongue at rest in the mouth for fasciculations and atrophy
Ask the patient to stick out their tongue. The tongue may deviate to the side of any lesion present.
