Cranial Nerve Exmination Flashcards by Linhsen Le

What are the mnemonics to remember the 12 CN ?

Oh Oh Oh To Touch And Feel Very Good Vagina Ah Heaven
Some Say Money Matters But My Brother Say Big Brain Matters Most

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What are the test of the olfactory nerve ?

Smell test on indication.
First check nasal patency then test one nostril at a time then hold various familiar substance under open nostril.

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Clinical significance of CN 1 findings ?

Anosmia : rhinitis, minor head injury
Hyposmia : neurodegenerative disease
Parosmia : generally cacosmia, temporal lobe problems

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What are the test of the optic nerve ?

Visual acuity
- must be intact
Visual field :
- test all for quadrant for both eyes one at a time
- test both eyes together : to test higher cerebral function
Fundoscopy
Pupillary light reflex
- AFLR

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What are the main type of visual field lesion ?

Prechiasmatic lesion : lost of visual field in one eye
- problem in optic nerve
- glaucoma, optic neuritis
- amaurosis

Chiasmatic lesion : defect in both temporal visual field
- Bitemporal hemianopia
- pituitary tumor

Homonymous hemianopia : both eyes have the same field side affected
- complete loss of left or right visual field

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What is visual inatention ?

When in Donders test the patient can only see one movement (and not both) when both field are tested simultaneously but there was no problem on that side while testing separately.

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Interpretation of fundoscopy ?

Papillary oedema : intracranial hypertension, ischaemia, retrobulbar neuritis

Preretinal hemorrhage : subarachnoid hemorrhage

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Pupillary light reflex pathway ?

Afferent :
- optic nerve, chiasm, optic tract
- pretectal nucleus in midbrain
- Edinger Westphal nuclei = accessory oculomotor nucleus

Efferent :
- parasympathetic tract of oculomotor nerve
- ciliary ganglion to pupillary sphincter

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Function of oculomotor nerve ?

Pupil constriction and dilatation
Lens accommodation.
Raising upper eyelids.
Eye movement except : looking laterally and looking internally down (towards the tip of the nose)

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Function of trochlear and abducens nerve ?

Trochlear : innervate superior oblique muscle
- look inward down : tip of nose

Abducens : lateral rectus
- look laterally

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What test do you perform for CN 3, 4, 6 ?

Pupillary light reflex
Ocular alignement = Hirschberg test
- shine light 30 cm away
Eye movement
Convergence response
- 1 m away then move it quickly toward them and see adaptation

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What are abnormality of the ocular alignment called ?

Esotropia : abnormal inward deviation
Exotropia : abnormal outward deviation
Hypertropia : abnormal upward deviation
Hypotropia : abnormal downward deviation

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Technique of eye movement test ?

Patient follow your finger at a 30-60 cm distance, with their eyes without moving the head.
Patient gaze shouldn’t be diverted more than 45° : limit of binocular vision. Larger angle cause physiological nystagmus.

Check :
- nystagmus within 45° angle
- diplopia

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Clinical significance of ptosis ?

Loss of sympathetic fibers of CN 3 : superior tarsal muscle :
- ipsilateral pupil is dilated

Horner’s syndrome : slightly constricted pupil => miosis

Loss of motor fibres of CN 3 : levator palpebrae muscle
- other eye muscle also affected

Muscular disease => bilateral ptosis

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Findings of oculomotor nerve lesion ?

Affected pupil doesn’t have a direct light reflex : efferent defect of the eye

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Type of strabismus ?

Paralytic strabismus : one of the muscle is lost
- angle of deviation increase when looking in the direction of action of affected muscle

Concomitant strabismus : angle of deviation remains the same when looking in any direction

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What is gaze palsy ?

When there’s no diplopia but both eyes cannot be moved to a certain position
It’s indicative of a central disorder.

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What happen when there’s an obvious strabismus without diplopia ?

The visual acuity is unimpaired.
Probably long standing strabismus since childhood. One of the 2 image is being suppressed which prevent diplopia.
Present in concomitant strabismus.

Anatomy of the trigeminal nerve ?

Ophthalmic, maxillary and mandibular branches.
They join in the gasserian ganglion = trigeminal ganglion near the tip of the otocranium.

What are the test possible for the trigeminal nerve ?

Facial sensation : test the 3 dermatomes preferably via fine touch

Corneal reflex : only done in comatose patient
- afferent pathway through ophthalmic branch

Strength of the masticatory muscle

Masseter reflex : patient open mouth slightly, one finger on chin, strike it downward and watch for reflective closing
- afferent pathway via proprioceptive sensory pathway of trigeminal nerve

What are the clinical significance of the trigeminal nerve test ?

Impaired facial sensation

Corneal mandibular reflex : deviation to of the jaw to the contralateral side when cornea touched

Failure of sensation in the cornea => corneal reflex failure
- dismissed in contact user

Weak masticatory muscle : mouth hanging open

Heightened masseter reflex :
- lesion above pons : corticobulbar tract

What are the different type of problems with the corneal reflex ?

The cornea isn’t felt : trigeminal nerve on ipsilateral side is affected

Cornea is felt but blink response isn’t present : facial nerve is affected

If no corneal reflex and unilateral sensorineural hearing loss => acoustic neuroma = Vestibular Schwannoma

Anatomy of facial nerve ?

Sensory fibres : taste from anterior 2/3 of tongue
Parasympathetic fibres : parotid, mandibular, sublingual and lacrimal gland.
Motor fibres :
- around the mouth : receive unilateral signal decussating from the cortex
- around the eyes innervated by both hemisphere

What are the test of the facial nerve ?

Facial symmetry and expression : raising eyebrows, closing eyes tightly, puffing out the cheek, pursing the lips, showing teeth

Loss of taste
Corneal reflex
Function of stapedius muscle : sound louder on affected side => hyperacusis

Central facial nerve lesion ?

Loss of innervation of muscle around mouth contralateral to the lesion. Less strong muscle on the contralateral eye but not lost.

Peripheral facial nerve lesion ?

Loss of innervation of muscle around the mouth, forehead, ipsilateral eye. Half of the face Bell’s sign : when patient try to close their eyes, the white sclera becomes visible as a result of the eye turning upward.

What are clinically significant findings in facial nerve ?

Loss of CN 7 and 8 : vestibular Schwannoma Lesion proximal to splitting of chorda tympani : loss of taste on that side Bilateral CN 7 lesion : Guillain-Barré syndrome, poliomyelitis, myasthenia gravis, myopathy Clearly reduced corneal reflex : loss of peripheral function Loss of CN 7 : hyperacusis

What are the examination for CN 8 ?

Nystagmus test : eye movement test Dix-Hallpike manoeuvre

What is nystagmus ? What are the physiological nystagmus ?

= involuntary rhythmic eye movement comprising fast and slow phase End gaze nystagmus : looking at distant point to the side and extinguishes rapidly Optokinetic nystagmus : occur when travelling on a train and focusing eyes on a fixed point outside

How do you classify nystagmus ?

Direction of the fast phase : horizontal, vertical, torsional Grade : - 1 : only occur when patient look in fast direction - 2 : also occur when looking straight ahead - 3 : also when looking in the slow phase direction

What are the 2 most common symptoms of the CN 8 ?

Hearing loss : usually otological but also neurological (vestibular schwannoma, pontocerebellar infraction, meningitis) Rotational vertigo / unsteadiness : vestibular system, visual system, proprioception

What are the characteristics of peripheral nystagmus ?

Transient horizontal or mixed horizontal/rotational. Vomiting, vertigo, sensorineural hearing loss. Positional or during rapid head movement. Romberg’s : tendency to fall in the direction of the lesion Hypermetria.

What are the characteristics of central nystagmus ?

Spontaneous without vertigo, vomiting, hearing loss. Bidirectional. Dissociated : alternatively present in one eye but not the other. Vertical : medulla oblongata or midbrain lesion Rotational : medulla oblongata lesion / rotational Abnormality in coordination and equilibrium : already with eyes open

What is the function of the glossopharyngeal nerve ?

Transport impulses from the taste buds to the posterior tongue and innervates the stylopharyngeus muscle, posterior tongue, pharyngeal wall and tonsils.

What is the function of the vagus nerve ?

Innervate voluntary muscle of palate, larynx, pharynx, esophagus muscle, bronchi, heart, lungs, ileum, part of the colon and outer auditory canal.

What do you test for cranial nerve 9, 10 ?

Mobility of palatal arch (9-10) and uvula (10) Pharyngeal reflex (gagging) : on indication Taste perception

What are the clinical findings of CN 9 ?

Loss of motor fibers CN 9 : contralateral pharyngeal arch raised unilaterally during phonation. Loss of sensory fibres CN 9 : no sensation on pharyngeal wall, dysphasia

What are the clinical finding of CN 10 ?

Loss of CN 10 : curved uvula at rest Loss of motor fibres CN 10 : contralateral curtain sign (pharyngeal wall pull to one side)

What signify aphonia ?

Acute phase of unilateral recurrent nerve lesion with vocal fold in paramedical position : healthy cord rest against the paralyzed fold - hoarseness Acute phase of bilateral recurrent nerve lesion : vocals cord in median position due to adductor dominance - inspiratory stridor, pinched high voice

What do you assess in CN 11 ?

Strength of sternocleidomastoid muscle : pushing against their opposite mandible Assess strength of trapezius muscle : pushing against their raised shoulder

What are the clinical findings of CN 11 ?

Unilateral loss : impossible to rotate head contralaterally If pathology near jugular foramen : it could affect CN 9, 10, 11 as they all exit through it.

What do you assess in the hypoglossal nerve ?

Shape, position of tongue Movement of tongue. Strength of tongue.

What are the clinical findings of CN 12 ?

Fasciculation of the tongue : anterior horn cell disorder - usually not completely motionless Unilateral loss of CN 12 : atrophic tongue ipsilaterally - can deviate towards unaffected side as healthy muscle pull strongly inward - extended towards affected side as healthy muscle pull strongly the other side