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Neurology Clinical Frameworks > Cranial Nerve Lesions > Flashcards

Cranial Nerve Lesions Flashcards

1
Q

What would damage to CN I from a head injury or space occupying lesion cause?

A

Anosmia

Loss of sense of smell

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2
Q

What is CN II

A

Optic nerve

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3
Q

Summarise the journey of CN II

A

Originates in the retina and travels via the optic chiasm and optic tract to the lateral geniculate nuclei.

From here the optic radiation carries fibres to the occipital cortex.

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4
Q

Optic nerve damage (ie. Anterior to the optic chiasm) is associated with?

A

Monocular visual loss
—Reduced acuity, reduced colour vision, scotoma

Relative afferent papillary defect
—on examination of papillary light reflex

Papilloedema or optic atrophy (on fundoscopy)

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5
Q

What could cause CNII damage?

A

Demyelination (optic neuritis/retrobulbar neuritis)

Ischaemia (ischaemic optic neuropathy)

Compression (eg by tumour)

Vitamin B12 deficiency

Hereditary optic neuropathies

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6
Q

Name CN III

A

Oculomotor

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7
Q

Describe CNIII’s journey.

A

Originates in midbrain, passes through cavernous sinus. And superior orbital fissure and supplies four extraocular muscles, the levator palpebrae superioris and the sphincter pupillae

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8
Q

What muscles does CNIII innervate

A

Inferior oblique
Superior rectus
Inferior rectus
Medial rectus

Levator palpebrae superioris (lifts eyelid)
Sphincter pupillae (constricts pupils under control of parasympathetic)
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9
Q

What would a palsy of CNIII lead to?

A

Ptosis, failure of addiction and upward gaze (eye points down and out) and a dilated pupil.

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10
Q

What can cause CNIII palsies?

A

Divided into two main groups:
Compressive - surgical
Microvascular - medical

Compressive causes:
Berry aneurysm of posterior communicating artery
Hernias ion of the uncus (temporal lobe). Across tentorum cerebellum as result of raised intracranial pressure.

Microvascular palsies may not be painful and tend to spare the pupil (ie it remains reactive)
Causes include diabetes mellitus, hypertension and vasculitis.

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11
Q

Name CNIV

A

Trochlear nerve

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12
Q

What does CNIV supply?

A

The superior oblique muscle

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13
Q

Name CNVI

A

The abductees nerve

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14
Q

What does CNVI supply

A

The lateral rectus muscle - responsible for abduction of the eye.

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15
Q

What would a lesion to CNVI cause?

A

Inability to abduct the eye on the affected side and diploplia, especially on looking down.

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16
Q

What could cause a CNVI lesion?

A

Raised intracranial pressure, multiple sclerosis, hypertension and diabetes mellitus.

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17
Q

What is Horner’s Syndrome?

A

Horner’s syndrome is the result of a unilateral sympathetic nerve lesion.

Characterised by:
•ptosis
•Meiosis (constricted pupil)
•Apparent enopthalmus ( Eye appears sunken)
•Facial anhydrosis (loss of sweating).

Should be distinguished from CNIII lesion as both cause ptosis.

Important causes include:
apical lung tumour (Pancoast’s tumour)
Carotid dissection
Brain stem stroke

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18
Q

Describe the journey of CN1

A

Begins as multiple small branches in the nasal mucosa.
Enters the skull via the cribiform plate.
Synapses in the olfactory bulb and continues as the olfactory tract to the brain.

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19
Q

Name CN V

A

Trigeminal nerve

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20
Q

What does CNV supply?

A

Supplies all facial expression, but not taste via its three divisions (ophthalmic, maxillary and mandibular)
Motor fibres to muscles of mastication.

21
Q

What would a patient with CNV nerve palsy complain of?

A

Facial numbness or paraesthesia, may involve the tongue and buccal mucosa.

22
Q

What is the main cause of CNV nerve palsy?

A 
Brain stem (pontine) lesions, eg stroke, multiple sclerosis.
Lesions in the cerebellopontine angle, eg acoustic neuroma.
23
Q

Name CNVII

A

Facial Nerve

24
Q

What does CN VII supply?

A

Muscles of facial expression,
Taste from anterior two thirds of tongue (via chorda tympani)
The stapedus (restricts bony ossicle movement in the ear).

25
Q

What would an upper motor lesion of CNVII cause?

A

An upper motor neurone lesion of CNVII would produce weakness of the lower part of the face, sparing the forehead and eye closure.

26
Q

What could cause an upper motor neurone lesion of CNVII?

A

Stroke
Multiple sclerosis
Brain tumours

27
Q

What would a lower motor neurone lesion of CNVII cause?

A

A lower motor neurone lesion would produce weakness of all muscles of facial expression on the affected side.

28
Q

List potential causes of a lower motor neurone lesion in CNVII.

A

Most common is Bell’s palsy

Herpes zoster infection (Ramsay-Hunt syndrome)
Middle ear infection
Sarcoidosis
Parotid tumours
Guillain Barré syndrome.
29
Q

What is Bell’s palsy?

A

It is an acute unilateral, lower motor neurone facial weakness, resulting in pain or discomfort between the ipsilateral ear followed by unilateral facial weakness.

Full spontaneous recovery occurs in up to 90% but may take 9 months.

Cause is uncertain, viral infection has been postulated.

Short course of oral prednisone increases the likelihood of full recovery.
Eye protection is important as weakness of eyelid closure may allow corneal abrasions to occur.

30
Q

Name CNVIII

A

Vestibulocochlear nerve

31
Q

What does CNVIII carry?

A

Carries both auditory fibres from the cochlea and vestibular fibres (responsible for balance) from the semicircular canals.

32
Q

What would lesions of CNVIII cause?

A

Sensorineural deafness
Tinnitus
Vertigo
Nystagmus

33
Q

What could cause a lesion in CNVII?

A

Common causes include stroke, MS, trauma and cerebellopontine angle tumours (eg acoustic neuroma).

34
Q

Name CNIX

A

The glossopharyngeal nerve.

35
Q

What does CNIX do?

A

It provides sensation to the pharynx and taste to the posterior third of the tongue.

36
Q

Name CNX

A

The vagus nerve.

37
Q

What does CNX do?

A

Provides motor supply to the pharynx, larynx and upper oesophagus.

38
Q

Why are CN IX and X usually affected together?

A

They are closely related anatomically and run through the jugular foramen.

39
Q

Describe the clinical features seen due to damage of CN IX and X

A

Reflect impairment of pharyngeal control and swallowing.

Bulbar palsy (lower motor neurone)
•Nasal speech
•Dysphagia with nasal regurgitation
•Weak "bovine" cough
•Wasted tongue
•Absent gag reflex.
Pseudobulbar palsy (upper motor neurone)
•Spastic dysarthria 
•Dysphagia with choking
•Spastic, immobile tongue
•"Emotional lability"
•Brisk jaw jerk
•Brisk gag reflex.
40
Q

Give examples of causes of bulbar palsy.

A

Can result from motor neuron disease, myaestenia gravis, Guillian-Barré syndrome and muscular dystrophy.

41
Q

Give examples of causes of Pseudobulbar palsy.

A

Motor neuron disease, cerebrovascular disease and multiple sclerosis.

42
Q

Name CNXI

A

The accessory nerve.

43
Q

What does CNXI supply?

A

The trapezius and sternocleidomastoid muscles.

44
Q

What would lesions in CNXI cause?

A

Muscle weakness, impaired shoulder shrug and head rotation.

Isolated lesions are uncommon.

45
Q

Name CNXII

A

The hypoglossal nerve

46
Q

What does CNXII do?

A

Motor supply to the tongue.

47
Q

What would a lesion of CNXII cause?

A

Unilateral weakness, wasting and fasiculation of the tongue.

On protrusion of the tongue there is a deviation towards the affected side.

48
Q

What are possible causes of CNXII palsy?

A

They include malignant meningitis and base of skull fracture.

Neurology Clinical Frameworks (7 decks)

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