Cranial nerves ( function and palsies ) Flashcards

1
Q

Cranial nerve 1

A

Olfactory nerve

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2
Q

Function of cranial nerve 1

A

Smell

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3
Q

Pathway of cranial nerve 1

A

Cribiform plate

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4
Q

Cranial nerve 1 palsy

A
  1. head injury
  2. tumor of olfactory groove
  3. olfaction is temporarily lost after upper respiratory tract infection
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5
Q

Cranial nerve II

A

Optic nerve

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6
Q

visual pathway

A
  1. Light allowed in by pupillary aperture
  2. light is converted to action potential by retinal rod, cone and ganglion cells
  3. Nasal visual field -> temporal retina
  4. Temporal visual field -> Nasal retina
  5. Axons from the optic nerve decussate at the optic chiasm
  6. fibres from the nasal retina cross to form the optic tract
  7. each optic tract carres information from the contralateral visual hemisphere
  8. Reach lateral genticulate body
  9. then pass in the optic radiation through the pariteal and temporal lobes to reach the visual cortex of the occipital lobe
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7
Q

Ipsilateral mononuclear blindless

A

complete optic nerve lesion

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8
Q

bitemporal hemianopia

both temporal visual fields

A
  1. lesion at the optic chiasm
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9
Q

Homonymous hemianopia

right or left - one nasal field and one temporal field of each eye

A
  1. lesion at optic chiasm
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10
Q

homonymous quadrantanopia

A
  1. temporal lesiom
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11
Q

homonymous hemianopia with macular sparing

A

lesion at the optic cortex

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12
Q

cranial nerve III

A

Occulomotor nerve

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13
Q

cranial nerve III function

A
  1. Eye movement
    - Medial rectus
    - Inferior rectus
    - Superior rectus
    - Inferior oblique
  2. Levator Palpebrae superioris -
  3. Pupillary constriction
  4. Accomadation
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14
Q

Pathway of Cranial nerve III

A
  1. Superior orbital fissue
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15
Q

Cranial nerve III palsy

A

Palsy results in

  • ptosis
  • ‘down and out’ eye
  • dilated, fixed pupil
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16
Q

Causes of cranial nerve III lesion

A
  1. aneurysm of Posterior communicating artery
  2. infarction of the nerve - diabetes
  3. mid brain infarction or tumor of midbrain
17
Q

Cranial nerve IV

A
  1. trochlear nerve

2. supplies superior oblique muscle

18
Q

Cranial nerve IV palsy

A
  1. Palsy results in defective downward gaze → vertical diplopia
  2. commonly caused by head injury
  3. mostly bilateral but very rare
19
Q

Cranial nerve V

A
  1. largest cranial nerve
  2. three branches ;
    - V1 - opthalmic nerve
    - V2 - Maxillary nerve
    ( both purely sensory)
    - V3 - Mandibular nerve
    ( motor as well as sensory)
20
Q

Cranial nerve V - V1

A
  1. superior orbital fissure

2. sensory information from the scalp and forehead, the upper eyelid, the conjunctiva and cornea of the eye, the nose

21
Q

Cranial nerve V - V2

A
  1. The maxillary nerve (V2)
  2. carries sensory information from the lower eyelid and cheek, the nares and upper lip, the upper teeth and gums, the nasal mucosa, the palate and roof of the pharynx,
  3. Foramen rotundum
22
Q

Cranial nerve V - V3

A
  1. Foramen Ovale
  2. carries sensory information from the lower lip, the lower teeth and gums, the chin and jaw
  3. mandibular division (V3) of the trigeminal nerve controls the movement of eight muscles, including the four muscles of mastication: the masseter, the temporal and the medial and lateral pterygoids
23
Q

Cranial Nerve VI

A
  1. Abducens
  2. controls lateral rectus muscle
  3. superior orbital fissure
24
Q

Cranial Nerve VI palsy

A
  1. Palsy results in defective abduction → horizontal diplopia
  2. Eye cannot be fully abducted and esotropia (inward eye deviation) may be visible
25
Q

Cranial nerve VI palsy causes

A
  1. Multiple sclerosis
  2. Wernicke’s encephalopathy
  3. Pontine stroke