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Neuroendocrine Blue Boxes > Cranial Nerves > Flashcards

Cranial Nerves Flashcards

1
Q

What are the intracranial portions of CNs susceptible to?

A

Compression bc of tumor or aneurysm. Sx are gradual onset.

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2
Q

Which nerves, bc of their close proximity to the cavernous sinus, are susceptible to compression or injury related to pathologies (infections, thrombophlebitis)

A 
CN III (oculomotor)
CN IV (trochlear) 
CN V1 (ophthalmic)
CN VI (especially)
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3
Q

Anosmia

A

CN I (olfactory) injury

  • Frequently assctd w/ URI, sinus disease, head trauma
  • Usually unilateral (test each nare separately)
  • If all the nerve bundles on one side are torn, a complete loss of smell will occur on that side
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4
Q

What can cause anosmia

A
  • URI
  • Sinus disease
  • Head trauma
  • Cribiform palate fx
  • Aging
  • Injury to nasal mucosa, olfactory nerve fibers, olfactory bulbs, or olfactory tracts
  • Tumor or abscess in the frontal lobe
  • Meninge tumor (meningioma)
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5
Q

What can happen to CN I in severe head injuries

A

The olfactory bulbs may be torn away from the olfactory nerves or some nerves may be torn as they pass thru fractured cribiform palate

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6
Q

What can anosmia be a clue for

A

A clue for cranial base fracture and CSF rhinorrhea

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7
Q

Olfactory Hallucinations

A

May accompany lesions in temporal lobe of cerebral hemisphere
Lesion irritating the lateral olfactory area=temporal lobe epilepsy or “uncinate fits” (imaginary odors and involuntary lip/tongue movements)

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8
Q

Optic Nerve (CN II) injuries

A
  • Demyelinating Diseases
  • Optic neuritis
  • Visual field defects
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9
Q

Demyelinating diseases and optic nerves

A

Since the optic nerves are actually tracts (surrounded by sheath formed by oligodendrocytes) rather than neurolemma, they are susceptible to demyelinating diseases of CNS, like MS.

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10
Q

Optic neuritis

A

Lesions of the optic nerve that cause diminution of visual acuity, w/ or w/o changes in peripheral vision fields.

May be caused by inflammatory, degenerating, demyelinating, or toxic disorders (methyl and ethyl alcohol, tobacco, lead mercury)

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11
Q

What does the optic disc appear as in optic neuritis

A

Optic disc appears pale and smaller than usual

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12
Q

Visual field defects

A

Defect depends on where the pathway is interrupted. Defects caused by compression of the optic pathway may result from tumors of pituitary gland or berry aneurysms of ICAs. Lesions often develop insidiously, so visual changes may not occur until late stage.

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13
Q

Complete lesion of optic nerve

A

Blindness in temporal and nasal fields of ipsilateral eye

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14
Q

Complete lesion of optic chiasm

A

Reduces peripheral vision

Results in bi-temporal hemianopsia (loss of vision of one half of the visual field of both eyes)

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15
Q

Complete lesion of R optic tract

A

Eliminates vision from left temporal and right nasal visual fields.
Lesion of R or L optic tract causes a contraleteral homonymous hemianopsia.
Most common in strokes.

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16
Q

Injury to CN III

A

Results in ipsilateral oculomotor palsy w/ the eye ABducted and depressed w/ the pupil dilated

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17
Q

Compression of CN III

A

Commonly caused by rapidly increasing intracranial pressure from extradural hematoma. Compresses CN III against the crest of the petrous part of the temporal bone. Autonomic fibers are affected first so pupils dilate progressively on the injured side. First sign of CN III compression is ipsilateral slowness of pupillary response to light.

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18
Q

Aneurysm of posterior cerebral or superior cerebellar artery

A

May exert pressure on CN III bc CN III passes between these vessels. effects depend on severity. CN III lies on lateral wall of cavernous sinus, it is also vulnerable to sinus infections.

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19
Q

CN IV injury

A

May be torn w/ severe head injuries. Lesions of trochlear nerve or its nucleus cause paralysis of superior oblique muscle. Can’t turn affected eye inferomedially. Characteristic sign of CN IV injury is diplopia (double vision) when looking down.

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20
Q

How can one compensate for diplopia

A

By inclining the head forward and laterally toward the side of the normal eye.

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21
Q

Injury to CN V causes

A
  • Paralysis of muscles of mastication w/ deviation of the mandible towards side of lesion
  • Decreased sensation to soft tactile, thermal, or painful sensations in face
  • Loss of corneal reflex (blinking when cornea is touched) and sneezing reflex
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22
Q

What can cause a CN V injury

A
  • Trauma
  • Tumors
  • Aneurysms
  • Meningeal infections
  • Poliomyelitis
  • Polyneuropathy (disease affecting several peripheral nerves)
  • Intermedullary tumors or vascualr lesions (sensory and motor nuclei in pons and medualla may be destroyed)
  • MS (isolated lesion of spinal trigeminal tract)
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23
Q

Causes of facial numbness

A

-Dental trauma
-Herpes zoster ophthalmicus
-cranial trauma
Head and neck tumors
Intracranial tumors
-Idiopathic trigeminal neuropathy

24
Q

Trigeminal neuralgia

A

Principle disease affecting the sensory root of CN V. Painful episodic pain that is restricted to areas supplies by maxillary and/or mandibular divisions.

25
Q

Dental Anesthesia

A

CN V is important in dentistry bc it is the sensory nerve of the head.

  • Superior alveolar nerves (branches of CN V2): Can’t reach. maxillary teeth anesthetized and solution reaches terminal dental nerve branches.
  • Inferior alveolar nerves (CN V3): readily accessible.
26
Q

What can cause CN VI (abducent) paralysis

A
  • Intracranial pressure
  • Tumor
  • Aneurysm of cerebral arterial circle
  • Pressure from atherosclerotic ICA in the cavernous sinus
  • Septic thrombosis of cavernous sinus
27
Q

CN VI paralysis

A

May be caused by a tumor. Impaired lateral rectus muscle. Causes medial deviation to the affected eye (adducted by the unopposed action of medial rectus).

28
Q

In CN VI paralysis, diplopia is present in all ranges of movement of the eyeball except?

A

Except on gazing to the side opposite the lesion.

29
Q

What is the most frequently paralyzed cranial nerve

A

CN VII (facial)

30
Q

CN VII lesion near origin or near geniculate ganglion

A
  • Loss of motor, gustatory, and autonomic functions

- Motor paralysis of facial muscles to superior and inferior face on ipsilateral side.

31
Q

Central CN VII lesion (lesion of the CNS)

A
  • Contralateral inferior facial muscle paralysis

- Forehead wrinkling not impaired bc it is innervated bilaterally

32
Q

CN VII lesions between the geniculate ganglion and chorda tympani produce what kinds of effects

A

-Contralateral inferior facial muscle paralysis but that lacrimal gland is NOT affected

33
Q

Why is CN VII vulnerable to compression and swelling?

A

Since it passes thru the facial canal in the temporal region, it’s vulnerable to compression secondary to viral neuritis just before it emerges from stylomastoid foramen

34
Q

What can damage CN VII

A
  • Inflammation via infection
  • Knife and gunshot wounds (branches of CN VII are superficial, so especially susceptible to this)
  • Cuts
  • Temporal bone fracture (sx immediate)
  • Birth injury
  • Tumors of brain and cranium
  • Aneurysms
  • Meningeal infections
  • Herpes
35
Q

Although CN VII injuries cause facial muscle paralysis, sensory loss where is rare?

A

Area of skin on posteromedial surface of ear and around opening of ext. acoustic meatus is rare.

36
Q

What happens to hearing when CN VII is injured?

A

Hearing is not usually impaired, but ear may become more sensitive to low tones when the stapedius (supplied by CN VII) is paralyzed.

37
Q

CN VII lesions may cause

A

Tinnitus, vertigo, and impairment/loss of hearing

38
Q

A central CN VIII lesions may invovle ____

A

Either the cochlear or vestibular divisions of CN VIII

39
Q

Deafness Types

A
  1. Conductive deafness (involves external or missle ear
  2. Sensorineural deafness (damage to cells in the inner ear) which results from disease in the cohlea or in pathway from cochlea to brain
40
Q

Acoustic Neuroma

A
  • Slow-growing benign tumor of neurolemma (schwanna cells)
  • Tumor begins in the vestibular nerve while inside the internal acoustic meatus
  • Early sx= hearing loss
  • Dysequilibrium and tinnitus in 70% of patients
41
Q

Trauma & Vertigo

A

Vertigo is hallucination of movement involving person or environment. Spinning, but may be felt as swaying back and forth. Associated sx includes NV. Usually related to a peripheral vestibular nerve lesion.

42
Q

CN IX (glossopharyngeal) injury symptoms from tonsillectomy

A

Isolated lesions of CN IX or its nuclei are uncommon and are not associated with perceptible disability. Trauma to nerve is iatrogenic, most common from inadvertent injury during tonsillectomy). Sx include absent taste to posterior 1/3rd of tongue, diminished gag reflex on ipsilateral side of lesion. May produce changes in swallowing.

43
Q

Injuries of CN IX resulting from infections or tumors are accompanied by what?

A

Involvement of adjacent nerves (CN X, XI, and IX all pass through jugular foramen) leading to multiple cranial nerve palsies called jugular foramen syndrome (dysphagia and dysarthria more apparent)

Pain in CN IX distribution may be associated w/ involvement of the nerve in a neck tumor

44
Q

Deviation directions when gag reflex is diminished

A

“Curtain sign” Soft palate and posterior wall of pharynx deviate to the contralateral side of the injury.

45
Q

Glossopharyngeal Neuralgia

A

Uncommon and unknown cause. Paroxysms (sudden intense episodic pain) initiated by swallowing, protruding the tongue, talking, or touching palatine tonsil. Pain w/ eating when trigger areas are stimulated.

46
Q

What branches may get injured in a CN X injury

A
  • Pharyngeal branches
  • Superior laryngeal nerve
  • Recurrent laryngeal nerve
47
Q

CN X pharyngeal branches injury

A

Results in mild to severe dysphagia

48
Q

CN X Superior Laryngeal Nerve injury

A

Anesthesia to superior larynx and paralysis of cricothyroid muscle. Weak voice that tires easily.

49
Q

CN X recurrent laryngeal nerve injury

A
  • May be caused during aoritc arch aneurysm and during neck operations
  • Dysphonia (weakness/hoarsness of voice) due to vocal fold paralysis
50
Q

What does paralysis of both recurrent laryngeal nerves cause

A

Aphonia (loss of voice) and inspiratory stridor (harsh, high pitched respiratory sound). Paralysis usually results from thyroid and larynx cancer and/or from surgery on thyroid, neck, esophagus, heart, and lungs.

51
Q

Why is a L recurrent laryngeal nerve injury more common

A

Bc it has a longer course

52
Q

What can a proximal lesion of CN X cause

A

It will affect the pharyngeal and superior laryngeal nerves, causing difficulty swallowing and speaking.

53
Q

CN XI (spinal accessory nerve) injuries

A

-Due to subcutaneous passage through lateral cervical region, iatrogenic injury may occur during lymph node biopsy, cannulation of IJV, carotid endarterectomy.

54
Q

CN XI lesion

A

paralysis of ipsilateral trapezius. Manifests as unilateral inability to shrug shoulder, impaired rotation to affected side, or winging of scapula at rest.

55
Q

Hypoglossal (CN XII) nerve injuries

A

Paralysis of ipsilateral half of tongue, resulting in dysarthria. TOngue atrophies, and now has a wrinkled appearance. When protruded, the tongue apex deviates TO the paralyzed side because of the UNOPPOSED action of the genioglossus muscle on the normal side of the tongue.

56
Q

When can CN XII be compressed

A

During head rotation, resulting from a medially directed or elongated styloid process. Sometimes assctd w/ ossification of stylohyoid ligament (Eagle syndrome)

57
Q

What is the most common cause of trauma to the CN XII

A

Mostly iatrogenic during carotid endarterectomy, endotracheal intubation, other airway device insertion and use.

Neuroendocrine Blue Boxes (3 decks)

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