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Brain and Behaviour > Eyes: Orbit, Reflexes and Movements > Flashcards

Eyes: Orbit, Reflexes and Movements Flashcards

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1
Q

What two movements are needed for the accommodation reflex?

A

Eye vergence and Pupillary constriction

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2
Q

What is the ciliary body and what is the result of its contraction?

A

The ciliary body is a ring of muscle that surrounds the lens. Contraction of this ring of muscle relaxes the suspensory ligaments of the lens enabling the lens to recoil and get rounder/fatter in shape

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3
Q

Why is the function of the ciliary body?

A

It allows you to accommodate (focus) on objects

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4
Q

In the accommodation response, which cranial nerve nuclei causes pupil constriction and lens fattening?

A

(parasympathetic) Edinger-Westphal nucleus - CN III stimulates the ciliary ganglion to cause pupil constriction (sphincter pupillae) and lens fattening (ciliary body)

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5
Q

Which sphincter causes pupil constriction?

A

Sphincter pupillae

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6
Q

In the accommodation response, which cranial nerve nuclei causes vergence?

A

CN III nucleus causes adduction of the eye (medial rectus) - vergence

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7
Q

If the PTN, EWN and LGN is damaged, what will you see in the patient?

A

Their pupillary light reflect and accommodation reflex will not work

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8
Q

If only the PTN and LGN is damaged but the EWN is working, what will you see in the patient?

A

Accommdation reflex will work (EWN safe) but the pupillary light reflex will not work

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9
Q

What is the Argyll-Robertson (Prostitute’s) pupil?

A

Argyll-Robertson (Prostitute’s) pupil is seen in tertiary neuro syphilis and diabetic neuropathy. There is NO pupillary light reflex BUT the accommodation reflex/response is WORKING

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10
Q

What can cause EWN damage and what is the result?

A

No direct or consensual reflex on damaged side
Pupil dilated and unreactive
Cause: Vascular/tumour/brainstem

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11
Q

What can cause CN III compression and what is the result?

A

No direct or consensual reflex on damaged side
Pupil dilated and unreactive
CNIII Compression = loss of all CNIII functions
CNIII Vascular lesion = sparing of pupillary functions

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12
Q

Name the three eyelid muscles and their innervation

A 
Levator palpebrae superioris (CN III)
Orbicularis oculi (CN VII)
Superior Tarsal (Sympathetic)
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13
Q

Which eyelid muscles lift the eyelid and which ones close?

A 
Levator palpebrae superioris (CN III) - lift
Orbicularis oculi (CN VII) - close
Superior Tarsal (Sympathetic) - lift
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14
Q

What is the difference seen on the patient when either the levator palpebrae superioris or superior tarsal are damaged?

A

If the levator palpabrae is damaged, a full ptosis is seen. If the superior tarsal is damaged, only a slight ptosis is seen.

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15
Q

What happens to the eye/lid if CN VII is damaged?

A

EPIPHORA - Excessive watering of eyes as eyelids can’t sweep tears to drain them. Therefore the tear fluid runs down the eyes.

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16
Q

What is the golden rules of eye muscles innervation?

A 
All extraocular muscles are innervated by CN III except
Superior oblique  (the muscle with a trochlea) = trochlea nerve (CN IV)
Lateral rectus (the abductor muscle) = abducens nerve (CNVI)
SO4 and LR6
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17
Q

What are the 6 eye muscles?

A 
SR – Superior rectus
IR – Inferior rectus
MR – Medial rectus
LR – Lateral rectus
SO – Superior oblique
IO – Inferior oblique
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18
Q

Where do the rectus muscles of the eye originate from?

A

The rectus muscles originate from a common tendinous ring located at the posterior of the orbit

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19
Q

Where does the inferior oblique muscle arise from?

A

Inferior oblique arises from antero-medial floor of the orbit; it is like a hand/hammock sitting under the eye

20
Q

Which cranial nerves pass through the superior orbital fissure?

A

CN III
CN IV
CN V1/a
CN VI

21
Q

What are the three perpendicular axes which the eye can move?

A

Transverse = Look left or right

Sagittal = Look up or down

Coronal = Torsion (twisting in and out)

22
Q

Why do some clinicians prefer to not use the H pattern method to test eye movement?

A

This testing pattern isolates the actions of specific muscles and is not used by all clinicians as it can detect large deficits but night miss subtle ones

23
Q

What do the medial and lateral rectus muscles do?

A

Adduct and abduct the eye respectively.

24
Q

What is special about the H pattern method to test eye movement?

A

The ‘H’ testing process involves moving the eye into a new starting position (different to the neutral anatomical position) using lateral or medial rectus, and then looking up or down

25
Q

Which eye muscles would you use to look down at a book?

A

Medial rectus and superior oblique

26
Q

What are the symptoms if there is a weakness in the superior oblique muscle?

A

Double vision while reading or walking downstairs.

27
Q

What is Hering’s law?

A

Extraocular muscles normally have equal and simultaneous innervation

28
Q

What happens if a given CNVI or its nucleus is damaged?

A

No lateral movement of the affected eye
Ipsilateral eye rests in adducted position = convergent squint
Horizontal diplopia
Diplopia worse when looking toward the affected side

29
Q

What does CN III innervate?

A

Motor supply to x4 muscles that move the eye, x1 that opens the eyelid, the sphincter pupillae and the ciliary body

30
Q

What are the symptoms of a CNIII nerve lesion?

A

Complete ptosis on affected side
Down and out position of affected eye
Divergent squint
Horizontal and vertical diplopia
Dilated pupil on affected side that’s unreactive to direct or consensual light
Consensual pupil reflex intact in contralateral (unaffected) eye

31
Q

What are the symptoms of a CN IV nerve lesion?

A

Upward deviation and extorsion (outward rotation) of the affected eye
Vertical diplopia: worse when descending stairs / reading paper
Torsional diplopia: double vision where the images twisted apart from each other
Patient tilts head away from lesion to help prevent diplopia (counteracts extorsion produced by inferior oblique)

32
Q

What can be the cause of diplopia?

A

CNIII, IV or VI lesions can cause diplopia and cause a patient to alter the resting position of their head

33
Q

What is the movement called when the eyes scan target to target?

A

Saccade (fast movement)

34
Q

What are the multiple control centres that eye movement is under the influence of?

A

Vestibular nuclei & parapontine reticular formation

Frontal eye field (frontal cortex)

Saccade centres (several locations)

Visual association areas

35
Q

What is the MLF?

A

The medial longitudinal fasciculus is a neuronal tract wiring CN nuclei for eye movement together and enables conjugate gaze (it also enables tracking neck movements)

36
Q

What does the MLF connect?

A

MLF connects CNIII, IV and VI with vestibular nuclei, cerebellum & neck muscle lower motor neurons

37
Q

Action potentials in the MLF travel from which nuclei?

A

Action potential travels from CNVI to CNIII

38
Q

To allow conjugate gaze and look right, which two CN nuclei (mention left/right) are needed?

A

Right VI and (contralateral) left III

39
Q

What type of controls is the MLF under?

A

Automatic and voluntary control

40
Q

If a patient can look towards the right and can read (convergence) but when looking to the left, their right eye cannot look look medially? What is wrong with them?

A

The medial rectus is responsible for moving the eye medially, but in this case, we know that it is not damaged because the patient is able to do convergence. Therefore, we know that the right eye’s medial rectus is innervated by CN III and is not getting any signal from the left CN IV. These two are connected by the right Medial longitudinal fasciculus. Therefore this is a Right MLF lesion.

41
Q

What can cause internuclear opthalmoplegia?

A

Internuclear opthalmoplegia results from lesions of the MLF - Cuts the interneuron connections between CNVI and CNIII. Can be caused by tumour, stroke, multiple sclerosis (demyelination)

42
Q

What is bilateral internuclear ophthalmoplegia?

A

Both the MLF are damaged. The patient has right and left lateral gaze and are able to converge during accommodation. The convergence test shows us that the CN III nuclei is not damaged.

43
Q

What is the Doll’s eye movement?

A

Typically the doll’s eyes reflex is elicited by turning the head of the unconscious patient while observing the eyes. The eyes will normally move as if the patient is fixating on a stationary object. If there is a negative doll’s eyes reflex then the eyes remain stationary with respect to the head.

44
Q

What is the Vestibulo-Ocular Reflex?

A

When head is rotating axially in a given direction the lateral semicircular canals make both eyes look to the opposite side

45
Q

If at rest, the eyes drift to the right and then jerk back, what is this movement called?

A

Nystagmus

46
Q

If the patient has Right lateral semicircular canal, which way would they look?

A

A lateral semicircular canal or vestibular nucleus makes the eyes look to the opposite side
Therefore, they would look to the left

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