Labs (M1) Flashcards
Where is the nucleus for CN VI (and at one level)? 1. What does it innervate? 2.
- beneath the floor of the fourth ventricle (junction of pons and medulla)
- ipsilateral LR
For Type II Duane’s Retraction syndrome is abduction or adduction impaired?
adduction
What is the yolked muscle for the superior rectus? 1. Superior oblique? 2
- inferior oblique
2. inferior rectus
What is the position the eye must be in to isolate the vertical action of the obliques?
adducting eye (54deg)
What is the ocular muscle layer that has high oxidative enzymes and supports prolonged contraction?
orbital layer
What are the signs of Inter-nuclear Ophthalmoplegia?
- adduction lag
- may have nystagmus on abduction
- convergence unaffected
Where is the origin of the MR? 1. Insertion? 2. What are the muscle movements (primary to tertiary)? 3
- annulus of Zinn
- 5-6mm behind cornea
- adduction
What are the possible paretic muscles for a right hyper deviation (left hypo) that increases in right head tilt?
RSR, RSO, LIO, LIR
While covering the paretic eye and doing the H test will the look of the covered eye be an overshoot or undershoot?
undershoot
What is the position the eye must be in to isolate the vertical action of the recti?
abducting eye (23deg)
For Type I Duane’s Retraction syndrome is abduction or adduction impaired? 1. What causes retraction? 2
- abduction
2. adduction
What parts of the brain detect motion?
- middle superior temporal lobe
2. middle temporal lobe
What is the stimulus for a saccade?
target displacement on the retina
Where is the nucleus for CN III (and at one level)? 1. What does the inferior bifurcation innervate? 2. Superior bifurcation? 3
- mesencephalon (superior colliculus)
- IR, IO, MR, parasympathetic (all ipsilateral)
- SR, LPS (all ipsilateral)
What is a partial paralysis of muscle function called?
paresis
What are the possible paretic muscles for a right hyper deviation (left hypo) in primary gaze?
RIR, RSO, LIO, LSR
What is the pathway for the left eye when making a saccade to the right?
frontal cortex through the omnipause neurons to the paramedian pontine reticular formation (PPRF) through the MLF to CN III to medial rectus
What presents like a RIO palsy but is restrictive in nature? 1. What is used to decide between the two? 2. Is this congenital or acquired? 3
- Brown’s Syndrome
- ductions (full in non-restrictive) and forced ductions (full in non-restrictive)
- congenital or traumatic
What is the law that states that contraction of an agonist muscle occurs concurrently with the relaxation of the antagonist muscle in the same eye?
Sherrington’s law of reciprocal innervation
What are the steps for the Park’s procedure?
- determine direction of the vertical deviation in primary gaze
- determine if vertical is greater in right or left gaze
- determine if vertical deviation is greater with right or left head tilt
What are the eye movements that compensate for head motion and rotations?
vestibular eye movements
Where is the origin of the SR? 1. Insertion? 2. What are the muscle movements (primary to tertiary)? 3
- annulus of Zinn
- 8mm behind cornea
- elevation, intorsion, adduction
What is the pathway for the left eye when making a vestibular eye movement to the right?
vestibular nuclei to paramedian pontine reticular formation (PPRF) through the MLF to CN III to medial rectus
Where is the origin of the IO? 1. Insertion? 2. What are the muscle movements (primary to tertiary)? 3
- anterior floor of orbit (near lacrimal fossa)
- posterior globe
- extorsion, elevation, abduction
Where is the origin of the SO? 1. Insertion? 2. What are the muscle movements (primary to tertiary)? 3
- body of sphenoid (trochlea effectively)
- posterior globe
- intorsion, depression, abduction
Where is the nucleus for CN IV (and at one level)? 1. What does it innervate? 2.
- lower mesencephalon (inferior colliculus)
2. contralateral SO
What is the pathway for the right eye when making a saccade to the right?
frontal cortex through the omnipause neurons to the paramedian pontine reticular formation (PPRF) to CN VI to the lateral rectus
What is a total loss of innervation or muscle function called?
paralysis
What are the possible paretic muscles for a right hyper deviation (left hypo) that increases in left gaze?
RIO, RSO, LSR, LIR
While covering the normal eye and doing the H test will the look of the covered eye be an overshoot or undershoot?
overshoot
What does Inter-nuclear Ophthalmoplegia mimic? 1. What is its etiology? 2
- partial CN III palsy (MR)
2. MS or vertibrobasilar disease
Where is the origin of the LR? 1. Insertion? 2. What are the muscle movements (primary to tertiary)? 3
- annulus of Zinn
- 7mm behind cornea
- abduction
Where is the origin of the IR? 1. Insertion? 2. What are the muscle movements (primary to tertiary)? 3
- annulus of Zinn
- 6-7mm behind cornea
- depression, extorsion, adduction
What is it called when an ocular muscle is tethered to the globe over more area than just the insertion?
muscle pulleys
What could mean either a paralysis or a paresis?
palsy
What is the pathway for the right eye when making a vestibular eye movement to the right?
vestibular nuclei to paramedian pontine reticular formation (PPRF) to CN VI to lateral rectus
Which cranial nerve exits the brain dorsally?
CN IV
What is the ocular muscle disorder in which co-contraction of MR and LR (due to CN VI developing incorrectly) causes retraction of the globe on adduction? 1. Is this congenital or acquired? 2
- Duane’s Retraction syndrome
2. congenital
For Type III Duane’s Retraction syndrome is abduction or adduction impaired?
both abduction and adduction
What type of muscle are ocular muscles?
striated
What is the grade given for a 2mm over-action? 1. And 1mm under-action? 2
- grade 2 (+2)
2. grade 1 (-1)
What is the ocular muscle layer that has high glycolytic enzymes and is for twitch movements?
global layer
What is the law that states during any eye movement, ocular innervation is such that the magnitude of rotation of the two eyes is equal?
Hering’s law of equal innervation
