Term
| what is eye movement considered a "window" into? |
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Definition
| what is happening in the brain, particularly the brainstem between the subnuclear groups |
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Term
| what are the CN involved in eye movement? |
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Definition
| CN3 oculomotor (4 muscles), CN4 trochlear, CN6 abducens |
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Term
| what are the muscles involved in eye movement? |
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Definition
| medial rectus, lateral rectus, superior rectus, inferior rectus, inferior oblique, and superior oblique |
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Term
| what is conjugate eye movement? |
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Definition
| when both eyes are moving in the same direction by the same amount. types: saccades (scanning - rapid eye movements which change visual fixation to a new object), smooth pursuit (tracking - movement which keeps and object of interest imaged on the fovea), and nystagmus (oscillatory movement - smooth pursuit and saccades alternate) |
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Term
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Definition
| eyes moving in opposite directions (relative to each other) such as w/accommodation (convergent/divergent) for looking at nearby objects. |
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Term
| what muscles are innervated by CN3? what are the associated movements? |
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Definition
| medial rectus (adduction), inferior rectus (downward gaze and adduction, extorsion), superior rectus (upward gaze and adduction, intorsion), and inferior oblique (upward gaze and abduction, extorsion) |
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Term
| what muscle is innervated by CN4? what is the associated movement? |
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Definition
| superior oblique (SO4LR6) = downward gaze, abduction, intorsion |
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Term
| what muscle is innervated by CN6? |
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Definition
| lateral rectus (SO4LR6) = abduction |
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Term
| what are the yolked pairs of eye muscle/movement for ab/adduction? |
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Definition
| medial rectus: adduction/lateral rectus: abduction. |
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Term
| what are the yolked pairs of eye muscle/movement for up/downward gaze? |
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Definition
| superior rectus: upward gaze, adduction, intorsion/inferior rectus: downward gaze, adduction, extorsion |
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Term
| what are the yolked pairs of eye muscle/movement for down/upward gaze? |
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Definition
| superior oblique: downward gaze, abduction, intorsion/inferior oblique: upward gaze, abduction, extorsion |
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Term
| what do the 2 legs of the H test isolate? the center? |
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Definition
| legs: the superior/inferior rectus pair and the inferior/superior oblique pair. the center: the medial and lateral muscles. |
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Term
| where are the 2 oculomotor nuclei? what are their functions? |
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Definition
| the oculomotor nucleus is located in the midbrain and controls movement through CN3. the edinger-westphal nucleus is located in the midbrain and controls pupil and lens function through CN3. |
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Term
| where is the trochlear nucleus? |
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Definition
| in the midbrain, which controls eye movement through CN4 |
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Term
| where is the abducens nucleus? |
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Definition
| in the pons, which controls eye movement through CN6 |
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Term
| what is the blood supply to CN3? |
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Definition
| posterior cerebral, superior cerebellar, and basilar arteries (aneurysms in these arteries can compress the nerve - remember parasympathetic/light reflex pathway association) |
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Term
| what is the blood supply to CN4? |
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Definition
| superior cerebellar and posterior cerebral (aneurysms in these arteries can compress the nerve) |
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Term
| what is the blood supply to CN6? |
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Definition
| AICA, PICA, basilar and vertebral (aneurysms in these arteries can compress the nerve) |
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Term
| what is the pathway of CN4? |
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Definition
| from the *contralateral location on the midbrain to the superior oblique (downward gaze, abduction, intorsion) |
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Term
| what are the clinical symptoms of a trochlear nerve lesion? how will pts compensate? |
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Definition
| double vision (diplopia) and loss of downward gaze. pts will usually tilt their head to the unaffected side so the “normal” eye can intort to improve vision. |
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Term
| what is the pathway of CN6? |
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Definition
| from the pons *ipsilaterally (over the trigeminal) to the lateral rectus. the facial nerve wraps around the abducens nucleus, so if there is problem w/either - both will likely be affected |
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Term
| what are the clinical symptoms of a abducens nerve lesion? |
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Definition
| diplopia and blurry vision |
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Term
| what is the somatic motor pathway of CN3? |
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Definition
| from the midbrain at the level of the superior colliculus (oculomotor nucleus) *ipsilaterally to the medial rectus, inferior rectus, superior rectus, and inferior oblique. |
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Term
| what is the somatic autonomic (parasympathetic) pathway of CN3? how is it positioned on CN3? |
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Definition
| from the edinger-westphal nucleus in the midbrain to the constrictor pupillae and ciliary muscles. the parasympathetic innervation on CN3 lies on the external surface of the nerve - and thus more vulnerable to compression (apparent as a defect in pupillary function). |
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Term
| what is the accommodation reflex associated w/CN3? |
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Definition
| the eyes converge (medial rectus), the lens becomes thicker (*ciliary muscles contract, relaxing suspensory ligaments), and the pupils shrink (sphincter pupillary muscle contracts): parasympathetically mediated for near vision. |
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Term
| what is the sympathetic innervation to the eye? |
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Definition
| from the spinal cord (superior cervical ganglion) through CN3 = dilation of the pupil |
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Term
| what is the light reflex pathway? |
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Definition
| bilateral input from CN2 -> pretectal nucleus of the superior colliculus -> bilateral projections to the edinger-westphal nucleus -> ciliary ganglion/red nucleus -> sphincter pupillae muscles bilaterally. therefore, even if light input is in one eye only, the pupils should both constrict equally. |
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Term
| go over lesions in the light reflex pathway and their clinical presentation |
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Definition
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Term
| what are the classic symptoms associated w/R CN3 palsy? |
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Definition
| strabismus: inability to direct both eyes toward the same object. diplopia: double vision. ptosis: R-sided compensation by raising eyebrows. dilation: decreased tone of constrictor pupillae muscle in R eye. downward and abducted R eye position (unopposed R superior oblique/R lateral rectus) |
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Term
| what characterizes the innervation involved in lateral gaze (conjugate eye movement)? |
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Definition
| signal coming from the frontal eye field through the superior colliculus down to the lateral gaze center (paramedian pontine reticular formation (PPRF)) in the pons (CN6 - lateral rectus). then CN6 has to communicate w/CN3 (medial rectus) in the midbrain via the ascending medial longitudinal fasiculus. this allows lateral gaze, either to the L or R (prevents diplopia). |
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Term
| what happens if there is a lesion in the ascending medial longitudinal fasiculus? |
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Definition
| the abducens (lateral rectus) is not able to communicate w/the oculomotor (medial rectus) and the eye which would be looking medially to allow lateral gaze remains pointing straight ahead - however these pts can accommodate (both medial rectus muscles will still work together). |
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Term
| check common eye abnormalities chart in ppt |
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Definition
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