Flashcards in More week 2 Deck (18):
What is the Frontal Eye Field?
The cortical area responsible for initiating horizontal and vertical gaze.
What is the Paramedial Pontine Reticular Formation?
Brainstem region responsible for control of horizontal eye movements.
What is the cause of Parinaud Syndrome?
Compression of dorsal midbrain, pretectum and dorsal region of riMLF; pineal tumor, hydrocephalus
Discuss the 2 groups of Abducens nerve neurons
Group 1: innervates lateral rectus of ipsilateral eye
Group 2: Axons cross midline, travel rostrally in MLF, innervate OMN and medial rectus of contralateral eye.
What 3 things can cause an imbalance between the left and right FEFs?
2. Seizure (increased activity)
3. The result of a cortical lesion/insult (decreased activity), results in the eyes being deviated conjugatively TOWARD the side with the lower level of activity.
Describe the effects of a right CN6 palsy
Right eye deviated medially; Can't direct laterally
Describe the effects of a right Abducens nucleus lesion.
Left conjugate gaze normal; No right conjugate gaze
Describe the effects of a right PPRF lesion?
same as right abducens nucleus
Describe the effects of a left MLF lesion.
left conjugate gaze normal, right gaze normal with right eye but not with left eye; lack of drive to left OMN from right abducens nucleus.
How do you determine if the lesion is in the MLF and not in the OMN or CN3?
If vergence is normal, then OMN and CN3 on the affected side are normal.
Discuss the Vestibulo-Ocular reflex
Eye movement is equal in magnitude but opposite in direction of movement of head; Stabilizes image on retina during head movements.
Describe the directional use of the VOR
Left Semicircular canals activated when head turned left, causing eyes to turn rightand vice versa
What are the characteristics of damage to the vestibular appartus?
1. Unilateral damage results in spontaneous nystagmus due to imbalance in left vs right SCC activity 2. Eyes drift to affected side due to greater activity in unaffected SCC system 3. At limit, eyes snap back to center, displaying a beat toward the normal side 4. Damage to left vestibular system = right beating nystagmus 5. Damage to right vestibular system = left beating nystagmus
Discuss the Oculocephalic Maneuver
If eyes move along with head movement, instead of in opposite direction, brainstem dysfunction is indicated
Describe the effects of Relative Afferent Pupillary Defect.
Decreased sensitivity of affected eye to light due to lesion in the retina or optic nerve 2. Direct response of affected eye decreased, but Consensual response of affected eye is normal
Describe the actions of the affected eye in a swinging flashlight test (RAPD)
Dilation of the pupil
What is Horner's syndrome? Presentation?
Loss of sympathetic innervation to eye; Anhydrosis, pupil constriction