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Med Neuro2 Lect9

Med Neuro2 Lect9 Vestibular III

Describe generally what happens with the Vestibulo-ocular Reflex (VOR) When you Turn your head in one direction, the Eyes will move the opposite.
Mechanism behind the VOR 1.Fluid moves opposite to movement, Inc signal on the side of movement, dec on opposite side. 2.Vestibular Nuc projects onto contralateral CN VI Nuc. 3.Activates CN VI opposite of movement, CN III on same side of movement. **Eyes look away from move
How does the velocity of rotation of the head relate to the velocity of rotation of Eyes EQUAL in Velocity, OPPOSITE in direction. **faster you move your head, the stronger the signal that will be sent to VI motor nuclei and the more powerful the contraction generated
3 main types of Eye movements 1.Saccades. 2.Smooth Pursuit. 3.Nystagmus
Saccades Quick jumps of the eye, the cortex only takes in info when the eye are fixed, it fills in the rest. **Done when we look at the horizon.
Smooth Pursuit Occurs when you follow/track a specific object. Uses the VOR to keep the eyes on target and the background is blurred.
Nystagmus Eyes slide slowly off target which if followed by a quick jump (saccade) back onto the target. **Patient is unaware of saccade b/c they do not take on info during it. They only get blurry vision. **Vertigo: wolrd spinning around you
Describe Physiological Nystagmus 1.Spin Pt to the R. 2.R vestibular signal Inc, L dec. 3.R vestibular nuc activates VI nuclei on L side. 4.Eyes drift L causing saccades to R. 5.Saccades appear as R Nystagmus
What could inducing nystagmus in a patient be used for? Ensuring there Brainstem and Vestibular system (VOR) are intact.
Describe Spontaneous Nystagmus 1.L ear is damaged, Dec signal from L. 2.Brainstem interprets Inc R signal & Dec L signal as R movement. 3.Activates L VI nuclei & slow drift to L. 4.Causes saccades & Nystagmus to the R.
In the case of Spontaneous Nystagmus, what side will the Nystagmus ALWAYS present towards? Towards the healthy ear, AWAY from the damaged ear.
Which ear is damaged in a patient with R spontaneous Nystagmus? LEFT
What else besides Ear damage can cause spontaneous Nystagmus? What is this called? Cervical spine damage (C1-C3) will send signals to the contralateral vestibular nuclei. **Cervicocephalic Reflex
Where is the Paramedian Pontine Reticular Formation (PPRF)? What is its function? Near the midline (just off center) in the caudal pons. **Integration center controlling the horizontal gaze (interpertting all the inputs: Vestibular, frontal cortex, cervical, light touch).
What contols the PPRF? The Frontal Eye Fields in the Ipsilateral frontal cortex. **L Cortex controls the R horizontal gaze.
What is the rule of gaze with a stroke? The patient will LOOK TOWARDS THE LESION. **b/c they lose control over the contralateral horizontal gaze.
What is the Caloric Test used for? To determine if the brainstem is still intact
Which direction should a patient get nystagmus when their ear is irrigated with warm water (Caloric Test) SAME SIDE
Which direction should a patient get nystagmus when their ear is irrigated with cold water (Caloric Test) OPPOSITE SIDE
What is the Doll's Head Maneuver? when is it useful? Done on unconcious pateints You forcefully rotate patient's head and watch eye to see if they stay the same. **If they do then the brainstem is intact
If the Eyes stare straight when the head is rotated in an unconcious patient (Doll's Head Man), what does this indicate? Stroke, damage to the Frontal cortex OR the PPRF (PPRF is not usually damaged).
Created by: WeeG
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