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Exam 1 Neurology of Pursuits
lecture #6
23
Medical
Graduate
06/12/2012

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Term
NOT
Definition
Nucleus of the Optic Tract
Term
VPF
Definition
Ventral Paraflocculus (a part of the cerebellum & primary structure in VOR cancellation when the target moves at the same rate as your head & body)
Term
Q
Definition
A
Term
What is the latency and velocity of a pursuit? Velocity in athletes?
Definition
Vel = 70°/sec and Latency = 100-130 msec (faster than saccades); Vel = Up to 130°/sec in athletes
Term
Can you make a pursuit without a moving target?
Definition
According to Kundart, no. "…retinal slip is critical to trigger pursuits" and "Without a moving target, you make a series of small saccades rather than a true pursuit" The caveat is that as long as the visual cortex THINKS there is motion, pursuits can be triggered.
Term
Pursuits and saccades share much of the same neurological pathway. Why is critical observation of pursuits comsidered less clinically useful?
Definition
Because pursuit deficits don't always have the "localizing value" that saccadic deficits do. (Can't always play "Where's the lesion?" with pursuits.)
Term
Where do horizontal eye movements (pursuits and saccades) occur?
Definition
Pons (specifically the pons and vestibular nucleus (CN VI and CN VIII))
Term
Where do vertical and torsional pursuits occur?
Definition
The midbrain (INC)
Term
What very major part of the visual pathway is used in pursuits but NOT saccades? (Hint: Think of any foveation needs.)
Definition
The Primary Visual Cortex (V1)
Term
Global motion = what part of the brain?
Definition
V5 aka MT ("Moving Target"… but not really)
Term
Loss of vision in either V1 or V5 (MT) can cause what pursuit condition?
Definition
A "scotoma of motion" aka akinetopsia in the hemisphere opposite the lesion - an "MT" hemisphere (Get it?! Hah!)
Term
Local motion = what part of the brain?
Definition
V3 aka MST ("Do the local motion V3")
Term
Loss of vision in V3 (MST) can cause what pursuit condition?
Definition
A directional pursuit deficit toward the side of the lesion
Term
If a pt has impaired ipsiversive horizontal pursuits, where might the lesion be?
Definition
The Frontal Eye Fields in the prefrontal gyrus at the top of the head.
Term
If a pt has impaired vertical pursuits, where might the lesion be?
Definition
Surprisingly, the pons.
Term
What if one side of the VPF (ventral paraflocculus) breaks? Bilateral VPF and the flocculus? Just bilateral flocculus?
Definition
Unilateral VPF lesion = mild pursuit deficit
Bilateral VPF & flocculus lesions = severe pursuit deficit & VOR goes nuts
Bilateral flocculus lesions = no biggie. Pursuits are just fine.
Term
What do vermis lesions cause?
Definition
Ipsiversive horizontal pursuit deficits
Term
What do fastigial nucleus lesions cause?
Definition
Contraversive horizontal pursuit deficits
Term
Catch-up saccades indicate a gain that is too high/low? Backup saccades?
Definition
Catch-up saccades = gain too low; Backup saccades = gain too high
Term
Normal vertical pursuit asymmetry is more likely found when the patient is attempting to pursue an object up/down?
Definition
Up. Vertical targets are harder to pursue looking up vs moving downward
Term
Your patient is being spun in a chair and fixating on their own outstretched thumb. You see corrective saccades. What does this indicate?
Definition
The corrective saccades are OKN quick phases due to deficient VOR cancellation in the direction of chair rotation
Term
A cerebral hemisphere lesion will present with what effect on pursuits? …saccades?
Definition
Ipsiversional pursuit dysfunction toward the lesion; Hypometric saccades away from the lesion.
Term
Pursuits and VOR Cancellation are managed/affected by what structure?
Definition
The cerebrum
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