NEUROANATOMY - Supranuclear Gaze Pathways Flashcards
What are the originators of vertical saccades? (2)
- frontal eye fields
- superior colliculus
What is the functional centre for horiontal eye movements / gaze?
The PPRF (paramedian pontine reticular formation)
What are the 4 main systems to maintain fast eye movement?
- Saccades
- Pursuit
- Vergence
- Vestibulo-ocular
What is the pathway for horizontal saccades? Where is the horizontal center located?
IN THE PONS.
Frontal eye fields in area 8 of frontal lobe (saccades) + parietal-occipitojunction (pursuit) –> superior colliculus –> CONTRALATERAL PPRF –>
1. ipsilateral 6th nerve nucleus –> ipsilateral LR
2. MLF –> contralateral 3rd nerve nucleus –> contralateral MR
What is the pathway of vertical saccades? Where is the vertical center located?
THE THALAMO-MESENCEPHALIC JUNCTION IN THE DORSAL MIDBRAIN
Frontal eye fields & parietal-occipital junction –> superior colliculus —> contralateral RIMLF (rostral interstitial nucleus of medial longitudinal fasciculus) –> interstitial nucleus of cajal –> third nerve subnuclei
Why is an upgaze palsy more common than a downgaze palsy?
upgaze pathway is mediated by single posterior commisure, downgaze pathway is bilateral
What does the medial longitudinal fasciculus connect?
ipsilateral 6th nerve nucleus in pons to the contralateral 3rd nerve nucleus in the midbrain
How can you tell if an INO is a pons lesion or a midbrain lesion?
Convergence test
If able to converge –> 3rd nerve nucleus is still intact in the midbrain –> PONTINE LESION
If not able to converge –> 3rd nerve nucleus is affected –> MIDBRAIN LESION
What is the velocity of smooth pursuit movements?
What is the velocity of saccadic movements?
smooth pursuit: 30-50 degrees / second
saccades:
saccadic - 800-1000 degrees / second
What is the latency of smooth pursuit movements?
What is the latency of saccadic movements?
smooth pursuit - 150ms
saccades - 100ms
