Week 2.05 Neuro-opthalmology Flashcards
What is involved in the supranuclear pathway
Saccades
Pursuits
Vestibular
What are the frontal eye fields for
FEF contain neurons that generate information
Generates saccades in the contralateral direction
E.g. FEF on the left controls the right eye saccades
What’s the parieto-occipital temporal cortex
Smooth pursuit eye movements in ipsilateral direction
Left parietal lobe controls pursuits in the left eye
What gaze centres do we have
Vertical gaze centre
Horizontal gaze centre
Where is the horizontal gaze centre and where is the vertical gaze centre
Horizontal gaze centre (PPRF) is in the pons at the level of the 6th nerve nucleus
Vertical gaze centre is in the midbrain near the 3rd and 4th nerve nucleus
Saccadfic eye movements
Rapid versional eye movements
Target displacement - stimulus
Latency 200 - 250ms short latency
Speed 30-700 deg
Signals initiated in contra-lateral frontal pre-motor area
What does the saccadic pathways look like
Saccade to the right
Left FEF sends signals to superior colliculus
And then to the vertical and horizontal gaze centres
The signal is transmitted through the medial longitudinal fasiculus
Horizontal gaze centres also sends out signals to relax LLR and RMR
Sends signals to 6th and 3rd
Pursuit eye movements
Signals initiated in the ipsilateral occipital - parietal area
Tracking eye movements
Stimulus - fixated target which moves
Latency 125ms
Speed 30-50
Slower than saccades
Pursuit movement pathway
Pursuit to the left
Initiated by left side so left parietal lobe
Signal transmitted to superior colliculus to pons
Then to vertical and horizontal gaze centres
6th nerve and third nerve initiated
Vestibular eye movements
Initiated by semi-circular canals via vestibular nuclei in the pons
Eye movements that compensate for changes in head position
Stimulus - head moves
Latency 10-100ms
Speed up to 300deg/s
Vestibular movement pathway
Semi-ocular canals send signals to vestibular nucleus and then to the horizontal gaze centres
Sends signals via 6th and 3rd nerve nucleus
Vestibulo-ocular reflex
Stabilises eyes on visual image during head and body movements
Vestibular nuclei inputs via MLF control EOM
Cold water irrigation of ear should produce nystagmus with eyes beating in contralateral direction
Cold Opposite Warm Same (COWS)
What are horizontal eye movements controlled by
Lateral rectus and medial rectus
What are vertical eye movements controlled by
SR, IR, IO muscles
Ventral region mediates…
Dorsal region mediates…
..downgaze
…upgaze
What is a gaze palsy
Inability to make conjugate ocular movement in one direction
Does not cause diplopia since visual axes remain parallel (both eyes fail to move)
What is a gaze palsy due to
Caused by lesion/damage to supranuclear/internuclear pathways
Frontal lesions cause
Unilateral saccadic palsies
Occipital lesions cause
Unilateral pursuit palsies
Supranuclear lesions do not affect what
Does not affect vestibular reflexes
Progressive supranuclear palsy
- later in life
- difficulties with mobility
- difficulties swallowing and speech
- mental slowing
- eye movement changes first sign
- slow vertical saccades - especially downwards
- horizontal saccades become hypometric
- loss of convergence
Huntingdon disease
- disturbance of voluntary gaze, particularly saccades
- initiation of saccades are difficult with prolonged latencies
- blink or head movement necessary to start saccades
- gaze holding is left in tact as it VOR
If you have damage to a cranial nucleas vs nerve
Cranial nucleus = gaze palsy as both eyes can’t move
Cranial nerve = incomitant deviations one eye fails to move out
How to record a gaze palsy
Right lateral gaze palsy
