what is a Supranuclear disorder
Supranuclear motility disorders result in palsies of conjugate movement. Cant look right or left restriction of position of eye movement
Gaze Palsy
Affecting one or more movement systems
Diplopia is rare
Anatomy and Physiology
Brainstem control of smooth pursuit, saccades and vestibulo-ocular movement
Horizontal Gaze Centre – Pons
Vertical Gaze Centre - Midbrain
Horizontal Gaze Centre
· PPRF – Paramedian Pontine Reticular Formation
· Level of the sixth nerve nuclei in the Pons
· PPRF controls movement to the ipsilateral side LR and contralateral MR via the MLF
If problem in PPRF won’t send message to 6th and that won’t send message to MLF of contracteral eye restricting smooth pursuit to that direction
Vertical Gaze Centre
- Upper Midbrain
- riMLF – Rostral Interstitial MLF most important for downgaze - Edinger westpal nucleus problem - can accommodate but dont react to light
- INC – Interstitial Nucleus of Cajal. Vertical neural integrator to provide gaze holding – maintain fixation
- Posterior Commissure is important for upgaze and eyelid control - band of fibres up in midbrain where problems usually happen - paranoids syndrome sits at this level in
Burst neurones in riMLF send messages to the IIIN nucleus for upgaze and IIIN and IVN for downgaze
Vertical gaze main
Paranoids – cans look up
Supranuclear palsy - can’t look down
ROSTRAL INTERSTITIAL NUCLEUS OF THE MEDIAL LONGITUDINAL FASCICULUS
located in the mesencephalon at the rostral termination of the MLF.
This nucleus includes cells from the interstitial nucleus of Cajal.
The riMLF has connections to motor neurons in the oculomotor and trochlear nuclei, as well as to the PPRF.
Posterior Commisure
- Dorsal and rostral to the riMLF is the posterior commissure, a fiber tract that contains some scattered neuronal cell bodies.
Lesions in this region produce abnormalities of upward gaze.
It is likely that the fibers for upward gaze leave the riMLF and pass through this region before reaching the oculomotor and trochlear nuclei.
Involvement of the posterior commissure may be part of the dorsal midbrain syndrome (Parinaud Syndrome).
Superior Colliculus
The superior colliculus can generate visually directed saccades independently and may play a role in the control of pursuit eye movements.
In primates, ablation of both FEFs and both superior colliculi is necessary to produce permanent saccadic defects.
Vestibular system – abnormal eye movements
Supranuclear all affected
Infranuclear one muscle affected
Gaze Palsy examples
- supranuclear lesions do not affect vestibular reflexes, so these remain intact (test by calorics or dolls head reflex)
- frontal lesions cause unilateral saccadic palsies
- occipital lesions cause unilateral pursuit palsies
- pontine lesions affect horizontal gaze but not vertical
- upper midbrain lesions affect vertical gaze
- horizontal saccadic gaze palsies are most common
INO – most common horizontal palsy
MS most common aetiology of ION usually
Women in 20s if older think vascular
Parinaud’s , Progressive Supranuclear Palsy, INO, One and a half Syndrome
- Parinaud’s – loss of upgaze saccades
- Progressive Supranuclear Palsy – loss of downgaze saccades
- INO – loss of adduction with ataxic nyst of abd eye
One and a half Syndrome – INO plus horizontal gaze palsy
what is a skew deviation
vertical strabismus
- Caused by a supranuclear lesion in the posterior fossa.
- Because skew deviation may clinically mimic trochlear nerve palsy, it is sometimes difficult to differentiate the 2 conditions.
Features of skew
- Vertical strabismus – resulting from peripheral and central lesions
- Diplopia is present unlike most supranuclear palsies
- Torsional nystagmus may be present
- Transient are common in Unilateral INO
- Part of the ocular tilt reaction with head tilt and torsion
Differential diagnosis of skew
- Fourth Nerve Palsy - eye is extorted cant intort
- Bilateral Inferior Rectus u/a and Superior Oblique o/a can give the appearance of a Skew on right and left gaze
- Intorsion of the hypertropic eye and extorsion of the hypotropic. Similar to a half cycle of see-saw nystagmus
- IVN palsy would give you excyclotorsion in the hypertropic eye
- Look for torsion on fundus photography
check notes for skew vs SO palsy
Clinical Tips for skew
- The head tilt is towards the hypotropic eye and does not allow fusion of the vertical deviation
- Same as IVN palsy
- Unable to fuse with prisms or surgery
- In Skew the deviation is less when the patient is lying down
- This is not the case for IVN palsy (Wong et al 2011)
- Upright Supine Test
Upright Supine Test - Wong 2011
- Vertical deviation present in primary position
- When the patient is asked to lie down or tilt their head back to almost flat
- The deviation should reduce by 50% or more if a Skew Deviation is present
