Supranuclear & Intranucler Disorders

Question 1

Describe supranuclear disorders?

Answer 1

• Signals which control ocular movement are initiated in cerebral hemispheres
• They are then transmitted to gaze centres in the brainstem & oculomotor nuclei in the midbrain & pons, & leave the brain in the 3rd, 4th & 6th CNs
• Supranuclear neuronal pathways: conduct impulses from cerebral hemispheres to gaze centres
• Supranuclear motility disorders result in palsies of conjugate movement (gaze palsies)
• Frontal eye fields (in brain) determines a saccade
• Needs to pass down through parietal occipital lobe before reaches brainstem
• Smooth pursuit (covered so far) is what is tested on ocular motility when they follow your light
• Small lesion e.g. MS – gives INO
• Bigger lesion or bigger infarct affects both vertical & horizontal gaze
• Supranuclear is a problem of conjugate gaze  the other topics covered have been one eye

Question 2

Describe the horizontal gaze centres?

Answer 2

• Anatomically ill-defined with pontine paramedian reticular formation (PPRF) each side of midline at level of 6tth nerve nuclei
  o If lesion on PPRF then info still going to frontal eye fields but then not continuing to LR or MR – seen in stroke
• Saccades = initiated contralateral frontal pre-motor area (Area 8)
  o Saccadic movement for horizontal has to be initiated in frontal eye fields
• Pursuit = initiated ipsilateral occipito-parietal area
• Vestibular reflexes = initiated vestibular nuclei in the pons
• Each centre controls horizontal movement to same side & projects to the ipsilateral abducens nucleus & to MR sub nucleus of the 3rd nerve on opposite side via the contralateral medial longitudinal fasciculus (MLF)
• 1 and a half – horizontal gaze palsy with INO

Question 3

Describe the vertical gaze centres?

Answer 3

• Anatomically ill-defined
• It is generally an accepted view that a region of the midbrain serves to coordinate the up & down movements of the eye
• However, much less is known about the mechanisms governing the control of vertical gaze
• The key region for vertical gaze movements lies in the rostral midbrain (the structure is called the rostral interstitial nucleus of the MLF (riMLF))
  o riMLF is a much higher centre in brain
  o Progressive supranuclear palsy – cannot look down initially
  o Parinauds – cannot look up initially
  o Interstitial nucleus of Cajal
• The region of the riMLF appears to be most important for generating downgaze, whereas the posterior commissure region appears most important for generating upgaze
  Parinauds, INO, 1 and ½ = vertical gaze palsies
  Vertical gaze is much higher up

Question 4

Which part of the brain is responsible for saccades?

Answer 4

• FEFs initiate saccades
• Testing smooth pursuit – looking for ductions and versions
• If px cannot initiate a saccade – then neurogenic or supranuclear problem
• If can make a small saccade – then mechanical problem
• If they don’t get the message to make the saccade then could be a saccadic problem – problem in FEF

Question 5

Describe gaze palsies in general? Give examples?

Answer 5

• An inability to make a conjugate ocular movement in one direction
  o Conjugate ocular movement – can’t look up/down/left/right
  o Right horizontal gaze palsy – can’t look right
• This does not cause diplopia sine the visual axes remain parallel
• By investigating each reflex & conjugate movement in turn, it is possible to establish where a lesion exists
  o Parinauds – can’t look up
• Examples:
  o Supranuclear lesions do not affect vestibular reflexes, so these remain intact (test by calorics or dolls head reflex)
   Eyes can move but they cannot choose to follow the target – if move their head then their eyes move
  o Frontal lesions cause unilateral saccadic palsies
  o Occipital lesions cause unilateral pursuit palsies
  o Pontine lesions affect horizontal gaze but not vertical
   Common e.g. astrocytoma
  o Upper midbrain lesions affect vertical gaze
   Dorsal midbrain syndrome
  o Horizontal saccadic gaze palsies are most common
   Since lots of pathology around PPRF

Question 6

Describe Parinauds Syndrome?

Answer 6

• Relatively rare & is caused by lesions in upper midbrain
  o More common in young children
• Pineal tumours are more common in adolescent males
• Metastases & gliomas
• Hydrocephalous – dilatation of 3rd ventricles results in compression of posterior commissure
• Atherosclerosis, Embolism, Vasculitis
• Clinical Signs:
  o Loss of saccades on up-gaze (loss of vertical saccades with retention of fairly normal smooth pursuit movement vertical gaze palsy
   Abnormal head posture – chin down (eyes come up as cannot look up)
• Think ‘chin down eyes up’
  o Absence of OKN when stripes are rotated down due to lack of fast phase on up gaze – OKN will be normal when rotated upwards
   Px trying to follow drum – they cannot look up so they converge
  o In progressive lesions may be followed by loss of downgaze & eventually complete vertical gaze paralysis affecting smooth pursuit, VOR movements & a loss in Bell’s phenomenon
  o Both pupils are dilated usually with a reduction in light response but normal constriction on accommodation – light/near dissociation
   No response of pupils to light but miose to accommodation
  o The convergence retraction nystagmus is seen spontaneously or (more usually) on attempted upgaze
   The lesion is thought to cause disinhibition of ocular motor nuclei allowing bursts of co-firing of the EOMs
   Convergence retraction nystagmus – disjugate nystagmus – both eyes are converging & pulling back in so get a globe retraction
  o As MR is most powerful muscle this results in convergence & a retraction of globe
  o Upper eyelid retraction ‘Collier’s Sign’ the affected eyelid is retracted & usually associated with lid-lag & most likely best seen on downgaze – one or both eyelids can be affected
   Collier’s Sign – sun setting sign – increase in ICP

Question 7

Describe internuclear ophthalmoplgia (INO)?

Answer 7

• Caused by lesions in medial longitudinal fasciculus (MLF), the area carrying internuclear neurones between 6th & 3rd nerves
• Type depends on precise location of the lesion in MLF
• Can be unilateral or bilateral:
  o Unilateral:
   Interneurons from one 6th nerve nucleus affected, causing loss of adduction of the affected MR in attempted conjugate gaze
  o Bilateral:
   Interneurons from both 6th nerve nuclei affected – often asymmetric
• Saccadic, pursuit & vestibular systems are all affected
• Get abducting nystagmus of other eye (reasons for this is not clear)
• Convergence can remain intact
• Pxs rarely complain of diplopia
• Cause; MS is commonest cause of unilateral (&often bilateral) INO in younger px (may be presenting feature)
• In the older px, small blood vessel occlusion is likely in unilateral INO & tumour is a possibility in bilateral
• Most spontaneously recover, except if tumour
• Eye sitting EXO as problem with adduction

Question 8

Describe 1 and 1/2 syndrome (paralytic pontine exotropia)?

Answer 8

• Lesion affecting both horizontal gaze centre & adjacent MLF = gaze palsy +INO
• The only remaining horizontal movement is abduction of the unaffected LR with abducting nystagmus i.e. gaze palsy to one side, INO to the other
• Complete “one and a half” syndromes are uncommon, but partial is more common
• Cause: tumour is likely
  o Normally 2 lesions or one v big lesion

Question 9

Describe progressive supranuclear palsy?

Answer 9

Is a medical condition chararcterised by an inability to control facial muscles – slurred speech presenting symptom brainstem
Initially involves downgaze, subsequent defective up & horizontal gaze
Syndrome associated with other diseases treat that first – MS, Parkinson’s, tumour, trauma
EPS are associated with antipsychotic drugs or anything that blocks dopamine functions in the brain
Old px – falling – fall backwards
Dementia – gets worse and worse over 10 years (fatal)

Question 10

Describe Skew Deviation?

Answer 10

• Vertical strabismus
• Must be differentiated from a 4th nerve palsy
• Resulting from disruption of input into the IIIN & IVN nuclei
• Associated with CNS disease – not like vascular 6th or vascular 4th
  o Tends to be stroke or tumour
  o Inner ear problems or balance problems that often give px the skew
  o Peripheral ability for px to know where eyes should be in relation to their heaad
• Features:
  o Vertical strabismus – resulting from peripheral & central lesions
  o Diplopia is present unlike most supranuclear palsies
   Often confused with 4th
  o Torsional nystagmus may be present
  o Transient are common in unilateral INO
   INO – if lesion is big enough & in same level enough then can get skew
  o Incomitant or comitant
  o Part of ocular tilt reaction with head tilt & torsion
   Px has vertical e.g. L>R – if lay head back then this changes position of where the plain is & skew deviation should go completely if it is a skew (if 4th they will still have a vertical lying down)
• Skew will either reduce by 50% or disappear entirely
• Upright supine test
   Peripheral & central vestibular lesions result in a head tilt towards the same side as the lesion
   Rostral lesions of MLF & INC (interstitial nucleus of Cajal) result in head tilt towards opposite side of lesion
• Reason for this is due to crossover of vestibular nuclei in the contralateral MLF
  o Head tilt is towards the hypotropic eye & does not allow fusion of the vertical deviation
  o Same as IVN palsy
  o Unable to fuse with prisms or surgery
  o In Skew the deviation is less when the patient is lying down
   This is not the case for IVN palsy
  o Pxs with skew find it difficult to fuse with prism – as not same, things not connecting
  Verticals – you must prove if it is a 4th or a Skew

Question 11

Describe the Upright Supine Test?

Answer 11

• Vertical deviation present in primary position
• When px is asked to lie down or tilt their head back to almost flat
• Deviation should reduce by 50% or more if a Skew deviation is present

Question 12

Compare the features of Skew Deviation vs SO Palsy?

Answer 12

Skew:
Hypertropic Eye: Ipsila/contr to side of lesion
Deviation: Concom/Incom/Int/Alt
Torsion: Hyper Eye intorted
Hypo eye extorted
Head tilt: Towards hypo eye
BHHT: Inconclusive
Upright/supine test: Vert reduces by 50%
Other CNS signs: Common

SO Palsy:
Hypertropic Eye: Ipsilateral side of lesion
Deviation: Initially incom-concom
Torsion: Hyper eye extorted
Head tilt: Towards hypo eye
BHHT: Hyper increases on ipsilateral head tilt
Upright/supine test: No change
Other CNS signs: Rare