Supranuclear Motility Disorders

Horizontal gaze centre: pons

• PPRF
• Sixth nerve nucleus
• Mediate to medial rectus subnucleus in midbrain via MLF (an interneurone)

Vertical gaze centre: midbrain

• Thalamo-mesencephalic junction

Saccades

• Contralateral frontal eye fields

Pursuits

• Ipsilateral parieto-occipital-temporal (POT) region

See separate Chapter on supranuclear control of eye movements.

The vestibulo-ocular reflex (Doll’s head manoeuvre) communicates with the infranuclear pathways (nucleus, peripheral nerve etc downstream.

• Therefore an intact VOR may suggest the deficit is supranuclear

Horizontal gaze abnormalities

Stimulation of the horizontal gaze centre (PPRF/sixth nerve nucleus inpons) on one side causes a conjugate movement of the eyes to the same side

Horizontal gaze palsy

• Lesions of the PPRF or sixth nerve nucleus

  • A lesion to the sixth nerve nucleus disrupts signal to both:
    • The lateral rectus, and
    • The third nerve subnucleus for medial rectus (via the MLF)
  • Therefore a nuclear sixth produces a horizontal gaze palsy to the ipsilateral side

• Eyes cannot move across the midline to the side of the lesion (cannot look in direction of lesion)

• Vestibulo-ocular reflex is preserved with a PPRF lesion (supranuclear) butnotin a VI nucleus lesion

• No diplopia

Internuclear ophthalmoplegia

• Lesion in the MLF
  • Demyelination
  • Stroke
  • Tumour

• Unilateral INO:

  • Straight eyes in the primary position
  • Loss of adduction of the ipsilateral eye (to the lesion)
  • Nystagmus of the contralateral eye on abduction
  • Normal gaze to the side of the lesion
  • Convergence is intact if lesion is small and anterior in the MLF and below the midbrain
    • There is supranuclear control to the third nerve nuclei for convergence that is independent of the sixth nerve nucleus
  • Slow adduction saccadic velocity on the affected side compared to abduction velocity of the contralateral eye: this is a cardinal feature

• Bilateral INO:

  • Left gaze: right eye cannot adduct and left eye ataxic nystagmus (overshoot of the eye)
  • Right gaze: left eye cannot adduct and right eye ataxic nystagmus
  • A rostral midbrain lesion also gives a convergence deficit causing bilateral exotropia: ‘wall-eyed bilateral INO (WEBINO)

• May be associated with:

  • Abnormal VOR
  • Skew deviation: ipsilateral hypertropic eye

One and a half syndrome (a dorsal pontine syndrome)

• Lesion of the MLF and PPRF/sixth nerve nucleus: typically apontinestroke/lesion
• Ipsilateral horizontal gaze palsy and ipsilateral INO
• Contralateral abduction is the only preserved horizontal eye movement (vertical gaze is unaffected)

Tonic gaze deviation

• Damage to the frontal eye field

  • Strokes, trauma, tumour

• Loss of initiation of eye movements to the contralateral side

• Eyes deviate to the ipsilateral side

Vertical gaze palsies

The vertical gaze centre is located at the junction between the thalamus and the midbrain (thalamo-mesencephalic junction).

Parinaud syndrome (dorsal midbrain syndrome)

The dorsal midbrain contains

• Edinger-Westphal nucleus (CNIII)
• Pretectal nuclei

Lesion in the posterior commissure and pretectal areas

• Hydrocephalus (eg. aqueduct stenosis)
• Meningitis
• Tumour eg. pinealoma in children
• Trauma/head injury
• AV malformation
• Demyelination
• CVA
• Degenerative (Wernicke’s encephalopathy)

Features

• Lid retraction bilaterally (Collier’s sign): due to disruption of inhibitory input to the levator

• Near-light dissociation with mydriasis: due to disruption of the light pathway, with sparing of the near pathway which is more rostral

• Convergence-retraction nystagmus: due to co-contraction of medial and lateral recti on attempted upgaze (not a true nystagmus)

• Supranuclear upgaze palsy(cp PSP): initially saccades, then pursuit movements, then VOR. Due to posterior commissure disruption where the upgaze pathways converge

• Others:

  • Straight eyes in primary position
  • Loss of convergence
  • Skew deviation

• An MRI of the brainstem is indicated

Progressive supranuclear palsy aka Steele-Richardson-Olsezewski syndrome

• Rare progressive neurodegenerative disease: tau protein accumulation

• An atypical Parksinsonian syndrome

• Onset over age 40

• Supranuclear gaze palsy primarily of downgaze first

• Latterly, loss of horizontal movements and global gaze palsy

• Loss of convergence

• Lid apraxia can lead to corneal exposure

• Square wave jerks: ‘nystagmoid’ movements (not a true nystagmus)

  • Saccadic intrusion: small amplitude, horizontal shift/intrusion away from fixation followed by a pause then a quick return to fixation
  • Often seen in normal patients
  • >9 per minute associated with Parkinson’s disease or progressive supranuclear palsy

• Pseudobulbar palsy

• Extrapyramidal signs, rigidity

• Frequent falls due to gait problems

• Dementia

Skew deviation

• Rare

• Vertical deviation with cyclotorsional disturbance

  • Not due to cranial nerve palsy or muscle issue
  • Typically concomitant (ie both eyes hypertropic)
  • But may be incomitant (ie. one hypertropic and the other hypotropic) which may be confused with a ** fourth nerve palsy**. Consider a skew and fourth nerve palsy when presented with any vertical gaze deviation
    • The upright-supine test can be used to differentiate: with a skew, the vertical deviation willdecrease(>50%) with the patient supine compared to upright (but will remain constant with a fourth nerve palsy)

• Usually due to brainstem or cerebellar stroke

• May be associated with perceived tilting of the visual field (‘ocular tilt reaction’)

Monocular elevation deficit (double elevator palsy)

• Congenital or acquired. Causes:

  • Type 1: inferior rectus restriction. Forced duction test positive
  • Type 2: deficient innervation to elevators
  • Type 3: supranuclear (eg lesions in the pretectum?)

• Congenital ptosis/pseudoptosis due to fascial attachments between levator and superior rectus

  • Dystrophy or maldevelopment of the levator and superior rectus complex

• Poor/absent Bells phenomenon

• Chin up posture

• Management: depends on forced duction test

  • Type 1: inferior rectus recession
  • Others: Knapp procedure: transposition of the medial and lateral recti to superior rectus