This has come up many times in the exam; the college loves to throw pictures of divergent eyeballs at the candidate, asking them to generate differentials. However, this chapter does not serve as the best resource for answering them.

Examples include:

However, this chapter does not serve as the best resource for answering them. The nerve-specific chapters listed above are better for exam revision. This chapter only brings together the information into one big table, so that it is available in one spot. The best offsite resource for this, which consolidates several textbooks worth of information into one article, is a piece by M.Karatas from the European Journal of Neurology (2009). One should get access to this article - one way or another.

Because this is a "brief summary", I have restrained myself from presenting ridiculously detailed diagrams of the neural pathways responsible for the generation of the sustained conjugate gaze and saccadic eye movement. Instead, you find below a table which only describes the pathology and its clinical features.   Generally speaking, a thorough understanding of this fascinating topic is not required for the fellowship exam; it is sufficiently complex to require a long time to process, but is sufficiently rare to yield very few marks per unit of effort. The time-poor candidate may excuse themselves from the reading of the rest of this chapter.

Disorders of Conjugate Gaze, Associated Lesions and Their Possible Causes
listed dumbly, without any explanation whatsoever, to facilitate mindless rote-learning

Disorder

Clinical features

Location of lesion

Possible causes

Internuclear ophthalmoplegia
  • slowing of eye movement
  • inability to adduct one eye
  • nystagmus of the other abducting eye.

(i.e. looks like a 6th nerve palsy, but with nystagmus of the "good" eye)

  • Lesion is not enhanced by caloric stimulation.
  • Adduction can not be enhanced by caloric stimulation.
  • Medial longitudinal fasciculus (MLF)
  • "caused by damage to the internuclear neurons that exit from the abducens nucleus, cross to the other side, arise in the MLF, and terminate in the subnucleus of the medial rectus in the nuclear complex of the third cranial nerve"
  • The lesion is on the same side as the eye with the adduction weakness.
Unilateral lesion:
  • Brainstem stroke
  • Fourth ventricular tumors
  • Arnold-Chiari malformation
  • Head trauma
Bilateral lesion:
  • Multiple sclerosis
  • Brainstem encephalitis
  • Wernicke encephalopathy
  • Overdose of phenothiazines, tricyclics, β-blockers, lithium
  • Pseudo-internuclear ophthalmoplegia (myasthenia gravis)
"One and a half" syndrome
  • Loss of all horisontal movement in one eye (this is the "one")
  • Loss of adduction in the other eye
    (this is the "half")
  • Paramedian pontine reticular formation
  • Simultaneous MLF damage
  • Lesions are ipsilateral to the "one" eye.
  • Brainstem stroke
  • multiple sclerosis
  • Pontine aneurysm or AV malformation
Horisontal gaze palsies
  • conjugate eye deviation to the side of the lesion
  • association with contralateral hemiparesis
  • contralateral frontal lobe
  • patient looks towards the affected lobe
  • Stroke
  • Tumor
  • Haemorrhage
  • Trauma
  • saccadic eye deviation to the side of the lesion
  • vestibulo-ocular reflex and response to
    caloric stimulation are normal
  • paramedian pontine reticular formation
  • patient looks away from the affected pons
  • Stroke
  • Tumour
  • loss of all adduction eye movements - a classical "6th nerve palsy"
  • Cannot be overcome by caloric stimulation
  • Lesion of the abducens nucleus or the abducens nerve
  • Bilateral horisontal palsy
  • Bilateral hemiparesis (quadriplegia)
  • Bilateral swallowing palsy
  • Normal vertical eye movements!
  • Bilateral pons
  • "Locked-in syndrome" due to bilateral pontine infarction, following basilar artery thrombosis
Vertical gaze palsies

Upward gaze palsy:

  • limtation of upward eye movement
  • loss or decrease in upward saccades
  • dorsal midbrain
  • pretectal area

Downward gaze palsy:

  • limitation of downward eye movement
  • loss or decrease in downward saccades
  • both rostral interstitial nuclei of
    the MLF in the ventral midbrain
Total ophthalmoplegia
  • Limitation of eye movement in any direction
  • non-localising finding;
  • if one had to blame a single brain region, one would point to the midbrain, as this is where the third nerve nuclei are.
  • progressive supranuclear palsy
  • Miller Fisher Syndrome (a variant of Guillain Barre)
  • Whipple disease
  • Wernicke encephalopathy
  • Overdose of phenytoin, phenothiazines, tricyclics, lithium, baclofen
  • Cavernous sinus thrombosis or infection
Tonic gaze deviation

Horisontal deviation

  • Sustained fixation of the eyes in one horisontal direction (i.e. fixed gaze to the right or the left)

(see Question 24.4 from the first paper of 2009)

  • Ipsilateral frontal lobe stroke ("paralytic" lesion)
  • Contralateral frontal lobe epilepsy ("irritative" lesion)
  • Contralateral pontine lesion
    (eyes tonically deviate away from the damaged pons, and towards the side of the hemiparesis)
  • Stroke
  • Tumor
  • Haemorrhage
  • Trauma
  • Epilepsy with a strongly lateralised focus

Sustained upward gaze deviation

  • eyes "rolled up"
  • usually, nonlocalising
  • oculogyric crisis
  • epilepsy

Sustained downward gaze deviation

  • eyes "rolled under"
  • usually, nonlocalising
  • hydrocephalus
  • metabolic encephalopathy
  • thalamic hemorrhage

 

References

The LITFL summary of cranial nerve lesions is without peer in terms of useful information density.

Walker, H. Kenneth, W. Dallas Hall, and J. Willis Hurst. "Clinical methods." (1990).

Karatas, M. "Internuclear and supranuclear disorders of eye movements: clinical features and causes." European Journal of Neurology 16.12 (2009): 1265-1277.

This one is not available as free fulltext, but it's that good that you should travel through the rain and snow to your local medical library to get a hold of it.

Baloh, R. W., J. M. Furman, and R. D. Yee. "Dorsal midbrain syndrome Clinical and oculographic findings." Neurology 35.1 (1985): 54-54.

Warren, Naomi M., and David J. Burn. "Progressive supranuclear palsy."Practical neurology 7.1 (2007): 16-23.

Marco Mumenthaler, Heinrich Mattle "Fundamentals of Neurology: An Illustrated Guide" vis Google Books. Georg Thieme Verlag, 2000.