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A 40-year-old woman presents with sudden diplopia and bad headache while at work. She notes that the left image is higher than the right one and that the images get further apart when she looks up, down, or to the left. On examination, she has an exotropia and left hypotropia when looking straight ahead, and there is reduced adduction, depression, and elevation of the right eye.

  • What additional signs should you look for?
  • What nerve, muscle, or structure has been affected?
  • What is your chief worry in a case like this, and how would you investigate it?

Diplopia is the experience of seeing more than a single image. In the majority of cases, it is due to the fact that the 2 eyes are not pointing at the same location in space (ocular misalignment). Thus, images of an object fall on different locations of the retinae of the 2 eyes, giving rise to the impression of 2 objects rather than 1.

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DiplopiaSeeing a duplicate copy of an image, colloquially referred to as "double vision."
Monocular diplopiaDiplopia with only one eye viewing.
Binocular diplopiaDiplopia present only when both eyes are open.
PolyopiaSeeing multiple copies of an image.
AbductionMoving the eye away from the nose.
AdductionMoving the eye toward the nose.
ElevationMoving the eye up.
DepressionMoving the eye down.
ComitantDiplopia that does not vary with gaze direction.
EsotropiaCrossed eyes; eyes pointing medially with respect to each other.
ExotropiaEyes that are pointing laterally with respect to each other.
HypertropiaOne eye elevated with respect to the other.
PhoriaA tendency for the eyes to be misaligned when one eye is covered; with both eyes open, the subject's ocular motor control system can use vision to align the eyes so that there is no diplopia.
Microvascular palsyPalsies attributed to small-vessel ischemia, often related to hypertension or diabetes.

Binocular diplopia stems from dysfunction of a broad range of motor structures, ranging from muscle, neuromuscular -junction, nerves in their course within and outside the brainstem, and prenuclear brainstem control problems. This anatomic division is a useful approach to evaluation and differential diagnosis.

Differential Diagnosis

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Site of PathologyDiagnosis
Ocular myopathyGraves ophthalmopathy1 (Figure 60–1)
Orbital myositis
Muscle entrapment (Figure 60–2)
Neuromuscular junctionMyasthenia gravis2
Cranial neuropathy (III, IV, VI)3–5 (Figures 60–3 and 60–4)Microvascular disease (diabetes) Tumor
Cerebral aneurysm
Supranuclear (brainstem) disorders6Stroke
Figure 60–1

Graves ophthalmopathy. Note that in straight-ahead gaze (bottom image) the eye is slightly lower and is proptotic. In upward gaze (right top image), the right eye cannot elevate. The ...

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