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The patient in this video is viewing an optokinetic strip moved first to his left and then to his right.
What abnormality is this maneuver bringing out?
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As the optokinetic (OKN) strip is moved to the patient’s left, it evokes involuntary leftward conjugate pursuit, followed by rightward conjugate recovery saccades
in a repetitive sequence that allows you to see that both eyes are making adequate rightward saccades. But when the strip is moved to the patient’s right, the evoked
saccades in the left eye have much lower amplitude than the evoked saccades in the right eye, bringing out an abducting saccadic deficit in the left eye--an eye that has
a sixth nerve palsy.
The OKN strip (or drum) maneuver has five main clinical uses: 1) displaying a subtle abduction deficit in sixth nerve palsy, as you saw here; 2) displaying a subtle internuclear ophthalmoplegia, which would be manifest by relatively low-amplitude ADDUCTING saccades; 3) displaying convergence retraction of the eyes when the strip is moved downward in dorsal midbrain syndrome; 4) displaying a relatively reduced contraversive saccadic amplitude IN BOTH EYES when the strip is moved in the direction of a damaged parietal lobe; 5) displaying intact nystagmus when the strip is moved in one or more directions in a patient with factitiously impaired sight. The correct answer covers the first of these five diagnostic uses of the OKN strip; the incorrect answer choices cover three of the other uses, and the fifth use is for you to try out!
The OKN strip (or drum) maneuver has five main clinical uses: 1) displaying a subtle abduction deficit in sixth nerve palsy, as you saw here; 2) displaying a subtle internuclear ophthalmoplegia, which would be manifest by relatively low-amplitude ADDUCTING saccades; 3) displaying convergence retraction of the eyes when the strip is moved downward in dorsal midbrain syndrome; 4) displaying a relatively reduced contraversive saccadic amplitude IN BOTH EYES when the strip is moved in the direction of a damaged parietal lobe; 5) displaying intact nystagmus when the strip is moved in one or more directions in a patient with factitiously impaired sight. The correct answer covers the first of these five diagnostic uses of the OKN strip; the incorrect answer choices cover three of the other uses, and the fifth use is for you to try out!
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