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A 45 year old woman reports episodes of blurred vision coincident with a twitching sensation in her left eye.
This disturbance is called
Correct! You are looking at small-amplitude torsional oscillations of the left eye, a condition
called superior oblique myokymia. Patients report momentary diplopia or blurred vision, and a twitch in the affected eye. The intermittent eye
movement—always confined to one eye---is caused by activation of the superior oblique muscle, either by instability in the contractile properties of the
muscle or by inappropriate firing in the fourth nerve. It is not a nystagmus but a fasciculation, defined as a brief asynchronous contraction of muscle groups.
Why it happens is a mystery.
This condition is often misdiagnosed as nystagmus, but the clues are the unique twitching sensation and the fact that the eye movement is strictly monocular!
Although some observers advocate brain imaging to rule out intracranial causes of fourth nerve dysfunction, the yield is so low that imaging should be reserved for patients who have other evidence of brainstem or peripheral nerve dysfunction.
Medications that reduce muscle irritability or nerve conduction sometimes work. Clinicians have also reported success with adrenergic beta-blocking agents administered topically or orally. Surgical weakening of the superior oblique muscle has been done for this condition, but the chances of causing persistent diplopia are high, necessitating additional eye muscle surgery that is not always successful.
The other answer choices you had here all involve BINOCULAR OSCILLATIONS, not the monocular oscillations you saw in this patient. When you see ocular oscillations, decide whether they affect one eye or both. It makes a difference!
This condition is often misdiagnosed as nystagmus, but the clues are the unique twitching sensation and the fact that the eye movement is strictly monocular!
Although some observers advocate brain imaging to rule out intracranial causes of fourth nerve dysfunction, the yield is so low that imaging should be reserved for patients who have other evidence of brainstem or peripheral nerve dysfunction.
Medications that reduce muscle irritability or nerve conduction sometimes work. Clinicians have also reported success with adrenergic beta-blocking agents administered topically or orally. Surgical weakening of the superior oblique muscle has been done for this condition, but the chances of causing persistent diplopia are high, necessitating additional eye muscle surgery that is not always successful.
The other answer choices you had here all involve BINOCULAR OSCILLATIONS, not the monocular oscillations you saw in this patient. When you see ocular oscillations, decide whether they affect one eye or both. It makes a difference!
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