• 10 SECTION Nystagmus
Epileptic Nystagmus
Key Facts
•Horizontal jerk nystagmus during seizure
•Horizontal gaze and head deviation to side contralateral to seizure focus
•Usually accompanied by tonic–clonic movements of face and extremities on side of gaze deviation
•Usually resolves within minutes but may be sustained (partial status epilepticus)
•When seizure ends, eyes may deviate to opposite side but nystagmus stops
Clinical Findings
•Fast, moderate amplitude horizontal jerk nystagmus in direction of gaze
•Eyes deviated in direction of fast phase
•Face and extremities often twitching or contracted on side contralateral to seizure focus
Ancillary Testing
•If electroencephalogram is being recorded, epileptic discharges will be captured
•Interictal electroencephalogram may also be abnormal
•MRI often shows lesion at seizure focus
Differential Diagnosis
• Nothing else causes this combination of findings!
Treatment
•Directed at underlying lesion
•Anticonvulsants
Prognosis
• Depends on ability to control seizures
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Fig. 10.15 Epileptic nystagmus. The eyes are deviated to the right and display a jerk nystagmus with a fast component to the right.
Nystagmus Epileptic
Fig. 10.16 Occipital arteriovenous malformation causing epileptic nystagmus. Axial T2 MRI shows a mass of inhomogeneous signal in the left parieto-occipital region (arrow) that proved to be an arteriovenous malformation.
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Nystagmus
“Nystagmus” of Extraocular Muscle
Dysfunction
Key Facts
•Jerk nystagmus in direction of gaze in presence of impaired extraocular muscle function (cranial neuropathy, neuromuscular transmission failure, extraocular myopathy)
•Occurs in field of action of weak or restricted extraocular muscle
•Usually low amplitude, unsustained, and appears only in extreme gaze
•May be confused with myasthenia gravis or internuclear ophthalmoplegia
Clinical Findings
•Low-amplitude, unsustained jerk nystagmus in field of action of dysfunctional extraocular muscle
•Usually other evidence of cranial neuropathy, neuromuscular transmission failure, or extraocular myopathy, but may be subtle
• 10 SECTION
Ancillary Testing
•Tests for myasthenia gravis may be positive
•Brain or orbit imaging may be abnormal
Differential Diagnosis
•Myasthenia gravis
•Internuclear ophthalmoplegia
Treatment
• Depends on condition
Prognosis
• Depends on condition
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Fig. 10.17 Nystagmus of extraocular muscle weakness. The right eye has reduced adduction from medial rectus malfunction and displays a few beats of left-beating (jerk) nystagmus in left gaze. Any disorder of ocular motor nerves, myoneural junction, or extraocular muscle can produce mild oscillation of the eye when it is brought into the appropriate field of action.
Dysfunction Muscle Extraocular of “Nystagmus”
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