• 10 SECTION Nystagmus
Congenital Motor Nystagmus
Key Facts
•Appears within first 6 months of life
•Unknown cause
•Isolated finding or associated with strabismus or developmental delay
•Diagnosis based on noting features of nystagmus, its early onset, and lack of any contributory neurologic findings
•May be difficult to exclude congenital sensory nystagmus (see Congenital sensory nystagmus)
Clinical Findings
•Horizontal pendular nystagmus in primary position converting to jerk nystagmus on sidegaze
•Remains in same plane in all fields of gaze (uniplanar)
•Nystagmus often disappears or its amplitude markedly diminishes in eccentric gaze position (eccentric null zone)
•Patient often adopts face turn to get eyes into null zone
•Covering one eye often exacerbates jerk nystagmus in the open eye (latent nystagmus)
•Patient does not report oscillopsia (but usually does report blurred vision)
•Head nodding may be present
•Visual acuity ranges from 20/40 to 20/200 for distance viewing
• May be better for reading and in eccentric face turn position
•No structural abnormalities on ophthalmologic or neurologic examination
•In a rare variant, primary position right-beating nystagmus gives rise to primary position left-beating nystagmus in fixed cycles (periodic alternating nystagmus)
Ancillary Testing
•Electroretinography is normal but may be necessary to rule out Leber congenital amaurosis
•MRI is normal
Differential Diagnosis
• Congenital sensory nystagmus
•Sidebeat, upbeat, or downbeat nystagmus
•Acquired binocular pendular nystagmus
•Spasmus nutans
•Square wave jerks
•Ocular flutter or opsoclonus
•Ocular dysmetria
Treatment
•If there is a face turn, perform extraocular muscle surgery (Kestenbaum procedure) to shift null zone to primary position, particularly if visual acuity is better in eccentric face turn position
•Do not inject botulinum toxin into extraocular muscles or retrobulbar space—it is ineffective and causes intolerable side effects
•Avoid large extraocular muscle recessions, which have not been successful
Prognosis
• Lifelong condition in which visual acuity may always be subnormal but stable
• Eye muscle surgery may be successful in eliminating face turn
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Fig. 10.2 Congenital motor nystagmus. In primary position, there is a lowamplitude right-beating nystagmus that increases in amplitude on right gaze. In left gaze, there is a left-beating nystagmus. In upgaze and downgaze, the nystagmus remains in the horizontal plane (uniplanar).
Nystagmus Motor Congenital
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• 10 SECTION Nystagmus
Congenital Sensory Nystagmus
Key Facts
•Appears within first 6 months of life
•Eye movements look like those of congenital motor nystagmus
•Common causes:
•Leber congenital amaurosis
•achromatopsia
•aniridia
•albinism
•optic neuropathy
Clinical Findings
•Eye movements identical to those of congenital motor nystagmus (see Congenital motor nystagmus)
•Eyes may appear otherwise normal (Leber congenital amaurosis, achromatopsia, intracranial tumor)
•Narrowed retinal arterioles (Leber congenital amaurosis), hypoplastic iris (aniridia), iris transillumination defects (albinism), small optic nerve (optic nerve hypoplasia, craniopharyngioma)
•Visual acuity ranges from near normal to finger counting
Ancillary Testing
•Electroretinography may show reduced amplitude in Leber congenital amaurosis
•MRI may show atrophic optic nerves, cerebral malformations or tumors
Differential Diagnosis
•Congenital motor nystagmus
•Sidebeat, upbeat, or downbeat nystagmus
•Acquired binocular pendular nystagmus
•Spasmus nutans
•Square wave jerks
•Ocular flutter or opsoclonus
•Ocular dysmetria
Treatment
• None except for anterior visual pathway tumor
Prognosis
• Depends on underlying lesion
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Fig. 10.3 Congenital sensory nystagmus. The nystagmus has features identical to that of congenital motor nystagmus, but the patient has an identifiable abnormality of the retina or optic nerves that impairs vision.
Fig. 10.4 Retinal achromatopsia. Optic discs are slightly pale and foveal reflex is absent in a completely colorblind and visually impaired child with congenital sensory nystagmus.
Nystagmus Sensory Congenital
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