Value of electrodiagnostic assessment in nonsyndromic microcephaly

Area of Science:

• Ophthalmology
• Neurology
• Pediatrics

Background:

• Nonsyndromic microcephaly is a condition characterized by an abnormally small head size without other associated syndromes.
• Visual impairments are frequently observed in children with microcephaly, but the underlying causes are not always clear.

Purpose of the Study:

• To assess the diagnostic value of electroretinogram (ERG) and visual evoked potentials (VEP) in evaluating visual function in children with nonsyndromic microcephaly.
• To correlate ERG and VEP findings with visual acuity and neuroimaging results.

Main Methods:

• An observational case series involving six children with nonsyndromic microcephaly (aged 8.5 to 158 months).
• Evaluations included flash ERG (photopic, flickering, scotopic, dark-adapted), VEP (flash/pattern-reversal), visual acuity, and ophthalmic examinations.
• Brain CT scans were performed for some participants.

Main Results:

• Three children had normal ERG and VEP responses; two had poor vision, and one showed schizencephaly on CT.
• The other three children exhibited abnormal ERG, primarily with reduced photopic amplitudes.
• Two of these had retinal pigmentary changes, poor vision, brain atrophy, and reduced VEP amplitudes.

Conclusions:

• Abnormal ERG is a frequent finding in nonsyndromic microcephaly, often affecting cone photoreceptors more than rods.
• Reduced ERG amplitudes do not consistently correlate with poor visual acuity.
• Visual dysfunction in these children is likely attributable to posterior visual pathway defects or brain developmental abnormalities.