Patient selection: unexplained visual loss
Clinical features suggesting jNCL:
(1) age at presentation <= 10 years
(2) A fundoscopic exam may:
(2a) be normal
(2b) show bull's eye maculopathy
(2c) show pigmentary and/or atrophic change
(3) cognitive decline
(4) behavioral changes
(5) progressive motor disturbances
(6) presence of vacuolated lymphocytes in the peripheral blood smear
(7) abnormal electroretinogram
(8) an affected sibling
Findings on an electroretinogram (ERG) may include:
(1) undetectable rod-specific ERGs
(2) electronegative maximal response
(3) reduced and delayed cone flicker ERGs
(4) reduction in the b-to-a ratio in the photopic single flash ERG with a-wave delay
(5) undetectable ERG
(6) an abnormal photopic ON and preserved photopic OFF response
A child suspected of having jNCL can be tested for the underlying genetic defect.
