Photoparoxysmal response in late infantile neuronal ceroid-lipofuscinosis.

A patient presented with rapid developmental regression whose MRI findings suggested a leukodystrophy, but nerve, muscle, skin, and bone marrow biopsies were unrevealing. A characteristic photoparoxysmal response on electroencephalogram provided an important clue for the correct diagnosis of late infantile neuronal ceroid-lipofuscinosis, which was confirmed later with electron microscope examination of a brain biopsy. In patients with rapid neurologic deterioration, diagnosis of neuronal ceroid-lipofuscinosis should be considered and an electroencephalogram should be performed using photic stimulation to look for characteristic findings.