Evolution of the retinal function by flash-ERG in one child suffering from neuronal ceroid lipofuscinosis CLN2 treated with cerliponase alpha: case report.

Introduction: Neuronal ceroid lipofuscinoses (CLN) are neurodegenerative disorders among the most frequent, inherited as an autosomal recessive trait. Affected patients can present with progressive decline in cognitive and motor functions, seizures, a shortened life span and visual deficiency. CLN2 is one of the rare CLN that benefits from treatment by cerliponase alpha an enzyme replacement therapy. Preliminary results on treated animal models have shown delayed neurological signs and prolonged life span. However, cerliponase alpha did not prevent vision loss or retinal degeneration in those animal models. Cerliponase alpha has currently been delivered to a few CLN2-affected patients. We report the case of one patient suffering from CLN2 treated with intracerebroventricular infusions of cerliponase alpha 300 mg every two weeks. Evolution of his retinal function was assessed by three successive flash-ERG and flash-VEP recordings throughout his treatment over a 4-year period.

Results: Before treatment at the age of 4 years 5 months, patient's retinas were normal (normal fundi and normal flash-ERG). After 29 infusions at the age of 6 years 10 months, a-wave combined response was absent, while cone and flicker responses were normal. After 80 infusions at the age of 8 years 9 months, a-wave cone response was absent with b-wave peak time increased, and no combined response.

Comments: Despite treatment, our patient's retinas showed a progressive abnormal and inhomogeneous function. Rods function was altered first, then the scotopic system and afterward, the cones. This result differs from those recorded in animal models. The relative preservation of cone functioning for a while could not be unequivocally attributed to enzyme replacement therapy as we lack comparison with the evolution of flash-ERGs recorded in untreated subjects.