Higher order visual dysfunction and myoclonic-atonic seizure: an atypical presentation of CLN6 neuronal ceroid lipofuscinosis.

Neuronal ceroid lipofuscinosis is a rare childhood neurodegenerative disease, classified under the spectrum of progressive myoclonic epilepsy (PME). Cognitive decline, seizures including myoclonus, vision loss and ataxia are the commonly described manifestations of this illness. While visual failure in this disease is largely attributed to retinal, macular degeneration and optic atrophy, with this index case, we report an atypical presentation in the form of higher order visual dysfunction. The pattern of cognitive regression has further been explored here with higher order visual dysfunction and language regression being the predominant manifestations, stemming from an involvement of bilateral occipitoparietal/occipitotemporal networks. Yet another unique feature of this case also lies in the occurrence of myoclonic-atonic seizure, a semiology rarely reported before in PME.