Aims. In this paper we describe the clinical characteristics, and particularly the epileptic seizures and electroencephalographic findings, in 15 patients with a pathology diagnosis of late infantile neuronal ceroid lipofuscinosis (NCL). Patients and methods. Nine female and six male patients were studied and their clinical records covering the period February 1990 to June 2003 were analysed. Neuroimaging, neurometabolic studies, ERG, PE and repeated EEG were carried out in all cases. Results. The mean age on onset of the disease was 3 years (range: 1-5 years). The initial symptom was epilepsy in all cases. Massive myoclonias and myoclonic-atonic seizures were the most frequent kinds of attacks. Focal myoclonias were observed in six patients. Other types of epileptic seizures observed included generalised tonic-clonic, absence, motor focal and complex focal. The epileptic seizures were resistant to therapy. Progressive neurological and visual impairment, pyramidal and cerebellar signs, as well as mental retardation were present in all cases. Intercritical EEG recordings showed diffuse paroxysms with spike and polyspike waves, multifocal spikes and, less often, focal spikes that were predominant in posterior regions. Photostimulation showed high amplitude (300-450) occipital spikes during the application of light stimulation between 1 and 8 Hz. ERG, VEP and SSEP results were pathological. Images showed signs of brain and cerebellar atrophy. Seven of the patients died between 8.5 and 11 years of age. Conclusions. Late infantile NCL must be considered in the case of a child aged between 1 and 5 years who presents seizures that are predominantly generalised myoclonias and myoclonic-atonic, in association with progressive neurological deterioration including pyramidal, cerebellar and visual signs and an EEG trace showing occipital paroxysms triggered by low frequency photostimulation.
