doi: 10.1053/ejpn.2000.0456 available online at http://www.idealibrary.com on Illl~i" European Journal of Paediatric Neurology 2001 ; 5(Suppl. A): 167-173 ORIGINAL ARTICLE Northern epilepsy syndrome (NES, CLN8) - MRI and electrophysiological studies L LAURONEN, 1"2 P SANTAVUORI, 3 A HIRVASNIEMI, 4 E KIRVESKARI, 5 J HUTTUNEN, 1 T AUTTI 2 1BioMag Laboratory, Medical Engineering Centre, 2Department of Radiology, Helsinki University Central Hospital, Helsinki, Finland; 3pediatric Neurology, Hospital for Children and Adolescents, Helsinki, Finlanc~ 4Department of Pediatrics, Kainuu Central Hospital, Kainuu, Finland; 5Department of Clinical Neurophysiology, Helsinki University Central Hospital, Helsinki, Finland Northern epilepsy syndrome (NES, EPMR, progressive epilepsy with mental retardation, CLN8), an inherited childhood-onset epilepsy with mental retardation, has been recently characterized to belong to the family of neuronal ceroid lipofuscinoses (NCLs). In this study, four patients (ages 26-44 years) with NES and eight healthy controls underwent magnetic resonance imaging (MRI) and electrophysiological evaluation with somatosensory evoked magnetic field (SEF) studies. The findings in NES were compared with the known findings in juvenile NCL (JNCL, CLN3) and Finnish variant late infantile NCL (vLINCLF~N, CLN5) that manifest around the same age as NES. Also post- mortem MRI was performed on one brain. On the MRIs, slight to moderate cerebellar atrophy was seen in all patients, whereas only two patients had slightly enlarged cerebral sulci. None of the MRIs demonstrated signal intensity abnormalities that are commonly seen in JNCL and vLINCLnN and are considered to reflect the Wallerian degeneration after neuronal death. Generally SEFs in NES were within normal limits, indicating that the disease had not impaired the function of the neurons on the somatosensory pathway. In conclusion, MRI imaging and SEF findings suggest that the cerebral neuronal death and dysfunction in NES are minimal compared with JNCL and vLINCLNN. Keywords: Neuronalceroid lipofuscinoses.Northernepilepsy syndrome.CLN8.MRI. Somatosensory evokedmagneticfields. SEF. Introduction Northern epilepsy syndrome, NES, an inherited childhood epilepsy with mental retardation, has recently been characterized to belong to the family of neuronal ceroid lipofuscinoses (NCLs) and has been denoted as CLN8.1 The NES gene, CLN8, localized to chromosome 8, encodes a putative transmembrane protein. 2 The clinical picture of NES can be divided into three successive stages. The disorder begins with epilepsy at the mean age of 6.7 years (range 5-10 years); the first stage lasts until puberty and is characterized by an increasing frequency of gen- eralized tonic-clonic seizures and borderline or mild retardation. During the second stage in young adulthood the frequency of seizures diminishes and the mental decline is slower, but first signs of clumsiness in fine motor tasks appear. The third stage of permanent disability includes few seizures and continuing retardation, evident clumsiness, balance difficulties and often decreased visual acuity. 3 A computer tomography (CT) study of NES patients revealed cerebral atrophy in all patients whose epilepsy had lasted more than 12 years. 4 Cerebellar and brain stem atrophy were already evident in puberty or early adulthood. 4 The electroencephalogram (EEG) shows slowing of the background activity, abundant diffuse or inter- mittent delta and theta activity and scanty epileptiform activity with varying localization and form. 5 Visual evoked potentials (VEPs) have been Correspondence: Leena Lauronen,BioMagLaboratory,PO Box 442, FIN-00029,HUS, Finland e-maih Isipila@cc.helsinki.fi 1090-3798/01/05/A167+7 $35.00 © 2001 European Paediatric Neurology Society