title: Periventricular nodular heterotopia: classification, epileptic history, and genesis of epileptic discharges.
abstract: OBJECTIVE
  Periventricular nodular heterotopia (PNH) is among the most common malformations of cortical development, and affected patients are frequently characterized by focal drug-resistant epilepsy. Here we analyzed clinical, MRI, and electrophysiologic findings in 54 PNH patients to reevaluate the classification of PNH, relate the anatomic features to epileptic outcome, and ascertain the contribution of PNH nodules to the onset of epileptic discharges.
  
  
  METHODS
  The patients were followed up for a prolonged period at the Epilepsy Center of our Institute. In all cases, we related MRI findings to clinical and epileptic outcome and analyzed interictal and ictal EEG abnormalities. In one patient, EEG and stereo-EEG (SEEG) recordings of seizures were compared.
  
  
  RESULTS
  We included cases with periventricular nodules, also extending to white matter and cortex, provided that anatomic continuity was present between nodules and malformed cortex. Based on imaging and clinical data, patients were subdivided into five PNH groups: (a) bilateral and symmetrical; (b) bilateral single-noduled; (c) bilateral and asymmetrical; (d) unilateral; and (e) unilateral with extension to neocortex. The latter three groups were characterized by worse epileptic outcome. No differences in outcome were found between unilateral PNH patients regardless the presence of cortical involvement. Interictal as well as ictal EEG abnormalities were always related to PNH location.
  
  
  CONCLUSIONS
  The distinctive clinical features and epileptic outcomes in each group of patients confirm the reliability of the proposed classification. Ictal EEG and SEEG recordings suggest that seizures are generated by abnormal anatomic circuitries including the heterotopic nodules and adjacent cortical areas.
authors.affiliation: Division of Experimental Neurophysiology and Epileptology, Neurological Institute C. Besta, Milan, Italy. battaglia@istituto-besta.it
authors.forename: Giorgio
authors.initials: G
authors.lastname: Battaglia
authors.forename: Luisa
authors.initials: L
authors.lastname: Chiapparini
authors.forename: Silvana
authors.initials: S
authors.lastname: Franceschetti
authors.forename: Elena
authors.initials: E
authors.lastname: Freri
authors.forename: Laura
authors.initials: L
authors.lastname: Tassi
authors.forename: Stefania
authors.initials: S
authors.lastname: Bassanini
authors.forename: Flavio
authors.initials: F
authors.lastname: Villani
authors.forename: Roberto
authors.initials: R
authors.lastname: Spreafico
authors.forename: Ludovico
authors.initials: L
authors.lastname: D'Incerti
authors.forename: Tiziana
authors.initials: T
authors.lastname: Granata
mesh_terms: D000293:Adolescent; D000328:Adult; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000002:abnormalities* / Q000473:pathology / Q000503:physiopathology; D002552:Cerebral Ventricles / Q000002:abnormalities / Q000473:pathology; D002648:Child; D002675:Child, Preschool; D002828:Choristoma / Q000150:complications* / Q000503:physiopathology; D004567:Electrodes, Implanted; D004569:Electroencephalography / Q000379:methods / Q000706:statistics & numerical data; D004828:Epilepsies, Partial / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology; D004827:Epilepsy / Q000175:diagnosis / Q000209:etiology* / Q000473:pathology; D005260:Female; D005500:Follow-Up Studies; D007839:Functional Laterality; D006801:Humans; D007223:Infant; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009421:Nervous System Malformations / Q000145:classification / Q000473:pathology / Q000503:physiopathology; D017063:Outcome Assessment, Health Care; D013238:Stereotaxic Techniques