Myoclonus epilepsy and ataxia due to KCNC1 mutation: Analysis of 20 cases and K(+) channel properties.

Ann. Neurol.2017 May;81(5):677-689. doi:10.1002/ana.24929

Karen L Oliver ¹ , Silvana Franceschetti ² , Carol J Milligan ³ , Mikko Muona ⁴ , Simone A Mandelstam ⁵ ,

Karen L Oliver ¹ , Silvana Franceschetti ² , Carol J Milligan ³ , Mikko Muona ⁴ , Simone A Mandelstam ⁵ , Laura Canafoglia ² , Anna M Boguszewska-Chachulska ⁶ , Amos D Korczyn ⁷ , Francesca Bisulli ⁸ , Carlo Di Bonaventura ⁹ , Francesca Ragona ¹⁰ , Roberto Michelucci ¹¹ , Bruria Ben-Zeev ¹² , Rachel Straussberg ¹³ , Ferruccio Panzica ² , João Massano ¹⁴ , Daniel Friedman ¹⁵ , Arielle Crespel ¹⁶ , Bernt A Engelsen ¹⁷ , Frederick Andermann ¹⁸ , Eva Andermann ¹⁹ , Krystyna Spodar ⁶ , Anetta Lasek-Bal ²⁰ , Patrizia Riguzzi ¹¹ , Elena Pasini ¹¹ , Paolo Tinuper ⁸ , Laura Licchetta ⁸ , Elena Gardella ²¹ , Matthias Lindenau ²² , Annette Wulf ²² , Rikke S Møller ²¹ , Felix Benninger ²³ , Zaid Afawi ⁷ , Guido Rubboli ²⁴ , Christopher A Reid ³ , Snezana Maljevic ²⁵ , Holger Lerche ²⁵ , Anna-Elina Lehesjoki ⁴ , Steven Petrou ²⁶ , Samuel F Berkovic ¹

+ et al

Author information

¹ Epilepsy Research Centre, Department of Medicine, University of Melbourne, Austin Health, Heidelberg, Victoria, Australia.
² Department of Neurophysiology, C. Besta Neurological Institute IRCCS Foundation, Milan, Italy.
³ Ion Channels and Disease Group, Epilepsy Division, Florey Institute of Neuroscience and Mental Health, Parkville, Victoria, Australia.
⁴ Neuroscience Center, University of Helsinki, Helsinki, Finland.
⁵ Department of Medical Imaging, Royal Children's Hospital, Melbourne, Victoria, Australia.
⁶ Genomed Health Care Center, Genomed, Warsaw, Poland.
⁷ Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
⁸ Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy.
⁹ Department of Neurological Sciences, University of Rome, La Sapienza, Rome, Italy.
¹⁰ Department of Pediatric Neuroscience, C. Besta Neurological Institute IRCCS Foundation, Milan, Italy.
¹¹ Unit of Neurology, Bellaria Hospital, Bologna, Italy.
¹² Edmond and Lily Safra Children's Hospital, Sheba Medical Center, Ramat Gan, Israel.
¹³ Epilepsy Unit, Schneider Children's Medical Center of Israel, Petah Tikvah, Israel.
¹⁴ Department of Clinical Neurosciences and Mental Health, Faculty of Medicine, University of Porto, Porto, Portugal.
¹⁵ Comprehensive Epilepsy Center, New York University Langone Medical Center, New York, NY.
¹⁶ Epilepsy Unit, Gui de Chauliac Hospital, Montpellier, France.
¹⁷ Department of Clinical Medicine, University of Bergen, Bergen, Norway.
¹⁸ Departments of Neurology & Neurosurgery and Paediatrics, McGill University, Montreal, Quebec, Canada.
¹⁹ Departments of Neurology & Neurosurgery and Human Genetics, McGill University, Montreal, Quebec, Canada.
²⁰ High School of Science, Medical University of Silesia, Department of Neurology, Upper Silesian Medical Center, Katowice, Poland.
²¹ Institute for Regional Health Research, University of Southern Denmark, Odense, Denmark.
²² Department of Neurology and Epileptology, Epilepsy Center Hamburg-Alsterdorf, Hamburg, Germany.
²³ Department of Neurology, Rabin Medical Center, Beilinson Hospital, Petah Tikvah, Israel.
²⁴ Danish Epilepsy Center, Filadelfia/University of Copenhagen, Dianalund, Denmark.
²⁵ University of Tübingen, Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, Tübingen, Germany.
²⁶ Centre for Neural Engineering, Department of Electrical Engineering, University of Melbourne, Parkville, Victoria, Australia.

摘要

OBJECTIVE:To comprehensively describe the new syndrome of myoclonus epilepsy and ataxia due to potassium channel mutation (MEAK), including cellular electrophysiological characterization of observed clinical improvement with fever. METHODS:We analyzed clinical, electroclinical, and neuroimaging data for 20 patients with MEAK due to recurrent KCNC1 p.R320H mutation. In vitro electrophysiological studies were conducted using whole cell patch-clamp to explore biophysical properties of wild-type and mutant KV 3.1 channels. RESULTS:Symptoms began at between 3 and 15 years of age (medianâ=â9.5), with progressively severe myoclonus and rare tonic-clonic seizures. Ataxia was present early, but quickly became overshadowed by myoclonus; 10 patients were wheelchair-bound by their late teenage years. Mild cognitive decline occurred in half. Early death was not observed. Electroencephalogram (EEG) showed generalized spike and polyspike wave discharges, with documented photosensitivity in most. Polygraphic EEG-electromyographic studies demonstrated a cortical origin for myoclonus and striking coactivation of agonist and antagonist muscles. Magnetic resonance imaging revealed symmetrical cerebellar atrophy, which appeared progressive, and a prominent corpus callosum. Unexpectedly, transient clinical improvement with fever was noted in 6 patients. To explore this, we performed high-temperature in vitro recordings. At elevated temperatures, there was a robust leftward shift in activation of wild-type KV 3.1, increasing channel availability. INTERPRETATION:MEAK has a relatively homogeneous presentation, resembling Unverricht-Lundborg disease, despite the genetic and biological basis being quite different. A remarkable improvement with fever may be explained by the temperature-dependent leftward shift in activation of wild-type KV 3.1 subunit-containing channels, which would counter the loss of function observed for mutant channels, highlighting KCNC1 as a potential target for precision therapeutics. Ann Neurol 2017;81:677-689.

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