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Juvenile Myoclonic Epilepsy: the Janz Syndrome

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    Juvenile Myoclonic Epilepsy: the Janz Syndrome. Edited by b schmitz and t sander. (Pp 207, £42.50). Petersfield: Wrightson Biomedical, 2000. ISBN 1 871816 42 4.

    Have you ever had that feeling that something is just on the tip of your tongue but you can't quite get at it or that if only you had one more piece of the jigsaw, you would be able to see the whole picture? Welcome to juvenile myoclonic epilepsy. It is one of the most rewarding conditions in epilepsy to diagnose and treat. Indeed juvenile myoclonic epilepsy has the unusual, dual virtues of being both common and treatable. But what is it? This book introduces the condition—prevalence 3%-11% of all epilepsy, easily diagnosed if you think to ask for early morning twitchiness or clumsiness, characteristic EEG appearance etc. But then come all the tantalising clues that leave one on the brink of understanding. It is obviously genetic and a linkage to chromosome 6 has been suggested for years, now honed down to near the HLA gene. But a recent analysis has tried to subdivide juvenile myoclonic epilepsy according to electroclinical criteria to obtain more homogeneous groups for genetic analysis and this has suggested genetic heterogeneity. Why are there so many focal elements in this generalised epilepsy syndrome? These include focal clinical seizure manifestations, focal EEG changes, focal imaging changes such as thickening of the grey matter detectable by mathematical techniques. What is the overlap with other syndromes such as childhood absence epilepsy and why are seizures triggered by reading or praxis in some cases?

    At least all can agree that it usually gets better with valproate but comes back if you stop the drug. Unfortunately this text does not discuss other newer medications. Experience with them is largely anecdotal except the treatment of the myoclonus with benzodiazepines and piracetam.

    This book summarises our knowledge of juvenile myoclonic epilepsy in a readable and concise but comprehensive text. The trouble is that we are on a threshold between descriptive knowledge and understanding so juvenile myoclonic epilepsy remains one jigsaw piece short of a picture. It will be of interest primarily to those in the epilepsy and genetics fields.