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Variable course of Unverricht-Lundborg disease: Early prognostic factors
Laura Canafoglia1, Edoardo Ferlazzo1, Roberto Michelucci1
1From the Department of Neurophysiopathology and Epilepsy Centre (L.C., C.T., F.P., S.F.) and Pediatric Neurology (T.G.), IRCCS Foundation C. Besta Neurological Institute, Milan; Department of Medical and Surgical Sciences (E.F., A.G., U.A.), Magna Graecia University, Catanzaro; Regional Epilepsy Centre (E.F., U.A.), Bianchi-Melacrino-Morelli Hospital, Reggio Calabria; Unit of Neurology (R.M., E.P., P.R.), IRCCS Institute of Neurological Sciences, Bellaria Hospital, Bologna; Pediatric Neurology and Muscular Diseases Unit (P.S.), DINOGMI-Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genoa, G. Gaslini Institute; Department of Neuroscience and Epilepsy Centre (A.M.), G. Martino Policlinico AOU, University of Messina; Institute of Neurological Sciences (A.G.), National Research Council, Mangone, Cosenza; Department of Neurology (V.B.), S. Anna Hospital, Como; Department of Neurology and Psychiatry (M.F.), Neurology Unit, Sapienza University, Rome; Epilepsy Center (F.B.), Department of Child Neuropsychiatry, C. Poma Hospital, Mantua; and Department of Neurology and Epilepsy Centre (A.B.), San Donato Hospital, Arezzo, Italy.
Objective:
To explore the course of Unverricht-Lundborg disease (EPM1) and identify the risk factors for severity, we investigated the time course of symptoms and prognostic factors already detectable near to disease onset.
Methods:
We retrospectively evaluated the features of 59 Italian patients carrying the CSTB expansion mutation, and coded the information every 5 years after the disease onset in order to describe the cumulative time-dependent probability of reaching disabling myoclonus, relevant cognitive impairment, and inability to work, and evaluated the influence of early factors using the log-rank test. The risk factors were included in a Cox multivariate proportional hazards regression model.
Results:
Disabling myoclonus occurred an average of 32 years after disease onset, whereas cognitive impairment occurred a little later. An age at onset of less than 12 years, the severity of myoclonus at the time of first assessment, and seizure persistence more than 10 years after onset affected the timing of disabling myoclonus and cognitive decline. Most patients became unable to work years before the appearance of disabling myoclonus or cognitive decline.
Conclusions:
A younger age at onset, early severe myoclonus, and seizure persistence are predictors of a more severe outcome. All of these factors may be genetically determined, but the greater hyperexcitability underlying more severe seizures and myoclonus at onset may also play a role by increasing cell damage due to reduced cystatin B activity.