Abstracts

The progressive myoclonus epilepsies comprise a heterogenous group of diseases wich are clinically characterised by myoclonus with variable localisation, generalized tonic-clonic seizures, progressive dementia of variable severity and neurological symptomes, usually cerebellar. It is generally accepted that the locomotory disablement is due to cerebellar ataxia. We observed that in the course of the disease negative myoclonias are one of the most striking symptom and hypothesised that they were the main reason for locomotor disability. Negative myoclonias are very difficult to recognise without ictal polygraphic recordings in freely moving patients.We performed ictal polygraphic video-EEG-recordings (16 channel EEG, 8 channel surface EMG) in 13 patients with EPM1 (Unverricht-Lundborg Disease), proven by mutation of the CSTB Gene, 1 MERFF with a mitochondrial point mutation and 2 EPM2 (Lafora disease), proven by skin biopsy. All 16 patients presented with negative myoclonias of short duration either isolated or in combination with myoclonus. They were provoked by voluntary movement. The duration of the muscular atonia was between 100 and 300 ms. Except 3 patients with EPM1 all where wheelchair bound, mainly due to fear of falls, caused by the frequent muscle atonias. We have shown, using simultaneous EEG/EMG recordings in freely moving patients, that the locomotor disability is in fact mainly due to negative myoclonus in voluntary innervated muscles.