Special Sessions

The etiology of the syndrome of dystonia has always been difficult. While in some patients, such as those with post-hemiplegic dystonia, there is an obvious lesion, in most patients there is no obvious lesion. In the midtwentieth century, there was a very strong feeling that most such dystonia, particularly the most common, adult onset focal dystonias were functional. One of David Marsden’s lasting contributions to Neurology was to make clear that most such patients had an organic disorder. His voice was sufficiently powerful, that for some time, no patient presenting with focal dystonia was considered functional. However, it was subsequently recognised that a minority of such cases are indeed functional. There are many etiologies of dystonia syndromes and functional is one of them. While there are some clinical clues to separate organic and functional, many patients cannot be diagnosed easily. This has led, for example, to some functional patients getting DBS. It would be good if there were laboratory tests that could differentiate these two classes of etiology, but another conundrum is that many such abnormal clinical neurophysiological tests are abnormal in both entities. Tests that might be useful include the blink reflex recovery curve and paired associative stimulation to assess plasticity. More work is needed in this area for both understanding and help with clinical diagnosis. Disclosure: Nothing to disclose. E U R O P E A N J O U R N A L O F N E U R O L O G Y