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The two major problems with searching for any information on the internet on movement disorders (or indeed any other subject) are that of “data overload”, and finding good quality information that is pitched at the correct level. WEMOVE is quite simply the most outstanding website on all subjects related to movement disorders. It avoids both of the above issues with high quality information that is appropriate for both a medical and lay audience (http://www.wemove.org/). It includes an extremely useful email alert service (EMOVE) which sends updates of recent papers on a wide spectrum of movement disorder related topics or presentations from scientific meetings (to register go to http://www.wemove.org/emove/). In addition there are slide sets which are very useful for teaching—I recently had to give a talk on Parkinson's disease at very short notice, and was able to put the entire talk together using their slides in less than two minutes!
WEMOVE also links to many patient support web sites on Parkinson's disease, dystonia, essential tremor, and Wilson's disease to name but a few. Unfortunately many of these other sites are not that easy to navigate around, or don't provide particularly useful information. However, two good examples are the Restless Legs Syndrome Foundation (http://www.rls.org/) and the “Virtual Hospital” at University of Iowa with good patient information on Tourette's (http://www.vh.org/Patients/IHB/Psych/Tourette/TouretteSyndrome.html).
For a more UK based approach, a good starting point is the Glaxo Neurological Centre at the Walton (http://glaxocentre.merseyside.org/charity.html). You will find links there to the Parkinson's Disease Society, Huntington's Disease Association, MSA (Sarah Matheson Trust), PSP Society, Tourette's Association, and many other UK based neurological charities.
It is perhaps a shame that there are not more sites which use the potential advantages of the web to illustrate movement disorders with video, such as on-off phenomena in Parkinson's disease or even some functional neurosurgery (for example, http://medweb.bham.ac.uk/http/depts/clin_neuro/teaching/tutorials/parkinsons/parkinsons2.html).
Massachusetts General Hospital has a very useful site looking at functional neurosurgery for Parkinson's disease, which also has useful links including the unified Parkinson's disease (UPDRS) and Hoehn and Yahr rating scales (http://neurosurgery.mgh.harvard.edu/PDsurgery.htm).
In summary, if you are to visit one web site related to movement disorders it would have to be the WEMOVE site, which also has the advantage of the most easy to remember web address (http://www.wemove.org/)!