Mini Medical School #3
Dystonia - The Basal Ganglia
Welcome back, class. Did y'all have a good Memorial Day vacation? Good, so now you're ready to tackle a little more neuroscience, especially that area of the brain that is most relevant to you - the basal ganglia and its relationship to dystonia.
As you'll remember, in the last class I described dystonia as a disorder of "wrong tone" in which the affected muscles have excessive contraction causing twisting or writhing movements. More precisely, the Dystonia Medical Research Foundation describes dystonia as " syndrome dominated by sustained muscle contractions, frequently causing twisting and repetitive movements or abnormal postures" and which is involuntary. That's all good to know, but what in the heck causes it? I am chagrined to say that we neurologists only have an incomplete understanding of the answer, but we think we are getting closer.
First, a little history. Did you know that the first report of a patient with dystonia occurred 40 years after the Civil War (the war of Northern Aggression in my part of the country) and not until the 20 th century? In 1901 a man named Desarac described a 17-year-old girl with a twisting neck and other abnormal movements of her foot, pelvis, and arms. He used the term torticollis spasmodique , from which we arrive at the anglicized version we use today. Now, of course, this girl was not the first soul to be afflicted with the disease, and in fact there is artwork of ancient civilizations depicting others similarly afflicted. However, after the fall of Rome the world went through a nasty little period of history - say, about 1,200 years - when people didn't really try to figure anything out and just accepted their lot as God's will or "the way things are" so very few people were interested in methodically studying the human body and teaching others about it until the Enlightenment of the 17 th century. Unfortunately, it still took another 200 years for people to develop an understanding of the nervous system, and early reports, I'm sorry to say, attributed most movement disorders, including dystonia, to hysteria, something that still occurs among less well-informed physicians today (many of you know this firsthand I'll bet). It was not until 1911 that physicians correctly decided that dystonia was a brain disease, not a psychiatric one related to bad parenting, unresolved Oedipal complexes, or some other hogwash.
But, if a brain disorder, what is the cause, and where in the brain is the problem? Like many disturbances of movement, dystonia appears to arise from trouble in a perplexing, but fascinating, region of the brain called the basal ganglia ( basal - bottom or deep, and ganglia - collection of nerve cells) which are paired structures deep inside the brain. As illustrated in the diagram, nerves in these regions connect to and interact with many other brain areas, many of which are important in normal muscle contraction and the smooth planning and control of muscle movement. For years neurologists have had hints of the function of the structure. For example, from time to time a patient would suddenly develop violent, uncontrollable flailing of an arm or leg. When the brain of the person was examined after death, often they would find a stroke in an area of the basal ganglia called the subthalamic nucleus. In patients with Huntington's disease, a terrible illness of dementia and abnormal movements, the caudate nucleus is shrunken and degenerated. Finally, it became quite clear that Parkinson's disease - a disorder causing slowness, rigidity, and tremor - was the result of loss of nerve cells in another related structure called the substantia nigra. From these observations and others scientists surmised that dystonia may be related to the basal ganglia and its connections to the rest of the brain, for dystonia has some of the signs and symptoms of these illnesses.
It still remains a mystery how dystonia develops or even which parts of the basal ganglia are not working properly, for in nearly every examination of brains of patients with dystonia no definite disease process is identified. Nevertheless, recently successful treatment of dystonia has been achieved with electrical stimulation of very specific locations in the basal ganglia - the parts called the putamen and globus pallidus. Such evidence is nearly incontrovertible in its support that the basal ganglia is the seat of dystonia, and that makes the future history for this ailment quite bright. Perhaps the next century will look back at our state of knowledge with the same amusement we do of our forefathers who might have believed that dystonia was the consequence of having a uterus.
Dr. Gwynn, Medicine Man
993-F Johnson Ferry Rd. NE Suite 120
Atlanta, GA 30305
(404) 256-3720
