Primary Generalised Dystonia is also known as Dystonia Musculorum Deformance (DMD). Most cases commence in childhood (age 0 to 13 years), though some not appear till the teen years (age 13 to 20 years); adult onset is rare. Primary dystonia typically begins as a focal disturbance that progress either inexorably until it involves both sides of the body and leads to the patient's death from respiratory difficulties as a result of truncal involvement or up to a point after which it becomes static. It is our observation that younger the age of onset, longer and more extensive the progress and vice versa, a conclusion also reached by other workers.
The various motor abnormalities in primary dystonia consist of phasic and/or tonic elements. Depending on the distribution of abnormal movements, primary dystonia may be described as generalised, hemi-dystonic, segmental or focal; multi-focal primary dystonia, which affects two or more disjunct body sides, also occurs. The common treatment for dystonia consists of drugs like Levodopa, Trihexphenidyl Hydrochloride and Tetrabenzine. The role of surgery in dystonia is limited to patients who have failed to respond after certain time of medical treatment. Various surgical procedures have been tried including thalamotomy, pallidotomy and lesioning of other basal ganglia structures. Currently the most common surgical procedure used for treating dystonia is either pallidotomy
or pallidal stimulation. Proper case selection is very important in achieving good surgical outcome. Patients who have primary dystonia or familial dystonia secondary to genetic abnormalities such as DYT-1 gene abnormality are the candidates most suitable for functional neurosurgical procedures. Dystonia secondary to infection or other insults doesnot respond as well. Another consideration before undertaking surgery is the arrest of the progress of the disease. Till the disease is completely arrested in its progress, surgery should not be attempted.
In patients with unilateral dystonia, pallidotomy or pallidal stimulation can be performed. However, in patients with bilateral generalised dystonia with truncal involvement, deep brain stimulation of the globus pallidum internus is the surgery of choice. The results of deep brain stimulation for dystonia are not apparent in the immediate post-operative period. It takes few months for the benefit of this surgery to be realized after careful programming and drug adjustments. However the advantage of deep brain stimulation surgery over lesional surgery is that the titration of the therapy can be performed even after the completion of the surgery by externally regulating the voltage and other parameters of stimulation.