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Dear Neelam and others interested in DBS/STN , I enclose a little summary of my experience in Ghent with indication, results and side effects. If you have any further questions, please don't hesitate to contact me. DBS in advanced Parkinson's disease. The hallmark treatment of Parkinson's disease is pharmacological. However, chronic treatment with levodopa (Sinemet), frequently combined with dopamine agonists (e.g. Permax, Parlodel) usually leads to motor complications such as wearing off effect, on/off phenomena and/or dyskinesias. In addition gait disturbances and freezing become a real problem. After many adjustments of medication dosages, the Parkinson patient is pharmacologically untreatable. There remains a condition, in which there is a very narrow window of a benificial clinical response. At one end of the spectrum one finds severe off periods and on the other end an on response with severe invalidating dyskinesias. For decades, thalamotomy and pallidotomy have been an alternative treatment for a selected Parkinson patient group. However, with the introduction of levodopa in the early seventies, the surgical treatment became almost obsolete. Deep brain stimulation in Parkinson's disease was introduced more than a decade ago, initially for the treatment of tremor (thalamic stimulation), later also for most of the other Parkinson symptoms (pallidal and subthalamic stimulation). The advantage of DBS is that this treatment is reversible, carries less risk for the patient and DBS parameters can be modified. A major advantage of DBS and in particular chronic stimulation of the subthalamic nucleus (STN) is the effect on gait and freezing episodes, but also tremor. In addition, the anti-Parkinson medication can be reduced, which leads to improvement of the dyskinesias. From January 1996 until July 1997 37 patients received unilateral pallidal stimulation with marked improvement of tremor and dyskinesias. For most other symptoms medication was required and frequently the dose needed to be increased. Therefore, in the summer of 1997 it was decided to stop pallidal stimulation and to change to subthalamic stimulation in patients with advanced PD in particular because other centers had good results in PD patients with freezing and gait disturbances. In addition, other PD symptoms, including tremor improved. From July 1997 I have been involved in STN surgery of 59 PD patients, 38 males and 21 females, mean age 65 years. 11 patients had previous unilateral GPi stimulation, who one to two years after GPi stimulation had severe gait disturbances and freezing episodes. The patients were selected on the basis of freezing and gait disturbances with a otherwise good response to levodopa. None exhibited dementing features as determined with neuropsychological testing. Patients with mild atrophy and peri-ventricular white matter changes were accepted as candidates Many patients had dyskinesias and reduced ADL scores. After STN surgery, the medication could be reduced on average by 50%, which probably is responsible for the reduction or cessation of dyskinesias in all patients. Gait, freezing, rigidity, akinesia and tremor, if present, significantly improved in all patients. Speech did not improve and worsened in patients, who already had severe speech disturbances pre-operatively. The two year follow up of 14 patients revealed similar post-op UPDRS scores to the 3 month post-op scores. In these patients only minor adjustments of anti-Parkinson medication were necessary. The complications were minor. There were three hemorrhages, two cortical at the level of the electrodes and one small brainstem hemorrhage at the level of the oculomotor nuceus, which caused a transient diplopia. All three patients fully recoverd from their hemorrhage. Transient post-operative confusion appeared in five patients lasting for several days. In conclusion, stereotactic STN surgery appears to be a very safe procedure for patients with advanced Parkinson's disease, while the response to stimulation is remarkable for all PD symptoms, but in particular gait disturbances and freezing, while anti-Parkisnon's medication could be reduced by at least 50%. The effect is sustained at least two years after surgery. STN surgery is a very could alternative treatment for patients with advanced Parkiosnon's disease. Chris van der Linden, M.D. St. Lucas Hospital Ghent Dept. of Movement Disorders Groene Briel 1 9000 Ghent 32 9 2246528