In the past few years surgical treatment for Parkinson's disease has generated considerable interest and hopes for advanced Parkinson's disease patients. There are various surgical procedures available for treating Parkinson's disease at the moment. Over last few years (four to five years) Subthalamic Nucleus is being considered as the most important target site for alleviating Parkinson's disease symptoms. The surgery for this is called Subthalamic Nucleus stimulation. This is being performed only at few select centers outside India and at the moment JHRC is the only center in India where this operations have been independently performed.

We would like to continue our lead and gain sufficient data and experience to contribute substantially into the research in this field. The clinical material that we have, along with the infrastructure of our hospital and the expertise of our team can generate high quality research that can be recognised on the world platform.

This is one of the most rapidly advancing fields of Neurology and Neurosurgery, where new techniques are being evolved. For example, the surgery of STN lesioning is being evaluated as an alternative to Deep Brain Stimulation. If we are successful, it will prove to be a major research breakthrough in bringing the surgical treatment for Parkinson's disease available to masses, as the cost of this surgery is one eighth of the cost of Deep brain stimulation.

We are planning to study the effect of Deep Brain stimulation(DBS) on movement disorders, with special reference to Parkinson's disease. DBS involves implantation of four contact point electrodes deep within the brain in one of the selected target site, stereotactically. This is than connected to the Implantable pulse generator (IPG) which is subcutaneously implanted in the infraclavicular region. The IPG is programmed to deliver desired current settings of voltage, frequency and pulse width through the selected electrode contacts, in unipolar or bipolar mode. The high frequency stimulation through these electrodes has a lesion like effect on the selected target sites. They selectively and reversibly inhibit the function of the stimulated group of neurons.

DBS has been used for the treatment of intractable pain from 1950's. Tremor was the first movement disorder to be reported to be alleviated by DBS of thalamic target1. The site of stimulation, was ventrointermedius nucleus of the thalamus. This therapy was useful in relieving tremors of Parkinson's disease, Essential tremor and tremors of multiple sclerosis. Encouraged by these results from 1994, deep brain stimulation of Globus pallidum internus was used for the treatment of advanced Parkinson's disease2. This was useful in improving the symptoms of drug induced dyskinesias, pain, rigidity and dystonia. However, the patient had to continue taking anti Parkinson's disease drugs. This led to the thinking of alternative target.

It was observed that lesioning of STN in the monkeys rendered parkinsonian by 1-METHYL-1,2,3,6-tetrahydropyridine(MPTP) intoxication was effective in relieving all parkinsonian motor symptoms3. Similar benefits were obtained in rat models of Parkinson's disease4. This was claimed to be the site of choice5. However, this operation in humans entailed the risk of inducing ballism. Encouraged by the results of DBS for tremor and having confirmed that its effects were reversible, Prof. Benabid performed the first STN stimulation in 1993. Over last few years many centers in the world have started performing STN stimulation. It is advocated for Parkinson's disease patient suffering from either severe motor complications of chronic levodopa therapy; major blockade in off-motor periods often associated with painful dystonia and/or tremor; and dyskinesias during on-motor periods that allow walking and doing common motor activities at least for short periods during the day. The patients are so severly disabled that most of them have lost their jobs and are dependent on some help even for the activities of daily living like bathing, dressing, turning in bed, shaving, etc. The results published by the French group have shown that at five years follow up there was improvement in the Unified Parkinson's disease rating score(UPDRS) by 60%, off motor phases tended to disappear, and patients needed no more help in the activities of daily living6. Similar results have been achieved by other centers7,8,9.

We have performed thirty five cases of bilateral STN stimulation at our hospital.

Lesioning of STN is known to produce abnormal involuntary movements(AIM) along with the improvement in symptoms of Parkinson's disease. It is also known that hemiballistic movements occurring after infarctions involving STN are usually transient11-15. This has also been borne out by functional neurosurgical groups of NIMHANS, Banglore and Bristol, England. (Personal communication) Following encouraging personal experience with STN stimulation, we decided to investigate the benefit of selective STN lesioning in patients suffering from advanced akinetic rigid Parkinson's disease, presuming that the AIM's occurring following STN lesion would be shortlived. We performed unilateral STN lesions in two patients suffering from akinetic rigid Parkinson's disease for more than eight years. One patient was Hohn and Yahr(H&Y) grade 5 and another was grade 4 in off phase. STN lesion was carried out stereotactically. Following surgery, both the patients had immediate improvement in their tremors, posture, gait, akinesia and rigidity on the contralateral side. One patient suffered from mild AIM's of the scapula on the contralateral side. The other patient suffered from hemiballistic movements of the lower limb on the contralateral side. These side effects cleared within one week in the first patient and within two weeks in the second patient. The benefecial effect on Parkinson's disease symptoms however, continued.

In 1992 Laitinen published his results of Pallidotomy for Parkinson's disease. In this series of 38 patients, he reported improvement in 92% of the patients undergoing surgery.16 This single paper changed the course of the history of surgical treatment for Parkinson's disease. There was a widespread resurgence of interest in performing pallidotomy. Patients suffering from advanced Parkinson's disease, developed drug induced side effect of dyskinesia following 7-8 years of medical treatment. At this point they have reached a state where, without drugs they become akinetic and rigid and with medication they have this uncontrolled side effect of dyskinesia. Due to this, their good "on" periods are limited to only 25-30% of the day and rest of the period, they are either "off" or dyskinetic.

Pallidotomy had been found to be very useful for this. This was known to resolve not only the contralateral dyskinesias but also the ipsilateral dyskinesias. It also relieves the dystonia and pain found in advanced Parkinson's disease. It reduces the unpredictable off periods. We have performed 35 pallidal surgeries. This is one of the largest series in India. We have been able to achieve the results described above. Patients have been able to resume back their work following successful surgery. We have developed our own method of performing Pallidotomy. During the course of surgery, we have gained valuable experience that is different from that described in world literature. For e.g. the stimulation responses to motor stimulation and the thresholds for safe lesioning are much higher than the western population. We need to analyze our data and publish this, for it to have effective value.