Deep Brain Stimulation (DBS) is a treatment for selected patient suffering from Parkinson’s disease dystonia and most forms of tremors. Recently, the use of DBS therapy has been extended for the treatment of intractable epilepsy, refractory Obsessive compulsive disorders, depression and Progressive supranuclear palsies.
DBS consist of implantation of very thin DBS Lead which contains four electrode contacts into the target area in the brain. The lead extends through a small opening in the skull and is connected to the extension that is then connected to an impulse generator or pacemaker which is implanted under the skin over the chest. (Fig. 1) The entire system is implanted beneath the skin. DBS exerts its therapeutic effect by delivering electrical impulses to the target region.
Deep Brain Stimulation is an alternative to ablative surgeries conventionally offered for Parkinson’s disease and other related movement disorders. The common targets for DBS surgery within the brain, for movement disorder include, subthalamic nucleus (STN) for Parkinson’s disease, ventro-intermedius nucleus of thalamus for tremors, and pallidum for dystonia. Though each of this target sites can be used for different movement disorder, we believe that these are best for the respective disease as indicated.
The therapy of Deep Brain Stimulation requires additional expertise over conventional stereotactic techniques that are required for functional neurosurgical procedures for movement disorder. It requires careful understanding of the principles of DBS, understanding of the disease being treated and combining the medical therapy along with stimulation to achieve smooth control of the disease. Jaslok Hospital & Research Center has been able to develop a multi-disciplinary team to undertake this surgery.
The team comprises of Neurosurgeon, Neurologist, Clinical research fellow, Parkinson’s disease nurse, neuropsychiatrist and physiotherapist. Expertise of speech therapist, occupational therapist and other specialists is obtained when required.
How Deep Brain Stimulation surgery works?
The brain cells function by electrically encoding, processing and transmitting information. Deep brain stimulation affects the electrical functions of neurons, but the mechanism by which it alters those functions, are unknown. According to some hypothesis, the reduction of the effects of an abnormal neuronal activity occurs because of inhibition, depolarization blockade or the adjustment of neuronal activity to a constant rate.
Inhibition : The depolarization of axons terminating in target structure by deep brain stimulation causes these terminals to discharge and release neurotransmitters. Deep Brain Stimulation may cause a flood of inhibitory neurotransmitters that effectively shuts down neurons in thetarget structures.
Depolarization blockade : If a neuron is constantly depolarized but below the threshold need to produce an action potential, the threshold for producing an action potential increases. Consequently, neurons find it more difficult to fire because the threshold increases.
Altering erratic neuronal activity : Deep Brain Stimulation alters the abnormal discharge activity that results from the disease. It has been suggested that irregular or chaotic firing of neurons may be more disruptive of normal function than a constant and regular pattern of activity. It is possible that Deep Brain Stimulation drives the abnormally discharging neurons into a pattern of more regular firing that is less deleterious.