Deep Brain Stimulation

Deep Brain Stimulators for Parkinson’s Disease and Essential Tremor

In 1997 another procedure to treat the tremor of Parkinson’s Disease and essential tremor received approval from the U.S. Food and Drug Administration, namely stereotactic insertion of a deep brain stimulator into the thalamus. This has the advantage that instead of destroying the overactive cells that cause symptoms in Parkinson’s disease it instead temporarily disables them by firing rapid pulses of electricity between four electrodes at the tip of the lead. The lead is permanently implanted and connected to the pulse generator installed underneath the skin of the chest.

Recent results with the deep brain stimulator have identified another very promising target for interrupting the pathway of overactive cells in Parkinson’s Disease, namely the subthalamic nucleus (STN). Although procedures to inactivate cells in the STN have not been performed for nearly as long, initial results suggest that it may provide even better relief of, rigidity, bradykinesia, and hypokinesia than the other targets with equivalent or fewer risks of side effects.

Deep brain stimulators are also under investigation for control of dyskinesia and dystonia, whether related to Parkinson's Disease or not. Promising targets for this indication include the subthalamic nucleus and the globus pallidus.

Implant Sites and Indications for DBS

v     Ventrointermediate Nucleus of Thalamus

Ø      High frequency stimulation of chronically implanted deep brain stimulators (DBS) in the Vim thalamus is an effective method to suppress tremor of various origins. Vim thalamic stimulation will eliminate 90-100% of tremor in Parkinson's and 90-95% tremor in Essential Tremor.

Ø      Implanted electrode stimulation is the surgical treatment of choice for the second thalamic surgery in cases where symmetrical tremor exists. A deep brain-stimulating electrode is implanted contralateral to the original thalamotomy, rather than risk the motor and speech deficits that occur in bilateral thalamotomy.

Ø      Thalamic stimulation may reduce l-dopa requirements in Parkinson's patients.

v     Globus Pallidus

Ø      Intraoperative Stimulation

§      Intraoperative stimulation in the anterior pallidal regions for the treatment of Parkinson's disease resulted in an immediate reversal of akinetic states despite enforced abstinence of medications.

Ø      Globus Pallidus DBS is Capable of Improving Parkinson's Akinetic Symptoms.

§     Implanting a deep brain stimulation lead stereotactically into the right anterior pallidum using a stimulation trials at 100 Hz caused reproducible reversal of akinetic symptoms and simultaneous microelectrode recording of the posteroventral pallidum revealed decreased neural activity during anterior pallidal stimulation.

§     Dramatic improvements in tremor, dystonia, bradykinesia, and akinesia are noted within seconds of stimulator activation. This case reveals the potential for therapeutic pallidal stimulation for Parkinson's akinetic symptomatology.

v     Subthalamic Nucleus Stimulation

Ø      Subthalamic DBS is capable of reversing akinetic Parkinson's symptoms, in accordance with the PD model of hyperglutaminergic activity. However, many required bilateral implantation for symmetrical results.

Deep Brain Stimulation for the treatment of motor disorders

Experimantal electrical stimulation of various brain nuclei in man is increasingly applied in the treatment of motor disorders, such as Parkinson and essential tremor, rigidity, akinesia and diskinesia, and certain psychiatric disorders such as obsessive-compulsive disorder. To allow improvements of the stimulation technique, scientists are investigating optimum electrode positioning, electrode geometry as well as to which part of the neuron (cell body, dendritic, axon) is best to stimulate.