Deep Brain Stimulation

Unlike lesion procedures, DBS leaves electrodes in place in the brain to deliver continuous stimulation. The electrodes are powered by a programmable stimulator (like a pacemaker), which is implanted in the chest wall. The stimulator is connected to the electrodes by thin wires (leads) that are tunneled under the skin in the neck and scalp. The stimulator can be turned on and off by a magnet waved over the surface. Many patients turn the stimulator off at night or during periods of prolonged activity, to prolong battery life. Batteries can be replaced as needed, generally after 5 years. Since the battery is in the chest wall, brain surgery is not required to replace them.

Adjusting the stimulator and medications after electrode implantation is a major time commitment on the part of the neurological team and patient. The maximum effect of the procedure is achieved once that adjustment occurs, which may be weeks or even months after the procedure itself.

Risks for DBS procedures include surgical risks (hemorrhage, infection) as well as hardware complications. These include leads breaking, electrode malfunction, stimulator failure and battery failure.

Thalamic DBS
Like thalamotomy, thalamic DBS is primarily effective against tremor. Bilateral procedures are possible, but with a higher risk of adverse effects. Compared to thalamotomy, thalamic DBS has a lower risk of severe side effects.

GPi DBS
Effects of GPi DBS tend to mimic those of pallidotomy. Dyskinesia improvement is a major effect, along with some improvement in tremor, rigidity, and bradykinesia, primarily in the off-medication state. Bilateral DBS is better tolerated than bilateral pallidotomy.

Subthalamic Deep Brain Stimulation ( DBS)
The subthalamic nucleus has become a major target for deep brain stimulation (DBS), with many teams considering it the target of choice for control of PD. It leads to improvement of all major motor features of PD, with improvement of motor scores of 40% to 60% in the off condition, and 10% in the on condition. Levodopa dosage reduction is typically around 30%, with resulting improvement in dyskinesias. Bilateral procedures appear to be superior to unilateral, with only a slightly increased risk of complications.

As DBS has become more common, rare but serious neuropsychiatric adverse events have been increasingly reported. Onset or worsening of depression occurs post-operatively in a small percentage of patients, often in those who were at increased risk before the procedure. Suicide, a well-known risk in depressed patients, has been reported in a small handful of patients. Pre-operative neuropsychiatric evaluation and post-operative follow-up is a critical part of patient care.

	Experimental Therapies