Programming cases for DBS in Parkinson’s Disease, dystonia, and tremor

Scenario

A 64-year-old male with an 11-year history of Parkinson's disease and bilateral segmental lead Subthalamic nucleus (STN) Deep Brain Stimulation (DBS) electrodes and implantable pulse generators (IPGs) placed 2 weeks prior to the visit presents to clinic for initial programming of his device. His primary symptoms were bradykinesias in both the upper and lower limbs. Up to the year prior to surgery, the patient was managed well medically and was on levodopa and an additional dopamine agonist. In the year prior to the DBS surgery, he had started to require more medication and was “on” for only about half hour at his peak medication dose. Surgery had been uneventful and bilateral STN leads were placed. The patient had no other comorbidities.

Initial programming of the device consists of trialing all ventral/dorsal electrodes in ring mode so that the stimulation field is cylindrical (the complete ring is stimulated) in a monopolar fashion. Initial stimulation parameters are set to a frequency of 180 Hz and a pulse width of 60 uSec. Stimulation is slowly raised until the patient feels adverse symptoms. In this case, he reports slight tingling in the opposite face, which resolves after a few seconds on one of the contralateral contacts. Other symptoms might include abnormal sensations such as persistent “tingling,” abnormal motor sensations such as “pulling” or changes in speech such as “slurring” or reduced vocal volume. Increasing stimulation amplitude for him generally resulted in a reduction in the severity of his bradykinesia, although some contacts seemed to have a more immediate effect as active and passive limb motion and gait after most of the setting changes were tested. If no adverse events were appreciated, the stimulation was raised to 4 mA. After testing all four ring mode contacts in this manner, the contact with the lowest amplitude that significantly reduced the bradykinesias, while also having the highest amplitude that induced adverse events, was used as an initial focus to start programming with going forward.

• Variation : Adverse effects are at or below the level needed for beneficial effects -- The programming configuration to try is to move to a bipolar stimulation pattern. Start with the most ventral contact as the anode and the next dorsal ring as the cathode. Follow the trial parameters used during the initial programming mentioned previously. Test all bipolar ring configurations once again looking for the amplitudes of beneficial therapy and adverse effects. Use the configuration with the lowest amplitude needed for treatment of the tremor and the highest amplitude that begins to generate adverse effects to provide the largest therapeutic window.

• Variation : Adverse effects are still at or below the beneficial effect for tremor in a bipolar configuration -- In this case, moving to the segmented sections of the rings is appropriate. All segments should be individually interrogated once again to locate the amplitudes of best therapeutic effect as well as the amplitudes of negative effect. Testing individual segmented contacts in a monopolar configuration should be tried first. If there is not enough beneficial effect for reducing the tremor, then moving to segments directly ventral and dorsal tied together is appropriate.

Scenario (continued)

A day after the initial programming, the patient returned to the clinic with significant cramping in his upper extremities. Multiple attempts to change the electrode contacts by moving to segmental contacts and changing to more dorsal contacts were performed, leaving several minutes at most settings to determine whether changes could be appreciated. Some configurations reduced the cramping but did little to improve the bradykinesias. Additionally, pulse width and frequency changes were tried with similar results. Often, a simple but disciplined adjustment can be performed by working through each contact change and adjusting frequency up and then down, pulse width up and then down, and raising amplitude for each change without an adverse effect. Simple testing of limb stiffness can easily be determined at each change as well as gait testing if results seem promising. This plan was followed generally in this patient, but none of the aforementioned programming modifications improved the cramping while not improving the bradykinesia. Such a stalemate within the universe of parameter changes is suggestive that a reasonable balance of benefits without adverse consequence is unlikely and the patient had to be taken back to the operating room to have the lead moved more laterally.

Once the lead was repositioned, the system was able to be programmed to relieve dyskinesias without causing adverse side effects. Over the course of 2 years, however, the patient noticed that improvements had significantly diminished in the lower extremities but were still present in his upper extremities. Additionally, the patient was noticing pain in one limb. It was assumed these were effects of loss of programming efficacy and/or progression of disease state. Multiple programming adjustments were again tried for him, as well as medication modifications. No improvements were seen in the lower extremities, and in fact, in some cases, there was also worsening of his upper extremities. Owing to the effect localized primarily in his lower extremities or back and, with deeper questioning, when he was upright but not sitting, the patient was sent for a lumbar computed tomography myelogram. The study demonstrated significant stenosis from L3 to L5. Program settings were returned to their original parameters, and he was sent to a surgeon to consider an operation for his stenosis and neurogenic claudication.

Programming for DBS in GPi for dystonia