DBS can complement an optimized medication regimen for patients with Parkinson’s Disease.
Unfortunately, at some point along the course of the diagnosis of PD, the brain no longer responds consistently to the medications. The effective window (known as ON time) is shorter, and thus there is more OFF time (when the patient feels slow, sluggish, or frozen because the medications haven’t kicked in yet or have worn off too soon). In addition, there are increased dyskinesias (involuntary movements), which refer to abnormal involuntary movements (not including tremor). ON/OFF fluctuations and dyskinesias are known collectively as motor complications.
Whereas levodopa concentration fluctuations can contribute to unpredictable shifts between ON and OFF time, DBS remains constant through the day, meaning that there is consistent efficacy throughout the day. Patients note a significant improvement in ON time – meaning an addition of 5 good hours of productivity during the day. DBS helps free patients from the worry of whether their medication is going to kick in at the right time for them to drive to work, participate in a meeting, have a meal, or pay a visit to a friend. This improves quality of life dramatically.
DBS can also significantly reduce dyskinesia. DBS for PD can be done in one of two sites: globus pallidus interna (GPi) or subthalamic nucleus (STN). When DBS targets STN, patients tend to have a reduction of their levodopa dose, in turn resulting in less dyskinesias. When DBS targets GPi, patients tend to require the same dose of levodopa, but the dyskinesias are reduced significantly even without any change in the dose of levodopa. The degree of sensitivity to medication (the degree of dyskinesia at low doses) as well as other factors will determine whether our team recommends GPi or STN implantation.
Symptoms that do not respond to levodopa (such as balance problems) are unlikely to improve with DBS. Also if a patient with PD has no response (benefit) when taking adequate doses of levodopa, they are unlikely to experience any benefit from DBS. Sometimes patients would have a good response to levodopa, but they cannot tolerate the optimal dose. This can be determined by doing a pre- and post-medication examination while the patient is in the clinic, giving a high dose of medication on an empty stomach. Patients who have good benefit to levodopa but cannot tolerate it may be good candidates for DBS. Patients should expect DBS to provide the same benefit as their best response to levodopa, but in a more consistent and reliable way. Please note that DBS is not a cure, and does not benefit imbalance, cognition, or freezing.
The only exception to the rule that DBS provides the same benefit as the best response to levodopa is tremor. Many patients with tremor-predominant PD find that while other motor symptoms (slowing, stiffness, shuffling, small handwriting) improve with medication, the tremor may not respond as much, or at all. These patients do still enjoy significant benefit in tremor reduction with DBS, by about 75%.
By the numbers:
- Since 1995, more than 135,000 patients with movement disorders have been treated with DBS worldwide.
- DBS was FDA-approved for advanced PD in 2002.
- In 2016, DBS was FDA-approved for use in earlier stages of PD: four years after onset and four months after the development of motor complications.
Who is a good candidate for DBS?
- Good initial response to levodopa
- On-off fluctuations (at least four months)
- Troubling dyskinesias
- Disabling tremor
- Absence of dementia or severe depression
- Normal MRI for age
- Good medical health
- Realistic expectations
Potential benefits of DBS
- Improved “on-time” (gain of 5 hours/day on average)
- Reduced tremor (75% improved on average)
- Improved quality of life
- Reduced need for medication (25% reduction on average)
Potential risks of DBS
Post-operative headache and pain are possible but typically resolve gradually a few weeks after the procedure. Neck pain is also possible in the short term. Infection of the leads, extension or battery is very low risk and our surgical team does their utmost to prevent this. Hemorrhage is extremely low risk but when it occurs may lead to stroke-like symptoms. Most frequently, hemorrhage does not result in permanent complications. Lead fracture or migration, also very low risk, may require repeat surgery.
Problems with speech, language and mood; muscle tightness, slurred speech and vision symptoms can be related to the stimulation and thus can usually be reduced or eliminated by adjusting the stimulation.