Part 3 · Treatment
Deep-brain stimulation
A thin lead in the subthalamic nucleus or the globus pallidus delivers small, rapid electrical pulses from an implanted pulse generator. Step through the surgery and the first switch-on, raise the amplitude to see how far the field spreads, and watch the abnormal beta rhythm settle.
Who is a candidate?
Selection is a specialist decision, but the published criteria are public. Set a profile and see how it lines up with them. This is a study aid built from consensus statements and trial entry rules, not an assessment of any person. 44,184
Mostly what levodopa helps, more evenly
- Off-time and swings: on-time without troubling dyskinesia rose 4.6 hours a day against none on medical therapy. 369
- Dyskinesia: in people followed for about 17 years, time with dyskinesia was 75% lower than before surgery and dopaminergic medication about half. 39
- Tremor, even when levodopa does not control it. 44
- Quality of life over medical therapy in randomised trials. 81,324,379
Axial signs, speech, thinking
- Freezing of gait, postural instability and cognitive decline often develop over time. 44
- Speech was the only motor item not improved at 5 years, and STN stimulation can worsen speech and gait in some people. 44,179
- Verbal fluency falls moderately after STN-DBS. 279
- No treatment, DBS included, is rated clinically useful for slowing progression. 111
What the trials found
Six randomised trials and two long-term cohorts carry most of the evidence. The bars show each trial's own outcome, so they cannot be compared across cards. The MDS evidence review rates bilateral STN and GPi stimulation "clinically useful" for both motor fluctuations and dyskinesia. 111
Risks
| Risk | How often | Notes |
|---|---|---|
| Bleeding in the brain | 2.9% per patient, 1.6% per lead; about half symptomatic. 59 | From 63 studies and 13,056 patients. All-cause mortality was 0.4%, with haemorrhage behind 22% of deaths. Microelectrode recording, systolic pressure over 140 mm Hg and paths through sulci were risk factors. 59 |
| Infection | 4.9% of procedures (95% CI 4.1–6.1%). 343 | 61.2% at the generator pocket; most centres remove the generator, give antibiotics and reimplant. Consensus range 0–15%, the most commonly reported complication. 44,343 |
| Hardware | Lead erosion 1–2.5%, fracture 0–15%, migration 0–19%. 44 | Ranges from the 2011 consensus. |
| Suicide | Completed 0.45%, attempted 0.90% after STN-DBS. 366 | In 5,311 patients, the first-year suicide rate was 12.6 to 15.6 times the expected rate. Postoperative depression, being single and earlier impulse-control disorders were associated factors. 366 |
| Thinking and mood | Verbal fluency: semantic d = 0.73, phonemic d = 0.51. 279 | The only moderate declines in a 28-study meta-analysis; executive function and verbal memory declined slightly. A subset may have more depression, apathy or impulsivity. 44,279 |
| Weight gain | Men +3.4 kg, women +2.6 kg at 3 months. 230 | Daily energy expenditure fell 7–13%. 230 |
| Stimulation effects | Set by where the current spreads. 175 | Muscle pulling from the internal capsule, slurred speech, double vision, tingling and dyskinesia, depending on the neighbouring structure reached. 175 |
Focused ultrasound: a lesion instead of a lead
The US approval timeline
Every date below is a decision date in the FDA premarket approval database. Play it to see the devices and indications arrive. 103
Dates from FDA PMA records (decision dates). Blue: DBS systems; hollow blue: changes to the Parkinson's indication; red: focused ultrasound (FUS) lesioning. The wide axis is broken between 2003 and 2014.
The other device-aided route: infusions
For advanced fluctuations, a pump can replace pills with a continuous supply. NICE advises against DBS when best medical therapy controls symptoms, and best medical therapy can include apomorphine infusion. 241 The details of how levodopa levels swing, and how infusions flatten them, are in Levodopa over time.