Deep brain stimulation and fall risk in Parkinson's

Deep brain stimulation (DBS) is often described as a breakthrough for Parkinson's disease. And for many symptoms, it truly is. But families considering DBS deserve honest information about what it can and can't do for balance and falls — because the picture is more complicated than the headlines suggest.

This article isn't meant to discourage anyone from pursuing DBS. It's meant to help you ask better questions, set realistic expectations, and plan a comprehensive fall prevention strategy regardless of whether DBS is part of the picture.

How deep brain stimulation works

In DBS surgery — a form of stereotactic surgery — a neurosurgeon implants thin electrodes into specific deep brain structures, most commonly the subthalamic nucleus (STN) or the globus pallidus internus (GPi). These electrodes are connected by thin wires that run under the skin to a pulse generator implanted under the collarbone — sometimes called a "brain pacemaker."

The device delivers continuous high-frequency electrical stimulation that modulates the abnormal neural circuits in the basal ganglia. It's important to understand what DBS does not do: it doesn't replace dopamine, and it doesn't stop disease progression. Instead, it changes the firing patterns of the thalamocortical circuits that have been disrupted by dopamine loss. Think of it as correcting the signal, not restoring the chemical.

What DBS does well

For the right candidate, DBS can be remarkably effective at treating specific Parkinson's symptoms:

• Tremor — often the most dramatic improvement, sometimes virtually eliminating resting tremor
• Rigidity — significant reduction in muscle stiffness
• Bradykinesia — improved speed and ease of movement
• Motor fluctuations — DBS reduces "off" time by approximately 60%, meaning fewer sudden episodes of immobility during the day, as measured by UPDRS Part III (the motor examination section of the Unified Parkinson's Disease Rating Scale)
• Levodopa-induced dyskinesias — by allowing substantial medication reduction, DBS often dramatically decreases the involuntary writhing movements caused by high-dose levodopa

These improvements in appendicular symptoms (those affecting the limbs) can reduce certain fall risk factors. If someone was falling because of severe tremor, debilitating off periods, or wild dyskinesias, DBS may help those particular falls significantly.

The gait and balance paradox

Here's what families need to understand, and what doesn't always make it into the optimistic conversations before surgery: DBS has inconsistent effects on axial symptoms — the ones that involve the trunk, gait, balance, posture, and freezing of gait. Some patients improve. Some see no change. And some actually worsen.

This paradox exists for several important reasons:

Gait involves circuits beyond the STN

Walking and maintaining balance depend on a complex network that extends well beyond the subthalamic nucleus. The pedunculopontine nucleus (PPN), the cerebellum, brainstem locomotor regions, and spinal pattern generators all play critical roles. Stimulating the STN or GPi simply doesn't reach all of these circuits.

Non-dopaminergic pathways drive axial symptoms

As Parkinson's progresses, gait and balance problems become increasingly driven by cholinergic pathways (involving acetylcholine) and noradrenergic pathways (involving norepinephrine) — not just the dopaminergic circuits that DBS primarily modulates. This is why balance and gait problems tend to respond less well to both levodopa and DBS over time.

Stimulation parameters involve trade-offs

The programming settings that work best for limb tremor and rigidity may not be the same settings that help gait. In some cases, the stimulation parameters optimized for limb symptoms can actually interfere with walking. Gait hypokinesia — small, shuffling steps — can sometimes worsen with certain stimulation settings.

Medication reduction can unmask balance problems

After DBS is implanted, levodopa doses are usually reduced — sometimes substantially. This is a benefit in many ways (fewer dyskinesias, less wearing-off). But levodopa may have been partially helping with balance and posture in ways that only become apparent once the dose is lowered. The medication reduction can unmask underlying postural instability that was being partially compensated.

STN vs. GPi: does the target matter for falls?

The two most common DBS targets — the subthalamic nucleus (STN) and the globus pallidus internus (GPi) — have somewhat different profiles. Some evidence suggests that GPi stimulation may be slightly better for gait and balance, possibly because GPi-DBS does not require as much medication reduction, meaning levodopa can continue to support axial function. However, both targets primarily improve appendicular (limb) symptoms, and neither reliably solves gait and balance problems.

Newer research is exploring different targets altogether. Pedunculopontine nucleus (PPN) stimulation is being investigated specifically for freezing of gait and balance dysfunction. Early results are mixed but the concept is promising: rather than trying to fix gait through a target designed for limb symptoms, go directly to a locomotor control center. This remains experimental and is not widely available.

Other emerging approaches include dual-target stimulation (STN plus PPN), adaptive or "closed-loop" DBS that adjusts stimulation in real time based on gait signals, and lower-frequency stimulation protocols that may be better for axial symptoms than the standard high-frequency settings.

Who benefits most for fall risk?

DBS is most likely to reduce falls in patients whose falls are primarily driven by:

• Motor fluctuations — if your parent falls mostly during wearing-off periods, when medication wears off and they become suddenly stiff and slow, DBS's ability to smooth out these fluctuations can meaningfully reduce fall frequency
• Levodopa-induced dyskinesias — if falls are happening because of severe involuntary movements caused by medication peaks, the medication reduction enabled by DBS can help
• Severe tremor — if tremor is so pronounced that it destabilises standing or walking, the dramatic tremor suppression from DBS can improve stability

DBS is less likely to help falls driven by:

• Postural instability — the characteristic loss of balance reflexes in mid-to-advanced PD that doesn't respond well to levodopa
• Freezing of gait that doesn't respond to levodopa — if freezing episodes occur even when medication is working (known as "on" freezing), DBS is unlikely to resolve them
• Cognitive impairment — falls related to impaired judgment, inattention, or impulsivity won't improve with DBS, and significant cognitive impairment is generally a contraindication for DBS surgery
• Camptocormia or Pisa syndrome — these severe postural deformities (forward bending or lateral leaning of the trunk) sometimes worsen after DBS, though some patients do improve

Questions to ask the DBS team

If your family is considering DBS, these questions can help you understand how it might — or might not — affect fall risk:

• "How will DBS affect my parent's balance and walking specifically — not just their tremor and stiffness?"
• "Are their falls mainly during off periods or on periods? Which type is DBS more likely to help?"
• "How much will medication be reduced after surgery, and how might that affect their gait?"
• "What does the levodopa challenge test predict about their balance after DBS?"
• "What is the rehabilitation plan after DBS? Will there be DBS-specific physical therapy?"
• "What are the surgical risks themselves — including risks of bleeding, infection, and worsening of balance or speech?"
• "If their gait worsens after DBS, what programming adjustments can be tried?"

After DBS: the importance of rehabilitation

DBS is not a one-time fix. It's the beginning of an ongoing process of optimization.

Programming takes months. After the device is turned on (usually a few weeks after surgery), the DBS team begins adjusting stimulation parameters — voltage, frequency, pulse width, and which electrode contacts are active. Finding the settings that best balance limb improvement, gait function, speech, and side effects is an iterative process that takes multiple visits over months. Gait can fluctuate significantly during this period.

Physical therapy post-DBS is critical. Many specialized centers now offer DBS-specific rehabilitation programs. The brain has been compensating for Parkinson's symptoms in certain ways for years, and DBS changes the equation. Physical therapy helps the brain and body adapt to the new movement patterns. Without rehab, patients may not realize the full benefit of DBS for mobility.

Exercise remains essential. DBS does not replace the need for regular physical activity. Continued gait training, balance exercises, strength work, and cardiovascular exercise are just as important after DBS as before. Some patients, feeling much improved, become more active after DBS — which is wonderful. But others, especially if expectations were unrealistic, may become discouraged and reduce their activity. This is a real risk for increased falls.

Fall prevention strategies still apply. Home safety modifications, proper footwear, assistive devices, and a fall response plan remain important regardless of DBS status. The device helps, but it doesn't make falls impossible.

The bottom line

Deep brain stimulation can be life-changing for the right candidate. It's one of the most significant advances in Parkinson's treatment. But for fall prevention specifically, the evidence is nuanced. DBS reliably improves limb symptoms — tremor, rigidity, bradykinesia, motor fluctuations — and these improvements can reduce certain types of falls. But it has inconsistent and sometimes worsening effects on the axial symptoms that most commonly cause falls in advancing PD: postural instability, freezing of gait, and gait hypokinesia.

The most important thing families can do is go in with realistic expectations. Ask the DBS team specifically about gait and balance, not just tremor. Understand what the levodopa challenge test predicts. Commit to post-surgical rehabilitation. And continue comprehensive fall prevention — exercise, home safety, medication optimization, physical therapy — regardless of DBS status.

DBS doesn't replace a fall prevention plan. At its best, it makes one part of that plan work better.