From the Guidelines
Constant current stimulation from Axonics is generally considered better than constant voltage stimulation for sacral neuromodulation therapy. This is because constant current delivers a more consistent and predictable level of stimulation to the target nerves, regardless of changes in tissue impedance, resulting in more stable symptom relief for conditions like overactive bladder and fecal incontinence 1. The Axonics system uses constant current stimulation with amplitudes typically ranging from 0.5 to 5.0 mA, pulse width usually set between 180-450 μs, and frequency between 5-130 Hz, which can be adjusted by the clinician to optimize therapy for each patient. Some key benefits of constant current stimulation include:
- Lower overall energy usage
- Potentially longer battery life compared to constant voltage systems
- Reduced frequency of battery replacement procedures for patients with implanted devices
- Improved consistency of nerve activation, contributing to better long-term clinical outcomes and patient satisfaction compared to older constant voltage systems 1. However, it's essential to note that both types can provide effective therapy when properly optimized. In the context of sacral neuromodulation, the American Urological Association (AUA) and the Society of Urodynamics, Female Pelvic Medicine & Urogenital Reconstruction (SUFU) recommend offering sacral neuromodulation, among other options, to patients with overactive bladder who have an inadequate response to or have experienced intolerable side effects from pharmacotherapy or behavioral therapy 1. Key considerations for sacral neuromodulation therapy include:
- Patient selection and individualized treatment plans
- Mode and frequency of administration
- Treatment burden and patient preferences
- Potential for combination therapy to enhance effectiveness. Overall, constant current stimulation from Axonics is the preferred choice for sacral neuromodulation therapy due to its consistent and predictable stimulation, lower energy usage, and potential for better long-term clinical outcomes.
From the Research
Comparison of Constant Current and Constant Voltage Stimulation
- The effectiveness of deep brain stimulation (DBS) is dependent on the density and location of stimulation in a given brain area 2.
- Constant-current (CC) stimulation has been demonstrated to be effective in new implanted parkinsonian and dystonic patients, and switching from constant-voltage (CV) to CC therapy in patients chronically stimulated with CV implantable pulse generators (IPGs) has been shown to be safe and effective 3.
- A study comparing electrical measurements on constant voltage and constant current ECT machines found that more energy was delivered by the constant voltage machine, but the spread of energy delivered was comparable 4.
- The implementation of new technology in patients with chronic DBS, switching from non-rechargeable constant voltage to rechargeable constant current stimulation, has been shown to be safe and feasible 5.
- Clinical evidence supports the maintenance of current regardless of changes to impedance, with CC stimulation eliminating diplopia and objective findings of eye deviation with compression of the scalp overlying the hardware despite changes in impedance 6.
Key Findings
- CC stimulation has theoretical advantages over CV stimulation, including the ability to maintain current regardless of changes to impedance 2, 6.
- Switching from CV to CC therapy in patients with chronic DBS has been shown to be safe and effective, with stable clinical outcomes and high patient satisfaction 3, 5.
- The choice between CV and CC stimulation may depend on individual patient factors, such as the underlying disease and DBS target 5.