The RNS System, manufactured by NeuroPace, is the first FDA-approved closed-loop brain-responsive neurostimulator. Approved via PMA in 2013, the RNS System continuously monitors ECoG signals from up to two cortical or depth electrode leads, detects patterns indicative of seizure onset, and delivers brief electrical pulses to disrupt the seizure before it spreads — all automatically, without patient awareness or intervention.

How It Works

  1. Continuous monitoring: The implanted neurostimulator records ECoG from cortical strip or depth electrodes placed at the seizure focus
  2. Detection: Onboard algorithms analyze the ECoG in real time for patterns matching the patient's seizure onset signature (customized during programming)
  3. Stimulation: Upon detection, the device delivers brief electrical pulses (typically 1-2 mA, 100-200 Hz, lasting 100-200 ms) to the seizure focus
  4. Disruption: The stimulation disrupts the evolving seizure, often preventing clinical symptoms from developing
  5. Logging: All detections and stimulations are logged, providing a detailed record of seizure activity over time

Clinical Results

The RNS pivotal trial (randomized, sham-stimulation-controlled, 191 participants) demonstrated a median 53% seizure reduction at 2 years, with progressive improvement over time — reaching median 70-75% reduction at 5+ years. This progressive improvement is attributed to the device's continuous neuromodulatory effect reshaping seizure networks over time.

BCI Significance

The RNS System is significant for the broader BCI field because it:

  • Proved the closed-loop BCI concept: Demonstrated that real-time neural signal detection and responsive stimulation are safe and effective in a chronic human implant
  • Established a regulatory precedent: Navigated the full FDA PMA pathway, providing a template for future BCI device approvals
  • Demonstrated chronic implant viability: Devices have functioned for 10+ years in patients, proving that implanted brain electronics can operate reliably over extended timeframes
  • Validated responsive neurostimulation: Showed that brief, targeted stimulation can modulate neural dynamics without the continuous stimulation required by DBS

Technical Specifications

  • Leads: Up to 2 cortical strip electrodes (4 contacts each) or depth electrodes
  • Channels: 4-8 recording/stimulation contacts
  • Battery: Rechargeable (replaced every ~4-8 years)
  • Data storage: Records and stores ECoG segments triggered by detections
  • Programmer: External wand for wireless device interrogation and parameter adjustment