Brain Surgery Inside: How Doctors Watch Brain Signals While Patients Sleep
In neurosurgery, the goal is to excise as much tumour tissue as possible while preserving critical neural pathways. A key technique involves monitoring cortico‑cortical evoked potentials (CCEPs)—brain waves that travel between different cortical areas. Historically used during awake surgeries to map language, CCEPs are now being applied under general anaesthesia.
A systematic review of studies published up to March 2025 identified 14 primary papers and an additional 5 relevant citations. The majority investigated language tracts, especially the arcuate fasciculus; a minority examined visual pathways.
Methodology
- Stimulus: A single electrical pulse (0.3–1 ms) delivered at a low frequency (1–9 Hz), alternating current direction each time.
- Recording: Surface electrodes on the cortical surface captured responses.
Findings
| Modality | Number of Papers |
|---|---|
| CCEPs | 15 |
| SCEPs | 7 |
- First Wave (N1): Detected across all studies; latency varied with stimulation and recording sites.
- Second Wave (N2): Absent under anaesthesia, indicating suppression of certain cortical responses while preserving the primary N1 signal.
Clinical Implications
- CCEPs: Confirm functional integrity of critical pathways during surgery.
- SCEPs: Offer proximity information relative to the surgical site.
Both modalities appear safe and effective under general anaesthesia, potentially improving outcomes for patients with tumours adjacent to essential brain functions.
