Neurology & EEG Engineering
Electrode impedance and signal quality, intraoperative neuromonitoring criticality, evoked-potential systems, and the 10-20 electrode system.
Neurology equipment measures extremely small electrical signals from the body - EEG signals are typically in the microvolt range - which makes signal integrity, not just equipment function, the central engineering concern for this department.
Electrode impedance
Electrode-skin impedance drives EEG/EMG signal quality more than almost any other single factor. A high-impedance electrode produces noisy, artifact-heavy data that can look like an amplifier fault but isn't - checking impedance (most systems have a built-in impedance-check function) is the first troubleshooting step for a poor-quality-signal complaint, not the last, and it's a much faster check than assuming an amplifier or board-level fault.
The 10-20 electrode placement system
Standard EEG electrode placement follows the international 10-20 system, named for the 10% and 20% skull-measurement intervals used to position electrodes consistently across different head sizes. Understanding this system matters for troubleshooting: a signal artifact that follows a specific, named electrode position (e.g. consistently at Fp1) points toward that specific electrode or its lead, while an artifact affecting all channels simultaneously points toward a shared cause - grounding, amplifier, or environmental interference.
Intraoperative neuromonitoring (IONM)
IONM equipment carries a meaningfully different risk profile than diagnostic EEG/EMG, because a mid-case failure has an immediate, real surgical-decision consequence - the surgeon may be actively relying on real-time nerve-function feedback to guide the procedure, particularly in spinal and skull-base surgery where nerve damage risk is high. This is why pre-case verification of IONM equipment is treated as genuinely non-negotiable rather than best-effort, on the same tier of seriousness as the daily anesthesia machine check in Chapter 23.
Evoked-potential systems
Evoked-potential systems (somatosensory/SSEP, motor/MEP, auditory/BAER) add a stimulus-delivery subsystem on top of standard amplification - a fault can be on either the stimulus-generation side or the recording side, and isolating which one is failing first saves significant troubleshooting time. A practical isolation test: if the stimulus-generation output can be independently verified (with a scope or a known test load) as producing a correct stimulus, the fault is downstream in the recording/amplifier chain, and vice versa.