4.1 Recording Technique & Documentation

Why Recording Technique Dominates the Exam

ABRET (American Board of Registration of Electroencephalographic and Evoked Potential Technologists) weights Performing the Study at 75% of the R.EEG.T. exam. Recording technique and documentation sit at the center of that weight because a diagnostically useful electroencephalogram (EEG) is created by the technologist's decisions during acquisition, not afterward. A poorly documented or technically degraded record cannot be rescued by the interpreting physician.

The technologist is the only person who sees the patient, the raw tracing, and the clinical state simultaneously. That responsibility is why so many exam items test what you do at the bedside.

Running the Routine EEG

A routine (standard) EEG is the baseline neurodiagnostic study. ACNS minimum technical standards call for at least 20 minutes of technically satisfactory, interpretable recording for a routine adult study; in practice most labs record 20-40 minutes to reliably capture wake, drowsy, and sleep.

Core steps during acquisition:

• Verify the International 10-20 System electrode placement and confirm impedances are balanced and below the lab standard (commonly less than 5 kilohms, and ideally similar across electrodes).
• Record a calibration / biocalibration at the start so amplifier and channel behavior is documented.
• Acquire a stable eyes-closed awake baseline to evaluate the posterior dominant rhythm.
• Capture eyes-open to confirm alpha attenuation (alpha blocking / reactivity).
• Allow and document drowsiness and sleep when the patient can sleep.
• Perform ordered activation procedures (hyperventilation, photic stimulation) at appropriate points.

Technologist Annotations and Observations

Annotations are contemporaneous notes the technologist enters onto the tracing in real time. They are part of the legal medical record and are weighted heavily on the exam because interpretation accuracy depends on them.

Document at minimum:

• State changes: eyes open, eyes closed, drowsy, asleep, awakening, alerting maneuvers.
• Patient behavior: movement, talking, chewing, swallowing, coughing, sweating, tremor, restlessness.
• Stimuli and responses: auditory or noxious stimulation and the patient's response (used for reactivity and in coma/ICU studies).
• Technical changes: montage changes, sensitivity changes, filter changes, electrode repair, photic and hyperventilation start/stop.
• Clinical events: any spell, behavioral arrest, jerk, or staring episode, with the time and a description of semiology.

A helpful exam principle: if it was not annotated, the physician cannot assume it happened. An asymmetry that is actually a head-turn artifact, or a "slowing" that is really drowsiness, can be misread as pathology when state is not documented.

Recording the Awake, Drowsy, and Sleep States

Normal EEG changes by state, so the technologist must deliberately capture each state and label it.

• Awake (eyes closed): A well-organized posterior dominant rhythm (alpha range, roughly 8-13 Hz in adults) that attenuates with eye opening.
• Drowsy: Alpha fragments and attenuates, slow lateral eye movements appear, and in children hypnagogic hypersynchrony may occur.
• Sleep: Vertex sharp waves, sleep spindles (~11-16 Hz), K-complexes, and positive occipital sharp transients of sleep (POSTS) appear. Capturing sleep increases the diagnostic yield for epileptiform discharges.

The technologist optimizes sleep capture by lowering lights, reducing noise, scheduling after partial sleep deprivation when ordered, and avoiding unnecessary alerting once the patient drifts off — while still annotating state transitions.

Montage Switching as a Recording Skill

A montage is the specific arrangement of electrode derivations displayed on the tracing. ACNS recommends recording with multiple montages so findings can be confirmed and localized; the technologist actively switches montages during the study rather than relying on a single view.

• Longitudinal bipolar ("double banana"): Chains electrodes front-to-back. Localizes a focal abnormality by phase reversal.
• Transverse bipolar: Chains electrodes side-to-side across the head. Useful for confirming midline or lateralized findings.
• Referential (e.g., to a common or averaged reference, or ear/mastoid): Shows the true amplitude and field of a discharge; helpful when bipolar cancellation hides a broad field.

When a possible focal sharp wave appears in longitudinal bipolar, a skilled technologist switches to a transverse and a referential montage to confirm it is cerebral and to better define its field. Recognizing that bipolar montages can cancel a widespread field while a referential montage reveals it is a frequently tested concept.

Optimizing the Recording

Optimization is continuous, not a one-time setup:

• Maintain low, balanced impedances and repair drifting or popping electrodes promptly.
• Adjust sensitivity (gain) so waveforms are readable without clipping; reduce sensitivity for very high-amplitude tracings (e.g., children) and increase it for low-amplitude records.
• Use filters appropriately: a low-frequency filter (high-pass, e.g., ~1 Hz) reduces slow sweat/movement drift, and a high-frequency filter (low-pass, e.g., ~70 Hz) reduces muscle artifact — but document every filter change because aggressive filtering can hide real slow or fast activity.
• Apply a notch (60 Hz) filter only when 60 Hz interference cannot be eliminated by fixing electrodes and grounding.

The exam emphasizes that filters and notch should mask artifact only after the source is addressed, never as a first response, because they can also distort genuine EEG.

Ictal Documentation Responsibilities

During any clinical event the technologist becomes the primary documenter of the ictal (seizure) record. The expected actions:

1. Mark the time the event begins on the tracing.
2. Test and document responsiveness: call the patient's name, give simple commands, test memory (a word to recall), and assess language.
3. Describe semiology: where movements start, spread, eye/head deviation, automatisms, posturing, incontinence, and duration.
4. Optimize the recording: switch to a montage that better localizes onset, adjust sensitivity, reduce avoidable artifact, and ensure the patient is safe.
5. Document the postictal state and when the patient returns to baseline.

Patient safety always comes before perfect signal quality — but a calm technologist can usually do both. Accurate ictal documentation directly determines whether the event can be classified and localized.