1.3 Recording Strategy, Protocol Planning & Patient Communication
Key Takeaways
- The LTM recording strategy must be tailored to the clinical question, selecting standard 10-20, expanded 10-10, or specialized inferior temporal (T1/T2) derivations based on suspected seizure focus.
- Inferior temporal electrodes (Silverman T1/T2 or 10-10 equivalents FT9/FT10, TP9/TP10) substantially enhance detection of anterior and basal mesial temporal lobe discharges that are missed by standard 10-20 temporal electrodes.
- ACNS guidelines mandate time-code synchronization of video, audio, and EEG signals to within 1 video frame (<100 ms), along with continuous infrared video surveillance and unobstructed camera line-of-sight.
- Patient and family orientation on immediate event button activation at earliest aura onset, unobstructed camera positioning, and bedside cognitive testing directly determines the diagnostic quality of EMU recordings.
- Continuous audio-visual monitoring requires signed informed consent addressing privacy rights, HIPAA/HITECH security compliance, fall/seizure precautions, and established multidisciplinary Seizure Action Plans (SAP).
1.3 Recording Strategy, Protocol Planning & Patient Communication
A successful long-term monitoring (LTM) study requires strategic planning, customized technical design, and clear patient communication. Rather than applying a rigid, one-size-fits-all setup, the neurodiagnostic technologist must formulate an individualized recording strategy tailored to the specific diagnostic questions posed by the medical team. This includes selecting optimal electrode arrays, establishing activation protocols, educating patients and caregivers on event capture, obtaining informed legal consent, and coordinating emergency response workflows.
1. Defining Monitoring Objectives & Study Duration
Before initiating recording, the technologist must identify the explicit clinical objectives and planned duration of the admission:
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| LTM STUDY DESIGN & OBJECTIVE ALIGNMENT |
| |
| CLINICAL OBJECTIVE PLANNED DURATION TECHNICAL & PROTOCOL REQS |
| -------------------------- ----------------- ------------------------- |
| Diagnostic Spell 24 to 72 hours - Standard 10-20 Montage |
| Differentiation (Until 2-3 spells - Single-lead ECG sync |
| (Epileptic vs. PNES) captured) - Patient/caregiver event |
| button training |
| - Provocative suggestion/HV|
| |
| Presurgical Localization 3 to 7+ days - Expanded 10-10 or T1/T2 |
| (Temporal vs. Extratemporal)(Capture 3-5 - Structured ASM tapering |
| habitual seizures)- Ictal SPECT setup ready |
| - Standard ictal testing |
| |
| ICU cEEG Non-Convulsive 24 to 48 hours - Rapid collodion/cap setup|
| Seizure Surveillance (Post-arrest/coma) - Real-time qEEG trends |
| 3-14 days (SAH) - Artifact/impedance check |
| |
| Ambulatory Diagnostic 24 to 72 hours - Secure collodion wrap |
| Event Capture (Home) (Natural routine) - Push-button event diary |
| - NO rapid drug tapering |
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2. ACNS Technical Guidelines: Video, Audio & Synchronization Setup
According to American Clinical Neurophysiology Society (ACNS) guidelines for long-term video-EEG monitoring, the acquisition system must satisfy rigorous technical performance benchmarks:
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| ACNS TECHNICAL SPECIFICATIONS FOR LTM |
| |
| PARAMETER ACNS MINIMUM STANDARD RECOMMENDED PRACTICE |
| -------------------- ------------------------- ----------------------- |
| Sampling Rate >= 256 Hz per channel 512 Hz - 1024 Hz |
| A/D Conversion >= 16-bit resolution 24-bit resolution |
| Common Mode Rejection >= 90 dB (CMRR) >= 110 dB |
| Electrode Impedances < 5,000 Ohms (5 kOhm) < 2,000 to 3,000 Ohms |
| Time Synchronization EEG-Video-Audio <= 1 frame Network Time Protocol NTP|
| (< 33 to 100 ms) hardware synchronization |
| Video Resolution Standard Definition (SD) Full HD (1080p / 4K) |
| Video Frame Rate >= 30 frames per second 30 to 60 fps |
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Camera Placement, Lighting & Audio Configuration
- Camera Positioning: High-definition IP cameras equipped with motorized Pan-Tilt-Zoom (PTZ) must be wall- or ceiling-mounted at an angle that provides an unobstructed view of the patient's entire body, face, and extremities. The camera must capture both full-body convulsions and subtle facial/digital automatisms.
- Lighting & Infrared (IR) Illumination: The EMU room must be equipped with low-intensity, indirect night-lighting and cameras featuring automatic infrared illumination. Direct backlighting (e.g., unshaded windows behind the patient) causes silhouetting and obscures motor semiology during daytime and nighttime recording.
- Audio Surveillance: High-sensitivity omnidirectional ceiling microphones must capture vocalizations, respirations (stertorous post-ictal breathing), and verbal interactions during bedside ictal testing without acoustic clipping.
- Time Synchronization: Video, audio, and EEG data streams must be precisely time-locked via Network Time Protocol (NTP) or dedicated hardware sync pulses. The time discrepancy between clinical semiology and the electrographic trace must not exceed 1 video frame (typically < 33 ms, maximum 100 ms) to ensure accurate determination of whether clinical behavior preceded or followed electrographic onset.
3. Tailored Electrode Montages & Specialized Derivations
Electrode selection and spatial distribution govern the spatial resolution and diagnostic sensitivity of the electroencephalograph.
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| ELECTRODE ARRAY SYSTEM HIERARCHY |
| |
| [1] STANDARD INTERNATIONAL 10-20 SYSTEM (21 Scalp Electrodes) |
| - Baseline setup for routine EEG and general diagnostic EMU admissions|
| - Electrodes spaced at 20% and 10% intervals of head circumference |
| - Limitations: Inadequate spatial coverage for basal temporal & |
| small neocortical epileptogenic foci. |
| |
| [2] EXPANDED 10-10 SYSTEM (Modified Combinatorial Nomenclature) |
| - Incorporates intermediate electrodes (e.g., AFz, FC1, CP3, PO7) |
| - Provides high-density spatial sampling for focal cortical dysplasia |
| and neocortical presurgical evaluations. |
| |
| [3] SPECIALIZED INFERIOR TEMPORAL ELECTRODES (T1 / T2 or FT9 / FT10) |
| - Placed inferior to standard anterior temporal leads (F7 / F8) |
| - Directly records anterior temporal pole & parahippocampal gyrus |
| - Essential for mesial temporal lobe epilepsy (MTLE) evaluations |
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True Inferior Temporal Electrodes (Silverman T1/T2)
Standard 10-20 anterior temporal electrodes (F7/F8) are situated over the frontotemporal convexity, relatively distant from the inferior and anterior aspects of the temporal lobe. Consequently, epileptiform discharges originating from the parahippocampal gyrus, hippocampus, and anterior temporal pole project a horizontally or obliquely oriented electrical dipole that may be undetectable at standard F7/T3 or F8/T4 electrodes.
To overcome this limitation, true inferior temporal electrodes (T1 and T2)—or their standardized 10-10 equivalents FT9 and FT10 / TP9 and TP10—are applied:
- Anatomical Landmarking for T1/T2: T1 (left) and T2 (right) are placed 1 cm superior to the external auditory meatus and 1 cm anterior (or measured as one-third the distance from the external auditory meatus to the outer canthus of the eye, elevated 1 cm perpendicular to that line).
- Diagnostic Yield: Studies show that adding true T1/T2 or 10-10 inferior temporal electrodes increases the sensitivity for detecting anterior mesial temporal spikes and ictal onsets by 20% to 35% compared to standard 10-20 montages alone.
Mandatory Auxiliary Polygraphic Channels
Modern LTM requires auxiliary polygraphic channels synchronized to the digital EEG:
- Dedicated Single- or Dual-Lead ECG: Essential for detecting ictal arrhythmias (asystole, bradycardia, tachycardia) and differentiating cerebral spikes from pulsatile vascular artifacts.
- Surface Electromyography (EMG): Placed over the anterior tibialis (detecting periodic limb movements during sleep), deltoid/biceps (detecting initial myoclonic jerks in JME or tonic stiffening), or masseter.
- Respiration & Pulse Oximetry: Thoracic/abdominal respiratory effort belts, nasal thermistors, and continuous pulse oximetry (SpO2) are critical for monitoring ictal/post-ictal central or obstructive apnea, oxygen desaturation, and SUDEP risk mitigation.
- Electrooculography (EOG): Vertical and horizontal eye movement leads to distinguish frontal slow waves and sharp transients from blinks, saccades, and lateral nystagmus.
4. Activation Procedure Planning & Safety Protocols
Activation procedures are standardized provocative maneuvers designed to precipitate interictal epileptiform discharges or clinical seizures in a controlled setting.
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| ACTIVATION PROCEDURE SAFETY MATRIX |
| |
| ACTIVATION METHOD PRIMARY CLINICAL VALUE MAJOR CONTRAINDICATIONS |
| -------------------- ------------------------- ----------------------- |
| Hyperventilation (HV) - Provokes 3 Hz spike- - Severe Cardiopulmonary |
| (3 to 5 minutes) wave in Absence Epilepsy. disease (recent MI) |
| - Provokes focal spikes in - Moyamoya Disease |
| Temporal Lobe Epilepsy. - Sickle Cell Disease |
| - Recent Stroke / TIA |
| - Severe active HTN |
| - Acute ICH / SAH |
| |
| Intermittent Photic - Provokes Photoparoxysmal - None absolute, but |
| Stimulation (IPS) Response (PPR) in Idiop. stop immediately when |
| (1 to 30+ Hz flashes) Generalized Epilepsies. generalized PPR begins |
| to avoid full convulsion|
| |
| Sleep Deprivation - Lowers seizure threshold - Unsupervised ambulatory|
| (Overnight partial / - Activates NREM interictal patients at risk of |
| complete wakefulness) discharges and seizures. severe drop attacks |
| |
| Anti-Seizure Med. - Enables capture of 3-5 - Ambulatory setting |
| (ASM) Withdrawal habitual seizures in EMU. - Lack of IV access |
| - Guided by physician order- Lack of rescue orders |
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Hyperventilation (HV) Nuances
Hyperventilation induces respiratory alkalosis and hypocapnia (PaCO2 reduction), triggering intense cerebral vasoconstriction and transient cerebral hypoxia. In pediatric absence epilepsy, HV provokes generalized 3 Hz spike-and-wave paroxysms in > 85% of untreated patients. However, because of profound vasoconstriction, HV is strictly contraindicated in patients with Moyamoya disease (where vasoconstriction can induce acute ischemic stroke), sickle cell disease/trait (triggering vaso-occlusive crisis), severe chronic obstructive pulmonary disease (COPD), active unstable angina or recent myocardial infarction, and acute subarachnoid or intracerebral hemorrhage.
Intermittent Photic Stimulation (IPS) Protocols
IPS delivers stroboscopic flashes at frequencies ranging from 1 to 30 Hz (or higher) in dark and illuminated environments. Technologists must distinguish between normal photic driving (frequency-matched occipital rhythm) and an abnormal Photoparoxysmal Response (PPR) (generalized polyspike-and-wave discharges that outlast the flash stimulus). When a generalized PPR occurs, the technologist must immediately terminate the stimulation to prevent secondary generalization into a full tonic-clonic convulsion.
5. Patient & Caregiver Orientation, Education & Bedside Testing
The diagnostic yield of an EMU stay depends directly on the active engagement of the patient and their bedside caregivers.
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| EMU PATIENT & CAREGIVER EDUCATION WORKFLOW |
| |
| [1] EVENT BUTTON MARKER PUSH-BUTTON INSTRUCTIONS |
| - Instruct patient: "Press the button IMMEDIATELY at the very first |
| hint, feeling, or aura—before moving or speaking." |
| - Instruct family: "If the patient cannot press the button, the family|
| must press it immediately and call the nursing team." |
| |
| [2] AUDIO-VISUAL SURVEILLANCE RULES |
| - Keep bed linens below the waist/chest to ensure extremities and |
| body movements remain visible to the camera. |
| - Do not block the camera line of sight when standing beside the bed. |
| - Maintain appropriate room lighting; avoid turning off night-lights.|
| |
| [3] STANDARDIZED BEDSIDE ICTAL EXAMINATION PROTOCOL |
| - STEP 1 (Responsiveness): Call patient's name; assess eye contact. |
| - STEP 2 (Memory Test): Recite 2-3 memory words (e.g., 'VELVET', '74')|
| - STEP 3 (Language/Motor): Ask to repeat a phrase; command to raise |
| right arm, hold up two fingers. |
| - STEP 4 (Post-Ictal Recall): Test immediate recall of memory words; |
| assess for Todd's paresis and speech fluency. |
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6. Safety Precautions, Fall Prevention & Multidisciplinary Communication
Due to anti-seizure medication tapering, sleep deprivation, and post-ictal confusion, EMU patients are at extraordinary risk for catastrophic inpatient falls, fractures, and status epilepticus.
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| EMU SAFETY & SEIZURE ACTION PLAN |
| |
| SAFETY DOMAIN MANDATORY EMU PROTOCOL MEASURES |
| --------------------- ------------------------------------------------- |
| Fall Prevention - All 4 padded side rails fully raised at all times|
| - Bed maintained in lowest position with floor mats|
| - Strict 1:1 bathroom accompaniment; NO lock doors |
| |
| Airway & Resuscitation - Suction canister tested, functioning, Yankauer on|
| - Oxygen flow meter with mask & BVM at bedside |
| - Continuous SpO2 pulse oximetry monitoring |
| |
| Vascular Access - Patent, verified peripheral IV line at all times |
| - Physician-ordered rescue medications ready |
| |
| Emergency Triggers - Seizure lasting >= 3 to 5 minutes |
| - Cluster >= 2 seizures in 24h without baseline rec|
| - Severe post-ictal desaturation (SpO2 < 85%) |
| - Prolonged cardiac asystole (> 3 seconds) |
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Multidisciplinary Team Communication & Closed-Loop Escalation
Effective LTM requires tight coordination across a multidisciplinary EMU team consisting of neurodiagnostic technologists, bedside registered nurses, clinical epileptologists, neurosurgeons, and neuropsychologists:
- Daily Morning Clinical Handoff: Technologists review the preceding 24 hours of recording, summarizing event counts, electrode integrity, medication adjustments, and captured semiologies with the attending epileptologist.
- Real-Time Notification Workflows: Technologists must immediately notify nursing and medical staff upon detecting prolonged electrographic seizures, subclinical status epilepticus, critical cardiac arrhythmias (e.g., ictal asystole, severe bradycardia), or sudden loss of signal integrity.
- Closed-Loop Verification: When administering rescue medications or executing provocative protocols, technologist, nurse, and physician verify orders using closed-loop read-back protocols to prevent dosing or timing errors.
7. Informed Consent, Audio-Video Privacy & Regulatory Mandates
Continuous audiovisual recording is legally distinct from routine diagnostic testing because it captures continuous private biometric, behavioral, and vocal data.
Legal & Regulatory Framework
- Informed Consent for Video/Audio Recording: In addition to standard hospital treatment consent, a specific, specialized consent document must be executed. The patient or legal surrogate must be informed that video and audio are recorded continuously 24 hours a day.
- State Wiretapping & Privacy Statutes: Many jurisdictions operate under "two-party consent" wiretapping laws. Visitors, family members, and visiting healthcare personnel must be notified (via posted signage on the EMU entry doors and inside the room) that continuous audio recording is active in the room.
- HIPAA and HITECH Security Mandates: Video-EEG files containing identifiable patient faces and audio are protected health information (PHI). Data must be stored on encrypted servers with role-based access control, audit logging, and secure pruning protocols.
- Privacy Pauses: Policies must exist allowing temporary cessation of video recording or physical camera shuttering during intimate hygiene, toileting, or sensitive medical exams, provided the continuous electroencephalographic recording remains active.
A 32-year-old patient with drug-resistant epilepsy is evaluated for presurgical localization of suspected mesial temporal lobe epilepsy. Why does the neurodiagnostic technologist place true Silverman T1/T2 (or 10-10 equivalent FT9/FT10) inferior temporal electrodes in addition to the standard International 10-20 montage?
A pediatric patient with suspected absence seizures is undergoing inpatient long-term monitoring. During the pre-study intake, the technologist notes a medical history of Moyamoya disease. Why must the technologist withhold the hyperventilation (HV) activation procedure in this patient?
During orientation on the first day of an EMU admission, what is the most critical instruction the technologist must give the patient and their family regarding the event push-button marker?
A patient admitted to the EMU experiences an unexpected generalized tonic-clonic seizure. The seizure continues without interruption and reaches 4 minutes in total duration. According to standard EMU Seizure Action Plans (SAP), what is the mandatory immediate action?