The EEG operation specifications are still unclear?

Electroencephalogram is a detection technology that records brain electrical activity by placing appropriate electrodes on the head and using electronic amplification technology to amplify the spontaneous bioelectric activity of brain neurons by 1 million times, and convert pulsed direct current to alternating current.

According to different clinical examination purposes (such as judging the nature of clinical seizures or brain function), the EEG that is widely used clinically includes conventional EEG, long-term EEG monitoring, severe continuous EEG monitoring and portable mobile EEG, etc.

In view of the fact that the interpretation of EEG is usually affected by the number of electrodes, lead arrangement and monitoring quality, Shanghai experts in this field have reached the following consensus on the technical standards and operating specifications of clinical EEG for reference.

Compiled and compiled by Yimaitong, please do not reprint without authorization 01 Technical standards and operating specifications of clinical routine EEG ➤Clinical routine EEG examination is mainly used in the evaluation of awake patients in outpatient clinics to initially determine whether the patient has epileptiform discharges Or evaluate its brain function.

Digital EEG equipment is recommended.

The electrode type is a bridge electrode.
Disc-shaped electrodes and some special electrodes (such as sphenoid electrodes) can be used as needed, and the electrode recording will not cause the attenuation of the EEG signal in the frequency range of 0.
5 to 70 Hz.

 ➤When performing routine EEG examinations, 21 EEG electrodes (19 recording electrodes and 2 reference electrodes) should be placed according to the 10-20 system.
The recording electrodes are FP1, FP2, F3, F4, C3, C4, P3, P4 , O1, O2, F7, F8, T3, T4, T5, T6, Fz, Cz and Pz.

Newborns can choose to use a modified international 10-20 electrode placement system: 9 EEG recording electrodes (Fp1, Fp2, C3, C4, T3, T4, O1, O2 and Cz), 2 reference electrodes (ear or mastoid electrodes) ), 1 pair of submental myoelectric electrodes, 1 pair of ECG electrodes, and 2 eye movement electrodes.

 02 Technical standards and operating specifications for long-term EEG monitoring ➤Long-term EEG monitoring refers to an EEG that has been monitored for more than 2 hours.
It is divided into two types: inpatient and outpatient.

Since only 29% to 55% of interictal epileptiform discharges (IED) can be screened by routine outpatient EEG, prolonging the recording time of outpatient EEG (such as extending to 3.
5～4.
0h) can screen IED The incidence rate is increased to 80% to 90%, especially for focal epilepsy and non-epileptic seizures.

For long-term EEG monitoring, a combination of video and scalp EEG is recommended.

 ➤It is recommended to use disc-shaped or cup-shaped electrodes, which are firmly fixed on the scalp with special electrode paste and tape.
The electrode impedance should be <5000 Ω; patients with monitoring time> 24h should check the electrode connection and impedance regularly to try their best Reduce artifacts.

The electrode placement requirements are the same as those for conventional EEG, that is, at least 16 EEG recording electrodes should be placed according to the 10-20 system.

 ➤Patients may have seizures during long-term EEG monitoring.
Therefore, during the monitoring process, it is necessary to record whether there are seizures, when to start to stop anti-epileptic drugs, whether to use epilepsy induction test, and whether there are epilepsy-related adverse events.
Events (such as status epilepticus, epilepsy-related trauma, post-seizure psychiatric symptoms, and post-seizure severe hypoxemia, etc.
).

When monitoring, be equipped with protective bed rails, sputum suction and oxygen inhalation facilities, and fall prevention facilities.

 03 Severe EEG monitoring technology ➤ Severe EEG monitoring can be divided into severe intermittent EEG and severe continuous electroencephalogram (CCEEG).
CCEEG monitoring mainly uses digital EEG for a long time (several hours, several hours).
Days or weeks), continuous monitoring of patients with conscious state changes, status epilepticus, or critically ill patients at risk of acute cerebral ischemia, to detect secondary brain damage (such as epileptic seizures or cerebral ischemia).

Although CCEEG can help determine brain damage, it is not currently possible to diagnose brain death based on CCEEG results alone.

 ➤CCEEG is often used in critically ill patients.
The number of EEG recording electrodes is ≥16.
Leads such as eye movement, ECG, and EMG should be selected according to specific clinical needs.
The lead arrangement is the same as that of conventional EEG inspection 10-20 electrode placement system requirements . If the position where the electrode is placed on one side happens to have a drainage tube or a partial skull defect, the position of the electrode can be adjusted appropriately, and the position of the matched electrode on the opposite side should also be adjusted accordingly.

 ➤The EEG equipment can be fixed in the ICU or mobile; the equipment sampling rate, common mode rejection ratio, impedance and other requirements are the same as those of conventional EEG; it is best to have an independent power supply that is not shared with other monitoring equipment during monitoring.
To reduce interference.

EEG equipment should be equipped with camera recording and video recording to simultaneously observe the patient's seizure behavior.

The EEG storage device should be able to continuously store data> 24h at least, and it is generally better to store 5-7d data.

 Yimaitong is compiled from: Shanghai Medical Association Electroencephalography and Clinical Neurophysiology Branch.
Shanghai Expert Consensus on Clinical Electroencephalography Practice (2021) [J].
Shanghai Medicine, 2021, 44 (3): 141-147 .