| Background and ObjectiveFor many years, ECG, respiration and saturation of blood oxygen monitors havebeen used routinely in adult intensive care unit, but there were short of availablemethods to monitor cerebral function which would be propected in critical patients.Nowadays, with the development of computer technology and software cerebralfunction monitor has been available in hospitals, and more and more people payattention to it. As a result, the level of diagnosis and treament of serious cerebralfunction damage will raise. The basic principle of cerebral function monitor by usingEEG includes: EEG is close correlated with metabolism of cerebral nerve cells, so itis very sensitive to brain damage of ischemic and anoxyaemia. EEG can reflectnervous system function disorder in reversible time of brain damage and recoverybefore other clinical examinations, what's more it is the most effective method to findseizure. In addition, continuous EEG(CEEG) can offer dynamic information ofcerebral function, which is advantageous to reflect real time changes of cerebralfunction. In cerebral function monitors, the preponderance of CEEG includes: (1) itcan detect physiologic function; (2) cost of equipment and examination is relative low;(3) it is not dangerous and involved in radioactive isotope and radioactive ray; and (4)it can be continuous and real time monitor. In short, CEEG is a useful technology ofmonitoring cerebral function with advantages such as cheap, safety, convenience andimmediateness. But it can not be ignored of CEEG shortage: (1) it is inferior to CT and MRI in anatomy localization; (2) it can not make precise diagnosis; (3) it may beinterfered with some physiological changes; (4) it is the hindrance of wide use ofCEEG that common doctors without professional training have difficulties inidentifying and analyzing EEG. Athough quantitative EEG make identification andanalysis of EEG easier, it is still a problem needed study further that how to simplifyidentification and analysis of EEG; (5) there are many interferences in theneurological intensive care unit(NICU) such as all kinds of electromagnetism andpatient factors(e.g restlessness, cranial injury, scalp oedema and intracal drainagetube); and (6) routine examinations, nursing and image check also influence themonitor of CEEG.NicoletOne monitor is the one of the most advanced continuous EEG monitor atpresent. Raw EEG can be turned into some kinds of trends to reflect cerebral functionchanges directly by mathematical transformation. In September 2006, such a monitorwas bought in the neurological department of Nanfang hospital and used in the NICU.Baseing on above-mentioned situations, we take critical cerebal function damagepatients as investigative objects. To approach the relationship of seizure(especiallysubclinicle seizure) and EEG monitor, in addition the significance of diagnosis andtreatment of acute cerebrovascular diseases and brain edema, and final diagnosis ofbrain death by using continuous EEG monitor.Clinical dataTotally, the clinical data of 122 patients(87 male, 35 famale, aged 17-84, average50.43±18.17) undergoing cerebral function monitor routinely in NICU of theneurological department of Nanfang hospital were collected from September 2006 toFebruary 2007. Of all, cerebral infarction 32 cases, cerebral hemorrhage 29cases(basal ganglia hemorrhage 11 cases, 7 male, 4 female, aged 36-80, averaged68.00±12.67, bleed volume 7.53-71.07ml, averaged 30.46±18.73ml), subarachnoidhemorrhage(SAH) 5 cases, intracranial infection 19 cases(viral encephalitis 11 cases,cryptococcosis 2 cases, tuberculous meningitis 2 cases, suppurative encephalitis 4cases), seizure 15 cases(status epilepticus, SE 10 cases, 6 male, 4 female, aged 20-62,averaged 35.50±14.68), metabolic encephalopathy 4 cases, organophosphate poisoning 2 cases, cardiorespiratory resuscitation 4 cases, heroin spongiformleukoencephalopathy(HSLE) 3 cases, Creutzfeldt-Jakob disease(CJD) 2 cases.MethodsFrom September 2006 to February 2007, patients in NICU took CEEG monitorroutinely with the standard electrode setting of the International Federation forElectroencephalology and Clinical Neurophysiol, ten-twenty electrode system, 16channel amplifier, 8 channel referential derivation(Fp1-A1, C3-A1, T3-A1, O1-A1,Fp2-A2, C4-A2, T4-A2, O2-A2), and impedance of every channel must be less than20kΩ, sampling rate 128-2048 Hz. We used the software of NicoletOne monitor totransform raw EEG into some kinds of trends including amplitude integratedEEG(aEEG), envelope and band power. The band power was divided into absoluteband power(ABP) and relative band power(RBP). The monitor lasted at least 1 hourper patient, and another at least 1 hour monitor was taken after convulsion of statusepilepticus. The seizure was definite according to clinical symptom and EEG, andcorrelated clinical informations such as symptoms, physical signs, vital signs et al.were recorded in NicoletOne monitor at equal pace. The data were extracted fromrelative trends one time every second after monitor. Seizure of same patient wasdivided into seizure time and intermission, and basal ganglia hemorrhage of samepatient was divided into uninjured side and injured side. Averages of above data werecomputed respectively and analysed contrastingly between groups. The data weregenerally expressed in forms: (?)±S and analyzed with statistical software SPSS 13.0.Statistical analysis was performed with paired-samples t test to identify significantdifferences between relative groups. P≤0.05 was considered statistically significant.ResultsThere were 15 cases(12.30%) with seizure in all patients under CEEGmonitoring, including 10 of SE(8.20%), 8 of generalized convulsive status epilepticus(GCSE, 6.56%) and 7 of nonconvultive status epilepticus (NCSE, 5.65%). NCSEincluded 5 cases after generalized seizures, 1 case of complex partial statusepilepticus(CPSE) and 1 of electrographic status epilepticus. The logarithm of aEEGincreased obviously during seizure. Contrasting seizure time to intermission, upper bound and lower bound were increased by 27.9%(t=6.019, P＜0.001) and33.53%(t=5.438, P＜0.001) respectively. These data changes made an apparentphenomenon like a peak in trends. The change of the wave width(diference betweenupper and lower bound) was statistically nonsignificant. Envelope had the similarchange. In seizure time, wave amplitude increased 129.09%(t=3.229, P=0.010) and79.35%(t=1.640, P=0.135) in referential derivation and bipolar recording respectively.In ABP, wave amplitude increased in all bands, but only changes ofαandβweresignificant(t=2.528, P=0.032 and t=2.627, P=0.027 respectively). In RBP,αandδbands decreased butβandθbands increased, which formed a valley in trends. Thesechanges were not statistically significant.Theδactivity of in injured side of basal ganglia hemorrhage increased obviously.Its ABP and RBP increased 108.35%(t=3.061, P=0.012) and 37.76%(t=4.255,P=0.002) respectively. However,αandβbands decreased 35.29%(t=3.242, P=0.009)and 46.71% (t=4.374, P=0.001) respectively in ABP, and decreased 63.92% (t=6.777,P＜0.001) and 68.09% (t=9.053, P＜0.001) respectively in RBP. ABP ofθincreasedwithout statistical significance, and RBP had almost no changes. Six patients withoutcontraindication were undertaken with stereotactic computed tomographic-guidedaspiration. There were no obvious changes between pre- and postoperative EEG andtrends.In cerebral arterial thrombosis, frequency and amplitude of EEG in ischemicregion were both decreased, and RBP of slow wave increased. There was an obviousdevelopment in trends with the gradual aggravation of cerebral function. In patientsof brain death, EEG turned into flat wave(amplitude＜2μV), lower bound of aEEGwas less than 5μV, and ABP was very low.Conclusion1. In our data, incidence of seizure, SE and NCSE was 12.3%, 8.20% and 5.65%respectively. 62.5% GCSE was followed with NCSE. It is helpful to diagnoseseizure and subclinical seizure by using CEEG monitoring for patients with viralencephalitis which was the majorest etiopathogenisis of SE in NICU.2. During CEEG monitoring, It usually indicated seizure when aEEG, Envelope and ABP ofαandβall were seen as significant abrupt rises which were moredirect-viewing than EEG.3. In three trends for seizure diagnosis, aEEG and Envelope had maximum Se andPPT respectively. If these trends increased simultaneously, seizure was indicatedintensively.4. In acute basal ganglia hemorrhage, there were statistically significant decreases ofABP and RBP ofαandβand rise of ABP and RBP ofδin injured side.5. EEG and trends monitoring could help diagnosis of acute cerbral infarction,reflect cerebral function deterioration and judge brain death.
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