title: Application of non-invasive cerebral electrical impedance measurement on brain edema in patients with cerebral infarction.
abstract: OBJECTIVE
  To investigate the change of brain edema in patients with cerebral infarction by non-invasive cerebral electrical impedance (CEI) measurements.
  
  
  METHODS
  An invariable secure current at a frequency of 50 kHz and an intensity of 0.1 mA was given into a person's brain. CEI values of the bilateral hemisphere of 200 healthy volunteers and 107 patients with cerebral infarction were measured by non-invasive brain edema monitor. The results of perturbative index (PI) converted from CEI were compared with the volumes of brain edema, which were calculated by an image analysing system according to magnetic resonance imaging or computed tomography.
  
  
  RESULTS
  (1) In the healthy volunteers, PI values in the left and right hemisphere were 7.98 +/- 0.95 and 8.02 +/- 0.71 respectively, and there was no significant difference between the two sides (p>0.05). Age, gender and different measuring times did not obviously affect PI values (p>0.05). (2) In the cerebral infarction group, CEI measurements were more sensitive to the volumes of lesion, which were more than 20 ml. The positive ratio of PI was higher when the volumes of infarction were >20 ml (80.0%): the ratio of PI was 75.9% when the volumes of infarction were 20-50 ml and it was 83.3% when the volumes of lesion were more than 50 ml. PI was lower when the volumes were less than 20 ml. (3) PI of the infarction side increased obviously 3-5 days after onset; the difference of two sides was the most significant. There was a positive correlation between PI of the infarction side and volume of infarction.
  
  
  CONCLUSIONS
  PI may be a sensitive parameter for non-invasive monitoring of the change of brain edema in patients with cerebral infarction. CEI is a valuable method for the early detection of brain edema.
authors.affiliation: Department of Neurology, First Affiliated Hospital, Chongqing Medical University, Chongqing, China.
authors.forename: Lan Ying
authors.initials: LY
authors.lastname: He
authors.forename: Jian
authors.initials: J
authors.lastname: Wang
authors.forename: Yong
authors.initials: Y
authors.lastname: Luo
authors.forename: Wei Wei
authors.initials: WW
authors.lastname: Dong
authors.forename: Li Xu
authors.initials: LX
authors.lastname: Liu
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D001921:Brain / Q000473:pathology / Q000503:physiopathology; D001929:Brain Edema / Q000150:complications / Q000175:diagnosis* / Q000473:pathology / Q000503:physiopathology; D020520:Brain Infarction / Q000150:complications* / Q000473:pathology / Q000503:physiopathology; D017097:Electric Impedance; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged