A New Method Of Noninvasive Brain-edema Monitoring In Patients With Intracranial Tumor: Cerebral Electrical Impedance Measurement

Objective To explore the primary regularity of cerebral electrical impedance (CEI) change in healthy people and patients with intracranial tumor. To investigate the feasibility and reliablity of using noninvasive cerebral electrical impedance measurement to detect perioperative brain-edema in patients with intracranial tumor.Methods CEI of 200 healthy volunteers, 42 patients with intracranial tumor were measured by noninvasive brain-edema monitor. The results of perturbative index converted from CEI were compared with clinical manifestation, intracranial cerebral pressure , hematoma and surrounding edema which were calculated by image analysing system according to MRI or CT scan. Positive case was decided according to agreement between noninvasive cerebral impedance measurement and invasive measurement.Results In the normal groups, index of CEI in the left and right sides of cerebral hemispheres was respectively 7.98±0.95, 8.02±0.71, and there was no significant difference between the two sides(P>0.05). The ratio of positive case in all the patients was 78.6%(33/42). The ratio in patients with benign tumor was 81. 5%(22/27), and 73.3% (11/15) in patients with malignant tumor. As to the patients with supratentorial tumor and those with infratentorial tumor, the ratio was 76.7%(23/30) and 83. 3%(10/12), respectively. When concerned with cases of extracerebral tumor and those of intracerebral tumor, the ratio was 75.0%(18/24)and 83.3%(15/18). In patients whose tumor was totally removed, the ratio was 86.9%(20/23);while in other cases , the ratio was 68. 4%(13/19). It also can be devided into two groups acording to the volume of bleeding during operation : more than 600ml or less than 600ml. The ratio of the former was 68. 2%(15/22),the ratio of the latter was 90. 0%(18/20). The group of tumor less than 5cm in size has a ratio of 85. 7%(24/28)compared with 64. 3%(9/14) in the group of tumor larger than 5cm in size.There were no significant difference between all the above six match groups (P>0.05). There was significant difference between the groupe of bone replace and the group of bone removal during operation(P=0.028), the ratio being 85.7%(30/35) and 42. 9%(3/7), respectively.Conclusion CEI is a stable physical parameter reflecting the electrical character of human brain tissue.The noninvasive measurements do reflect intracranial events, and are able to detect the change of brain-edema or intracranial pressure in patients with intracranial tumor. It could be a good complement to clinical manifestation, CT and MRI. But. it also needs further research.