gms | German Medical Science

Objective: Reported brain tissue conductivities to date are usually obtained from sample investigation in vitro. In addition, there is a lack of information regarding conductivity of different brain tumors. This is a pilot study to investigate the feasibility of a new technique to perform an in vivo measurement of electrical resistivity of intracranial tissue and brain tumors.

Methods: Patients who were operated for glioma or brain metastasis were included into the study. Intraoperative measurement of tissue resistivity was performed using a bipolar probe with a defined distance between the two poles applying a constant current of 0.7 µA with a frequency of 140 Hz. The measurement was conducted on the dura, cortex and the exposed solid tumor tissue subsequently, each three times and the lowest value was recorded. Resistivity values were expressed in ohm (Ω).

Results: We included 14 patients, 6 with glioblastoma, 2 with anaplastic glioma, 3 with low- grade glioma and 3 with brain metastasis. Mean resistivity values were 3.5 Ω from the dura, 2.5 Ω from brain cortex, 1.3 Ω from low grade glioma, 0.9 Ω from anaplastic glioma, 0.5 Ω from glioblastoma and 0.67 Ω from metastasis. Resistivity values from dura were significantly higher than those from cortex (p=0.027) and values from glioblastoma were significantly lower than those from anaplastic and low- grade glioma (p=0,049) and comparable to those from metastasis (p=0.52).

Conclusion: The new technique enables in vivo measurement of electrical resistivity of brain tissue and brain tumors with reproducible results and without damaging brain tissue. First results showed a difference in tissue resistivity between brain tumors. Further studies will be necessary to validate the results and investigate the clinical application of this technique.