The energy metabolism of the brain in cerebral tumors is significantly impaired. According to PET, cerebral blood flow in the tumor region can vary within wide limits, but in most cases there is an increase (JL Tyler et al., 1987; KL Leenders, 1994). On the contrary, the extraction of oxygen from the blood and its consumption in the tissues of the tumor are reduced. The level of glucose consumption in the tumor area can be either increased or decreased. For malignant tumors, hypermetabolism of glucose is more characteristic (JB Alavi et al., 1987; JB Blacklock et al., 1987), but in isolated cases hypometabolism may be observed (T. Ogawa, et al., 1991). In areas of necrosis in the tumor, glucose metabolism decreases (G. Di Chiro et al., 1988).
With the development of intracerebral tumors, the acid-base balance of brain tissue changes significantly. According to numerous data, the extracellular space of the tumor is more alkaline compared with healthy brain tissue (JO Jarden, 1994). But a developing tumor creates a necrotic focus around itself, which has a lower pH compared with healthy brain tissue. In addition, the development of glial tumors is accompanied by ischemia and the associated transition to anaerobic oxidation, which leads to the accumulation of lactate and arachidonic acid, which also damage the neurons and glial cells surrounding the tumor (F. Staub et al., 1996).
The distribution of SCP in patients with brain tumors can be quite diverse, depending on the location and type of the tumor, as well as on the stage of the disease. There are few studies devoted to the analysis of AMR in tumors. K. Sano et al., (1977), in the presence of meningiomas, revealed a crater-like distribution of constant potentials in the tumor zone: above its center, the SCP was significantly reduced, and increased at the periphery. A local decrease in SCP with superficial intracerebral tumors was also detected in our previous studies .
We conducted a further study of SCP on 56 patients aged 43.5 + 2.5 years with cerebral supratentorial tumors (26 men and 30 women) who were treated in the clinic of nervous diseases of the Moscow Medical Academy named after I.M. Sechenov and the Institute of Neurosurgery RAMS them N.N. Burdenko. The diagnosis was confirmed with CTG in all cases. Many patients were subsequently operated on. According to a histological study, 11 patients had meningiomas, 2 had arachnoid endotheliomas, 5 had gliomas, and 3 had glioblastomas. Measurement of the SCP was carried out in 17 monopolar leads in accordance with scheme 10-20.
In the absolute majority of patients, SCP in unipolar leads and averaged SCP were almost 3 times higher than normal. The average SCP for intracerebral tumors was 14.0 + 2.3 mV, and for extracerebral tumors 15.5 + 2.5 mV. Of all the patients examined by us, only three of them had an averaged SCD that was not different from the norm. High SCP indicates brain acidification, which, obviously, was the result of pronounced necrotic processes developing as a result of ischemia, and the associated increase in glycolysis with the accumulation of lactate in the brain.