Intraoperative neuromonitoring in surgery of supratentorial brain tumors. Part 2. Assessment of sensory conductivity, impact at outcomes and method restrictions

Abstract

Among methods of assessment of sensory conductivity of neuromonitoring in surgery of supratentorial tumors somatosensory evoked potential phase reversal are used most commonly to identify location of central sulcus. Method's uniqueness lies in possibility of its usage in patients with severe paresis before operation. Its sensitivity reaches 97 % but decreases with tumor location in Rolandic area.In monitoring of visual evoked potentials integrity of visual pathways are estimated, that is actually in lesions of occipital and posterior temporal lobes. Accuracy of visual evoked potentials reaches 94 %. In contrast to mapping of visual pathways method is more unbiassed because is not founded on subjective patient's feelings and can be applied in general anesthesia.Neuromonitoring's usage increases extent of eloquent tumor resection in 2 to 5 times and decreases the number of permanent neurological deficit in 2 times after surgery.Accuracy of neuromonitoring decreases in reoperations and in ischemic damage due to angiospasm. To maintain high predictive value of the method amount of monitoring muscles should be inverse proportionally to the density of subcortical pathways in area of resection.