Observational Study of the Differences in Characteristics of the Spontaneous Electroencephalogram, Derived From the Left and Right Hemisphere in Patients With Unilateral Intracranial Tumor During Routine Anesthesia: Comparison With a Control Group Without Intracranial Pathology

Inclusion Criteria:

* Adult ≥ 18 - 80 years old
* Able to comprehend, sign, and date the written informed consent document to participate in the clinical trial
* Scheduled for "procedure"
* ASA Class I, II or III as assigned by the anaesthesiologist

Exclusion Criteria:

* Allergy or inability to tolerate "product"
* Body weight less than 70% or more than 130% of ideal body weight
* Pregnant or nursing females
* Participation in a clinical trial within the past 30 days
* Congenital mental disability or congenital anatomical brain abnormality
* A medical history of cerebrovascular accident or thrombosis
* A medical history of carotic artery occlusive pathology
* A medical history of degenerative cerebral pathology (MS, Dementia, ALS, para-or tetraplegia due to a traumatic disruption of the spinal cord)
* A medical history of severe psychiatric pathology (Schizophrenia, severe depression, alcoholism, drug abuse) Mild depression evoked by coping with the diagnosis of cancer is not excluded
* Patients with a history of epileptic insults. Patients receiving preventive anti-epileptic treatment due to the tumoral process are not excluded.
* Patients with low cardiac output conditions due to pre-existing cardiac pathology (Cardiac insufficiency, valve pathology, dysrhythmia, myocardial infarction). Patients presenting with stable coronary artery disease with a normal myocardial function are not excluded)
* Arterial hypertension is not an exclusion criteria, nor is the use of antihypertensive medication, except beta blockers for their potential interfering effects on spontaneous EEG.