Cortical activity of the brain can be monitored continuously by simple, cheap and non-invasive methods. Nevertheless routine monitoring in Neuro ICUs seldom includes traditional or processed EEG. Our clinical experience with the Cerebral Function Monitor (CFM) indicates that a reliable guide to treatment of acute cerebral lesion can be obtained in different clinical situations and steps of management.
Ischemia: the lower border voltage of the CFM correlates with the minimum level of cortical activity and mirrors different degrees of cortical metabolic depression. Cerebral oligaemia is reflected consistently in a an increase in periods of EEG suppression, particularly in the arterial boundary zones where the CFM electrodes are located. CFM is a reliable warning of impending ischaemia.
Therapy: during the administration of hypnotics, development of a burst suppression EEG pattern signifies adequate dosage for maximal reduction of cerebral metabolism (CMRO2), cerebral blood flow (CBF) and intracranial pressure. Values of CFM lower border voltage predict the efficacy of hypnotic agents in ICP reduction therapy after severe head injury. Hyperventilation, mannitol and i.v. anaesthetic agents may be beneficial or detrimental in different conditions of CBF and metabolic demand; concomitant recording of oxygen jugular bulb saturation (SjO2) and CFM identifies different clinical situations of the CBF/CMRO2 ratio (adequate perfusion, relative hyperaemia, compensated and non compensated hypoperfusion, cerebral infarct) and offers a clinical guide to targeted therapy.
Seizures: generalized and focal sub-clinical seizures are easily recognizable on the CFM trace; continuous EEG/CFM monitoring is mandatory in status epilepticus to choose and titrate drugs.
Research: continuous polygraphic recording of CFM together with ABP, ICP and SjO2 is a good method to appreciate spontaneous pathophysiological dynamics and the relationship between treatment, nursing and cerebral events. Frustrating artifacts and "wandering electrodes" could be eliminated by qualified nursing and improved ICU environment; early control of CBF/CMRO2 derangement and prevention of ischaemic secondary damage could take advantage from validated guidelines based on continuous EEG/CFM monitoring.