Neurophysiology

This testing method detects electrical activity generated by nerve cells using metal electrodes. Since EEG is the best nervous system examination considering temporal resolution, the images made up of several snapshots create an image reminiscent of a wave pattern. Waves can be divided into bands based on their size and speed, which are denoted by Greek letters (e.g. alpha, beta, delta, theta, gamma). The characteristics of the waves can be examined visually and with computer technology. The collected data informs us about the nature of the disease. The technique is the most basic diagnostic procedure for epilepsy diagnosis.

When epilepsy is suspected, we look for signs of seizures or the signs that appear between seizures, the so-called interictal epileptiform discharges. However, wave patterns may differ among various diseases. In the case of local damage to the nervous system, the EEG slows down, indicated by waves of less frequency but of larger amplitude, replacing the otherwise fast, small-amplitude rhythm. Alzheimer's disease is characterized by diffuse cortical slowing of EEG activity, involving all brain areas. However studies show that deceleration is greater in certain areas, for example slowing is more prominent in the case of temporal lobe. These changes picked up by EEG have a diagnostic value.

Advantages of EEG testing is that it is a painless, relatively inexpensive and a completely safe procedure. The number of electrodes can be varied arbitrarily, so even the most detailed mapping of brain activity can be carried out. The length of the recording can also be increased to several days, significantly increasing its diagnostic value. The disadvantage of the test is that its evaluation requires significant expertise.

The PSG examination is a complex technique which, in addition to the above discussed electroencephalography also examines blood oxygen levels, heart rate, breathing mechanics, leg and eye movements. Its primary field of application is investigation of sleep disorders. Usually, the patient is prepared in the evening and spends one or two nights at a sleep laboratory under special conditions. The advantage of the test it is completely painless and safe. It is suitable for the differential diagnosis of sleep problems, for the recognition of narcolepsy, obstructive sleep apnea syndrome (OSAS), sleep walking, and sleep paralysis. Its use in Alzheimer's disease is justified by the detection of potential associated sleep disorders and epileptic activity. In addition, determination of sleep structure is also of diagnostic importance, as data shows that components of sleep can change in certain neurocognitive disorders (e.g. decreasing sleep spindle number in Alzheimer's disease or REM sleep shortening in Parkinson's disease).