The reason for this is that there are many sources of error which must be eliminated before it is possible to rely on a QEEG analysis giving the correct result. Unqualified overuse of QEEG in clinical settings in the 1990s was criticised by the American Academy of Neurology, who stated that QEEG should always be used in conjunction with a standard EEG test interpreted by a neurophysiologist (6). Frequency analysis (QEEG) is built into several commercial EEG systems used in Norway today. Frequency analysis provides numerical values for the quantity of delta, theta, alpha and beta activity and the distribution can be shown in an x/y (frequency/quantity) graph (Fig. 1). With the development of modern computer technology, frequency analysis based on FFT (Fast Fourier Transformation) was researched in psychiatry and neurology (9, 10). The probability of finding epileptiform activity in a patient with epilepsy increases if the EEG is recorded while the patient is sleeping (9). This is a specific sign of epilepsy if the patient also has seizure symptoms which can fit the diagnosis. ¹ Also involved in synchronisation between brain regionsĮpileptiform activity consists of sharp waves or a «spike-and-wave» pattern. The purpose of this article is to provide a brief review of research into and practical clinical use of EEG in adult psychiatry. Can a quantitative analysis of the frequency content of EEG waves (QEEG) contribute to psychiatric diagnosis and treatment? This question has exercised the minds of researchers and clinicians for many years (6, 7). The third and final problem is associated with the classification of psychiatric disorders.
For example, frontal lobe brain tumours, autoimmune encephalitis and Lewy Body dementia in patients with Parkinson’s disease may first present with psychiatric symptoms and the patient will thus be referred initially for psychiatric assessment. Secondly, a number of acute and subacute brain diseases may produce emotional or cognitive core symptoms. Epileptic seizures can also mimic psychiatric disorders or trigger episodes with psychiatric symptoms. A corresponding relationship has also been identified between schizophrenia and epilepsy (5). At the same time, patients with depression have been shown to have a three-to-seven times greater risk of developing epilepsy (4). Many patients with epilepsy suffer from depression (2, 3).
Firstly, there is comorbidity between severe psychiatric disorder and epilepsy. Electroencephalography (EEG) is primarily of use in diagnosing epilepsy and other brain diseases (1), but there are other reasons why EEG is also an important diagnostic test in psychiatric practice.
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