A history and review of quantitative electroencephalography in traumatic brain injury

The electroencephalogram (EEG) is a physiologic measure of cerebral function that has been used by some to assess coma and prognosticate survival and global outcome after traumatic brain injury (TBI). Surface recordings of the brain's electrical activity reveal distinct patterns that indicate injury severity, depth of unconsciousness, and patient survival. The data produced with traditional qualitative studies, however, does not allow resolution and quantification of the wave frequency spectrum present in the brain. As a result, conventional EEG typically has only been used for gross and qualitative analyses and is not practical for use in long-term patient monitoring or as a sophisticated prognostic tool. One area of investigation that is working to address the limitations of conventional EEG has been the development and implementation of Fourier Transform (FT) EEG which resolves and quantifies frequency bands present in the brain. When FT analysis is applied to EEG, it provides concurrent and continuous monitoring, resolution, and quantification of all frequencies emitted. This review discusses the history and significance of conventional EEG and provides a review of how FT-EEG, commonly referred to as Quantitative EEG (QEEG), is being used in the clinical setting. The specific applications and significance of QEEG methods regarding treatment of patients with TBI are discussed in detail. The advantages, disadvantages, and future directions of QEEG in TBI are also discussed.

A brief history of psychiatry: millennia past and present. Part IV

Biological scientists have been trying to look inside the black box of the brain since the middle of the nineteenth century. Techniques in many disciplines were being developed in the last century that would lead beyond philosophical speculation about the mind/body relation and the meaning of insanity. Only in the last several years have molecular biology and the beginnings of understanding of its relation to mind, body, behavior, and the human environment made it possible to start to find solutions to some of the problems. Neurobiology, psychology, and sociology now seem much more closely related, albeit in enormously complex ways.

[Clinical neurophysiology and functional neuroimaging at the Société Française de Neurologie (1948-1998)]

The historical role of the French Neurology in the development of anatomo-clinical method is likely to explain why the first communications on electrophysiology were presented in Paris with some delay, as compared with other european societies where the neurophysiological tradition had been more lively. Though clinical neurophysiology, by essence, addresses the pathophysiology of neurological disorders, it has sometimes missed this target at its very beginning, when it aimed at providing data supposed to have some aetiological specificity, causing distrust among neurologists used to accept aetiological diagnosis only when based on post-mortem anatomical evidence. Thanks to the discovery of computerized tomography this time has been over for 25 years, and no one would question anymore the role of clinical neurophysiology and neuroimaging in Neurology, the former giving access to the timing of sensori-motor and cognitive pocesses and the latter to the localization of brain functions. This article reviews the neurophysiological literature published in the Revue Neurologique from 1948 to 1998.

Herbert Henri Jasper (1906-1999): an appreciation

Herbert Henri Jasper dedicated his life to studies of the brain in relation to the mind and behavior. He pioneered the application of the electroencephalogram (EEG) for the study of the electrical activity of the brain and used this technique in studies of consciousness, learning and particularly the examination of epileptic discharge. He utilized microelectrode recordings from single brain cells and combined this technique with microchemical analyses to study cortical and sub-cortical activity. He added substantially to our understanding of brainstem and thalamic reticular formations in conditions of consciousness and in relation to petit-mal epilepsy. His work with Wilder Penfield and associates over a quarter century elucidated the mechanisms of epilepsy and added to our understanding of the functional anatomy of the human brain. An enthusiastic and able organizer, Herbert Jasper was responsible for many international conferences on brain science and worked tirelessly to develop international collaboration among investigators of the nervous system, being one of the founders of the International Brain Research Organization and the Society for Neuroscience. His prodigious contributions in basic and clinical research will be recognized by the world community of brain science for years to come.

A new epileptic seizure classification based exclusively on ictal semiology

Historically, seizure semiology was the main feature in the differential diagnosis of epileptic syndromes. With the development of clinical EEG, the definition of electroclinical complexes became an essential tool to define epileptic syndromes, particularly focal epileptic syndromes. Modern advances in diagnostic technology, particularly in neuroimaging and molecular biology, now permit better definitions of epileptic syndromes. At the same time detailed studies showed that there does not necessarily exist a one-to-one relationship between epileptic seizures or electroclinical complexes and epileptic syndromes. These developments call for the reintroduction of an epileptic seizure classification based exclusively on clinical semiology, similar to the seizure classifications which were used by neurologists before the introduction of the modern diagnostic methods. This classification of epileptic seizures should always be complemented by an epileptic syndrome classification based on all the available clinical information (clinical history, neurological exam, ictal semiology, EEG, anatomical and functional neuroimaging, etc.). Such an approach is more consistent with mainstream clinical neurology and would avoid the current confusion between the classification of epileptic seizures (which in the International Seizure Classification is actually a classification of electroclinical complexes) and the classification of epileptic syndromes.

Ambulatory EEG monitoring

Advances in computer technology offer increased capabilities for ambulatory EEG monitoring. The technical specifications of currently available ambulatory EEG machines reasonably approximate inpatient EEG equipment. However, the evolution of ambulatory EEG from 3-channel analog cassette recordings to reformatable 32-channel digital devices with computer-assisted spike and seizure detection raises several unresolved issues. Should patients with nondiagnostic routine EEG receive ambulatory EEG? Is ambulatory EEG as accurate for patients with unclear clinical diagnoses as inpatient video-EEG monitoring? If the diagnostic yield of ambulatory EEG is less than inpatient monitoring, do outpatient savings still make the technique cost-effective? This article reviews the development of ambulatory EEG and the investigations of its clinical utility. An evidence-based analysis explores the benefits and limitations of ambulatory EEG, and offers aspects of its use which require additional clinical research.

Common applications of electrophysiology (EEG) in the past and today: the technologist's view

The field of electroencephalography (EEG) has witnessed a dramatic development during the last decade. The electroencephalogram that had been principally used as a 'post-hoc' diagnostic procedure is now fully used as an 'on-line' monitor of neural function with its excellent temporal resolution. Neurophysiological monitoring in the operating room, neurological intensive care unit (ICU) and during endovascular procedures allows early identification of impending neurological deficits before irreversible neurological impairment. Long-term monitoring of scalp and synchronized video-EEG recordings and invasive (depth and subdural) electrode studies are well-established tools in the localization of the epileptogenic region for identification of potential candidates for surgery. The advent of digital EEG with digital storage and the ability to manipulate data with digital reformatting, filter and sensitivity changes has allowed us to maximize the information and reduce artifacts. These changes have revolutionized the way in which EEG is performed and interpreted.

The zero of potential

It is convenient to select a reference point for recording ECG potentials on the torso or EEG potentials on the scalp. The body is a bounded, insulated volume conductor. As such, it is meaningless to seek a point whose potential is at true zero. The choice of a particular reference, and hence the amplitude assigned to a contour, does not change in any way the biophysical information contained in the potential distribution. It does not in any way change the relation between source and potential, except for an additive constant of no physical significance. Standardization of a reference is useful for comparing, more directly, data from different laboratories. An agreed upon reference is necessary when a limited number of leads are used for diagnosis. In the case of the electrocardiogram, the generally agreed upon reference is the WCT. The issue of the zero of potential seems to arouse passions that may sometimes inhibit scientific discourse.