OF THE USE OF BEAM, EEG AND PETT SCANS IN DETECTING BRAIN DISORDERS

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OF THE USE OF BEAM EEG AND PETT SCANS IN DETECTING BRAIN DISORDERS
OF THE USE OF BEAM EEG AND PETT SCANS IN DETECTING BRAIN DISORDERS

The human brain is not only one of natures greatest mysteries but also one of the most spectacular triumphs of evolution. This rather fascinating organ which gives the appearance of a single solid mass of flesh, tissue and membranes is packed with about ten billion nerve cells carefully enclosed in a specially designed bony compartment and entrusted with the task of controlling all the physiological and psychological processes connected with the human body. No wonder the structure and the working of the human brain have been the subject matter of intense speculation and systematic study.

Ever since the first electroencephalogram was taken by Hans Burger of Germany in 1924, doctors have been relying on the EEG lines (whose wavy patterns reflect the electrical activity of the brain) to draw inferences and conclusions regarding the thoughts, per­ceptions and directives from the brain to the various parts of the body.

However, doctors have been finding it increasingly difficult to interpret the information provided by the varying voltages and frequencies indicated in the EEG. The trouble is not that the EEG does not record enough data. The problem arises due to the fact that a physician is not able to make full use of it as the electrical noiseof the brain drowns out some significant messages given out. In other words, distortion prevents a proper appreciation of the evidence recorded.

However with the help of a technique known as BEAM (Brain Electrical Activity Mapping) involving high speed computers and sophisticated graphics, neurologists are begining to find their way through the distortion causing noise and producing the most useful and vivid images of the brain s electrical workings.

A large measure of credit for this new technology should go to a scientist in Boston in the United States whose BEAM machine transforms the output of the electroencephalograph into a colour contour map giving a picture of the electrical activity on the surface of the brain.

The equipment consists of a TV screen that displays the top view of the human brain with trapezoid-shaped ears and a triangular nose. Within the outline the EEG recordings are converted into sharply defined, often concentric patches of rich colours. The multicoloured patterns keep changing their shapes and outlines as the brain carries out its functions.

In the days before the BEAM machine was invented, a physician could only try to visualize in a rough manner this kind of image by examining the EEG tracings, whereas the BEAM machine enables a physician to actually see a topographic display of the brain which enhances the capacity of the electroencephalograph for diagnosing certain diseases such as epilepsy and brain tumour.

BEAM patterns can also help in pointing out aberrations in the waves that indicate an inability to read or other similar brain disorders. Scientists are hopeful of using BEAM to study mental illness, senility and even criminal behaviour.

It may, however, be noted that the BEAM technique does not add any new data to what the EEG furnishes. All that it does is to extract more information out of the minute electrical voltages that reach the scalp from the ten billion nerve cells underneath. The BEAM techniques has an advantage over other investigative processes, like Computerised Axial Tomography (CAT) scans which use powerful X-rays or Position Emission Transaxial Tomography (PETT) scans, which involve injection of a radioactive substance into the blood stream.

PETT scans (which were first made at the University of Pennsylvania in 1976) permit a probe of the brain without exploratory surgery while CAT cannot reveal more than what a surgeon’s knife can. PETT can reveal activity as well as structure, i.e. what is happening chemically inside the brain. In the latter procedure a radioactively tagged glucose-like chemical is introduced into the vein in the right arm. The glucose is consumed by the working brain cells after the substance enters the brain. PETT comes out with a computer map showing where exactly the chemical is being consumed.

If the region controlling emotional behaviour does not use much glucose indicating that it is relatively inactive (as in the case of a schizophrenic) then it will show up on the scan as a reddish brown patch. Doctors are now experimenting with PETT in diagnosing a variety of brain disorders.

PETT s two main drawbacks are it’s prohibitive cost —a single scan at present costs Rs 27000/00 in Hyderabad-and the fact that it depends on radiation from an injected radioactive substance. On other hand, the BEAM technique which is non-invasive in nature, involves only passive monitoring of the brain waves.

Its disadvantage, however, that it can obtain information only from the surface of the brain and the skull tends to muffle electrical signals. Scientists like to compare BEAM’s functioning with that of trying to analyse the conversation at a noisy party by listening through a wall or trying to find out where a stone had come from by merely looking at the distant ripples on the surface of a pond.

The analogy of a ripple is rather appropriate in the context of describing the BEAM technology in as much as its basic principle was initially adapted from a method originally conceived to locate the position of a submerged submarine. According to Peter Bartels, a mathematician at the University of Arizona, what the BEAM does is to pull out a signal that is virtually invisible and then display it in high contrast. (two other persons David Culver, a computer programmer who latter became a medical consultant, and Frank Duffy who had degrees in electrical engineering and mathematics, had also played a major role in designing the basic technology.)

Initial experiments done on victims of dyslexia, a disorder which to some extent affects a fifth of the school-going children in the United States and which is characterized by a reading disability, have yielded positive results.

A study involving thirteen normal children and eleven who were dyslexic revealed a consistent pattern of brain wave changes. Although many more experiments have to be conducted before a definite correlation can be established, doctors hope that very soon dyslexia can be spotted with a certain degree of accuracy in eight out of ten cases.

BEAM studies have yielded valuable data regarding dyslexia. In the EEGs of all patients having dyslexia there are indications of stronger alpha waves (indication of an inactive brain) in the sup­plementary motor region which plans complicated motor activity— a factor not previously associated with dyslexia. Duffy feels that BEAM would enable doctors to spot potential cases of dyslexia in children before they attend school and thus help in preventing pos­sible later psychological complications such as inferiority complex.

BEAM also seems to have a potential role in adding to the effectiveness of another aspect of electroencephalography known as evoked potentials. In this procedure the electrical reaction of the brain to a sudden stimulus, such as a flash of light, an abrupt click or a spoken word, is studied. The normal functioning of the brain would drown out response to any single stimulus; so the flash of light repeated hundreds of times and the results averaged so that the background noiseis eliminated.

BEAM then takes the average activity of the brain during the half second after each flash and slices it into 128 individual pictures, each one exposed for an extremely short interval. A display of these images in rapid sequence produces a movie of the brains response; waves of two different colours, red for positive and blue for negative wash from one side of the brain to another.

This kind of evoked potential movie was used to analyse the picture of the brain in a 33-year old factory foreman (the EEG appeared normal but on BEAM the wave form indicated an area of overly excitable brain tissue). A CAT scan was used later to locate the tumour. Scientists are hopeful of finding new possibilities for the use of BEAM technology. Some potential uses are:

  • Indications of early signs of epilepsy.
  • Distinctive patterns that could reveal indications of presence of manic depressive disorders, schizophrenia and Alzheimers disease.
  • Prediction of possibility of mental disorders (in later life) in new born babies.
  • Study of BEAM recordings during dreams which could throw light on the brains activity during sleep.
  • Studies of areas of the brain that would enable doctors to identify sociopathic personalities.

Rapid Strides

While the potential of BEAM has stimulated the imagination of doctors all over the world, Japan was one of the first countries to make rapid strides in this field; one Japanese company made a BE AM- like machine called topographical spectrum analyser. Harvard University was also planning to use the new technology in a big way.

When Macbeth driven to depths of despair by his wifes deteriorating mental state had cried out in agony to his doctor:

Canst thou not minister to a mind diseased Pluck from the memory a rooted sorrow Raze out the written troubles of the brain.

The doctors had suggested thatthe patient must minister to himself, hinting that unless Lady Macbeth extended her cooperation nothing could be done. Though such an approach is relevant even today in treating certain kinds of mental disorders, the BEAM method and other such modern scientific techniques would certainly enable physicians to have a better insight into the mysterious disorders and ailments that continue to plague the human brain.

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