Scanning the Brain

Electroencephalography (EEG)

Electroencephalography (EEG) measures brainwaves – the electrical patterns created by the rhythmic oscillations of neurons. These waves show characteristic changes according to the type of brain activity that is going on. EEG measures these waves by picking up signals via electrodes placed in the skull. The latest version of EEG takes readings from dozens of different spots and compares them, building up the picture of varying activity across the brain. Brain Mapping with EEG often uses Event-Related potentials (ERPs), which simply means that an electrical peak (potential) is related to particular stimulus like a word or a touch.
The QEEG reads a patient's real-time electro-cortical activity and compares it to a normative database to detect any dysfunctions. By comparing the acquired data to a normative database, the QEEG is able to detect minute changes in brain activity that other methods might not be able to detect. The QEEG also enables the discrimination between mechanical injury and diffuse axonal injury.

Brain waves occur at various frequencies, that is, some are quick, some quite slow. The classic names for these "EEG bands" are delta, theta, alpha and beta. The dominant wave pattern you see above is alpha; these waves happen between 8 and 13 times per second, or 8-13 Hertz (Hz). Alpha represents a sort of "idle" state, or "ready but not doing much" state and is normally fairly large over the back third of the brain when the eyes are closed and when you are awake. Alpha disappears when we either get mentally busy (e.g., open the eyes, start doing intense mental work even eyes closed) or when we become drowsy. Thus the presence of alpha can show the presence of an awake, resting state. If it is present at a fairly high voltage when the eyes are open, this would usually indicate an inattentive, day dreamy state. In fact we often see this sign in adolescents and adults with attentional difficulties.

When we get mentally busy and engaged, we should see alpha "block," or reduce significantly in size. In its place we see mostly smaller, quicker "beta" waves. The beta family of waves happen at frequencies from 16-40 Hz or higher.

Delta and theta waves are relatively slow. Delta is usually defined as waves occurring from 1-4 times per second (1-4 Hz). Theta occurs at 4-7 Hz. During drowsiness, first alpha disappears, then the size of theta waves begins to increase. As sleep begins, theta waves get quite large, then become mixed with and eventually give way to slower delta waves.

The presence of delta and theta waves in the waking, eyes open EEG is normal, but only if the waves are fairly small. High amplitude slow waves can be signs of various neurological and psychological problems, ranging from epilepsy to ADHD.
 

Magnetic Resonance Imaging (MRI)
Magnetic Resonance Imaging (MRI, sometimes called nuclear magnetic resonance imaging – NMR / NMRI) works by aligning atomic particles in the body tissues by magnetism, then bombarding them with radio waves. This causes the particles to give off radio signals that differ according to what sort of tissue is present. A sophisticated software system called Computerized Tomography (CT) converts this information into a three-dimensional picture of any part of the body. A brain scan taken this way looks like grayish X-Ray, with different, clearly delineated types of tissue.
 

Functional MRI (fMRI)
Functional MRI (fMRI) elaborates this basic anatomical picture by adding to it the areas of greatest brain activity. Neuronal firing is fuelled by glucose and oxygen, which are carried in blood. When an area of the brain is fired up, these substances flow towards it, and fMRI shows up the places where there is most oxygen. The latest scanners can produce four images every second. The brain takes about half a second to react to a stimulus, so this rapid scanning technique can clearly show the ebb and flows of activity in different parts of the brain as it reacts to various stimuli or undertakes different tasks. FMRI is proving to be the most rewarding of scanning techniques, but it is phenomenally expensive and brain wrappers often have to share a machine with clinicians who have more pressing claims to it. For this reason a a lot of experimental work is still done by the older technique.

Positron Emission Topography (PET)

Positron Emission Topography (PET) achieves a similar end result to fMRI – it identifies the brain areas that are working hard by measuring their fuel intake. The pictures produced by PET are very clear (and strikingly pretty) but they cannot achieve the same fine resolution as fMRI. The technique also has a serious drawback in that it requires an injection into the blood stream of a radioactive marker. The dose of radioactivity given in each scan is tiny but, for safety, no one person is generally allowed to have more than one scanning session (usually twelve scans) a year.

Near Infra-red Spectroscopy (NIRS)

Near-Infra Red Spectroscopy (NIRS) also produces an image based on the amount of fuel being gobbled at any moment by each part of the brain. It works by beaming low-level light waves into the brain and measuring the varying amount that is reflected from each area. NIRS is cheaper than fMRI and does not use radioactivity but it cannot (yet) give a clear picture of what happens in the deepest regions of the brain.

Magnetoencephalography (MEG)

Magneto encephalography (MEG) is similar to EEG in that it picks up signals from neuronal oscillation, but it does it on by homing in on the tiny magnetic pulse they give off rather than the electric field. It still has teething problems: the signals, for example, are weak and easily masked by interference. Yet it has enormous potential because it is faster than other scanning techniques and can therefore chart changes in brain activity more accurately than fMRI or PET.
 

SPECT

The brain is involved in everything we do. How we think, how we feel, how we act, and how well we get along with other people is related to the moment-by-moment functioning of the brain. When the brain works right, people tend to work right. When the brain is troubled, people tend to struggle being their best selves.

If we agree that mental disorders and difficult behaviors may be related to functional problems in the brain, and that brain SPECT imaging is a reliable measure of regional cerebral blood flow and thus activity patterns (1), then it follows that we should take advantage of this powerful tool when faced with complex situations or with patients unresponsive to treatment? How can we fully evaluate the cause for mental illness unless we look at brain function -- otherwise we are left to deduce or guess or assume what may be going on in the brain
 

Multi-modal Imaging

Multi Modal Imaging, which is becoming increasingly popular, combines two or more of these techniques to give a more complete picture.

The American Academy of Pediatrics, in its position statement on the use of medication for A.D.H.D., emphasizes that drugs should not be the only way a child’s A.D.H.D. is treated. The Committee on Drugs of the American Academy of Pediatrics developed the following position statement: “Medication for children with A.D.D. should never be used as an isolated treatment. Proper classroom placement, physical education programs, behavior modification, counseling, and provision of structure should be used before a trial of pharmaco-therapy is attempted.” Even the manufacturer of Ritalin has stressed this point.

Management of A.D.D. must always use a multimodal approach, which means that a variety of the management techniques discussed in this should be tried either before or in addition to medication. However, most of the alternatives to drugs take weeks, months, or even years to show results. With medication, some results can be seen in a matter of days or weeks, depending on which drug is used. Time is important to a developing child, who cannot afford to spend years waiting for behavior modification and learning strategies to gradually have their effect. For this reason, most professionals feel that children who’s A.D.H.D. is interfering with learning and development should be given medication along with other management techniques (but never instead of other tools). Once the child’s behavior and attention are improving and the no medication strategies seem to be working, the goal can be to lower the dosage of the medication, stop it altogether, or use the medication only only in as-needed situations. Having a lot of behavior and learning strategies piled on the child (and parents) is a heavy cross to bear over a long time. For some families, a short-term course of medication can lighten the load.

The best behavior modification can learning strategies in the world won’t wok if the child can’t concentrate. In our experience, medications may allow the behavioral and learning strategies to work sooner and better. They provide a window of opportunity for making noticeable progress. Once your child sees success in one area of his behavior or learning, this is likely to carry over into his other problem areas. The goal is to reduce the medication dosage and discontinue it as soon as possible, but only after it has helped other strategies work better.
 

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