| Would you believe that a brain-test invented in 1924 | | | | Fortunately, for purposes of diagnosis this is not |
| can detect abnormalities invisible to the | | | | usually necessary. Tell-tale changes in brain-waves are |
| latest-generation MRI scanner? The test in question is | | | | often present during the periods between |
| the electroencephalogram or brain-wave test, and for | | | | attacks-while the patient feels normal-that can reveal |
| certain medical conditions it is the key to accurate | | | | a tendency to epilepsy and even identify specific |
| diagnosis. | | | | sub-types. |
| In this era of rapidly developing technology for | | | | Two other common uses for EEG testing are for |
| medical imaging, one test that might seem downright | | | | assessment of confusional states and sleeping |
| old-fashioned is an electroencephalogram (EEG) or | | | | disorders. |
| brain-wave test. But by its very nature, the EEG test | | | | In people with confusion or memory loss, an EEG can |
| will continue to occupy a valuable niche in medical | | | | show different patterns depending on the cause. |
| diagnosis that brain-imaging tests-like CT scans and | | | | When confusion is caused by a depressed mood, the |
| MRI scans-will never fill. | | | | EEG remains normal. When confusion is caused by a |
| Rather than making pictures of the brain's anatomy, | | | | degenerative dementia like Alzheimer's disease or by |
| EEGs evaluate the brain's physiology. So while imaging | | | | a metabolic condition like a drug-overdose, the brain's |
| tests won't replace electroencephalograms, EEGs | | | | rhythms become slower. |
| won't replace imaging tests, either. The testing | | | | For evaluation of sleeping problems, an EEG is just |
| methods look at the brain from completely different | | | | one component of a battery of recording systems. |
| points of view, each valuable in its own way. | | | | Through concurrent monitoring of other biological |
| Broken into its parts, the term electroencephalogram | | | | processes-like breathing, blood-oxygenation, |
| means "electrical brain recording."Hans Berger, a | | | | heartbeat, muscle activity and eye |
| German scientist, got the ball rolling in 1924 with the | | | | movements-conditions such as narcolepsy and |
| first recordings of human brain-waves. Since then, the | | | | obstructive sleep apnea can be diagnosed. |
| basic principles of recording EEGs have remained the | | | | So what can you expect if your doctor refers you |
| same, but the electronics have gotten better-and | | | | for an EEG study? In many cases, you won't need to |
| smaller. In an EEG recording, tiny voltage-fluctuations | | | | make any special preparations for the test, but in |
| from the brain are picked up by a standard array of | | | | cases where epilepsy is under consideration, you |
| metal disks attached to the scalp and are then | | | | might be asked to stay awake for much of the |
| amplified electronically in order to create a permanent | | | | preceding night. Sleep-deprivation increases the |
| recording. | | | | likelihood of recording a seizure-related abnormality in |
| If you are old enough, you might remember the | | | | patients who have them. You are usually allowed to |
| 1960s fascination with alpha waves which people tried | | | | eat before the test. |
| to enhance via biofeedback devices. Alpha waves are | | | | The testing-session lasts about two hours, though |
| rhythmic brain-signals oscillating between 8 and 13 | | | | can be longer, especially if a sleeping problem is being |
| times per second that can be measured from the | | | | evaluated. The EEG technologist uses much of the |
| back of the head during quiet wakefulness. Additional | | | | testing-session to attach about two dozen metal-disk |
| voltage-rhythms encountered during clinical recordings | | | | electrodes to the scalp in standardized locations, and |
| include theta and delta waves that oscillate more | | | | then to test the electrical characteristics of each |
| slowly than alpha waves, and beta waves that | | | | electrode to ensure that good connections have |
| oscillate more rapidly. All four rhythms can be seen in | | | | been made.Once the electrodes are in place the |
| normal states of alertness, drowsiness or sleep, and | | | | recording session can begin. For most of the |
| should be the same on both sides of the brain. | | | | recording you lie quietly with your eyes closed. The |
| The premier use of EEGs is to evaluate people with | | | | technologist measures the brain-waves during quiet |
| known or suspected epilepsy (seizure disorders). | | | | wakefulness, and then if you fall asleep, that is |
| Seizures are highly electrical events in the brain that | | | | recorded, too. In additional parts of the test, you |
| cause temporary alterations in the patient's | | | | might be asked to breathe rapidly and deeply for |
| consciousness, perceptions or behavior. In healthy | | | | about three minutes (useful in detecting "absence" or |
| circumstances, the brain's approximately 20 billion | | | | "petit mal" epilepsy) or to watch flashing lights (useful |
| brain cells perpetually signal each other via electrical | | | | in detecting certain other kinds of epilepsy). Then the |
| impulses. Collectively, these impulses traveling among | | | | electrodes are disconnected and you go home. |
| networks of brain-cells are the means by which the | | | | A physician subsequently reads the recording and |
| brain performs its functions-like perceiving, pondering, | | | | makes a report. The report includes a description of |
| remembering, calculating and deciding. A poetic | | | | the observed rhythms of brain-waves, details of any |
| scientist described the brain and its normal functioning | | | | detected abnormalities and comments about their |
| as "an enchanted loom where millions of flashing | | | | possible significance. Your own doctor uses this |
| shuttles weave a dissolving pattern, always a | | | | report along with what else is known about your |
| meaningful pattern though never an abiding one; a | | | | condition to make a diagnosis. |
| shifting harmony of subpatterns." | | | | If you need an EEG, the good news is that the test |
| But in epileptic attacks, salvo upon salvo of excessive | | | | is not painful. No needles are involved. There is no |
| discharges overwhelm the brain's circuits and disrupt | | | | need to shave or otherwise remove hair. The bad |
| their normal functions. Suddenly, the enchanted loom's | | | | news is that the adhesive used to attach the |
| patterns are no longer meaningful or harmonious. A | | | | electrodes to your scalp can take a day or two to |
| seizure-in-progress is readily detected by an EEG | | | | scrub out, and might require mineral oil to remove. |
| recording. However, most patients under evaluation | | | | Beauty-shop treatments should be postponed until |
| for seizures don't oblige the doctor by having an | | | | after the EEG appointment; the hair-dresser's efforts |
| attack during a typical 30-90 minute recording session. | | | | will be ruined if the EEG comes second. |