TELEMETRY (making measurements at a distance) is not new. The electrical activity of the heart was telemetered by FM transmission in 1943. The technical achievements of the past 2 decades, however, have greatly advanced this science. Miniaturization of amplifiers and transmitters now offers a possible way of monitoring biological phenomena in free-moving patients in the hospital environment.
The following application in clinical neurology is an example. Neurologists frequently have patients whose symptoms suggest a seizure disorder, but whose routine electroencephalograms have been repeatedly normal. Activation techniques (hyperventilation, sleep, photic stimulation, pentylenetetrazol, and so forth) also may fail to bring out the abnormalities. Usually, patients cannot be studied electroencephalographically for prolonged periods of up to 24 hours or for days on end. Telemetry, by permitting freedom of movement, facilitates prolonged recording sessions. It also may find clinical application in patients with frequent, very brief, petit mal attacks. In order to evaluate