![]() 9 When the studies were obtained and reviewed carefully, most of the misread patterns were simple fluctuations of sharply contoured background rhythms or fragmented alpha activity. 9–11 One-third of the patients later found to have PNES have had previous EEGs that were interpreted as epileptiform that contributed to the misdiagnosis. Multiple papers have revealed that many patients with non-epileptic disorders such as syncope and PNES have the incorrect diagnosis of epilepsy perpetuated by the misreading of benign EEG patterns. Accuracy in reading EEGs is critical in both identifying patients who have an increased risk of having epilepsy and avoiding the misdiagnosis of epilepsy in patients without epilepsy. 8 These are widely recognized today as non-epileptogenic. 6,7 Studies from the early years of EEG showed higher percentages, usually around 2–4%, because they included 6 and 14Hz positive spikes or six-persecond waves as epileptiform. 4,5 In adults, the percentage is much lower, probably less than 2%. In children, up to 6.8% will have true epileptiform discharges without clinical epilepsy when photic stimulation is used. 2,3 The electroencephalogram (EEG) can be both helpful and misleading in diagnosis. 1 Likewise, in pediatric epilepsy centers, 15–39% have non-epileptic paroxysmal events. ![]() Studies in tertiary epilepsy centers have shown that 30% of adult patients referred for intractable ‘epilepsy’ have non-epileptic events, chiefly psychogenic non-epileptic spells (PNES). Or, your doctor may ask you to stay overnight in a special EEG monitoring unit where your brain activity will be monitored continuously.The accurate diagnosis of epilepsy is difficult. You will be able to go about your normal routine as the EEG is being recorded. In addition to the electrodes, you will wear or carry a special recorder for up to 3 days. ![]() If your doctor needs to monitor your brain activity for a longer period, an ambulatory EEG will be ordered. You may be asked to sleep during the test.You may be asked to do certain things during the test, such as breathe fast and deeply for several minutes or look at a bright flashing light. This is because movement can change the results. You need to lie still during the test with your eyes closed.The machine changes the electrical signals into patterns that can be seen on a monitor or drawn on paper. ![]() The electrodes are connected by wires to a recording machine. The disks are held in place with a sticky paste. Flat metal disks called electrodes are placed all over your scalp.You lie on your back on a bed or in a reclining chair.The test is done by an electroencephalogram technologist in your doctor's office or at a hospital or laboratory. ![]()
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January 2023
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