Questions posted in the
Neurology and Neurosurgery Forum have been answered by doctors from The Cleveland Clinic Foundation.
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Subject: Re: What is background activity on an EEG? Topic Area: Neurology - GeneralPosted by Lyn on May 11, 1999 at 09:31:55Recently my 23 year old daughter had an EEG test because she had experienced migraines and occasional seizures (only when ill) since she was about six years old. She also experienced numbness in part of her lower leg (no tingling) which lasted nearly a month. The neuro gave her a thougough physical including bloodwork as well as a nerve conduction test, an MRI and a 45 minute EEG. Everything was normal but he said the backgound activity on the EEG was borderline, neither abnormal nor clearly normal. I have found a lot about EEG tests on the Internet, but no mention of background activity. My daughter asked the doctor to explain the term and what could cause it. His answer was that he couldn't explain it more than to say that it was activity in the background and that maybe migraines could cause it. Could you please tell me more about background activity, and what things can cause it? I would appreciate any information or direction as to where I can find some good information. Thanks for your help! Lyn
Posted by CCF Neuro[P] MD, RPS on May 11, 1999 at 11:12:55 Dear Lyn: Background activity on the EEG is the electrical activity of the brain that is "normally" seen in the awake patient. It is called alpha activity and its frequency is 8-12 Hertz. Actually, no one is really quit sure of the origin of this electrical activity but the 8-12 is found in normal subjects. This activity will go away with sleep, also in patients with structural lesions or acute or chronic insults. Usually, when we see abnormal background we think about encephopathy. But, if only the background is marginally low, it likely doesn't mean anything. I hope that this answers some of your questions. Sincerely, CCF Neuro[P] MD
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