EEG waves were too small to be transmitted over long distances .
A first-year neurology resident is often intimidated by the complexity of interpreting the EEG . Unlike the EKG which has a limited number of waveforms to identify , making sense of EEG is a daunting task for the uninitiated . At the time of my initiation into EEG interpretation , the recording was done on special fan-fold paper , each page containing 10 seconds of data using 8 channels of ink recording ( Figure 2 : the author using an 8 channel EEG recorder in the 70s ). I vividly remember my first day of rotation at the EEG lab . There were several recordings from the previous day , which the EEG fellow had been getting ready , via handwritten reports , for presentation to the professor . I was impressed with the speed at which the professor flipped through the recordings , pointing out the normal and abnormal patterns , taking hardly 10 minutes for each study . One recording particularly caught my attention ; the professor made a diagnosis of Creutzfeldt-Jakob disease , just from the tracing - without any clue from the clinical history ! It became obvious to me that I must learn to visualize the entire page with 8 or 16 rows of data at once and practice speed reading techniques to interpret a 30-minute recording within 10 minutes as the professor did . Thankfully , when computers made their foray into medicine later , they brought drastic improvements , making interpretation more interactive ( ability to change the sensitivity , time base , filters and above all , the montage ). The advent of long-term recording ( lasting several days ) and continuous monitoring of EEG became possible , a huge leap forward . Then , instead of the routine EEG with 32 electrodes , we began to use a much larger number of electrodes to get more detailed recording , covering a much larger area of brain . However , we can still cover only a fraction of the total surface area of cerebral cortex , which is estimated to be about 2,500 cm . 2 The data to be analyzed has become huge and much more labor-intensive , forcing one to look at other options . Studies are showing that artificial intelligence ( AI ) through machine learning with the unique ability to quickly analyze massive data can indeed accurately interpret EEGs . 3 This is likely to be the wave of the future .
While EEG is an essential diagnostic tool in many neurological disorders , its major role is in the diagnosis and management of seizure disorders . The use of brain electric activity to precisely localize and resect the epileptic focus was pioneered by Herbert Jasper and Wilder Penfield in the 1940s and 50s at the Montreal Neurological Institute ( MNI ). Since then , surgical management of epilepsy has been developing rapidly and is offered in many centers worldwide . When I was asked to direct the epilepsy clinic at General Hospital ( ULH ) several decades ago , the first step was to develop a state of the art “ seizure monitoring ” facility for simultaneous EEG and video monitoring . The technique allowed identification of the phenotype of the seizures as well as the location of the origin of the abnormal brain electrical activity . Neurosurgery chair Dr . Henry Garretson had been trained at the
Montreal Neurological Institute by Dr . Wilder Graves Penfield and was eager to perform surgery for epileptic patients . The surgical procedure involved electrocortcography , recording EEG directly from the cerebral cortex to map out the area of the seizure focus precisely ( my role ). This was followed by functional mapping of the area ( applying electric stimulation to the exposed cortex to localize and protect the motor and speech areas ). Excision of the epileptogenic focus was the next step . Dr . Garretson and I felt amply rewarded when we could select a patient with incapacitating , medically refractory seizures and make him / her seizure-free and back to a productive life . Although initially only anterior temporal lobectomy was performed , the advent of subdural recordings to localize the seizure focus and perform functional localization prior to the surgery , extended the potential areas of resection . The technique of stereo-encephalography has further improved the precision of detection and localization of seizure focus .
By now many of you may be wondering about the dream of Hans Berger of unravelling the neurologic basis of telepathy . While telepathy has remained an attractive theme of several fictions , movies and sitcoms , more than 50 at the last count , most scientists do not accept its existence . Nevertheless , some researchers are still pursuing Berger ’ s dream as evidenced by recent studies using functional MRI . 4 Perhaps some form of “ thought transfer ” may become a reality with further progress in brain computer interface with ultrasensitive electrodes that can pick up brain electrical activity from vast areas of the brain .
Let me conclude with one of my favorite quotes from Francis Crick , the 1962 Nobel prize winner for identification of structure of DNA :
“ There is no scientific study more vital to man than the study of his own brain . Our entire view of the universe depends on it .”
References
1
Hass L F . Hans Berger ( 1873-1941 ), Richard Caton ( 1842-1926 ), and electroencephalography . J Neurol Neurosurg Psych 2003 ; 74:9
2
Adrian ED , Matthews BHC . The interpretation of potential waves in the cortex . J Physiol 1934 ; 81 ( 4 ): 440-471 .
3
Tveit J et al . Automated interpretation of clinical EEG using artificial intelligence . JAMA Neurol . 2023 ; 80 ( 8 ): 805-812
4
Venkatasubramanian G . et al . Investigating paranormal phenomena : Functional brain imaging of telepathy . Int J Yoga . 2008 . 1 ( 2 ): 66-71 .
Dr . Iyer practices at the Neurodiagnostic Center of Louisville and is a retired professor of neurology at the University of Louisville School of Medicine .
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