Manual Interpretation of EEGs: A Machine Learning Perspective Christian Ward, Dr. Iyad Obeid and Dr. Joseph Picone Neural Engineering Data Consortium College of Engineering Temple University Philadelphia, Pennsylvania, USA

NEDC TutorialNovember 8, Abstract The goal of this presentation is to describe, from a machine learning perspective, how an electroencephalogram (EEG) is manually interpreted. This presentation is not meant to be a comprehensive tutorial on diagnosing illnesses from EEG data. Instead, it attempts to document what physicians look for in the signals, and to describe these in terms that can be translated into signal processing and machine learning code. An extracranial EEG measures brain function indirectly through electrodes placed in an array on the scalp. Events of interest to physicians originate as nerve impulses deep in the brain. By the time these signals reach the scalp they are heavily filtered and spatially dispersed. Interpreting the underlying pathology or determining the diagnosis is an art because (1) the transduced signals at the scalp are very noisy due to their relatively low voltage (microvolts) and (2) the artifacts in the waveform that correlate with a pathology are context dependent (knowledge of the surrounding behavior is important). In this presentation, we review what diseases are diagnosed using EEGs, what artifacts are used to identify these diseases, and what properties of the signal correlate with these artifacts. Both time domain (e.g., waveform shapes) and frequency domain behavior (e.g., fundamental frequency) play an important role in identifying these artifacts.

NEDC TutorialNovember 8, A technician administers a 30−minute recording session. An EEG specialist (neurologist) interprets the EEG. An EEG report is generated with the diagnosis. Patient is billed once the report is coded and signed off. Manual Interpretation of EEGs

NEDC TutorialNovember 8, positions are defined as potential electrode locations: 24 to 36 channels are commonly used; 64 and 128-channel EEGs are used in research 10/20 configuration (black): yields 19 channels plus several reference channels (typically the ears and forehead) 10/10 configuration (gray): typically doubles the number of channels Differential voltages are typically measured between a sensor and an ear (e.g., F3-T9) Common reference points include the ears (T9 and T10), the nose (e.g., ???) and the heart/respiratory system (e.g., EKG1 and EKG2) Signal Transduction

NEDC TutorialNovember 8, Baseline EEG: 10/20 Configuration In a 10/20 configuration, 21 channels are included in a typical EDF file. The channel labels shown to the right are what appear in the EDF file as channel labels. EEGs with more electrodes add additional channels. However, these 21 channels are typically the first 21 channels in the file. The TUH EEG Corpus contains data collected with a minimum of 24 channels (21 signals plus three annotation channels) and 36 channels. Our baseline experiments focus only on the first 21 channels.

NEDC TutorialNovember 8, Epilepsy: a neurological disorder marked by sudden recurrent episodes of sensory disturbance, loss of consciousness, or convulsions. Stroke: a sudden disabling attack or loss of consciousness caused by an interruption in the flow of blood to the brain. Posterior Reversible Encephalopathy Syndrome (PRES): characterized by headache, confusion, seizures and visual loss. It may occur due to a number of causes, predominantly malignant hypertension, eclampsia and some medical treatments. Middle Cerebral Artery (MCA) Infarct: obstruction of one of the three major paired arteries that supply blood to the cerebrum. Other uses of EEGs include diagnosis of Alzheimer's disease, certain psychoses, and sleep disorders (narcolepsy). The EEG may also be used to determine the overall electrical activity of the brain, which is used to evaluate trauma, drug intoxication, or brain damage. The EEG may also be used to monitor blood flow in the brain during surgical procedures. The EEG cannot be used to measure intelligence Common Diseases Diagnosed With An EEG

NEDC TutorialNovember 8, Background: models all other artifacts not included in the above categories. Though there are some variations in these signals for infants whose brains are not fully developed, the basic composition of these signals is relatively age and subject invariant. Spike and Wave: … describe… … ………………… GPED Triphasic: … describe … … PLED: … describe … … Eye Blink: … describe why …… … Most Significant Primitives

NEDC TutorialNovember 8, Other Primitives NameAcronymDefinition Electrographic SeizureN/ARhythmic discharge or spike and wave pattern with definite evolution in frequency, location or morphology lasting at least 10 sec Periodic Epileptiform dischargesPEDRepetitive sharp waves, spikes, or sharply contoured waves at regular or nearly regular intervals and without clear evolution in frequency or location Perioidic Lateralized Epileptiform discharges PLEDConsistently lateralized PED Generalized PEDGPEDBilateral and synchronous PED with no consistent lateralization Bilateral PLEDBiPLEDPLED occurring bilaterally, but independently and sychronously Triphasic WavesN/AGeneralized periodic sharp waves or sharply contoured delta waves with triphasic morphology, at 1-3 Hz, with/without anterior-posterior or posterior-anterior lag Frontal Intermittent Rhythmic Delta Activity FIRDAModerate- to high-voltage monorhythmic and sinusoidal 1- 3 Hz activity seen bilaterally, maximal in anterior leads, no evolution

NEDC TutorialNovember 8, Classification of Diseases NamePrimary Marker(s) Secondary Marker(s) Epilepsy Stroke PRES MCA Infarct

NEDC TutorialNovember 8, Summary and Future Work Summary: Deep… For… NEDC… Future Work: Three… Two…

NEDC TutorialNovember 8, Brief Bibliography of Relevant Documentation [1]Tatum, W., Husain, A., Benbadis, S., & Kaplan, P. (2007). Handbook of EEG Interpretation. (Kirsch, Ed.) (p. 276). New York City, New York, USA: Demos Medical Publishing. [2]Wulsin, D. F., Gupta, J. R., Mani, R., Blanco, J. A., & Litt, B. (2011). Modeling electroencephalography waveforms with semi-supervised deep belief nets: fast classification and anomaly measurement. Journal of Neural Engineering, 8(3), [3]Jurcak, V., Tsuzuki, D., & Dan, I. (2007). 10/20, 10/10, and 10/5 systems revisited: Their validity as relative head-surface-based positioning systems. NeuroImage, 34(4), 1600–1611. [4]Pavlick, E. (2013). EEG Simulation. School of Engineering and Applied Sciences, University of Pennsylvania. Retrieved November 21, 2013, from [5]Claassen, J., Mayer, S. A., Kowalski, R. G., Emerson, R. G., & Hirsch, L. J. (2004). Detection of electrographic seizures with continuous EEG monitoring in critically ill patients. Neurology, 62(10), 1743–1748.