EEG ARTIFACTS

DR SRIRAMA ANJANEYULURESIDENT,NEUROLOGY

KING GEORGE HOSPITAL,VIZAG

Introduction

• Unwanted electrical activity arising from different sources, other than cerebral activity.

• EEG -highly sensitive recording device, easily interrupted by other electrical activity of very high voltages .

• Some readily distinguished, others closely resemble cerebral activity that their interpretation is taxing even to the most experienced eletroencephalographer.

CLASSIFICATIONPhysiological : from patient’s own,generator sources other

than the brain. – Eye movement

– Muscle ( EMG ) – Movement – Cardiogenic – Sweat

• Extraphysiological : Externally generated e.g. instrumental & environmental.

- IV drip, -ventilator

Cardiac artifacts

• ECG artifact-poorly formed QRS complex , left temporal leads.(BETS,IED,PLEDS)

• Ballistocardiographic-movement of head or body with cardiac contractions.

• Pacemaker-generalized across scalp , shorter duration.

• Pulse-electrode resting on vessel , frontal and temporal leads , follows ECG artifact.

Cardiac artifact

Cardiac artifact

Pacemaker artifact

Pulse artifact

ELECTRODE ARTIFACT-TYPES

• Two forms-brief transients limited to one electrode , low frequency rhythms across scalp region.

• Electrode pop-spontaneous discharges.• Electrode contact-poor contact.• Electrode/lead movement.• Perspiration-undulating waves >2 sec.• Salt bridge-lower amplitude.• Movement artifact.

Electrode pop

Electrode Movement artifact

Lead movement

Sweat artifact

Salt bridge artifact

EXTERNAL DEVICE ARTIFACT

• 50/60 HZ ambient electrical noise• Intravenous drip• Electrical devices-intravenous pumps,

telephone• Mechanical artifacts-ventilators,circulator

pumps

60 Hz artifact

IV drip

Electrical motor

Mechanical ventilator

Circulatory pump

MUSCLE ARTIFACT

• Glossokinetic• Photomyogenic• Surface EMG

Muscle artifact

Muscle and movement artifact

EMG artifact

Photomyogenic artifact

OCULAR ARTIFACT

• Blink• Eye flutter• Lateral gaze• Slow/rowing eye movements• Lateral rectus spike

Blink artifact

Eye flutter artifact

Eye flutter artifact

Lateral eye movement

Slow roving eye movement

Lateral rectus spike

Thank you