EEG ARTIFACTS

DR SRIRAMA ANJANEYULU

RESIDENT,NEUROLOGY

KING GEORGE HOSPITAL,VIZAG

Introduction

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

• EEG -highly sensitive recording device, easilyinterrupted by other electrical activity of veryhigh voltages .

• Some readily distinguished, others closelyresemble cerebral activity that theirinterpretation is taxing even to the mostexperienced eletroencephalographer.

CLASSIFICATION

Physiological : 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,circulatorpumps

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