ARTIFACTS Flashcards
WHAT TYPE OF MONTAGE?
BIPOLAR
WHAT ARTIFACT IS SEEN?
Pulse artifact mimicking PLEDs at the T6 derivation. Note the 1:1 relationship to the EKG and field limited to a single electrode.
WHAT ARTIFACT IS SEEN
Eye movement monitors demonstrating the in-phase cerebral origin of the diffusely slow background in this awake patient, and the out-of-phase movement of the eye blink artifacts during seconds 3 and 8.
Normally, the eye functions as an electrical dipole with a relative positivity of the cornea compared to the retina.
With an eye blink, the cornea rolls up with resultant positivity in the FP1/2 electrodes relative to the F3/4 electrodes and creates a downward deflection during the normal Bell’s phenomenon.
WHAT ARTIFACT IS SEEN
Artifact from three horizontal eye movements (looking left) followed by two vertical eye blinks.
During drowsiness, slow rolling (lateral) eye movements are similarly helpful. Lateral eye movements are usually easily recognized because they create phase reversals in the anterior temporal derivations that are of opposite polarity on opposite sides of the scalp EEG.
THIS IS AN ARTIFACT. BUT WHAT ABNORMALITY DOES IT MIMIC?
Eye movement monitors confirming a vertical eye flutter artifact with infraorbital electrodes (EOGs) during intermittent photic stimulation (IPS) to differentiate an artifact from frontal intermittent rhythmic delta activity
(FIRDA).
WHAT RESPONSE IS SHOWN
A photomyoclonic response during intermittent photic stimulation. Notice the spike-and-wave artifact created in the frontopolar channels.
The photomyoclonic response is an extracerebral response obtained from the frontalis muscles of the scalp. Contraction of the anterior muscles of the scalp produce EMG artifacts that vary from single to sustained myogenic potentials
WHAT ARTIFACTS ARE SHOWN PROMINENT DURING REM SLEEP?
Prominent lateral rectus spikes during rapid eye movement (REM) sleep. Spikes occur with rapid eye movements to the left, right, left, and right in the 4th to 6th second.
Each rapid eye movement is associated with a positive potential represented by a phase reversal on eye deviation to the side of the lateral rectus contracting
WHAT POTENTIALS ARE SHOWN?
ALSO SEEN IN TENSE INDIVIDUALS
Muscle artifact at T4 manifests as repetitive single myogenic potentials. Oz has continuous single electrode artifact, and a bifrontal burst of muscle artifact is seen in second 3 to 4. Note the 6-Hz positive bursts in the 8th second. Filter settings are 1 to 70 Hz.
WHAT MYOGENIC ARTIFACT IS SEEN?
A chewing artifact seen at regular 1- to 2-second intervals. Note the continuous myogenic artifact in the bitemporal regions.
Associated “slow” potentials during chewing reflect associated swallowing movements created by the tongue.
WHAT IS SHOWN?
Single electrode artifact at T5.
Potentials that are confined to a single electrode derivation are suspicious for a single (or common electrode in average/linked montages) electrode artifact
IS THIS AN EPILEPTIFROM ACTIVITY?
NO
Single electrode artifact at F7 mimicking a sharp wave.
WHAT KIND OF ARTIFACT?
60-cycle artifact is a function of the circuitry of the amplifiers and common mode rejection when electrode impedances are unequal. The frequency of an electrical line is represented in the EEG usually when poor electrode impedances produce a mismatch
WHAT HAS BEEN APPLIED IN THIS 60HZ ARTIFACT?
A 60-Hz artifact after notched filter application
WHAT ARTIFACT IS SHOWN?
A sphenoidal artifact that appears as a temporal sharp wave. Note the absence of a lateral field in the left temporal chain
AN INTUBATED PATIENT WAS BROUGHT TO THE EEG. WHAT KIND OF ARTIFACT?
A mechanical artifact induced by CPAP in a comatose patient in the ICU. Note the alternating polarity of the mechanical artifact and low voltage.
WHAT ARTIFACT IS SHOWN?
A telephone ring artifact during in-patient long-term video-
EEG monitoring.
