Differentiate causes of the increasing fast activity
Feature Muscle artifacts/60 Hz
+HFF
Breach effect Medication effect Paroxysmal fast activity
Cause Setting lower HFF (ie from
70 to 35) may cause higher
frequency artifacts to look
like beta activities
Burr Hole, skull defect Drug withdrawal: GABA agonist -
Benzodiazepine, Barbiturate,
Alcohol.
Overdosage of stimulant:
Amphetamine, cocaine
Interictal activity -
commonly found in LGS
Mechanism Muscle activities in the face
and mouth area.
Poor impedance, improper
ground scalp electrode ->
60Hz
Normal background with
fewer barriers: increased
amplitude of every activity,
and appears more hidden
low amplitude beta due to
lower impedance
-GABA agonist -rebound -
Hyperexcitability from depressant
withdrawal.
-Hyperexcited from a stimulant
-Underlying neuropsychiatric brain
It shares mechanisms with
the low amplitude fast activity
at the onset of tonic seizure-
reflecting rapid
hypersynchronization
EEG Pattern Frontal-temporal
dominant for muscle
Single channel for 60 Hz
Focal/lateralized -skull
defect site, increases beta
power the most, and every
activity in the background
also increases power &
spikier (apiculate)
Generalized Increase beta -> make
other activities apiculate.
Generalized ‘rhythmic’ 15-
35 Hz follow with slow activity
usually found in NREM esp N2
– DDx from excessive spindle
found in ADHD
EEG
example
