ABNORMAL EEG PATTERNS. BY SYED IRSHAD MURTAZA

1. Abnormal EEG Patterns
(AEPs)
BY:
Syed Irshad Murtaza
Neurophysiology Trainee
Technologist
AKUH. D. 8-03-2012

2. • Definition:
Any activity which does not correlate with the age
and state of the patient.
Abnormality could be of the following two main
types of activity.
1. Non epileptiform Abnormal pattern
2. Epileptiform Pattern

3. 1. Non Epileptiform Abnormal Pattern
Non epileptiform abnormal pattern consists of the
following types.
1. Slow waves
2. Asymmetry (Amplitudes & Frequency)
1. Slow waves
Slow waves are further divided into two types
Focal slow waves
Diffuse slowing

4. Slow waves
1-focal slowing :
Focal slowing means if slowing is restricted to only one
hemisphere or specific region .
The most prominent focal slowing is delta activity which
ranges 0.5 – 3.5 Hz.
Focal slowing may be continuous or intermittent.
Continuous focal delta slowing is usually due to localized
structural lesion (e.g tumor, stroke, abscess)
Intermittent focal polyrhythmic delta slowing is non specific
and could be due to migraine, trauma, post-ictal
dysfunction etc.

6. Diffuse slowing:
Diffuse slowing/generalized slowing means
synchronous and symmetrical slowing that
appears in the whole background throughout
the recording which indicates the involvement
of both hemispheres of the brain or cerebral
dysfunction.
While reporting diffuse slowing, age, state
(alertness) and medications of the patient must
be known.

7. 12 years old boy

8. 2. Asymmetry (Amplitudes &
Frequency)
Asymmetric background could be amplitude-wise
or frequency-wise.
More than 50% amplitude wise asymmetry and 1
or more than 1% frequency wise asymmetry
throughout the recording is considerable and it
shows hemispheric abnormality, considering
the age and state of the patient.

9. Amplitude asymmetry

10. 2. Epileptiform abnormal pattern
Epileptiform activity mainly consists of spike and
sharp waves.
Spike :
A transient clearly distinguished from the
background activity with pointed peak, duration
from 20-70 ms mostly followed by slow wave.
• Sharp wave :
• A transient which is clearly distinguished from
the background activity with pointed peak,
duration from 70-200ms.

11. Types of epileptic abnormal activities
1. Focal epileptiform activity:
Focal epileptiform activity (spike and sharp waves)
consists of spike and sharp waves that appear on one
or a few neighboring electrodes.
2. Generalized epileptiform activity:
Epileptiform discharges (spike and sharp waves) that
appear over most of all parts of both hemisphere and
usually have symmetrical shape, amplitude and timing
in corresponding areas.

14. Types of Epileptiform patterns
Types of Epileptiform patterns
Epileptiform abnormalities can be divided in to following
basic abnormal EEG patterns.
• Benign rolandic epilepsy (BRE)
• 3/sec spike and wave.
• Periodic lateralized epileptiform discharges (PLEDS).
• Triphasic sharp waves
• Sub acute sclerosing panencephalities (SSPE)
• Lennox gastaut syndrome (LGS)
• Hypsarrythmia (West Syndrome)
• Creutzfeldt-Jakob disease (CJD)

15. 1. Benign Rolandic Epilepsy (BRE)
Rolandic epilepsy (RE) is the most common human epilepsy, affecting
children between 3 and 12 years of age, boys more often than girls
(3:2).
Focal sharp waves in the centro-temporal area define the syndrome,
are a feature of several related childhood epilepsies and are
frequently observed in common developmental disorders (e.g,
speech dyspraxia (difficulty) , attention deficit hyperactivity disorder
and developmental coordination disorder).
Onset
– Usually 4-10 years , may persist till 12 years.
• May be unilateral or bilateral.
Sz timing
– Mostly increased in light sleep.
• Reference:
• Genetic evaluation and counseling for epilepsy
• Nature Reviews Neurology Review (01 Aug 2010)

17. 2. 3/Sec Spike and Wave
The three Hz spike and wave pattern is suggestive of
idiopathic Gen. epilepsy
• Characteristics
• It is classically described with typical absence epilepsies
when bursts of 3Hz spike and wave is Gen, regular,
symmetrical, synchronous and maximal in the anterior
head region with clinically fluttering of eyes and
automatism.
It usually occurs in patients aged b/w 5-12 years.
Onset 2 years and can be appeared till 14 years.
Often faster at onset and slows down toward end.
Accentuated (more prominent) by HV (50-80% pt) and

20. 3. Periodic Lateralized Epileptic Discharges
(PLEDs)
PLEDs are basically triphasic with sharply contoured wave
followed by a slow wave mostly occurring unilaterally with
duration 100-300 msec and amplitude 100-300 often
present with fast rhythm b/w discharges.
Characteristics:
• Periodic recurrence every 0.5-4.0 sec.
• With frequency of 1-2 sec.
• Etiology (Cause)
• acute infarction, CVA, tumor, anoxia and herpes simplex
encephalitis, abscess etc.

21. pleds
Periodic lateralized epileptiform discharges (PLEDS), regional left centrotemporal. The
repetitive discharges occur with a periodicity of about 1 second

22. 4. Triphasic sharp waves
These are typical and sharply contoured wave discharges.
Characteristics
Having three phase +, -ve and then +ve.
• Initial is sharp component.
• Appeared with rhythmic train of 1.5-2.5 /sec.
• Having medium to high voltage (>70uv) .
• Bilaterally synchronous and symmetrical
• These waves are having anterior posterior lag of 25-140 sec.
• Best seen in referential montage.
• Appeared in hypoxic state, subdural hematoma, intoxication (excite
by the action of a chemical substance ), mainly in hepatic
encephalopathy.
• Seen in deep impairement of consciousness but occasionally in

25. 5. Sub acute sclerosing panencephalities
(SSPE)
Characteristics
• Repetitive bursts of high voltage spike, sharp
and slow wave complexes, recurring after
every 4-15 seconds.
• More prominent in awaking state.
• It relates with measles and myoclonic jerks
• Gen. but maximum over fronto central areas.
• Frequency ranges 4-15/sec

26. SSPE (Cont’d)
• All the waves are Stereotyped
(morphologically similar)
• Bilaterally synchronous
• Periodic high voltage 300-1500uv of sharp
and slow waves complex with an irregular
delta wave superimposed.
• It is an inflammatory disease that occurs
in children and adolescents and is
believed to be caused by measles virus.

28. 7. Hypsarrythmia (West Syndrome)
Hypsarrhythmia is an abnormal pattern, consisting of high
amplitude and irregular paroxysmal sharp wave, spike, poly
spikes, independent, multifocal and focal spike on all
cortical region with a background of chaotic (disorderly)
and disorganized activity
It is a pattern seen in patient with infantile spasm
• Hypsarrhythmia is frequently found in patients with West
syndrome .
• Appeared at the age of 4-6 or 13 months.
• Clinically patient is mentally and physically retarded.
• Also diffuse slowing is present.

29. Hypssarrythmia

30. 6. Lennox gastaut syndrome (LGS)
• It is the disease of the later phase of hypsarrythmia which
usually shows slow spike and wave discharges and may
show discharges of gen spikes.
• Duration 2.5/sec or less.
• The discharges may be Gen and synchronous
• Highest amplitudes in midline frontal region (Fz).
• The discharges may become continuous during sleep.
• Patient gradually becomes mentally retarded.
• Within the age of 11-12 years most of the patients die, but
some may live upto 20 years, depending on the affecting of
syndrome.

31. 8. Creutzfeldt-Jakob disease (CJD)
• CJD is at times called a human form of mad cow
disease In which the brain tissue develops holes and
takes on a sponge-like texture. This is due to a type
of infectious protein called a prion.
• Prions are misfolded proteins which replicate by
converting their properly folded counterparts.
• CLINICAL SYMTOMS:
• Symptoms of CJD are rapidly progressive dementia, leading
to memory loss, personality changes and hallucinations.

32. (CJD) cont’d
• This is accompanied by physical problems such as speech
impairment, jerky movements (myoclonus), balance and
coordination dysfunction (ataxia), changes in gait, rigid
posture, and seizures.
EEG FINDINGS:
• Periodic discharges with sharp wave or a sharp triphasic
complex.
• 100 -300msec duration
• Repetition rate of 0.5-2/sec.
• Shows severely disorganized & generalized synchrony
background.
• Some cases show unilateral discharges over one

34. Thanks for your patience….