So if that's how the
how do seizures spread
throughout the brain?
Well typically seizures
start in the gray matter
in the cell bodies
of the gray matter
and spread along typical
white matter tracts.
And so the spread of the seizure is
dependent upon where that seizure starts.
With that being said, there's some
typical zones that we tend to see
that are related to seizure spread, that
help us to evaluate patients clinically,
and see the seizures with EEG.
The smallest area, the initial seizure
focus is called the ictal-onset zone.
And this is the brain area that's resulting
in the observed scalp EEG abnormalities
that drive the seizure,
this is where the seizure starts
in the scalp or where the
seizure starts on the brain.
This is surrounded by
a symptomatic zone,
the area of brain surrounding
that ictal-onset zone,
this is typically gray matter
that's responsible for the symptoms
that the patient has at
the onset of the seizure.
That symptomatic zone is often the zone
that contributes to aura formation.
And what we ask
patients about are here,
when patients are
describing their aura.
This is surrounded by the
the area of surrounding brain
that may be responsible for
interictal clinical deficits,
not the deficits during the seizure
but the findings between
seizures or interictally.
And similarly, this is also the territory
of brain that we call the irritative zone.
The area of surrounding
brain that may be responsible
for the interictal
Those are spikes and waves that
we look for in between seizures
that tell us that this is
where the seizure focus may be.
We know that that area where the spike
is coming from is a little bit bigger
than actually where the
seizure itself has started.
And then lastly,
we see the epileptic zones,
the brain areas involved in
seizure, generation and spread.
And typically, that's the area,
the smallest individual area
where that seizure begins.
That's that green area
on the chart here,
that's not something that we
can see on EEG or even on MRI,
that's where the seizure will start.
We can use this information
when we evaluate patients
and that's when we're talking
to patients throughout history,
we're evaluating the seizure
semiology, how the seizure begins,
how it progresses and how it ends,
and that semiology can tell us about
where the seizure is starting can
define some of those clinical zones.
The seizure focus determines
the seizure symptoms.
And so seizures that begin in the primary
sensory cortex present with paresthesias
often not negative sensory findings
but positive sensory findings,
tingling or electric shock
or electric discharges
that occur in a
region of the body.
Seizures that begin in the primary
motor cortex will cause clonic activity
and that's movement
of jerking of the arms
or legs or face or a
certain part of the body
or tonic activity that will
be a stiff and posturing.
Tonic activity can also be seen
from other frontal seizures.
The frontal lobe
is the motor lobe.
And areas in the
anterior frontal lobe
are involved in planning motor
movements, the supplementary motor area
which we call the SMA is
to causing dystonic
posturing of the body.
And we can see that type
of semiology from seizures
from high frontal
Ictal vomit or vomiting during a
seizure can come from the temporal lobe.
We can also divide the sides
of the brain into those
that are associated with
and the side of the brain
with sympathetic activity.
Typically, when we think of the
left brain is being parasympathetic
and the right brain is
driving sympathetic activity.
And so ictal spitting or urinary
urge incontinence or urinary urgency
is seen with left sided,
medial temporal ictal onset or seizures.
Olfactory auras, olfactory symptoms
can be seen with bifrontal seizures
or seizures in the orbital frontal
cortices, on either side of the brain.
Piloerection is seen
in dominant hemisphere
temporal lobe seizures.
Déjà vu is a symptom we can
see from seizures that develop
from the lateral temporal lobe and
that can be either temporal lobes.
The dominant or
non-dominant temporal lobes.
Déjà vu is not uncommon aura for
temporal lobe epilepsy, as you see here.
In the medial temporal lobe again, either
medial temporal lobes the right or left,
we can see abdominal symptoms or
rising nausea or abdominal fear.
A fear that's associated
with abdominal discomfort
and that can be a symptom
we see from seizures arising
from the medial temporal lobes.
About 60% of auras
involve sensory symptoms.
So sensory symptoms
are extremely common
and somewhere around 90% of
patients with frontal lobe epilepsy
will have contralateral
So some of these frequencies can help
us when we're evaluating patients.
Fencing is a really cool
posture that we can see
with SMA (supplementary
motor area) seizures.
You think of someone
who comes in and says,
"I wake up at night in this fencing
posture", or a bed partner may say that.
They sound crazy and those
actually can be seizures arising
from the supplementary
Early head tilting or head
movement, early version of the head
can be seen with seizures on
the ipsilateral frontal lobe,
whereas late head turning
can be seen with seizures
from the contralateral
So if the head early in the
seizure is turning to the right,
that may suggest a right
frontal seizure onset.
If the head is turning to the
right late in the seizure process
that suggests a left
sided frontal onset.
So you can see how we use
the patient's symptoms
to guide where the seizure
may be coming from.
if we consider seizure surgery,
those symptoms and that
localization is critical.
Pain is thought to come from the
contralateral sensory hemisphere.