So if that's how the seizures develop,
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 functional-deficit zone,
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 EEG discharges.
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,
but biochemically, 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 particularly susceptible
to causing dystonic posturing of the body.
And we can see that type of semiology from seizures
from high frontal epileptic areas.
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 parasympathetic activity
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
typically medial 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 dystonic posturing.
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 motor area.
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 frontal lobe.
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.
And ultimately, if we consider seizure surgery,
those symptoms and that localization is critical.
Pain is thought to come from the contralateral sensory hemisphere.