00:01
So what are the
types of seizures?
Once we make the diagnosis,
we've determined that the
spell is indeed a seizure.
00:07
Our first step is to figure
out what type of seizure it is.
00:10
And in general,
we categorize seizures in two ways,
as either partial and onset coming
from a specific area out in the cortex,
or generalized and onset and coming
from a deep focus inside the brain.
00:25
This terminology comes from
a long history of evaluating
seizures with surface
EEG/electroencephalography
on the surface of the brain.
00:35
And when we hook the brain up
to EEG we see out on the surface
that those seizures that come
from the cortex have an onset
and we can see where
the seizure begins.
00:44
Here you can see in the green area,
the seizure begins in the occipital lobe.
00:48
Those EEG electrodes near the occipital
lobe will show the seizure first,
and then you can watch
the seizures spread,
either along the where
pathway or the what pathway,
those ingrained white matter tracks that
help us understand what we're seeing.
01:03
And that spread we see
on the EEG for seizures
that have a focal onset
or focal onset seizures.
01:10
In contrast, generalized seizures
begin in a very deep focus,
they still begin in a
single area of the brain.
01:18
But you can see here in this
red deep focus in the midbrain
that deep focus can't be seen on the
surface EEG in a single location.
01:27
The seizure starts deep in the
brain, in the thalamus,
and expands out through the
internal capsule and the radiations
from the thalamus in
all directions equally.
01:36
Shows up on the surface
electrodes at the same time.
01:40
And on the EEG, it looks like it
just started all over the brain
or had a generalized onset.
01:46
At the end of the day, the seizure
is always coming from a single focus.
01:50
But we categorize seizures based on
how they appear on the surface EEG
as either focal onset or partial
onset or generalized onset.
02:00
And that's helpful because
when we think about seizures,
they have many different
descriptions from patients.
02:05
But we can categorize them,
and as either focal or
onset or generalized onset.
02:12
And we'll learn that
there are about 8
different seizure types
that occur in patients
and we can categorize all
those clinical descriptions
according to the
8 seizure types.
02:23
There are 3 types of partial
onset or focal onset seizures.
02:27
A focal onset seizure starts in one
area out on the surface of the brain
in the cortex of the cerebrum.
02:35
What's been historically
called simple partial seizures
are currently what's termed focal
seizures with retained awareness
begin in a specific
area of the brain
and are isolated and restricted
only to that area of the brain.
02:49
If the sensory cortex is involved,
they present with sensory symptoms.
02:53
If the motor cortex is involved,
they present with isolated motor symptoms.
02:57
Autonomic cortex,
autonomic findings,
and psychic areas or
limbic areas of the brain
have psychic auras,
which are focal seizures
with retained awareness,
that's one seizure type.
03:09
If a larger area of
brain is involved,
if a hemi area of brain one side of brain
is involved in this seizure activity,
we call those focal seizures
with altered awareness
or historically those were
called complex partial seizures.
03:24
Here the patient has altered
awareness as either passed out
or is unable to communicate or
altered awareness in some way.
03:32
Also with those sensory or motor phenomenon
depending on where the seizure may occur.
03:37
And then the third type of partial onset
epilepsy is secondary generalized seizures.
03:44
Those seizures may start in a focus,
they may start with retained awareness,
they may progress to
altered awareness.
03:50
But ultimately the entire brain
becomes involved in the seizure
and the patient will pass
out and jerk and shake
and sometimes have incontinence
and lateral tongue biting.
03:59
And those are secondarily
generalized seizures,
they started in a focus
and then generalized.
04:04
So those are the 3 types of
focal onset or partial epilepsy.
04:11
That's different from the
generalized seizures that we see,
these are seizures that have
seizure activity that involves
both hemispheres of the brain
equally and symmetrically.
04:20
And there are 5 types,
5 or 6 types of generalized seizures.
04:26
Absence seizures
are brief episodes,
where the patient has loss of
awareness or behavioral arrest.
04:35
Tonic-clonic seizures,
generalized seizures begin
with tonic-clonic episodes or
tonic-clonic motor activity.
04:42
Myoclonic seizures are
very brief single jerks,
and myoclonic jerks are not
always epileptic in origin
as we go to sleep as
we all go to sleep.
04:52
Sometimes the body will jerk
or have a myoclonic jerk
and that's non-epileptic
in origin.
04:57
Myoclonic seizures have
an epileptic origin
but have that same
myoclonic jerk.
05:03
Clonic seizures are jerking,
we can see tonic seizures
with just the retain
stiffening and atonic seizures.
05:10
And each of these 6 types
are generalized seizures.
05:17
So let's walk through each
of those seizure types.
05:19
It's very important to
understand what these looks like
and how patients describe them.
05:24
When a patient comes in
with a seizure evaluation,
we'll need to categorize
the type of seizure.
05:29
We said there are 3 types
of focal onset seizure,
there's what historically was
called the simple partial seizures
with retained consciousness.
05:37
Patients may describe an
abnormal smell or taste.
05:40
These may present with staring
spells, with retained consciousness,
and patients have retained
muscle tone during these events.
05:50
If the seizure
involves a larger area,
historically, these were
called complex partial seizures
or focal epilepsy with loss of
consciousness or altered awareness.
05:59
They may be preceded by an aura and
typically involves postictal confusion.
06:04
And complex ictal automatisms.
06:06
And these are
automatic behaviors
that occur automatically
reflexively during the seizure,
that may be lip smacking,
it may be chewing,
it may be a guttural
sound, it may be swallowing
and it's repetitive
activity that is reflexive.
06:20
And can frequently occur during
these complex partial seizures
or again, focal seizures
with altered awareness.
06:27
And then the last category was the
secondary generalized seizures.
06:29
These begin with an initial aura
and then progress to
involve convulsions.
06:35
That progression has been
termed a Jacksonian march.
06:38
And classically, the Jacksonian March
begins with motor activity in one limb
that progresses up the
limb more motor activity
involving the entire limb and then
generalizing throughout the body.
06:49
Secondary generalized seizures are
characterized by postictal confusion
and sometimes a Todd's paralysis, and
that's a weakness on one side of the body,
the side opposite where the
seizure began as a result
of that postictal depression
in brain activity.
07:04
For the generalized
seizures again,
we said that there are absence
types of generalized seizures.
07:09
These are primary generalized
and brief staring spells.
07:13
They often can be
confused by daydreaming,
they're seen typically in
children and associated
with this 3 Hz spike-and-wave
activity on the EEG.
07:22
That's different from
myoclonic generalized seizures.
07:25
These are typically
focal myoclonic jerks,
brief periods of loss of
consciousness but without convulsion
and very little
postictal confusion.
07:33
They may be characterized
just as a brief jerk.
07:37
Tonic seizures or focal,
isolated rigidity.
07:40
Typically a period of time,
a short period of seconds or minutes
characterized by tonic
activity, isolated rigidity
of either one part of the
body or the entire body.
07:52
Atonic seizures
are drop attacks.
07:54
These are where patients
lose postural tone.
07:56
They're common in children,
they're very difficult to control seizure
and can result in severe injury.
08:02
Patients will very suddenly lose all
postural tone and fall to the ground.
08:06
And many of these children wear a
helmet or some other protective device
because these seizures
cannot be predicted
and can result in severe
injury to the child.
08:16
And then generalized tonic-clonic
seizures look very similar
to the secondary generalized
tonic-clonic seizures,
but they don't have an aura.
08:24
They don't have a clearly
observed focal onset.
08:28
Most often they do involve
convulsion, but maybe non convulsive
in patients with primary
generalized epilepsy without aura.