So what are the types of seizures?
Once we make the diagnosis,
we've determined that the spell is indeed a seizure.
Our first step is to figure out what type of seizure it is.
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.
This terminology comes from a long history of evaluating
seizures with surface EEG/electroencephalography
on the surface of the brain.
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.
Here you can see in the green area, the seizure begins in the occipital lobe.
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.
And that spread we see on the EEG for seizures
that have a focal onset or focal onset seizures.
In contrast, generalized seizures begin in a very deep focus,
they still begin in a single area of the brain.
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.
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.
Shows up on the surface electrodes at the same time.
And on the EEG, it looks like it just started all over the brain
or had a generalized onset.
At the end of the day, the seizure is always coming from a single focus.
But we categorize seizures based on how they appear on the surface EEG
as either focal onset or partial onset or generalized onset.
And that's helpful because when we think about seizures,
they have many different descriptions from patients.
But we can categorize them,
and as either focal or onset or generalized onset.
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.
There are 3 types of partial onset or focal onset seizures.
A focal onset seizure starts in one area out on the surface of the brain
in the cortex of the cerebrum.
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.
If the sensory cortex is involved, they present with sensory symptoms.
If the motor cortex is involved, they present with isolated motor symptoms.
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.
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.
Here the patient has altered awareness as either passed out
or is unable to communicate or altered awareness in some way.
Also with those sensory or motor phenomenon depending on where the seizure may occur.
And then the third type of partial onset epilepsy is secondary generalized seizures.
Those seizures may start in a focus, they may start with retained awareness,
they may progress to altered awareness.
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.
And those are secondarily generalized seizures,
they started in a focus and then generalized.
So those are the 3 types of focal onset or partial epilepsy.
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.
And there are 5 types, 5 or 6 types of generalized seizures.
Absence seizures are brief episodes,
where the patient has loss of awareness or behavioral arrest.
Tonic-clonic seizures, generalized seizures begin
with tonic-clonic episodes or tonic-clonic motor activity.
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.
Sometimes the body will jerk or have a myoclonic jerk
and that's non-epileptic in origin.
Myoclonic seizures have an epileptic origin
but have that same myoclonic jerk.
Clonic seizures are jerking, we can see tonic seizures
with just the retain stiffening and atonic seizures.
And each of these 6 types are generalized seizures.
So let's walk through each of those seizure types.
It's very important to understand what these looks like
and how patients describe them.
When a patient comes in with a seizure evaluation,
we'll need to categorize the type of seizure.
We said there are 3 types of focal onset seizure,
there's what historically was called the simple partial seizures
with retained consciousness.
Patients may describe an abnormal smell or taste.
These may present with staring spells, with retained consciousness,
and patients have retained muscle tone during these events.
If the seizure involves a larger area,
historically, these were called complex partial seizures
or focal epilepsy with loss of consciousness or altered awareness.
They may be preceded by an aura and typically involves postictal confusion.
And complex ictal automatisms.
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.
And can frequently occur during these complex partial seizures
or again, focal seizures with altered awareness.
And then the last category was the secondary generalized seizures.
These begin with an initial aura
and then progress to involve convulsions.
That progression has been termed a Jacksonian march.
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.
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.
For the generalized seizures again,
we said that there are absence types of generalized seizures.
These are primary generalized and brief staring spells.
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.
That's different from myoclonic generalized seizures.
These are typically focal myoclonic jerks,
brief periods of loss of consciousness but without convulsion
and very little postictal confusion.
They may be characterized just as a brief jerk.
Tonic seizures or focal, isolated rigidity.
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.
Atonic seizures are drop attacks.
These are where patients lose postural tone.
They're common in children, they're very difficult to control seizure
and can result in severe injury.
Patients will very suddenly lose all postural tone and fall to the ground.
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.
And then generalized tonic-clonic seizures look very similar
to the secondary generalized tonic-clonic seizures,
but they don't have an aura.
They don't have a clearly observed focal onset.
Most often they do involve convulsion, but maybe non convulsive
in patients with primary generalized epilepsy without aura.