Let’s talk about seizures.
So what is a seizure?
An abnormal hypersynchronous –
Stop there for one second.
What the term hypersynchrony means in seizures
is that you have an abnormal epileptogenic
network, which you can study by ECoG not EEG,
that shows increased synchronous in certain points
of time. Usually, before a seizure, there will
be a transient moment of desynchrony between
the epileptogenic network and the surrounding
brain tissue. Then, synchrony will evolve over
time, and you end up with hypersynchrony only
later in the seizure. You can see these changes
only on an ECoG and you are unlikely to
see them on an EEG. Moreover, the topic of hypersynchrony
means coherence is increased between two points in the brain,
however, the correlation between these two
points might be lost. Important for you is
that seizures are due to hypersynchronous neuronal activity.
And what’s the difference
between a seizure and epilepsy?
We’ll get into that in a second.
But right now, let’s talk
about the definition.
So once again, an abnormal hypersynchronous
electrical discharge of
neurons in the brain.
It’s easy to read,
but please understand
the significance of it.
So what’s an epilepsy?
The tendency to experience
recurrent, unprovoked seizures.
The operative word,
Keep things simple.
A seizure is a hypersynchronous type of
electrical activity over a period of time,
whereas epilepsy would be unprovoked
type of seizure by the definition.
Once you get the definitions down,
obviously, we’re going to
get into further details.
Generalized seizures originate at some point within,
and rapidly engage “bilateral” neuronal networks.
These bilateral networks can include cortical and
subcortical structures, but in no way mean it includes
the whole brain. The keyword here is “bilateral” in origin.
Because the seizures originate from a bilateral
network, the symptoms can be different
from one seizure to another.
and you can have primary
You can have secondary but at
this point, current day practice,
we don’t really talk
about this so much, huh?
But our focus will be on primary
generalization with secondary.
But what we’ll do is,
we’ll get into focal,
meaning to say, you have
focal portions of the brain,
most commonly, the
medial temporal lobe.
Then at some point, a focal then can
go on to secondary generalization.
Focal seizures originate within a network limited to
one hemisphere. Keyword here is “one hemisphere”.
Secondary generalization means that at a later stage
in the seizure, there is involvement of both hemispheres.