00:01
In terms of the
risk of second seizure,
when we're looking
at the history,
we're looking for findings
that point us
towards a higher or lower risk
of developing a second seizure.
00:11
The risk of second seizure
after a focal seizure is about 60%.
00:15
compared to 40%
for generalized onset seizures.
00:18
Some generalized onset seizures
can be induced by hypoglycemia,
or hyponatremia,
or hypercalcemia,
or other electrolyte
or medication,
inciting factors.
00:29
And so focal onset seizures
should raise our suspicion
for a risk of a second seizure.
00:33
Seizures that occur
out of sleep
have a higher risk of patients
suffering a second seizure 60%
compared to those
out of wakefulness 35%.
00:42
So we never want to ignore
the risk of a nocturnal onset,
new first time seizure.
00:47
Of those with a second seizure
73% will occur in the same state.
00:52
So the state of the first seizure
really tells us
when we should be concerned
and help with counseling patients.
00:58
Frontal lobe seizures
are important.
00:59
They can look very uncommon
and present very uncommonly.
01:03
They can occur out of sleep
or in the early morning.
01:06
Patients often have
bizarre behavior.
01:09
Frequently
with retained awareness,
many patients are aware
during their frontal seizure,
with altered behavior,
or even psychogenic behaviors
that can mimic
a psychogenic spell.
01:20
Those seizures
that occur out of sleep,
particularly where we're concerned
about a frontal lobe origin
those patients
should undergo full evaluation.
01:28
And we should never
discount a spell out of sleep.
01:33
When we're thinking about
the studies that we perform
for a patient with
the first time seizure,
EKG is important to look
for cardiac abnormalities.
01:40
electrolytes in a
urine drug screen,
to look for potential
exacerbates for seizure.
01:45
A sepsis evaluation
may be needed
if we're concerned
for risk of infection
or a lumbar puncture
if meningitis is a possibility.
01:52
Head CT is typically done
to look for abnormal findings
that could suggest
nidus for seizure.
01:58
and particularly in patients
with an abnormal neurologic exam,
a focal onset seizure
where we need to look
for a mass lesion
or other predisposing history.
02:06
History of stroke or
traumatic brain injury.
02:09
Outside of the emergency department
we think about other studies.
02:13
Most patients undergo an EEG,
a brain MRI,
sometimes will consider
tilt table test
if we're worried about
convulsive syncope
and prolonged EEG,
either ambulatory EEG
in the outpatient setting
or admission to the hospital
to an Epilepsy Monitoring Unit.
02:28
Maybe you needed to characterize
what happens on the EEG
during the event
and differentiate between
an epileptic origin
or a non-epileptic origin.
02:39
When we're looking
at the EEG,
the goals of the EEG
are to observe
interictal epileptiform
abnormalities.
02:44
Those are epileptiform discharges
spikes that occur
in between episodes
and suggest a
reduced seizure threshold
or a focal origin
of the epileptic events.
02:55
They we're looking for
focal sharp waves
that spike and wave
that indicates an area of the brain
that is at risk to cease.
03:02
We also would like to observe
any ictal or interictal patterns
that would correspond to
a known seizure syndrome
or an epilepsy syndrome.
03:10
There are certain findings
on the EEG
and the one to think about
is a 3 Hz spike and wave finding
that we see with
absence epilepsy.
03:18
That 3 Hz spike and wave is seen
both ictally and interictally.
03:22
And it points towards a
diagnosis of absence epilepsy.
03:25
So we're also looking for those
characteristic findings on the EEG.
03:31
So what are we looking for
on the EEG
after a first time seizure?
Well, we're looking for
interictal findings
that may classify
the seizure type
and help us determine
that treatment.
03:42
There are certain specific
interictal EEG patterns
that can lead to
a precise diagnosis.
03:46
A 3 Hz spike and wave
points to absence epilepsy.
03:50
A 4 Hz spike and wave points
to juvenile myoclonic epilepsy.
03:55
In rolandic epilepsy,
we see centrotemporal spikes.
03:57
Infantile spasms,
hypsarrhythmia.
04:00
With Angelman syndrome,
we can see notched to delta waves.
04:03
In myoclonic epilepsies,
have a photo convulsive response,
where presentation
of a photic stimulus
and repeated photic stimulus
drives a convulsive response
either clinically or on the EEG.
04:16
We don't need to know all of
these patterns specifically,
but that we're looking for specific
interictal patterns on the EEG
that point us to a diagnosis
and can help select a treatment.
04:28
In addition,
we're also looking
for the non-specific
interictal EEG findings.
04:32
The spikes in waves that we may see
at a focus interictally
that would point us
to a risk of seizure.
04:42
So let's talk a little bit more
about epileptiform discharges,
those spike and waves
that we see on the EEG.
04:47
Interictal epileptiform discharges
are observed in normal patients
who don't have epilepsy,
as well as those with epilepsy.
04:55
We see them in about
2% to 4% of children,
and less than 1% of adults.
05:00
Normally,
in the normal general population.
05:04
Up to 12% of patients
with neurologic disease
with and without epilepsy
will have epileptiform discharges.
05:11
We can see them in dementia,
or Parkinson's disease,
and other conditions
like stroke.
05:16
And in those conditions
an epileptiform discharge
does not mean that the patient
will have a seizure,
but is it slightly higher risk.
05:23
And then around 30% to 55%
of patients on the initial EEG,
and up to 80% to 90% of patients
on serial EEG's
will have
epileptiform discharges
for those who have seizures.
05:36
Three 30 minute routine EEGs,
three 30 minute interictal EEGs
are sufficient to capture
80% to 90% of seizure patients
who will have an
epileptiform discharges.
05:49
So in conclusion,
normal patients can have
an abnormal EEG.
05:53
And patients with epilepsy
can also have a normal EEG
but three 30 minute EEGs.
06:00
If normal, start to draw a question
as to whether
this patient does have
an increased seizure risk?
So let's talk a little bit
more about
the risk of a second seizure.
06:11
The point of an EEG
after a first time seizure,
the goal of the EEG
after a first time seizure
is to evaluate the risk
of a second seizure.
06:20
If interictal epileptiform
discharges are observed
on the initial EEG,
then the risk of the recurrence
of recurrent seizures higher.
06:28
The general risk of seizure with
an abnormal EEG is about 50%.
06:34
With a normal EEG,
it's down to 25%.
06:37
So a normal EEG
after a first time seizure
is reassuring,
and we would not start
the patient on treatment.
06:43
An abnormal EEG
raises that risk.
06:46
And we may consider treatment
in the appropriate clinical setting.
06:51
Importantly,
EEG is performed
within the first 24 hours
of a seizure
are higher yield.
06:56
There's a 51% chance
of finding those
abnormal epileptiform
discharges.
07:00
So we like to do them early.
07:02
And EEG is performed
after the 24 hour period,
after that first time seizure.
07:07
The chance of finding
abnormal epileptiform discharges
goes down to 34%.
07:12
So if we're going to do the EEG,
we like to do it early.
07:15
And if abnormal,
it would raise our suspicion
for risk of a second seizure.
07:21
So let's talk about
the role of neuroimaging
and evaluating
the first time seizure.
07:25
There's a few things
we need to know.
07:27
First of all, all patients
with the first time seizures
should get imaging.
07:31
Second, we see both
CT and MRI performed.
07:35
There are
some nuances to that.
07:36
but what I want you to take away
is neuroimaging should be done.
07:40
If we look at the
AAN practice guideline,
it does not differentiate
between CT or MRI.
07:46
Both are okay.
07:47
Though there are some studies
that have favored MRI over CT.
07:51
An interesting study looked at
the expertise of the radiologist
showed that the sensitivity
of finding an abnormal lesion
for non-expert radiologists
was about 40%,
for expert radiologists 50%,
and the sensitivity for
an epilepsy radiology expert
was up to 91%.
08:09
So the data here
is a little confusing.
08:11
The key is that MRI is helpful.
CT is probably just as good.
08:16
And you'll see both of these
performed in patients
with first time seizures.
08:20
The chance of seeing an
epileptic focus on the MRI varies.
08:25
Overall, we see about 30%
of first time seizure patients
present with an abnormality
on their MRI.
08:32
If the CT is normal,
15% of patients will still have
an abnormality on the MRI.
08:37
And this is why sometimes
in patients where we're
have a strong suspicion
for an underlying lesion,
a normal CT scan
won't make us feel comfortable.
08:46
And we will still consider
an MRI for those patients.
08:50
And those patients
we're looking for things like
mesial temporal sclerosis,
a post-traumatic focus,
or a rare cortical dysplasia
that could be missed
on the CT scan.
09:00
A lot of things can be seen on MRI
that may drive seizures.
09:03
In this study of patients
who presented
with a new-onset
first time seizure
30% of patients had an
underlying focus on imaging.
09:12
And if all those findings,
we saw a varying range
of diagnoses.
09:18
Strokes were seen
in a third of patients
who had an abnormal MRI.
09:22
We saw post-traumatic lesions
in about a fifth of patients.
09:25
Mesial temporal sclerosis
in 6% of patients
with an abnormal MRI.
09:30
Neoplastic lesions can be seen
and more common
in patients as they age.
09:35
Cortical dysplasias
are uncommon,
but a very important
potential nidus for seizure
that can be missed with an
untrained eye on the MRI.
09:44
Cavernomas or vascular lesions,
other vascular malformations,
perinatal insults,
and other findings.
09:50
So many things
can be seen on the MRI
and about 30% of patients
will have an abnormal MRI
when presenting
with a first time seizure.
09:59
I think the key things to remember
about neuroimaging
is we're using neuroimaging
to differentiate
the risk of a second seizure.
10:06
We're using it
to evaluate those patients
who are at low risk
of a second seizure,
and we won't initiate
treatment
or high risk
of a second seizure.
10:13
And we may consider treatment
earlier for those patients.
10:17
If we look at the risk
of a second seizure at one year,
after first time presentation
with a normal CT or MRI,
it's about 40%.
10:25
So less than 50%.
10:27
With an abnormal MRI,
with an epileptogenic lesion
on the CT or MRI,
that goes up to 60%.
10:33
So again, when we find those
abnormalities on imaging,
we would favor treatment
or earlier treatment
in some of those patients
because of the higher risk
of a second seizure.