JICNAR○| Journal of the International
Child Neurology Association
A peer reviewed open access e-journal in Child Neurology
Paroxysmal fast activity: Does this EEG pattern occur only in
Lennox-Gastaut syndrome?
1
Claudia M.P. Bento1, Ana Carolina Coan1,Marilisa M. Guerreiro
1Department of Neurology - University of Campinas (UNICAMP) - Brazil
Corresponding author: Marilisa M. Guerreiro; Email: mmg@fcm.unicamp.br
Received: 23 July 2018
Accepted: 29 December 2018
Abstract
Background: Paroxysmal fast activity (PFA) is defined by fast paroxysmal events in the electroencephalogram (EEG),
usually associated with Lennox-Gastaut syndrome (LGS). Our aims were to verify the frequency of LGS and non-LGS in
EEGs with PFA; and to correlate the EEG features (spatial distribution, frequency, amplitude and duration) between the
two clinical groups.
Methods: We analyzed 38 EEG tracings with PFA from 38 patients. We evaluated the spatial distribution, frequency,
amplitude and duration of fast paroxysms. The two clinical groups (LGS and non-LGS) were statistically compared relative
to the EEG data.
Results: With regard to epileptic syndromes, 23 patients (60%) were classified as LGS and 15 patients (40%) as non-LGS.
Concerning spatial distribution, our results showed that 86.8% of the examinations showed symmetrical PFA and 13.2%
showed asymmetrical PFA. The statistical analysis did not show any difference between the two groups regarding the EEG
spatial distribution or other EEG data.
Conclusions: PFA can occur in other epileptic syndromes apart from LGS. The EEG features did not offer any distinction
between the two clinical groups. The PFA is not a specific EEG marker of LGS.
Kewords: cannabis, cannabinoids, cannabidiol, epilepsy, childhood.
© Bento CMP; licensee JICNA
Background
the EEG characteristics of PFA (spatial distribution, ampli-
tude, frequency and duration); to compare our results be-
The paroxysmal fast activity (PFA) is characterized by parox-
tween the two groups; and, to correlate the EEG data ob-
ysmal events in the electroencephalogram (EEG) with al-
tained from the two clinical groups (LGS and non-LGS) with
pha, beta and gamma frequencies (8 up to >30Hz), ampli-
the etiology (symptomatic and non-symptomatic).
tude higher than the baseline activity, lasting at least 0.2
seconds, and more frequent in the NREM sleep [1, 2, 3].
Methods
Traditionally the PFA is known as an essential feature for
the diagnosis of the Lennox-Gastaut syndrome (LGS) [4].
We have retrieved the exams which presented the keywords
However, it has been sporadically found in other epilep-
"recruiting rhythm" and "paroxysmal fast activity" from our
tic encephalopathies and even in focal epilepsies. It was
database. This research was carried out from January 2008
also found that their presence might be an indicator of tonic
to April 2017 in the Electroencephalography Unit of the
seizures and other refractory seizures, generally with poor
Clinic Hospital of UNICAMP. This is a tertiary hospital that
prognosis including mental deterioration [1, 5, 6, 7, 8, 9].
receives mainly referral patients. Amongst the 41,269 avail-
We aimed to investigate this subject due to existing con-
able EEG reports, 170 exams (0.412%) were undertaken in
troversies on this topic and the scarcity of significant studies.
45 patients, who presented at least one of their exams with
Our objectives were the following: to verify the frequency
PFA/recruiting rhythm. These two terms are most often de-
of patients with LGS and patients with other epileptic syn-
scribed in our practice and in this study were considered as
dromes (non-LGS) in EEG that presented PFA; to evaluate
synonyms.
1
Bento CMP et al. - JICNA 2019, 1(1)
The reports of the various EEGs of each patient were
The averages that were found were statistically analyzed.
checked by the main author (CMPB) and, when the inclu-
Clinical data were collected through an interview with
sion criterion was met, the examination was selected as a
either the patient or the parents (or caregivers) and, sub-
representative of the patient to be reviewed with the ad-
sequently, the review of the medical records to fill out a
visor (MMG) who has EEG credentials in our country. An
semi-structured questionnaire. The data evaluated were:
average of 8.7 exams were performed per patient, ranging
age, sex, neurological diagnosis, presence, onset and fre-
from 1 to 17 exams in each patient. The most recent EEG of
quency of the epileptic seizures, semiology of the epilep-
each patient presenting PFA was reviewed in detail.
tic seizures, type of the epileptic syndrome, relevant per-
The inclusion criteria were (1) PFA per definition on EEG
sonal antecedents, neuroimaging findings and medications
and (2) adequate clinical data to classify patient as LGS vs
already used and in current use. The clinical information
non-LGS. The PFA was characterized by paroxysmal events
was collected in order to allow that patients were classi-
in the EEG with alpha, beta and gamma frequencies (8 up to
fied as having or not LGS. Therefore, patients were divided
>30Hz), amplitude higher than the baseline activity, lasting
into two groups: patients with LGS and patients with non-
at least 0.2 seconds, and more frequent in the NREM sleep
LGS. The latter consisted of patients with developmental
[1, 2, 3].
and epileptic encephalopathies (DEE) and other epileptic
The PFA in EEG was classified as symmetrical or asymmet-
syndromes.
rical, according to the spatial distribution of the paroxysms
Epileptic seizures were defined according to ILAE classifi-
(PFAs and PFAa).
cation [10, 11, 12, 13] and updated according to the latest
It is considered PFAs when epileptiform activity is present
ILAE publication [6]. However, the etiology has not been
diffusely in practically all electrodes in both hemispheres of
updated according to the new ILAE classification, since not
the brain in a symmetrical way [3] (figure 1).
all patients presented neuroimaging. LGS was defined ac-
cording to the following triad:
(a) epileptic seizures: ax-
ial tonic, atonic and atypical absence; (b) EEG abnormali-
ties: bursts of diffuse slow spike-waves during wakefulness
and bursts of fast rhythmic waves and slow polyspikes and
above all generalized fast rhythms at about 10 Hz during
sleep; and (c) a slowness in intellectual growth and associ-
ated personality disorders [4].
Patients who presented structural lesions on neuroimag-
ing exam and/or a clear abnormal neurological examination
(including cognitive deficit) were named structural cases.
The two groups (LGS and non-LGS) were compared tak-
ing into account the EEG variables and etiology of epilepsy.
Figure 1 symmetrical PFA characterized by activity in both
The spatial distribution and characteristics of the PFA re-
hemispheres of the brain symmetrically.
garding amplitude, frequency and duration of paroxysms
were considered. A comparison between the two groups
was performed using the Mann-Whitney test or the Fisher’s
exact test [14, 15]. The level of significance adopted was
5%. This study was approved by the Ethical Committee of
our Institution (Number 1,974,229).
Results
Seven exams (out of 45 exams) were excluded, due to the
fact that the reviewed exams did not present PFA with the
definition adopted in this study. The remainder formed a
sample of 38 patients and, therefore, 38 EEGs for final anal-
Figure 2 symmetrical PFA characterized by activity in both
ysis (0.09% of the total exams in the period). In the total
hemispheres of the brain symmetrically.
sample of 38 patients, 71% (27/38) were male. Regard-
ing the classification of epileptic syndrome, 60% (23 pa-
In the present study, we considered PFAa epileptiform ac-
tients) of the patients were classified as having LGS and
tivities that could not be included in the definition of PFAs.
40% as non-LGS subdivided into other subgroups:
37%
Thus, we consider asymmetrical APR with clear hemispheric
(14 patients) as DEE and 3% (1 patient with temporal lobe
predominance (Figure 2).
epilepsy, patient 33) as other epileptic syndromes.
The systematic review of EEG allowed the quantitative
The results of the EEGs enabled to observe that there are
analysis of the amplitude, frequency and duration of PFA. patients with symmetrical PFA (PFAs), 33 patients in to-
2
Bento CMP et al. - JICNA 2019, 1(1)
tal, which corresponds to 86.8% of the tracings, and pa-
Discussion
tients who had asymmetrical PFA (PFAa), 5 patients in to-
tal (13.2%). As only 5 patients had PFAa, the test did not
In this study, we found 0.412% of all EEGs with PFA. This
present statistical significance. The comparison of the two
value differs from the data of other studies, being below
groups (LGS and non-LGS) with the spatial distribution of
the average frequency reported in the literature, which de-
PFA is shown in Table 1.
scribes the PFA between 4% and up to 28% in the EEGs of
tertiary centers [2, 3, 6]. We believe that this difference
Table 1 Comparison between LGS and non-LGS groups in rela-
is due to the fact that different professionals perform the
tion to spatial distribution of PFA (Fisher’s exact test)
analysis and the description of the exams in our service. In
addition, it is possible that the PFA has been described as
Non-LGS
LGS
Total p-value
polyspike activity and not as PFA or recruiting rhythm. An-
PFAa
1
(6,67%)
4
(17,29%)
5
other factor that we have to consider is that due to the dif-
PFs
14
(93,33 %)
19
(82,61%)
33
ficulty of sedation, several EEG records were carried out in
Total
15
23
38
0.6295
EE patients only on awakeness.
Concerning epileptic syndromes, 60% of them were clas-
PFAa = asymmetrical paroxysmal fast activity
sified as having LGS and 40% as non-LGS. No other study
PFAs = symmetrical fast activity
has evaluated the proportion of PFA among LGS and non-
LGS patients, since most studies solely addressed LGS pa-
tients [1, 6, 16]. The review of the EEGs allowed us to
The other EEG variables (amplitude, frequency and du-
observe that the spatial distribution of the PFA may be sym-
ration) were also analyzed in relation to both groups (LGS
metrical or asymmetrical (PFAs and PFAa). We have found
and non-LGS). The results are presented in Table 2. The
only another study that analyzed the focality of the PFA’s
amplitude ranged from 15 to 758 microvolts. The frequency
[3]. Therefore, we can infer that this subject is seldom ad-
ranged from 8 to 62 Hz. The duration ranged from 0.2 to
dressed probably because it is not very valued.
6 seconds. Thirty-six patients (94.7%) were classified as
We carried out a comparison between the groups of pa-
having structural etiology, 63.9% (23) of patients with LGS,
tients classified as having LGS versus non-LGS in relation to
33.3% (12) of patients with DEE and 2.8% (1) of patients
PFAs and PFAa. As only 5 patients presented PFAa, of whom
with other epilepsy syndromes.
only one non-LGS patient, the test did not present statistical
significance, perhaps due to the small sample. In any case,
Table 2 Comparison between LGS and non-LGS groups in rela-
our data suggest that symmetrical or asymmetrical EEG pat-
tion to spatial distribution of PFA (Fisher’s exact test)
terns do not allow the distinction between LGS and other
epileptic syndromes.
LGS
Variable
N Average Median p-value
Yes
Medium amplitude
23
176.13
143.0
0.0944
In the quantitative analysis, we have compared the LGS
No
Medium amplitude
15
232.97
203.0
versus non-LGS groups for the numerical EEG variables
Yes
Medium frequency
23
19.71
18.0
1.00
(amplitude, frequency and duration of PFA). This compari-
No
Medium frequency
15
20.22
18.5
son neither presented statistical significance and, therefore,
Yes
Medium duration
23
1.44
1.00
0.5576
the EEG variables also do not allow the distinction between
No
Medium duration
15
1.50
1.25
LGS and other epileptic syndromes. Other studies that eval-
uated the same numerical variables did not take into ac-
Structural etiology was considered when patients had ab-
count the groups analyzed in this study. It is thus not possi-
normal neuroimaging and/or clear abnormal neurological
ble to compare our findings with theirs.
examination, such as tetraparesis. The etiologies are shown
It was not possible to compare the structural versus non-
in Table 3. The three patients considered non-structural
structural groups in relation to the symmetrical or asymmet-
were: one had Down syndrome (genetic) and one had
ric PFA nor in relation to the numerical variables, since our
Doose syndrome (probably genetic).
sample did not allow the statistical analysis. The PFA does
not seem to have a preference amongst patients with ac-
The other patient presented with a normal neurological
quired structural, developmental or genetic etiology [3, 17].
examination, preserved intellectual level and normal com-
One of our patients presented temporal lobe epilepsy with
puterized tomography scan, but no MRI. Hence, the three
symmetrical PFA. It is possible that the PFA of this patient in-
patients were classified as non-structural etiology.
dicates secondary bilateral synchrony. Other studies [2, 18]
As previously mentioned, we have also performed the
reported that in localized epilepsies there may be PFA, and
comparison between the two groups considering the etiol-
therefore, they are better called as secondary bilateral syn-
ogy (structural and non-structural) in relation to the spatial
chrony epilepsy or secondarily generalized epileptic neural
distribution and numerical variables. However, only three
network. The only difference in relation to our work is
patients were non-structural, which did not allow a statisti-
the fact that these authors pointed out that some numeri-
cal analysis. Table 4 shows the demographic characteristics
cal variables (duration and amplitude) are more prominent
of the patients.
in the hemisphere ipsilateral to the lesion. In addition, 64%
3
REFERENCES
Bento CMP et al. - JICNA 2019, 1(1)
REFERENCES
Table 3 Comparison between LGS and non-LGS groups in relation to spatial distribution of PFA (Fisher’s exact test)
Etiologies
Number of patients (percentage) N=36
Malformations of cortical development
12
(33.33 %)
Hypoxic-ischemic encephalopathy
10
(27.77 %)
Unknown cause
5
(13.88 %)
Acquired stroke
3
(8.33 %)
Acute anoxia due to respiratory failure (cardiac arrest and/or drowning)
3
(8.33 %)
Meningoencephalitis
2
(5.55 %)
Hypothalamic hamartoma
1
(2.77 %)
Total
36
Table 4 Demographic characteristics of our patients
Patient/Age/Gender Age at Age at first seizure Perinatal insult Neurological examination Neuroimaging Etiology
Structural
Lennox-Gastaut syndrome
1/F
10
1y8m
No
BD
MRI
Tuberous sclerosis
Yes
Yes
2/F
9
5m
Yes
Tetraparesis + BD
MRI
CC dysgenesis
Yes
No
4/M
17
1day
Yes
Tetraparesis
MRI
Peri-intraventricular hemorrhage
Yes
Yes
5/M
12
3m
No
Tetraparesis
MRI
Unknown
Yes
No
6/M
15
2y
Yes
Tetraparesis
CT
Unknown
Yes
Yes
7/M
24
1y6m
No
Tetraparesis
MRI
Ito hypomelanosis
Yes
Yes
8/M
150
3m
No
Tetraparesis
CT
Lissencephaly
Yes
Yes
9/M
13
1y
Yes
L Hemiparesis
MRI
Perinatal vascular injury
Yes
Yes
10/M
12
3y
No
Normal
CT
Unknown
Yes
No
11/M
9
6m
No
R hemiparesis
MRI
Acquired stroke
Yes
Yes
12/F
15
3m
No
Hypotonia
CT
Lissencephaly
Yes
Yes
13/F
9
2m
Yes
Tetraparesis
No
Unknown
Yes
Yes
14/M
13
2y8m
No
BD
MRI
Acquired stroke
Yes
Yes
15/M
16
10m
No
L hemiparesis
MRI
Perinatal vascular injury
Yes
Yes
16/M
12
1y
No
R hemiparesis
MRI
Hypothalamic
Yes
No
17/F
14
4m
Yes
BD
MRI
Migrational disturbance
Yes
Yes
18/M
10
3days
Yes
BD
CT
Perinatal vascular injury
Yes
Yes
19/F
14
2m
No
BD
MRI
CC agenesis
Yes
Yes
20/M
21
7m
Yes
Tetraparesis + BD
CT
Unknown
Yes
Yes
21/F
53
9y
No
Normal
MRI
Focal cortical dysplasia
Yes
No
22/M
20
7y
No
Hypotonia
No
Down syndromes
No
Yes
23/M
39
2y
No
BD
MRI
Bilateral frontal lobe atrophy + Dandy-Walker complex
Yes
Yes
24/M
21
9m
No
L hemiparesis
MRI
R hemimegalencephaly
Yes
No
25/F
5
1y6m
No
Tetraparesis
No
Meningoencephalitis
Yes
Yes
26/M
16
2y6m
No
Intellectual deficiency
MRI
Doose syndrome
No
No
of their patients became seizure-free after surgical resection.
Author contributions
Therefore, the PFA may be present in patients with a struc-
All the authors contributed to data collection and also crit-
tural cause of epilepsy with secondary bilateral synchrony
ically reviewed the manuscript. The final version of the
and its presence does not always mean a poor prognosis
manuscript was approved by all the authors.
[2].
This is an Open Access article distributed under the
terms of the Creative Commons Attribution License
Conclusion
mits unrestricted use, distribution, and reproduction in any
Although the PFA is an important diagnostic feature of the
medium, provided the original work is properly credited.
LGS, our study has clearly demonstrated that the PFA can
The Creative Commons Public Domain Dedication waiver
also occur in other epileptic syndromes. The EEG charac-
teristics (symmetrical versus asymmetrical) as well as the
applies to the data made available in this article, unless
numerical variables (duration, amplitude and frequency) of
otherwise stated.
the PFA do not differentiate LGS from other epileptic syn-
dromes. Finally, the small sample did not allow statistical
Cite this article as:
correlation when the etiology was considered.
Bento, C. M., Coan, A. C., & Guerreiro, M. M.
(2019). Paroxysmal fast activity: Does this EEG pat-
Aknowledgments
tern occur only in Lennox-Gastaut syndrome?. Journal
of the International Child Neurology Association,
1(1).
Dr. Claudia M. P. Bento received a scholarship from the Na-
tional Council for Scientific and Technological Development
(CNPq) (Grant No 159593/2015-8).
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