Epilepsiu, 40(4).4854Y I. 1999
Lippincott William5 Kr Wilkins. Inc.. Philadelphia
0 Intemationnl Ixngue Apaimt Epilepy
Hypnotic Recall: A Positive Criterion in the Differential
Diagnosis Between Epileptic and Pseudoepileptic Seizures
Jar1 Kuyk, “Philip Spinhoven, and ?Richard van Dyck
lnstituut wor Epilep.siebc.strijdinK ‘Meer en Rosth-De Cruyuiushoeve, Heetristede; “Depurttnent o f Psychiatry, Leiden
University. Leiden; and +Department of Psvchiatry. Vrije Universiteit. Amsterdum, The Netherlands
Summary: Purpose: Because the diagnosis of pseudoepileptic
seizures (PESs) is mostly made by excluding epilepsy, avail-
ability of a positive criterion for PESs is of great importance.
This study was aimed at the validation of a diagnostic tech-
nique that intends to provide in such a positive criterion.
Methods: In 17 patients with epileptic seizures (ESs) and 20
patients with PESs, a hypnotic procedure was performed by an
investigator blind to other data to recover amnesia for the ictus.
If recall was obtained, the experimental diagnosis PES was
given: if not, ES was diagnosed. The experimental diagnoses
were compared with the clinical, EEG-confirmed diagnoses.
Hypnotizability was measured to determine the relation be-
tween the outcome of the test and hypnotizability of the pa-
Resulrs: Recall for the ictus was obtained in 17 patients. Each
of these had a clinical diagnosis of PES. Seventeen patients
with “no recall” had a clinical diagnosis of ES, and three
patients had PESs. This result yields a specificity of 100% and
a sensitivity of 85% for the recall technique. Hypnotizability
was significantly higher in patients with PESs than in patients
with ESs. In some “low hypnotizables,” recall was obtained,
and in some “high hypnotizables,” no recall was obtained.
Conclusions: A positive recall test indicates PES. A sub-
group of patients with PESs is characterized by a high level of
hypnotizability. Hypnotizability is not crucial for outcome of
the recall test. High hypnotic abilities are especially found in
disorders in which it is supposed that “dissociation” is in-
volved. It can be speculated that PES may be one of the dis-
sociative phenomena. Key Words: Pseudoepileptic seizures-
Diagnosing by exclusion is not a satisfying procedure.
This practice stems from a lack of appropriate or specific
tests. Diagnosis by inclusion requires the identification
of specific characteristics. The differential diagnosis be-
tween epileptic seizures (ESs) and pseudoepileptic sei-
zures (PESs) represents such a diagnostic problem. The
diagnosis of PES is mostly based on the exclusion of
epilepsy. The problem is, however, that whereas epilepsy
can be proven, to arrive at a diagnosis “no epilepsy” is
much harder, both for technical caveats and for the lack
of positive criteria for the diagnosis of PES (I).
Pseudoepileptic seizures can be defined as paroxysmal
involuntary behavior patterns mimicking epileptic
events, characterized by a sudden and time-limited dis-
turbance in controlling motor, sensory, autonomic, cog-
nitive, emotional, or behavioural functions (or a combi-
nation of these) and mediated by psychological factors.
A PES may manifest itself by an almost infinite variety
Accepted October 23, 1998.
Address correspondence and reprint requests to Dr. J. Kuyk at In-
stituut voor Epilepsiebestrijding, P. 0. Box 21, 2100 AA Heemstede,
of individual symptoms, as ES does, and they share
many symptoms (1).
The nomenclature for this type of seizure is diverse
and confusing. In this study, the term “pseudoepileptic
seizure” is used, because, unlike most other terms, there
is no confusion possible with identifiable other nonepi-
leptic events. The frequently used term “nonepileptic
seizure” also may refer to organic-mediated seizures
(e.g., syncope, transient ischemic attack, narcolepsy) and
a term such as “psychogenic nonepileptic seizures,”
may involve panic attacks, hyperventilation and posttrau-
matic stress disorder flashbacks (2). Furthermore, de-
scribing a disorder by negative criteria merely creates a
gross category of seizure-like events without clinical co-
herence and should be avoided (3).
It is estimated that c36% of the patients (mostly with
intractable seizures) referred to epilepsy centers have
PESs (4-6) and that 8-36% of this group also have epi-
Patient characteristics or ictal features can be of some
help in differentiating ES from PES, but the specificity in
individual cases is not high. This applies for motor phe-
nomena, vocalization, rocking of the body, pelvic thrust-
ing, kicking or pedaling, uni- and bilateral movements of
J. KUYK ET AL
the extremities, head movements, rapidity of postictal
recovery, incontinence, duration of seizures, tongue-
biting or other injuries, and autonomic changes (10).
More specific is that PES never arises from true sleep
(I 1,12), but accurate assessment is essential because it is
observed that PES often arise out of a trance-like state or
“preictal pseudo-sleep’’ characterized by closed eyes
and immobility, but with EEG evidence of wakefulness
(alpha rhythm, active EMG, rapid eye movements) (1 3).
Long-term video-EEG monitoring improved the dif-
ferential diagnosis between PES and ES to a great extent.
If a seizure can be captured by EEG and shows definite
epileptic activity, there is no doubt about the epileptic
origin. A false diagnosis of epilepsy can originate from
movement or muscle artifacts that disturb the EEG pat-
tern and can be misinterpreted as cerebral discharges.
Discharges also can be out of reach of the EEG. Complex
partial seizures originating in the frontal lobes, notably
from medial or orbital sites, are easily misinterpreted
because of the bizarre clinical features, and this type of
seizure often can not be detected by a surface EEG (14).
Furthermore, one EEG-confirmed seizure does not guar-
antee that PES does not coexist in the same patient.
Amnesia for the ictus is an attribute of generalized and
complex partial seizures, and a variable period of antero-
grade amnesia follows these seizures. Patients may in-
teract with their environment during a seizure, yet have
no subsequent recall of these events (15). Ictal amnesia
cannot be overcome, because the brain does not process
information during an epileptic seizure.
In the 1950s Peterson et al. and Sumner et al. (16,17)
used a hypnotic regression technique to discriminate be-
tween PES and ES. It was supposed that recovery of
amnesia for the seizure through hypnosis may provide a
positive criterion for the diagnosis of PES. In the com-
bined series of Peterson et al. and Sumner et al., 89
“hypnotizable” patients were investigated of i42 pa-
tients with seizures. The authors were able to differenti-
ate 39 patients with ESs and 50 patients with PESs on the
basis of amnesia reversal for the seizure. However, cri-
teria for ES and PES were not well defined, and the
clinical diagnostic tools were less sophisticated than
now. For these reasons, their results are difficult to
evaluate. In a pilot investigation, Kuyk et al. (18) con-
firmed the clinical diagnosis with this technique in four
of five PES patients. The potential importance of this
technique is that it could provide in a positive criterion
for the diagnosis of PES.
Hypnosis was used by Peterson et al. (1 6) and Sumner
et al. (17) to recover amnestic episodes in patients with
supposed psychogenic amnesia. There is evidence that
the amnesia in PESs is psychogenic in origin (1 9). The
evidence for memory improvement with hypnosis (hy-
permnesia) is mixed (20). Laboratory studies with
forced-choice procedures and nonsense material often
showed that hypnosis produces also incorrect recall and
confabulations together with an increase of confidence of
correctness of memories. On the other hand, free recall of
meaningful material may be enhanced by hypnosis (21).
To our knowledge, no systematic studies have been per-
formed concerning the recovering of psychogenic amne-
sia by using hypnosis. To prove that amnesia is really
recovered, independent confirmation of the recollection
has to be obtained.
Hypnosis is considered a multidimensional phenom-
enon in which absorption (narrowing of attention), dis-
sociation (parallel information processing), and suggest-
ibility are underlying factors (22,23). Susceptibility for
hypnosis is a normally distributed, stable trait that may
be partly genetically based (24,25). There are indications
that childhood psychological traumatization enhances
hypnotizability (26,27), but it is also suggested that higi-
hypnotizability is a risk factor for stress- or threat-related
psychological and somatic symptoms (28). Certain psy-
chopathologic conditions are related to higher levels of
hypnotizability (26,29-3 1). In patients with PES, there is
some evidence for increased hypnotizability ( 16,18), and
psychological trauma is frequently reported in the history
of these patients (19).
This study was undertaken to improve and test again
the “Peterson” procedure. A blind recall test is com-
pared with the actual clinical diagnosis of PES or ES. It
is therefore of importance that this diagnosis is accurate.
The best available gold standard for seizure diagnosis is
that typical seizures are confirmed by registration on
EEG. To determine whether the outcome is related to
hypnotizability, this variable is measured in all patients.
Twenty patients with ES and 20 patients with PES, all
admitted in a tertiary epilepsy center for evaluation of
their seizures, participated in random order in this study.
All PES patients had EEG-confirmed seizures (ictal
EEG), and in none of the ES and PES patients was the
existence of coexistent seizures of another origin sus-
pected. After the procedure was explained, informed
consent was obtained. By way of background informa-
tion, it was told that memory during seizures was inves-
tigated by means of hypnosis. The investigators were
blind to the clinical diagnoses.
To be included in the study, amnesia for the ictus has
to be present, and something to remember had to have
happened during the seizure. Only observed or video-
taped seizures were examined during the procedure. In-
structions were given to the staff not to inform the patient
about what had happened during the seizure and not to
show the videotape or to tell the diagnosis after EEG
Epdup,la. V d 40, No 4. I999
DIAGNOSIS OF PSEUDOEPILEPTIC SEIZURES 487
From the ES group, three patients were excluded from
the analysis: one patient had seizures only while sleeping
and had no recall of the preseizure period; one patient
was confused and mixed up two seizures; one patient had
frightening experiences during hypnosis (not related to
the seizure episode), and the procedure was stopped.
In the PES group, 16 patients were women and four
men; in the ES group, three patients were women and 14
men. The ages in the PES group were 17-52 years
(mean, 25 years); in the ES group, 20-59 years (mean, 37
years). Age of seizure onset was 8 4 1 years (mean, 19
years), and 1-58 years (mean, 17 years), respectively.
PES patients had seizures at average 5.4 years (range,
0.5-22 years), and ES patients, 20.9 years (range, 1 4 7
years). Interictal EEG indications for epilepsy were pres-
ent in five PES patients, and one ES patient had a normal
First, the patient was informed about hypnosis to cor-
rect possible misinformation. Next the hypnotizability
was measured. This enabled the patient to gain hypnotic
experience and to be familiarized with the procedure.
Hypnotizability was measured with the Dutch version of
the Stanford Hypnotic Clinical Scale for adults (SHCS;
32), as developed by Morgan and Hilgard (33). The
SHCS is a 30-min, five-item scale, which is individually
administered. A hypnotic relaxation induction is fol-
lowed by an ideomotor item and four cognitive items
(age regression, dream, posthypnotic suggestion, and
posthypnotic amnesia). SHCS scores are based on the
assessment of behavioral characteristics, as well as re-
ported experiences, and range from 0 to 5. Scores 0 and
1 indicate low hypnotic capacity; 2 and 3, medium ca-
pacity; and 4 and 5, high capacity (34).
After measuring hypnotizability, there followed an in-
terview in which the patient was asked to relate every-
thing that could be recalled about the last seizure, from
the time before the seizure to the seizure itself and its
immediate aftermath. Questions were asked about visual,
auditory, kinesthetic, cognitive, and emotional aspects of
each of the elements of the seizure that the subject could
remember. Next, hypnosis was induced with the hand-
levitation induction technique or with the induction pro-
cedure from the SHCS. It was suggested that the patient
would be able to remember everything about the seizure.
Subsequently, the patient was “led back through time”
to the moment just before the seizure, and again was
asked to report everything about the seizure. Most often
it was helpful to introduce a “screen metaphor,” on
which everything could be “seen” by the patient, while
offering the opportunity to get detailed information by
“winding and rewinding the film.” In fact, a free-recall
procedure was performed within the framework of the
screen metaphor, and only open questions were used.
The whole procedure takes at average -90 min. Finally,
the outcome was discussed with the patient. The whole
procedure was videotaped, to compare the recall with
and without hypnosis at a later stage. The whole test was
videotaped to enable control of scoring afterward.
The outcome of the recall test (the experimental diag-
nosis) was PES if ictal amnesia was reversed and the
recalled information could be confirmed. Confirmation
was obtained, when possible, by comparing the recalled
material with the videotape made during EEG registra-
tion of the seizure, and otherwise by asking the nursing
staff who had observed the seizure in question. If the
seizure in question had taken place outside the hospital
ward, relatives who had attended the seizure in question
were asked for confirmation.
If the amnesia persisted, the experimental diagnosis
was ES. To determine the outcome as objectively as
possible, videotapes of the recall sessions were assessed
independently by two observers (psychologists) ignorant
of the patient diagnoses. The criteria to be judged were
the following: “is there new memory material obtained
during the hypnosis interview in comparison to the
awake interview. More details about events already men-
tioned in the awake interview were not considered as
new memory material, nor was new information obtained
at the onset or ending of the seizure considered new
information.” Each rating was qualified as “sure,”
“fairly sure,” or “not so sure.” The strength of agree-
ment between the two observers and between the clinical
and the experimental diagnosis was computed by Co-
hen’s K (35). Sensitivity and specificity of the recall test
was computed. The t test for independent samples was
performed to analyze differences in hypnotizability in ES
Hypnotic capacity was assessed by the investigator
and afterward independently determined by the same two
observers, who had no knowledge about the patients and
their diagnoses. The two observers scored from the vid-
eotapes. In those cases in which there was no agreement,
a consensus score was computed: if an item was scored
positive by one and negative by the other observer, the
score of the investigator was decisive. Videotapes of two
patients failed technically, and these patients were scored
according to the assessment of the investigator. As a
measure of agreement between the observers, K was
computed on item level as well as on the total score.
The outcome of the recall test and the scores on the
SHCS are summarized in Table 1. A positive recall test
was found in 17 of the 37 patients. In all 17 patients, the
clinical diagnosis PES was given. Confirmation of recall
Epdepsia, Vol. 40, No. 4, 1999
J. KUYK ETAL.
TABLE 1. Putient characteristics and studv resctlts
No. Sex Recall”
diagn Obs 2
E E G ~
Pos. positive recall test resulting in the experimental diagnosis of
PES; neg, negative recall test resulting in the experimental diagnosis of
ES. ’’ -, no interictal EEG abnormalities; +, interictal EEG abnormalities
characteristic for epilepsy.
could be obtained in three patients by comparing the
information with the video-EEG recording of the seizure;
in six patients, it was confirmed by specialized nursing
staff, and in eight patients, by relatives who were present
when the seizure occurred.
Both observers agreed in all cases. Observer I and 2
qualified all assessments that resulted in the experimen-
tal diagnosis PES as “sure.” Observer 1 was “fairly
sure” in one and “not so sure” in another ES patient and
“sure” in the others. Observer 2 was “not so sure” in
one and “sure” in the other ES patients.
Sensitivity of the recall test refers to the ability to
identify accurately patients with PES (proportion of true
positives in the entire sample). Seventeen of 20 patients
with the clinical diagnosis PES were correctly identified,
so the sensitivity of this test is 17 of 20 or 0.85. The
specificity of the test refers to the ability of the test to
reject patients who do not have PES (proportion of true
negatives in the entire sample). All 17 patients with the
clinical diagnosis ES were correctly identificated, so the
specificity of the test is 17 of 17 or 1.0 (Table 2).
The measure of agreement of both observers in scor-
ing the SHCS was high (x2 = 136.597; df = 25; p <
0.000), yielding a K of 0.858 (95% CI, 0.73-0.99). On
item level, the K values are for item 1, 0.906; item 2,
0.825; item 3, 0.932; item 4, 0.935; and for item 5, 1.00,
indicating that on item level also, the measure of agree-
ment is quite satisfactory. In five of the I85 item scores,
the observers disagreed, in which cases, the score of the
investigator was decisive (three times negative, two
The average score on the SHCS in PES patients was
3.15 (SD, 1.20) and in ES patients 1.94 (SD, 1.63). This
difference is statistically significant (t(34.339) =
-2.593; p = 0.014). Compared with the SHCS scores of
Dutch normal control subjects (average score, 2.0; SD,
1.4) (36), PES patients scored substantially higher (effect
size, 0.84), and ES patients are comparable to normals
(effect size, 0.008). Eleven of the 17 PES patients earned
a score of 4 or 5 (only two ES patients reached this
level), indicating a high level of hypnotizability.
The results in this study indicate that the recall test is
a feasible and reliable method to use to establish PES. If
ictal amnesia is present and recall is obtained by this
technique and is externally confirmed, the diagnosis of
PES seems quite reliable. If no recall is obtained, the test
is inconclusive: the seizure may be an ES or a PES.
In our sample, there were considerable gender as well
as age differences within and between the PES and ES
groups. The proportion of females in the PES group was
larger than the proportion of males, and this is almost
without exception also found in other studies (37). The
age in PES patients was lower than that in the ES group,
which may possibly be explained by the fact that the ES
patients have a chronic disease and are more frequently
admitted to epilepsy centers than are PES patients after
the right diagnosis.
This is the first systematic study in which a standard-
ized measure of hypnotizability demonstrated above-
TABLE 2. Comparison of the experimental diagnoses made
by the recall test and the clinical diagnosis
I 7 (TN)
ES, epileptic seizure: PES, pseudoepileptic seizure; TN and FN, true
negative and false negative; TP and FP, true positive and false positive.
Epikpsin, Vol. 40. No. 4. /555
DIAGNOSIS OF PSEUDOEPILEPTIC SEIZURES
average hypnotic abilities in PES patients, which dis-
criminate them as a group from the normal population
and from patients with epilepsy. This is in agreement
with existing anecdotal evidence (1 6,3842). Hypnotiz-
ability shows a normal distribution in a non-clinical
population (34). Some psychopathologic conditions, in
which it is supposed that some degree of “dissociation”
is involved, show higher levels of hypnotizability, such
as dissociative disorders (29,30,42,43), posttraumatic
stress disorder (26,3 l), and eating disorders (4447). In a
group of Dutch psychiatric outpatients, mean scores on
the SHCS were not as high as the 3.15 we found in PES
patient?. For example, obsessive-compulsive disorder
patients (n = 39) scored 1.1 (SD, 1 .O); agoraphobia pa-
tients (n = 64) scored 2.3 (SD, 1.4) (36).
Psychological traumatic events are common anteced-
ents for dissociative symptoms and especially childhood
sexual, physical, and emotional abuse is associated with
the development of dissociative symptoms (48-50).
Relatively high rates of psychological trauma are indeed
reported in the history of patients with PES (5 1-54).
These data about hypnotizability and past trauma are in
line with the speculation that PES may be interpreted as
(at least in part) a dissociative phenomenon (1 8).
As can be seen in Table 1 , however, high or low
hypnotizability is not crucial for the outcome of the re-
call test. In the ES group, there are highs with a negative
test, and in the PES group there are lows in whom recall
was possible. Moreover, eight patients with ESs scored
positive on the amnesia item of the SHCS, and seven
patients with PESs scored negative on this item, whereas
recall during the test was nevertheless possible for the
patients with PESs. It can be speculated that in the pa-
tients with PESs with a positive recall test and a low
SHCS score, other factors intervened. Experience with
hypnosis or relaxation techniques may interact with the
formal standardized hypnotizability measure. Patient 3
(SHCS score, 0) was trained in yoga and relaxation tech-
niques and reported that the induction instructions con-
fused him. Those PES patients who remembered nothing
in both conditions may have a factitious disorder or may
simulate. This may be the case in patients 9 and 17, in
whom amnesia was maintained during hypnotic recall,
and hypnotizability (SHCS scores 0 and 1, respectively)
was absent or very low. Theoretically, it cannot be ex-
cluded that some patients feign amnesia for the ictus or
deny recovering amnesia. It is not very likely, however,
that those patients with PESs who do remember in hyp-
nosis what happened during the seizure deceived the in-
vestigator only in the alert state and not in hypnosis.
It is conceivable that hypnosis is not essential in the
procedure. Hypnosis is considered to be a multidimen-
sional phenomenon, in which the factor of suggestibility
(social influenceability) plays an important role in the
lower levels and the factor of dissociation plays a greater
role in the higher levels of hypnotizability (55). Different
factors can play a greater role in different patients. Hyp-
nosis is considered in our community by many people as
“magic,” and the ritual itself could be the essential in-
gredient of the procedure: patients can maintain that
what happened was unconscious and involuntary. This
could be investigated empirically by testing the recall
procedure with and without formal hypnosis. Simpler
procedures based on imagination may work as well. If
this were true, this might facilitate the use of the diag-
nostic recall technique in epilepsy centers, as most cen-
ters will not have staff experienced with hypnotic pro-
It is common practice to diagnose PESs by the exclu-
sion of epilepsy. Even if epilepsy cannot be demon-
strated, however, epilepsy is still possible. In this experi-
ment, the outcome of the recall test leads to a positive
criterion of the diagnosis of PES. To the best of our
knowledge, this is so far the only test that provides re-
liable evidence in diagnosing PES. The specificity of
100% implies that no patients with actual epilepsy are
identified as having PESs. Because the sensitivity is not
loo%, only a positive outcome is decisive. If no epilepsy
can be demonstrated and no recall can be obtained, clini-
cal judgment is on the basis of “soft signs,” and a ten-
tative diagnosis is left. Often a probe with antiepileptic
medication is done. As can be seen in this study, how-
ever, patients with PESs are especially suggestible. and a
strong placebo effect is conceivable.
A limitation of this study is that in the patients with
PESs, the experimental diagnosis was not always based
on that particular seizure that was video-EEG recorded.
The patients could make their own choice as to which
seizure they would focus on in the experiment. Although
we selected only patients in whom no coexistent seizures
of another origin were suspected, we cannot prove that
the seizure that was “recalled” definitely had the same
etiology as the video-EEG-confirmed seizure.
The results of this study are quite interesting also from
another scientific point of view. Although this study was
not specifically designed to investigate the quality of
recall obtained with hypnosis, we found in nine patients
fairly reliable confirmation of the recall (in three patients
by comparing the recall with the videotaped seizures
during EEG, and in six patients, the recall was confir-
mation by specialized nursing staff who had observed the
seizure in question; in the other eight patients, relatives
confirmed what was recalled). On the basis of experi-
mental research data, however, there is at present strong
doubt about the reliability of memories obtained through
hypnosis (20,56). These data seem to pertain especially
to “cued” recall. Our data, however, follow from free
recall. Free recall has been found to be less vulnerable to
memory distortion than recall using specific questions
and especially recall using leading questions, which have
Epilepsia, Vol. 40, No. 4, 1999
J. KUYK ET AL.
at present led to the “memory wars” over repressed and
false memory (57-59). These observations emphasize
that only free recall shauld be applied in this diagnostic
technique and that the use of cued recall must be
Acknowledgment: This study was supported in part by a
grant of the Dutch Society for Hypnosis. We thank the staff of
the Dr. Hans Berger Kliniek, the Epilepsy Center “Kempen-
haeghe,” and the Instituut voor Epilepsiebestrijding for their
support. Especially we thank Leo Dunki Jacobs, psychologist,
for performing the recall procedure in several patients.
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