dissociative experiences - epilepsy
experiências dissociativas - epilepsia
Dissociative disorders are characterized by a disruption of and/or discontinuity in
the normal integration of consciousness, memory, identity, emotion, perception, body
representation, motor control, and behavior[1]. Dissociative experiences occur on a continuum ranging from the minor or normative
dissociative states such as absorbtion or daydreaming customary to daily life to pathological
states such as dissociative identity disorder[2]. The prevalence rates has varied from a low of 1.0% to a high of 12.8% depending
on the cut-off point indicative of pathological dissociative symptomatology[3]
,
[4]. The Dissociative Experience Scale (DES) is the most widely used standard screening
tool utilized for assessing dissociative symptoms[3]
,
[4]
,
[5].
The strong linkages of dissociation to childhood emotional, physical or sexual trauma
have long been recognized. Dissociation is considered to serve as a defense mechanism
againts intolerable, trauma-associated memories and feelings[4]. Despite dissociative disorders are conceptualized in a separate spectrum, pathological
dissociation has been demonstrated to be higly co-occurring condition with mental
disorders including posttraumatic stress disorder, borderline personality disorders,
anxiety and mood disorders, and substance use disorder[4]. Dissociative experiences can also be observed in different types of brain pathology
such as epilepsy, head injuiry, tumor, encephalitis and intoxication[6]
,
[7].
It is known that complex partial seizures may resemble certain dissociative phenomena,
e.g., altered sense of self and amnesia, fugue states, dissociative convulsions, and
disturbed consciousness[3]
,
[6]
,
[8]. The symptoms of depersonalization/derealization associated with the temporal or
frontotemporal EEG abnormalities responding to anticonvulsant treatment have been
reported[6]. Also, dissociative disorders are more common in patients with epilepsy than in
the general population (range from 5 to 40% versus 0.3 to 3.4%)[3]. The higher prevalence of dissociative experiences may suggest an association between
epilepsy and dissociation. Epilepsy can increase one’s susceptibility to developing
dissociative experiences[3].
Devinsky et al.[9] investigated the possible relationship between dissociative states and epilepsy.
They used video-EEG monitoring to determine whether the patients have epileptic epizodes
in 6 multiple personality disorder (MPD) patients with previously diagnosed with epilepsy;
however, none proved to have epilepsy. In addition, they studied dissociative symptoms
in 71 epileptic patients and age-matched normal controls. The mean DES score was higher
in cases with complex partial seizures than in controls, and was significantly lower
than that of the patients with MPD. Partial seizure patients with dominant hemisphere
foci had higher depersonalization subscale scores than those with nondominant foci.
The authors suggest that epilepsy is not a primary pathophysiologic mechanism for
developing dissociative symptoms.
Once again, Devinsky et al.[10] compared the experience of dissociative symptoms in patients with focal and primary
generalized epilepsy and control subjects. Ictal depersonalization was observed in
15% of patients with partial seizures, occuring interictally in 10%. This symptom
was reported by 3% of healthy control subjects but by none of the patients with primary
generalized seizures. They found that derealization was more commonly seen among patients
with complex partial seizures during ictal as well as interictal periods than controls
(18%, 14% and 12%, respectively). However, derealization was present in only 5% of
patients primary generalized epilepsy. Different forms of dissociation such as distortions
of shape, size, and distance of objects were reported by patients with epilepsy but
were not reported by control group.
Psychogenic nonepileptic seizures (PNES) is characterized by a sudden onset and time
limited disturbance in controlling motor, sensory, autonomic, cognitive, emotional,
and behavioral functions resembling dissociative disorders[11]. Several studies have investigated the relationship between PNES and epilepsy[5]
,
[12]. It has been reported that PNES occur about 20% in patients with epilepsy[11]. A number of studies have found elevated levels of dissociation in patients with
PNES[13]
,
[14]. Patients with PNES often experience dissociative symptoms, increased dissociative
tendency and high hypnotisability. Some authors argued that dissociation underlies
the psychopathology of PNES[13]. These findings suggest that epilepsy is associated with dissociation.
Akyüz et al.[15] studied dissociative experiences, childhood abuse and anxiety in epileptic and pseudoseizure
female patients[15]. Both pseudoseizure and epileptic seizure groups had DES scores greater than those
of normal adult subjects. In addition, DES scores of the pseudoseizure group were
statistically higher than the epileptic group. In another study, the DES was administered
to patients with epilepsy and PNES, patients with epilepsy and no PNES and healthy
control individuals by Ito et al.[5] The authors found that patients with epilepsy and PNES scored significantly higher
on the DES than patients with epilepsy without PNES and nonclinical individuals. Alper
et al.[16] examined the dissociation in patients with complex partial epilepsy (CPE) and PNES.
There were no significant differences in total DES scores between the two groups.
PNES and CPE patients both had DES scores greater than those of normal adult subjects
and less than those of subjects with dissociative disorders.
Several studies have shown that PNES are commonly in patients with epilepsy. In contrast,
relatively few studies have investigated dissociative experiences in epilepsy patients.
The results of some studies showed higher levels of dissociation in patients with
epilepsy. However, others have found no correlation between epilepsy and dissociation.
In the recent past, Hara et al.[3] investigated dissociative experiences in 225 patients with epilepsy and 334 nonclinically
matched individuals using the DES[3]. They found that there was no significant difference in the DES score between the
group with epilepsy and the control group. Similarly, Wood et al.[17] found no difference in the DES scores between patients with psychogenic seizures
and with epilepsy. Because of the contradictory findings, further studies are needed
to understand the linkages between dissociative experiences and epilepsy. In this
study we aimed to investigate dissociative experiences in patients with epilepsy.
METHOD
Subjects
The subjects consisted of 98 patients with epilepsy and 60 healthy controls. Patients
were selected from consecutive admissions to the neurology department of the hospital
according to the following criteria: (1) epilepsy type either generalized epilepsy
or focal epilepsy (2) age at the time of evaluation ranging from 15 to 70 years; (3)
no history of psychosis, substance abuse, dementia, or progressive neurological disease
and (4) no clinically significant signs of other psychiatric disorders requiring treatment
(such as depression and anxiety disorders) at the time of the evaluation. All the
patients were diagnosed using video-EEG technique as per the International League
Against Epilepsy (ILAE) classification. Magnetic resonance imaging (MRI) was used
to diagnose the structural lesion. The control group was age-and education- matched
with the group with epilepsy.
Instrument
Socio-Demographic Questionnaire: The Sociodemographic questionnaire included questions about age, marital status, educational
level, employment status, duration of epilepsy, age of epilepsy onset, and frequency
of seizures.
Dissociative Experiences Scale (DES): The Dissociative Experiences Scale is a 28-item self-report questionnaire developed
for screening dissociative experiences including disturbances in memory, identity,
awareness, and cognition, not occurring under the influence of alcohol or drugs. The
possible response options increase by increments of 10% (“this never happens”) to
100% (“this always happens”). The Turkish version of the DES was demonstrated to have
good reliability and validity almost equal to its original form[18].
Beck Depression Inventory (BDI): The Beck Depression Inventory (BDI) is a 21-item self-report measure of depressive
symptom severity. Each item israted on a 0-3 and the total scores range from 0 to
63. The validity and reliability Turkish version of the BDI was demonstrated by Hisli[19].
Beck Anxiety Inventory (BAI): The Beck Anxiety Inventory (BAI) consists of twenty-one items self report used to
assess emotional, physiological, and cognitive symptoms of anxiety. Multiple choices
questions have four possible answers: not at all (0 points), mildly (1 points), moderately
(2 points), and severely (3 points). The test scores range between 0 and 63. The validity
and reliability Turkish version of the BAI was performed by Ulusoy et al.[20].
Procedure
The study received approval from the University Ethical Committee. Each participant
written informed concent form. The DES, BDI, and BAI was administered to all the individuals
of the two groups. We studied and compared the dissociative experiences and depression
and anxiety levels between patients suffering from epilepsy and healthy controls.
The group with epilepsy was further divided into according to EEG pattern of epileptiform
activity groups for analysis.
Statistical analysis
Descriptive statistics for continuous variables were presented as mean and standard
deviation. Student t-test was used to compare group means for the studied variables.
Chi-square test was carried out to examine relationships between groups and categorical
variables. Statistical significant level was considered as p < 0.05. The SPSS (ver.
16) statistical program was used for statistical analyses.
RESULTS
The mean age at first epileptic seizure was 16.2 years (standard deviation (SD) 7.8).
Duration of epilepsy was 108.3 months (SD 124.1). The median seizure frequency was
71.0 seizures/year (SD 146.0).
Comparison of age, gender, BAI, BDI and Dissociative Experiences Scale scores of the
group with epilepsy and the healthy controls shown in [Table 1]. The mean age of patients was 25.3 years (SD 10.2), and the mean age of controls
was 27.9 years (SD 4.3). There were no statistically significant differences in the
age and gender between the two groups (p > 0.05). Patients with epilepsy scored significantly
higher mean scores on the DES, BAI and BDI compared to control group (p < 0.01). Additionally,
subjects with pathological dissociation (DES ≥ 30) was greater in epilepsy groups
than in control group (p < 0.05). Twenty-eight epilepsy patients (28.5%) and 8 healthy
individuals (13.3%) had pathological dissociation.
Table 1
Comparison of age, gender, Beck Anxiety Inventory (BAI), Beck Depression Inventory
(BDI) and Dissociative Experiences Scale (DES) scores of the group with epilepsy and
the control group.
|
Mean ± SD
|
p-value
|
|
|
Epilepsy patients (n = 98)
|
Healthy controls (n = 60)
|
|
Age
|
25.3 ± 10.2
|
27.9 ± 4.3
|
0.066
|
|
Gender male /female
|
47 / 51
|
27 / 33
|
0.717
|
|
DES
|
23.8 ± 17.8
|
15.0 ± 10.6
|
0.001**
|
|
BAI
|
24.7 ± 13.2
|
12.0 ± 9.4
|
0.000**
|
|
BDI
|
20.4 ± 11.2
|
9.9 ± 6.6
|
0.000**
|
|
DES ≥ 30
|
28 (28.5%)
|
8 (13.3%)
|
0.016*
|
SD: standard deviation; *p < 0.05; **p < 0.01.
Comparison of age at onset of disease, duration of epilepsy and frequency of seizures
between epilepsy patients with and without pathological dissociation are presented
in [Table 2]. No significant differences between patients with pathological dissociation (n =
28) and patients without pathological dissociation (n = 70) were found in age at onset
and duration of epilepsy. Frequency of seizures was significantly higher in the patients
with pathologic dissociation compared to patients without pathological dissociation
(p < 0.05).
Table 2
Comparison of age at disease onset, seizure frequency and duration of epilepsy in
the epilepsy patients who has pathologic dissociation (DES ≥ 30) and who has not
|
Mean ± SD
|
p-value
|
|
|
DES ≥ 30 (n = 28)
|
DES < 30 (n = 70)
|
|
Age of epilepsy onset
|
17.6 ± 6.8
|
16.0 ± 7.9
|
0.376
|
|
Duration of epilepsy
|
85.6 ± 96.4
|
120.4 ± 133.2
|
0.238
|
|
Frequency of seizures
|
126.7 ± 226.0
|
49.7 ± 94.1
|
0.021*
|
DES: Dissociative experiences scale; SD: standard deviation; *p < 0.05.
Comparison of DES scores in groups with epilepsy according to EEG pattern of epileptiform
activity are shown in [Table 3]. The patients were divided into groups: generalized epileptiform activity (n = 34)
and focal epileptiform activity (n = 34) (p = 0.914), right hemisphere (n = 14) and
left hemisphere (n = 20) (p = 0.426), temporal epileptiform activity (n = 10) and
frontal epileptiform activity (n = 9) (p = 0.761). There were no statistically significant
differences among the groups with respect to DES scores.
Table 3
Comparison of Dissociative Experiences Scale (DES) scores in groups with epilepsy
according to EEG pattern of epileptiform activity.
|
DES
|
p-value
|
|
Generalized (n = 34)
|
23.47 ± 18.34
|
0.914
|
|
Focal (n = 34)
|
23.02 ± 15.23
|
|
Right hemisphere (n = 14)
|
20.50 ± 14.39
|
0.426
|
|
Left hemisphere (n = 20)
|
24.80 ± 15.90
|
|
Temporal (n = 10)
|
20.60 ± 13.04
|
0.761
|
|
Frontal (n = 9)
|
23.00 ± 20.35
|
DISCUSSION
In the current study, we found that the DES scores were significantly higher in the
patient with epilepsy than in the healthy individuals. The number of individuals with
pathologic dissociation (DES ≥ 30) was higher in the patients group than in the control
group. In addition, higher levels of dissociation were significantly associated with
frequency of seizures, but were not associated with duration of epilepsy and age at
onset of the disorder. The DES scores did not differ significantly with respect to
the various EEG parameters such as generalized or focal, right or left sided, and
temporal or frontal lobes epileptic activity. These findings suggest that patients
with epilepsy are more prone to experiencing dissociation. The high rate of dissociative
experiences in patients with epilepsy suggests some epilepsy-related factors precipitating
and maintaining dissociation. These predisposing risk factors could also be potential
shared aetiological, neurobiological mechanisms that may cause both epilepsy and dissociation.
There has been growing evidence for linkages between dissociation and epilepsy. Ito
et al.[5] reported that patients with epilepsy and PNES had significantly higher DES and DES
taxon (DES-T; a subset of DES score and an index of pathological dissociation) scores
than nonclinical individuals. In addition, high DES scores (> 30) were more frequently
observed in patients with epilepsy and PNES than in patients with epilepsy without
PNES and nonclinical individuals. DES score did not differ significantly with respect
to epilepsy-related variables including age at onset of epilepsy, duration of epilepsy,
types of epilepsy determined on the basis of ictal symptoms and EEG and neuroimaging
findings. Consistent with this research findings, we found no significant differences
between the high and low dissociation groups (cutoff score of 30) in terms of duration
of epilepsy and age of epilepsy onset.
Hara et al.[3] showed a significantly higher DES-T and DES score ≥ 30 (two indices for pathological
dissociation) in the group with epilepsy than the control group. On the other hand,
these pathological dissociation were significantly associated with duration of epilepsy
and seizure frequency. Duration of epilepsy correlated inversely with both the DES
scores and DES-T. Seizure frequency correlated with the DES-T but not with the DES
scores. The authors argued that the distress with frequent seizures and uncertainties
of the occurence of epileptic seizures may make patients with epilepsy more prone
to dissociation. In addition, as age advances, seizure frequency tends to decrease
as well as with age advancing, the DES indices decreased. In our study, we observed
that the patients who experience more seizure tend to have pathological dissociation.
Our results also demonstrated the presence of significantly increased incidence of
pathological dissociation (DES ≥ 30) in patients with epilepsy as compared with the
control group. Twenty eight (28.5%) of the 98 patient with epilepsy and eight of the
control (13.3%) had DES scores of 30 or above (p = 0.021).
The etiology of this high prevalence of dissociative experiences in patients with
epilepsy remains unclear. Wang et al.[21] have tried to find an answer from the neuropathological and sociodemographic perspectives.
The authors found that dissociative experiences were more prevalent in the patients
with epilepsy. Moreover, the dissociative experiences in patients with epilepsy are
not related to the neuropathological features such as location of lesion (temporal,
frontal, other lesion), presence or absence mesial temporal lobe epilepsy, side of
lesion (rihgt, left, both sides, no lesion), and type of seizure (focal seizures,
focal with secondary generalization, generalized tonic-clonic seizures). DES scores
are related to the sociodemographic parameters similar to those of the general population.
There was a higher dissociative symptoms in female, lower education and low socioeconomic
status.
Mula et al.[7] investigated whether there is an association between EEG lateralization and DES
scores. They did not find any difference in DES scores across different lateralities
(right/left or monolateral/bilateral). Hara et al.[3] found no link between dissociation and epilepsy types (temporal, frontal, parietal,
occipital and partial epilepsy with undetermined lobar foci), the presence of either
mesial temporal sclerosis or laterality of EEG abnormalities (left, right, bilateral).
In our relatively small sample, we found no significant difference in DES scores between
patients who had focal (n = 34) and generalized (n = 34), right (n = 14) and left
sided (n = 20), or temporal lobes (n = 10) and frontal lobes (n = 9) epileptiform
activity. The results appear to indicate lack of relation between dissociation and
EEG localization regarding to epileptiform activity.
On the other hand, previous studies also showed that patients with temporal lobe epilepsy
(TLE) experience several dissociative symptoms such as out of body experiences, near
death experiences, depersonalization and fugue[6]
,
[7]
,
[22]
,
[23]
,
[24]. Connections of EEG abnormalities with several dissociative syndromes including
dissociative identity symptoms have been described[22]
,
[24]. Temporal lobe epileptiform discharges and the limbic structures which are essential
regions for generation of complex partial seizures can lead to these symptoms[3]
,
[21]
,
[22]. Devinsky et al.[10] found that depersonalization was associated with complex partial (focal) epilepsy
rather than primary generalized epilepsy. Kuyk et al.[25] found higher dissociation in patients with TLE than nonclinical individuals. Devinsky
et al.[26] reported PNES groups (PNES only and PNES plus epilepsy) have a significantly higher
frequency of right hemisphere pathology compared with patients with epilepsy (without
PNES or any other psychiatric disorders). The authors have found the manifestation
of conversion disorder to be more common in right hemisphere lesions supporting the
mechanism of right hemisphere dysfunction.
In the recent years, despite the enormous amount of clinical, experimental, and theoretical
interest in this area, the neurobiological basis of dissociation is still poorly understood.
Functional disconnectivity syndrome has been assumed to explain the dissociative symptoms.
The authors investigated the hypothesis that a dysfunction of hemispheric interaction
might be a predisposition to dissociative psychopathology[27]
,
[28]. Spitzer et al.[27] examined the relationship between dissociation and interhemispheric structural asymmetry.
The researchers have found that the high dissociators (DES scores ≥ 30) had a significantly
lower left hemispheric excitability than righ hemispheric excitability. Ashworth et
al.[28] demonstrated that participants scoring high in dissociation displayed left hemispheric
lateralization. These findings suggest that dissociation involves a cortical asymmetry
with a left hemispheric superiority or, alternatively, a lack of right hemispheric
interaction[27]. Thus, an altered feelings of familiarity, depersonalization and derealization symptoms,
may be linked to the right hemisphere dysfunction. The functional deficits in the
sensorimotor and cognitive processes may play a crucial role in dissociation[28].
The relationship between epilepsy and dissociation is complex and some authors have
argued that dissociative experiences in epilepsy are often associated with comorbid
anxiety[7]. One theoretical view argued that dissociative reactions are associated with extremely
elevated psychological and physiological arousal state that occurs during a anxiety[29]. Sterlini and Bryant[29] described that extent anxiety and marked physiological arousal are strongly predictive
peritraumatic dissociation that occur during or immediately after a traumatic event.
Further, dissociative symptoms are commonly experienced during panic attacks. Mula
et al.[7] observed no difference in DES scores between patients with or without auras, but
DES scores correlated with the anxiety scores. In our study, BAI scores of patients
with epilepsy were significantly higher compared to the than control group (p = 0.000).
Taken together, our findings and other evidences might suggest that dissociative experiences
are more common in patients with epilepsy than in healthy controls. It appears that
this dose not result from localization related epilepsy. In contrast, some previous
studies showed that dissociative phenomena are associated with temporal lobe epilepsy
and the complex partial seizures[3]
,
[21]. These contradictory findings warrant further studies with large representative
samples.
