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Suggestive seizure induction (SSI) is an accurate diagnostic screening tool.
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The overall level of evidence is low.
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Various techniques of suggestions have high diagnostic yields.
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There are some risks and side effects of SSI.
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There are no known relevant predictive factors of successful SSI.
Abstract
Suggestive seizure induction is a widely used method for diagnosing psychogenic nonepileptic seizures (PNES). Despite seven decades of multidisciplinary research, however, there is still no unified protocol, no definitive agreement on the ethical framework and no consensus on diagnostic utility. This systematic review surveys the evidence at hand and addresses clinically relevant aspects of suggestive seizure induction. In addition to its use for facilitating the diagnostic process, its mechanism of action and utility in elucidating the psychopathology of PNES will be discussed.
In 1945, within the inaugural decade of clinical electroencephalography (EEG), Herbert Kupper reported the first instance of a seizure induced by hypnotic suggestion while his patient was hooked up to an electroencephalograph [
] to test the utility of seizure induction via hypnotic suggestion during EEG to distinguish psychogenic from epileptic events. In 16 patients with “convulsive disorder and concomitant electroencephalographic findings” hypnotic suggestion failed to induce a typical fit; however, it did provoke the habitual attacks in ten other patients with presumed epileptic seizures [
]. The EEG showed no ictal abnormalities and, thus, these ten patients were the first ever to be diagnosed with psychogenic nonepileptic seizures (PNES) using suggestive seizure induction (SSI).
Nowadays, video documentation of a typical event during simultaneous EEG co-registration is required for the definitive diagnosis of PNES [
Minimum requirements for the diagnosis of psychogenic nonepileptic seizures: a staged approach: a report from the International League Against Epilepsy Nonepileptic Seizures Task Force.
]. When long-term VEEG is unavailable, inconclusive or fails to record a spontaneous event, induction techniques are recommended to facilitate diagnosis [
Minimum requirements for the diagnosis of psychogenic nonepileptic seizures: a staged approach: a report from the International League Against Epilepsy Nonepileptic Seizures Task Force.
The era of evidence-based medicine has seen the validation and standardization of most diagnostic procedures in clinical practice, yet there have been relatively few attempts at unifying and systematically evaluating SSI [
], there is currently no established protocol, no universal consensus on the ethical framework, and only a limited selection of studies on diagnostic yield. This review aims to systematically survey the available literature and draw applicable conclusions for the ethically permissible and diagnostically efficient use of SSI in epileptology practice.
2. Methods
Studies on the clinical application of SSI were identified by searching PubMed (NCBI), ISI Web of Science (Thomson Reuters) and Google Scholar. Combinations of search terms associated with PNES and seizure provocation were used (see Appendix A for a complete list). All articles were assessed based on title and abstract, and, if eligible, were retrieved in full and re-assessed. Additionally, the reference lists of all selected articles were scanned for related citations. Only studies in English were considered. Studies that focussed exclusively on pediatric population were excluded. Non-peer-reviewed articles and published abstracts, as well as case reports and small case series (n < 10) were also excluded. Appendix B summarizes relevant studies that were excluded from the systematic review.
Next, to assess the quality and strength of each study, its methodological characteristics were identified based on the recommendations of the American Academy of Neurolgy (AAN) [
]. Specifically, the following characteristics of each study were extracted and assessed: purpose of study, cohort enrollment, setting, independent reference standard, comparison group, follow-up, formal psychiatric assessment, inclusion criteria, sample size, age, percentage of women, SSI technique, standardized protocol, timing of SSI, blinded evaluation, patient information, excerpt referring to patient information, degree of deception, yield, study conclusion, class of evidence, ethical committee approval.
Classes of evidence were assigned using Clinical Practice Guideline Process Manual of the AAN [
]. One study was classified using the criteria for prognostic accuracy; all other studies were evaluated based on one of two matrices available diagnostic procedures: diagnostic accuracy and population screening. For diagnostic accuracy, class III or higher requires an independent reference (“gold”) standard in terms of sensitivity [
]. Although long-term VEEG is frequently referred to as the “gold standard”, it is such only in terms of diagnostic confidence when positive, just as SSI is [
Minimum requirements for the diagnosis of psychogenic nonepileptic seizures: a staged approach: a report from the International League Against Epilepsy Nonepileptic Seizures Task Force.
]. A “gold standard” in terms of perfect (near 100%) sensitivity does not exist for PNES, since even long-term VEEG often remains inconclusive or negative in cases of suspected or confirmed PNES [
Usefulness of prolonged video-EEG monitoring and provocative procedure with saline injection for the diagnosis of non epileptic seizures of psychogenic origin.
] for the purpose of this review long-term VEEG was considered an adequate independent reference standard. Many systematic studies on SSI evaluated the diagnostic yield which is more appropriately reflected in the evidence classification criteria for population screening. The diagnostic yield, or calculated sensitivity of a diagnostic test, will depend on the pre-test selection criteria (i.e. disease prevalence) [
], for the practicing clinicians studies that reflect their own setting and patient sampling (i.e. tertiary referral center, suspected PNES) are most useful [
To assess the degree of deception involved in informing patients about SSI we classified the reported communication strategies into three categories: “explicitely deceptive”, when a statement is made that is untruthful (e.g. “a seizure will be produced […] by placing a vibrating tuning fork on the forehead and sending ‘electric vibrations’ through the brain”, [
]); “truthful but omissive”, when the information is technically truthful, but an exclusively organic process is still implied (e.g. “we will inject an IV drug that will perhaps help in inducing the usual spell […] We did not say the words ‘epileptic seizure’ in order to avoid lying to the patient”, [
Usefulness of prolonged video-EEG monitoring and provocative procedure with saline injection for the diagnosis of non epileptic seizures of psychogenic origin.
]); and “explicitely open”, when the information provided is technically correct and a psychological process is explicitely introduced as a possiblity before SSI (“The possible occurrence of both epileptic and psychogenic seizures during hyperventilation and photic stimulation was stressed”, [
Hyperventilation and photic stimulation are useful additions to a placebo-based suggestive seizure induction protocol in patients with psychogenic nonepileptic seizures.
Using the aforementioned search strategies and selection criteria 32 studies that examine the utility of SSI for the diagnosis of PNES were identified. Table 1 offers a summary; an expanded version of this table with all study characteristics listed in the “Methods” section is available as Supplementary Marterial. Overall, there was a marked methodological heterogeneity and low level of evidence. Only one study was considered Class II, 16 Class III and 15 Class IV. Common reasons for these relatively low classifications were that most studies were performed in specialized tertiary referral centers, few had control groups and in no study was SSI performed by an examiner blinded to pre-test conditions. These limitations, however, reflect the pre-selected population and clinical setting of most clinicians that are likely to routinely perform SSI.
Table 1Summary of studies on suggestive seizure induction.
Usefulness of prolonged video-EEG monitoring and provocative procedure with saline injection for the diagnosis of non epileptic seizures of psychogenic origin.
Hyperventilation and photic stimulation are useful additions to a placebo-based suggestive seizure induction protocol in patients with psychogenic nonepileptic seizures.
The majority of studies (82%) that reported gender distribution had a female predominance in their cohorts. Of the five studies with a higher proportion of men, four recruited from veteran populations. The reported mean age was between 21 and 47 years, with an age range spanning at least four decades in most cases (13 of 17 studies with available information). Overall, the demographic data of all studies combined reflects the patient characteristics known for PNES patients [
] and implies a sufficient level of generalizability for epileptology practice.
Almost all studies were performed at tertiary referral centers. Eight studies (25%) offered follow-up data. Seven studies (22%) reported some form of formal psychiatric and/or psychological assessment, which would help identify closely related psychiatric disorders (such as panic disorder, post-traumatic stress disorder and others). The most commonly examined SSI technique was intravenous saline infusion alone or in combination with other techniques (16 studies, 50%); ten studies (31%) examined hyperventilation and photostimulation.
In light of these observations, the following aspects of SSI that are of interest to clinicians are discussed below: ethical considerations; techniques of SSI; role in diagnostic workup; risks and side effects; psychobiological mechanisms; predictive factors; therapeutic effect.
4. Ethical considerations
The debate around the ethical justification of SSI has been addressed comprehensively on many occasions in the past [
]. Few studies have tested this assumption. Chen and colleagues report that “none of the 51 enrolled patients reported feeling deceived following the induction attempt” [
]. In line with this, when Goyal and colleagues asked 50 PNES patients (who had undergone a considerable battery of various induction methods) to characterize the experience via a questionnaire, 47/50 patients found SSI “patient friendly and satisfactory” and 44/50 indicated they would undergo SSI again in the future if needed [
Hyperventilation and photic stimulation are useful additions to a placebo-based suggestive seizure induction protocol in patients with psychogenic nonepileptic seizures.
]. Out of the 32 studies at hand, 24 report the strategies of patient information. Using the categorization described above, in the twelve studies published before 2000, the majority was catgorized as “explicitely deceptive”. In the twelve studies published after 2000, on the other hand, only one was categorized as “explicitely deceptive”, seven as “truthful but omissive” and four as “explicitely open” (see Fig. 1). A tendency towards more honest communication over the years becomes evident. Moreover, two recent studies show that honestly informing patients beforehand about the possibility of PNES does not impair the efficiency of SSI [
Hyperventilation and photic stimulation are useful additions to a placebo-based suggestive seizure induction protocol in patients with psychogenic nonepileptic seizures.
One of the chief arguments in support of the ethical license of SSI lies in the trade-off between the degree of deception involved and the efficacy of this procedure to establish a diagnosis and prevent years of inappropriate treatment [
Minimum requirements for the diagnosis of psychogenic nonepileptic seizures: a staged approach: a report from the International League Against Epilepsy Nonepileptic Seizures Task Force.
]. In 36 patients with PNES, 22 with epilepsy and 11 with both, Barry and colleagues established significantly higher hypnotizability in patients with PNES alone or dual pathology than those with epilepsy alone [
]. In patients with PNES (with or without concomitant epilepsy) 77% had typical seizures induced during hypnosis. Among other advantages, the authors stress its potential to function as a “conduit for long-term treatment”, referring to the therapeutic potential of hypnosis [
]. Khan and colleagues conducted a prospective study of 47 patients who underwent VEEG and SSI: 24 had spontaneous events under VEEG and, of those, 11 also had events under hypnotic suggestion (2009). This relatively low diagnostic yield of 46%, and the fact that none of the patients with inconclusive VEEG had inducible seizures led the authors to conclude, that alternative methods of SSI ought to be explored [
] but cannot be recommended for routine application outside the hands of experienced hypnotists within scientific studies.
In 1979, Remick and Wada first used intravenous agents during VEEG to provoke a seizure in a patient with presumed refractory epilepsy. A typical attack without any epileptiform EEG changes was induced and categorized as psychogenic [
] to test intravenous application of saline for SSI in 57 patients with poorly controlled or atypical seizures: while 3 had spontaneous PNES, 48 of the remaining 54 (89%) had induced PNES. Saline injection has since become the best documented method of SSI [
Usefulness of prolonged video-EEG monitoring and provocative procedure with saline injection for the diagnosis of non epileptic seizures of psychogenic origin.
Hyperventilation and photic stimulation are useful additions to a placebo-based suggestive seizure induction protocol in patients with psychogenic nonepileptic seizures.
]. Depending on the patient sample (i.e. the pre-test probability) i.v.-saline-based SSI can achieve a diagnostic yield of up to 89–91% in eventually confirmed PNES [
Usefulness of prolonged video-EEG monitoring and provocative procedure with saline injection for the diagnosis of non epileptic seizures of psychogenic origin.
]. However, saline injection provides a significant additional yield in protocols that begin with hyperventilation and photic stimulation and use saline only when necessary [
Hyperventilation and photic stimulation are useful additions to a placebo-based suggestive seizure induction protocol in patients with psychogenic nonepileptic seizures.
Openly discussing possible psychological factors beforehand and refraining from false statements can help (see previous section). A protocol incorporating both non-invasive and invasive techniques might help limit the use of placebo-based SSI to the necessary minimum, without striking it out of the epileptologist's armamentarium altogether [
Hyperventilation and photic stimulation are useful additions to a placebo-based suggestive seizure induction protocol in patients with psychogenic nonepileptic seizures.
Hyperventilation and photic stimulation are useful additions to a placebo-based suggestive seizure induction protocol in patients with psychogenic nonepileptic seizures.
An advantage of hyperventilation and photic stimulation is that both can be presented truthfully as methods that can potentially precipitate epileptic seizures [
Minimum requirements for the diagnosis of psychogenic nonepileptic seizures: a staged approach: a report from the International League Against Epilepsy Nonepileptic Seizures Task Force.
A patient with seizures of unknown or disputed aetiology will usually be monitored in an epilepsy monitoring unit for a few days before SSI is performed [
Minimum requirements for the diagnosis of psychogenic nonepileptic seizures: a staged approach: a report from the International League Against Epilepsy Nonepileptic Seizures Task Force.
]. This diagnostic sequence has the advantage of increasing the sensitivity regarding epileptiform abnormalities in interictal EEG in cases of epilepsy or dual pathology [
There are no universal guidelines on how many days of VEEG one should wait for a spontaneous habitual event before opting for SSI. In several retrospective analyses the majority (75–96%) of PNES occurred within the first 48 h of VEEG [
]. This establishes a reasonable minimum of VEEG, but uncertainty remains about a sensible upper limit. While in one study all psychogenic events occurred within 58 h [
]. Importantly, the reported numbers do not reflect the yield of all examined patients, but only the latency of events that were eventually recorded. In the study by Ribaï and colleagues the average VEEG duration was 4.6 days, and still 32% of PNES patients had inconclusive VEEG but positive SSI [
Usefulness of prolonged video-EEG monitoring and provocative procedure with saline injection for the diagnosis of non epileptic seizures of psychogenic origin.
]. The authors calculated a cut-off at 5.5 days of VEEG, after which the length of stay was associated with an increased risk of being inconclusive; no such cut-off was seen in 333 patients with epilepsy [
]. In the study by Chen and colleagues, none of the patients who had an unsuccessful SSI (9/51, 18%) had a spontaneous event afterwards during VEEG of 3.5 days on average [
It seems reasonable to recommend a VEEG-duration of 48–72 h before opting for SSI when PNES are suspected.
7. Risks and side effects
Although the induction techniques discussed so far are themselves reasonably innocuous in healthy subjects, there are certain risks and side effects reported for SSI. One commonly described effect is the induction of non-habitual events [
]. This difference might be an indicator of a higher suggestive potency of placebo injections. The possibility of inducing non-habitual events makes it imperative to always confirm the genuineness of recorded events by showing them to patients or their relatives.
On rare occasions, epileptic seizures can occur during SSI [
]. In such cases, careful examination of EEG and semiology should allow the distinction between pure coincidence (especially in patients with high seizure frequency), reflex seizures or stress-induced seizures [
] and is not specified in any of the SSI studies cited, it dictates caution in cases when patient history reveals prolonged or refractory (psychogenic) seizures.
A recent prospective study has challenged the common assumption that PNES, as opposed to epileptic seizures, seldom lead to ictal injuries [
]. Although the studies on SSI reviewed above do not specifically report on ictal injuries in induced PNES, one should arrange for appropriate precautions during SSI (e.g. a mattress for patients with ictal falls).
8. Psychobiological mechanisms
The presumed psychopathology of PNES is a matter of continuing research and debate, and has been reviewed elsewhere [
]. Assumptions about the mechanisms of SSI have to be formulated carefully in light of this uncertainty. Considering the wide variety of induction methods, both psychological and physiological effects have to be accounted for.
On a cognitive level, general suggestion and hypnotic induction offer certain insights. Studies have demonstrated convincing neurophysiological parallels between symptoms of dissociation induced by hypnosis and those inherent in disorders formerly classified as “hysteria” [
]. These discrepancies call for future studies using standardized measures of hypnotisability and uniform protocols of induction.
On a physiological level, stress induction appears to be a key factor in SSI. An abnormal reaction to emotional or psychosocial stress has been identified as a pivotal factor in the pathogenesis and maintenance of PNES [
Hyperventilation and photic stimulation are useful additions to a placebo-based suggestive seizure induction protocol in patients with psychogenic nonepileptic seizures.
]. Whether unpleasant methods are more “potent” due to a stronger stress reaction or a more convincing suggestion remains unclear. A closer examination of the physiological effects of SSI might elucidate crucial questions about the relationship between stress and PNES. It is unlikely that generic stress is solely responsible for induction, since it has only mild effects on physiological stress markers such as cortisol levels and heart rate variability in PNES patients compared to healthy controls [
]. In a small cohort, they identified eleven patients, who reported unpleasant auras (reminiscent of incipient panic attacks) preceding their seizures and a desire for them to “hurry up” in order to be relieved of those unbearable prodromal symptoms. This “wilful submission” can be interpreted as a conversion reaction in terms of the classical theory of hysteria: somatic manifestation of stress and anxiety [
Accordingly, in order to record a habitual PNES, two conditions might be necessary: a stressor and a permissive setting. When the usual stressor is internal (e.g. stemming from childhood trauma) the spontaneous occurrence of a PNES in a permissive setting (i.e. epilepsy monitoring unit) can be expected. This could explain the short latency of habitual PNES during VEEG despite partly low seizure frequencies [
]. If, however, the stressor is exogenous (e.g. conflicts with a family member or mental overload at work), a spontaneous attack might fail to occur in the relatively stress-free epilepsy monitoring unit despite reportedly high seizure frequencies [
]. To facilitate diagnosis an exogenous stressor (SSI) combined with a permissive attitude suggested by the examiner (“it is safe to have an attack here”) would be needed. Thus, SSI might not just be useful for economising a few days of VEEG, but could yield a diagnosis in patients that would otherwise remain inconclusive, as described previously [
Usefulness of prolonged video-EEG monitoring and provocative procedure with saline injection for the diagnosis of non epileptic seizures of psychogenic origin.
] might respond to different elements of SSI (e.g. suggestion or stress-induction). One promising approach to elucidate the mechanisms of SSI and PNES psychopathology in general is to look for predictive factors for successful induction.
9. Predictive factors for SSI
Only two studies have specifically investigated whether clinical or sociodemographic factors could predict the success of SSI in patients with established PNES. Wassmer and colleagues compared patients with positive (n = 41) and those with negative SSI (n = 25) in terms of semiology and patient history [
]. A similar undertaking by Chen and colleagues also failed to find any difference in 11 sociodemographic factors between patients with successful SSI (n = 42) and those with unsuccessful SSI (n = 9) [
]. However, there were statistical differences in the results of some psychological instruments: a higher score on the Structured Inventory of Malingered Symptomatology predicted a positive SSI. One could surmise, that a tendency towards malingering manifests itself as the elusive, but crucial element of wilfulness of seizure initiation explored by Stone and Carson [
] (see previous section). Furthermore, higher scores in subscales of the brief COPE inventory showed significant differences, suggesting that patients whose PNES can be induced rely more on action-oriented coping strategies [
]. The ratio of attack-free PNES patients on follow-up 4–7 years after diagnosis was higher in the group with previously positive SSI than in the group with negative SSI, but the effect was not statistically significant (44% vs. 33%, p = 0.82). Gambini and colleagues analyzed the long-term outcome of 27 PNES patients 14–38 months after diagnosis: out of 11 clinical and sociodemographic characteristics, the only factor that statistically predicted a better outcome was positive SSI [
]. Even when controlling for psychological and psychiatric therapy (themselves not statistically significant factors), diagnosis via SSI remained a highly significant predictive factor for good outcome. One explanation could be that positive SSI is an indicator for a certain subtype of PNES pathology that has a better outcome in terms of seizure frequency. On the other hand, it has been shown, that outcome hinges on understanding and accepting the diagnosis “psychogenic nonepileptic seizures” [
]. SSI might simply be a more coherent and convincing diagnostic test from the patient's point of view than several days of VEEG on an epilepsy monitoring unit. Whether the role of successful of SSI is merely predictive or in some way therapeutic remains to be addressed in future studies.
11. Conclusions
While the clinical significance, diagnostic pitfalls and therapeutic challenges of psychogenic nonepileptic seizures are widely recognized, there is still much uncertainty about psychopathology, staged diagnostic workup and optimal management. SSI is an accurate and effective tool that can facilitate and accelerate diagnosis, provide insights into disease mechanisms and even offer a promising therapeutic lever. The following conclusions can be gleaned from the research reviewed above:
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SSI is an essential diagnostic tool in the workup of suspected PNES, atypical seizures and paroxysmal attacks of unknown aetiology.
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Depending on pre-test selection of patients, it can have an excellent diagnostic yield.
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Various methods of SSI have been studied. There is strong evidence for the effectiveness of placebo-infusions, but also for suggestive hyperventilation and photic stimulation. A combination of two or three techniques is practicable and effective.
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Open patient information that avoids explicit deception will spare the therapeutic relationship and will not reduce the diagnostic yield.
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VEEG for 2–3(–5) days can be used to record spontaneous PNES, but should be supplemented by SSI when inconclusive.
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Patients and physicians should be aware of the potential risks and side effects of SSI, such as inducing non-habitual events or pseudostatus epilepticus.
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There are no known clinically relevant predictive factors of successful SSI in patients with PNES.
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There might be a therapeutic effect of diagnosis via SSI that demands further research.
Conflict of interest
All authors declare, that they have no conflicts of interest.
Appendix A. List of search terms used in various combinations
psychogenic
non-epileptic
nonepileptic
pseudoepilep*
pseudoseizure*
dissociative
hysterical
hysteroepilepsy
conversion
seizure*
event*
attack*
induc*
provo*
suggestion
facilitat*
Appendix B. List of relevant articles that were excluded from the systematic review
Tabled
1
Citation
Reason for exclusion
Cano-Plasencia R, Gómez-Marcos AM, Cano-Sánchez R. [Induction of pseudoseizures by placing inactive electrodes in the malar regions]. Rev Neurol. 2006 Dec 1-15;43(11):662–6.
Article in French
French JA, Kanner AM, Rosenbaum DH, Rowan AJ. Do techniques of suggestion aid the differential diagnosis of psychogenic versus epileptic seizures? Epilepsia 1987;28:612–3.
Non-peer-reviewed abstract
French JA. Suggestion as a provocative test in the diagnosis of psychogenic nonepileptic seizures. In: Rowan AJ, Gates JR. Non-epileptic seizures. Boston, MA: Butterworth–Heinemann, 1993:101–109.
Non-peer-reviewed book chapter
Klingler D, Trägner H. Sleep deprivation as a provocation method in electroencephalography in patients with non-epileptic cerebral disorders. Neurol Psychiatr (Bucur). 1984 Jan-Mar;22(1):51–3.
Kuyk J, Jacobs LD, Aldenkamp AP, Meinardi H, Spinhoven P, van Dyck R. Pseudo-epileptic seizures: hypnosis as a diagnostic tool. Seizure. 1995 Jun;4(2):123–8.
Hypnosis used for recall, not induction
LeVine WR, Ramirez C. Identifying pseudoseizures with anhydrous ammonia. Am J Psychiatry. 1980 Aug;137(8):995.
2 cases; ammonia used to stop seizures, not induce them; no EEG
Martínez-Taboas A. The role of hypnosis in the detection of psychogenic seizures. Am J Clin Hypn. 2002 Jul;45(1):11–20.
Small case series (n = 8)
Ney GC, Zimmerman C, Schaul N. Psychogenic status epilepticus induced by a provocative technique. Neurology. 1996 Feb;46(2):546–7.
Case report
Niedermeyer, E., Blummer, D., Holscher, E. and Walker, B.A. Classical hysterical seizures facilitated by anticonvulsant toxicity. Psychiatr Clin 1970; 3: 71–84.
3 cases; general facilitation, not specific induction
Olson DM, Howard N, Shaw RJ. Hypnosis-provoked nonepileptic events in children. Epilepsy Behav. 2008 Apr;12(3):456–9.
Pediatric population; small case series (n = 9)
Peterson DB, Sumner JW Jr, Jones GA. (1950) Role of hypnosis in differentiation of epileptic from convulsive-like seizures. Am J Psychiatry 107:428–433.
Hypnosis used for recall, not induction
Remick RA, Wada JA. Complex partial and pseudoseizure disorders. Am J Psychiatry. 1979: 136:320–323.
Case report
Schmalbach K, Mueller E, Salazar-Munos M, Bushart W. [Syncope and other nonepileptic attacks. (The value and limitations of provocation measures)]. Dtsch Med Wochenschr. 1962 Oct 5;87:2027–30.
Article in German
Staudenmayer H, Kramer RE. Psychogenic chemical sensitivity: psychogenic pseudoseizures elicited by provocation challenges with fragrances. J Psychosom Res. 1999 Aug;47(2):185–90.
Case report
Sumner JW, Cameron RR, Peterson DB. Hypnosis in the differentiationof epileptic from convulsive like seizures. 1952. Neurology. 1952; 27: 395–402.
Hypnosis used for recall, not induction
Wyllie E, Friedman D, Rothner AD, Luders H, Dinner D, Morris H 3rd, Cruse R, Erenberg G, Kotagal P. Psychogenic seizures in children and adolescents: outcome after diagnosis by ictal video and electroencephalographic recording. Pediatrics. 1990 Apr;85(4):480–4.
Pediatric population
Zalsman G, Dror S, Gadoth N. Hypnosis provoked pseudoseizures: a case report and literature review. Am J Clin Hypn. 2002 Jul;45(1):47–53.
Minimum requirements for the diagnosis of psychogenic nonepileptic seizures: a staged approach: a report from the International League Against Epilepsy Nonepileptic Seizures Task Force.
Usefulness of prolonged video-EEG monitoring and provocative procedure with saline injection for the diagnosis of non epileptic seizures of psychogenic origin.
Hyperventilation and photic stimulation are useful additions to a placebo-based suggestive seizure induction protocol in patients with psychogenic nonepileptic seizures.
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