Psychogenic non-epileptic seizures: can we make a positive diagnosis?

Many disorders other than epilepsy are characterized by paroxysmal events. Psychogenic non-epileptic seizures (NES) form one differential diagnostic group which mimic epileptic phenomena and are caused by various psychic disorders. The diagnosis of NES is mostly based on the exclusion of epilepsy. We review the histories of six patients, who were hospitalized in an epilepsy unit and were diagnosed as having psychogenic NES. Most of them had been previously given the diagnosis of epilepsy. It is suggested that for accurate diagnosis it is very important that a patient initially undergoes psychiatric assessment along with standard diagnostic procedures (e.g. neurologic, psychological and physical investigations), that may encourage making a positive diagnosis of non-epilepsy.     

Psychogenic (nonepileptic) seizures

Psychogenic (nonepileptic) seizures are among the most common and serious of all psychogenic neurological disorders. They account for approximately 20% of all intractable seizure disorders referred to comprehensive epilepsy centers and present with a reported annual incidence of approximately 4% that of true epilepsy. These events are serious and disabling. Indeed, compared with patients with true epilepsy, patients with psychogenic seizures exhibit more frequent, severe, and disabling seizures as well as a poorer quality of life. The diagnosis and management of psychogenic seizures remain challenging, although advances in video electroencephalographic (EEG) monitoring have improved the ability of physicians to identify these disorders accurately. The prognosis of these patients is still relatively poor, and a good outcome seems dependent on a young age at diagnosis, early diagnosis, less severe psychological comorbidities, and continued follow-up and management by the diagnosing neurologist or clinician. Additional psychological or psychiatric assessment may be beneficial, particularly in elucidating the etiology of the disorder as well as identifying comorbid disorders, and may help in the long-term management of these patients. This review presents the history, epidemiology, differential diagnosis, and management of psychogenic seizures, with particular attention to the use of diagnostic testing, including video EEG monitoring.     

Psychogenic pseudoepileptic seizures: clinical and electroencephalogram (EEG) video-tape recordings

This paper presents a clinical and electrophysiological analysis of type and duration of seizures recorded by means of long-term video electroencephalogram (EEG) monitoring, a method which enables accurate diagnosis of psychogenic pseudoepileptic seizures occurring with or without epileptic seizures. Analysis is based on 1083 patients, hospitalized at our department between 1990 and 1997, with a preliminary diagnosis of epilepsy. Psychogenic pseudoepileptic seizures were diagnosed in 85 patients (7.8%). In 48 patients, pseudoepileptic seizures alone were diagnosed (group 1), whereas 37 patients had a mixed condition in which pseudoepileptic seizures were accompanied by epileptic seizures (group 2). For comparison of duration of pseudo- and epileptic seizures a control group (group 3), consisting of 55 patients randomly selected from the population of patients suffering from epileptic seizures alone, was parceled out. Long-term video EEG monitoring was performed in 70 patients. In 55 (79%) of these patients 230 seizures (221 pseudoepileptic and nine epileptic) were recorded. In 30 patients (32%), the diagnosis was based on clinical observation of the seizures and on the number of EEG recordings, including activating procedures such as sleep deprivation, photostimulation, hyperventilation and anti-epileptic drug withdrawal. We found that the duration of epileptic seizures was significantly shorter than the duration of psychogenic pseudoepileptic seizures. Our study has exposed the difficulties involved in the diagnosis of psychogenic pseudoepileptic seizures and the negligible value of neuroimaging techniques and interictal EEG recordings in the differential diagnosis of epileptic versus nonepileptic seizures. In this study, psychogenic seizures were significantly more frequent in women than in men; patient history analysis did not confirm the hypothesis that sexual abuse may cause psychogenic seizures.     

What is the Significance of Subjective Events Recorded During Long-Term EEG Video Monitoring?

Summary: Purpose : Purely subjective events, identified as "seizures" by patients but not accompanied by any clinical or EEG changes, commonly occur during evaluation of patients for intractable epilepsy. We wished to determine the significance of such events.
Methods : We analyzed the frequency of subjective episodes in 379 adults who underwent EEG video monitoring as part of their evaluation for intractable epilepsy and the relationship of these experiences to epileptic and psychogenic nonepileptic (NES) seizures. We examined the results of tests of mental ability and of emotional, psychosocial, and quality of life (QOL) adjustment to determine if individuals with subjective events alone could be distinguished from those with epileptic seizures only, NES only, or no events, by these measures.
Results : We noted subjective events in 39% (147 of 379) of the patients. Of patients with subjective episodes, 52% also had epileptic seizures, 7% had NES, 1% had both epileptic seizures and NES, and 40% had subjective events alone. As a group, patients with subjective events alone were slightly more intelligent and less impaired neuropsychologically than people in the other groups, hut they performed more poorly on several important measures of adjustment.
Conclusions : The identification of persons with purely subjective episodes apart from all other episodes is important both phenomenologically and from a practical viewpoint.     

Ictal Behaviors During Nonepileptic Seizures Differ in Patients with Temporal Lobe Interictal Epileptiform EEG Activity and Patients Without Interictal Epileptiform EEG Abnormalities

Summary: Purpose: Ictal behaviors during psychogenic non-epileptic seizures (NES) vary considerably among individuals, and can closely resemble common semiologies of epileptic seizures (ES). We tested the hypothesis that behaviors during NES in patients who have temporal spikes would more closely resemble behaviors during ES in patients with temporal lobe epilepsy than would behaviors during NES in patients who do not have EEG spikes.
Methods: We identified 20 patients who had interictal temporal EEG spikes and EEG-video recorded NES (Study Group), 133 patients with temporal EEG spikes and recorded ES, without NES (Epileptic Group), and 24 patients with recorded NES and no epileptiform EEG abnormalities, without ES (Nonepileptic Group).
Results: The hypothesis was supported with regard to ictal motor behaviors. Motionless staring or complex automatisms occurred mainly during NES in the Study Group and during ES in the Epileptic Group. In contrast, convulsive movements or flaccid falls were most common during NES in the Nonepileptic Group. Duration of unresponsiveness was longer, and there were fewer postictal states in NES both in the Study and Non-epileptic Groups. Unresponsiveness was briefer and postictal states were more consistent in ES in the Epileptic Group, however.
Conclusions: Stereotyped motor activities during NES presumably represent learned behaviors. Processes underlying acquisition of ictal behaviors of NES probably differ in patients with interictal epileptiform EEG abnormalities compared to those without. Prior experiences and temporal lobe dysfunctions that are associated with epilepsy, and psychological characteristics that are unrelated to interictal epileptic dysfunctions, may determine ictal behaviors during NES.     

Video-EEG monitoring of paroxysmal events in the elderly

OBJECTIVES: To determine the importance of video-EEG monitoring (VEM) in elderly patients with various paroxysmal events. MATERIAL AND METHODS: We retrospectively identified 16 subjects > or = 60 years old out of 834 (1.9%; 7 females, mean age 67.8 +/- 7.7 years), who were admitted to the Video-EEG Unit between 1997 and 2005 and compared data between those with and without epileptic events. RESULTS: Epilepsy was confirmed in six patients, psychogenic non-epileptic seizures (NES) were diagnosed in seven, one patient had NES and epilepsy whereas the recorded events were non-conclusive in two. NES patients had a higher predisposition to psychiatric disturbances (P<0.02). Following VEM and management alteration, the frequency of monthly events decreased significantly for the cohort as a whole (P<0.001). VEM directly influenced the diagnosis, treatment and outcome of 14 of 16 (88%) patients. CONCLUSION: Video-EEM plays a vital role in the evaluation of paroxysmal events in the elderly, but is vastly underutilized in this population group.     

Incidence of Psychogenic Seizures in Adults: A Population-Based Study in Iceland

Summary: Purpose: We wished to determine the incidence of psychogenic nonepileptic (NES) seizures in a population-based study.
Methods: Cases were identified through review of the results of all long-term video-EEG studies made in Iceland during the study period.
Results: The incidence of NES was 1.4 in 100,000 person-years of observation. Age-specific incidence was highest in the youngest age group (age 15–24 years) and decreased thereafter. A strong female preponderance was observed.
Conclusions: The incidence of NES is equal to almost 4% of that reported for epilepsy from Iceland for persons aged ≥15 years. For people aged 15–24 years, the incidence of NES is equal to −5% of the incidence of epilepsy. Half the patients also had epilepsy.     

Psychogenic movement disorders in children: characteristics and predictors of outcome

Psychogenic movement disorders are defined as hyperkinetic or hypokinetic movement disorders associated with underlying psychological disorders. Psychogenic movement disorders account for 1% to 9% of all neurologic diagnoses. The assessment and treatment of psychogenic movement disorders can be complex. We report patients seen over the past 5 years, diagnosed with psychogenic movement disorder. We discuss in this article some patient characteristics and some strategies that are effective in the management of this group of patients. The case examples presented in the current article demonstrate the importance of two factors, a multidisciplinary approach and engaging the family, that are essential components in the treatment of psychogenic movement disorders.     

Seizure semiology in the elderly: a video analysis

PURPOSE: To describe the seizure semiology of patients older than 60 years and to compare it with that of a control group of younger adults matched according to the epilepsy diagnosis. METHODS: Available videotapes of all patients aged 60 years and older who underwent long-term video-EEG evaluation at the Cleveland Clinic Foundation (CCF) between January 1994 and March 2002 were analyzed by two observers blinded to the clinical data. A younger adult control group was matched according to the epilepsy diagnosis, and their seizures also were analyzed. RESULTS: Fifty-four (3.3%) of the 1,633 patients were 60 years or older at the time of admission. For 21 of them, at least one epileptic seizure was recorded. Nineteen patients had focal epilepsy (nine temporal lobe, two frontal lobe, two parietal lobe, eight nonlocalized), and two patients had generalized epilepsy. Seventy-three seizures of the elderly patients and 85 seizures of the 21 control patients were analyzed. In nine elderly patients and 14 control patients, at least one of their seizures started with an aura. Eleven elderly patients and 19 control patients lost responsiveness during their seizures. Approximately two thirds of the patients in both groups had automatisms during the seizures. Both focal and generalized motor seizures (e.g., clonic or tonic seizures) were seen less frequently in the elderly. CONCLUSIONS: Only a small percentage of the patients admitted to a tertiary epilepsy referral center for long-term video-EEG monitoring are older than 60 years. All seizure types observed in the elderly also were seen in the younger control group, and vice versa. Simple motor seizures were seen less frequently in the elderly.     

A comparative study of trauma and posttraumatic stress disorder prevalence in epilepsy patients and psychogenic nonepileptic seizure patients

PURPOSE: This study tests the hypothesis that trauma histories, including histories of physical and sexual abuse, and posttraumatic stress disorder (PTSD) are more prevalent in psychogenic non-epileptic seizure (NES) patients than in epilepsy patients. METHODS: Thirty-five inpatients with intractable seizures were evaluated for trauma history and PTSD. After these assessments, patients were diagnosed as having either epileptic or nonepileptic seizures through EEG monitoring. RESULTS: NES diagnosis correlated with PTSD and total number of lifetime traumas, adult traumas, and abuse traumas. Contrary to previous hypotheses, reported childhood sexual abuse (CSA) did not correlate significantly with NES diagnosis. However, CSA predicted PTSD in a discriminant analysis. CONCLUSIONS: We found evidence for the hypothesized relations between trauma, abuse, PTSD, and NES diagnosis. However, elevated levels in both seizure-disorder groups suggest that routine assessment for abuse, trauma, and PTSD might facilitate medical care and treatment for all intractable seizure patients.     

Psychogenic pseudosyncope: an underestimated and provable diagnosis

OBJECTIVE: The goal of this study was to estimate the frequency of psychogenic pseudosyncope in patients with "syncope of unknown origin." Twenty to thirty percent of patients referred to epilepsy centers for refractory seizures have psychogenic seizures. With syncope, about 20-30% of the cases remain unexplained after a complete evaluation, but, unlike in seizures, a psychogenic etiology is not usually investigated. METHODS: We prospectively evaluated patients referred to our epilepsy center for evaluation of recurrent syncope-like episodes, that is, limp, motionless fainting. All patients had a negative syncope workup. We performed EEG-video monitoring with activation by suggestion ("induction"), similar to what is used for diagnosis of psychogenic seizures. Activation was performed with patients standing or sitting up. The diagnosis of psychogenic pseudosyncope required: (1) an activation procedure that triggered the habitual event; (2) a clinical event of loss of postural tone and limp, motionless unresponsiveness with eyes closed; (3) normal EEG before, during, and after the clinical event, that is, no epileptiform abnormalities, a normal alpha rhythm during unresponsiveness, and no suppression of background or slowing as is typically seen in syncope. RESULTS: Ten patients were recruited over an 18-month period. Habitual syncope-like episodes were triggered in 9 of 10 (90%) patients, and all 9 were shown to have psychogenic pseudosyncope (eyes closed, motionless, unresponsive with normal EEG including normal alpha rhythm). In one patient, no episode was triggered, so a diagnosis could not be made. Among the 9 patients for whom episodes were recorded, age ranged from 21 to 60 (mean=36). Five were women. Duration of symptoms ranged from 6 months to 15 years (mean=4.2 years). Event frequency ranged from four per day to two per month. Prior evaluations for syncope included ECG in all patients, two-dimensional echocardiogram in three, Holter monitoring in two, and tilt-table test in five. Four patients had undergone cardiac catheterization, and one had received a pacemaker. Neurologic tests included CT of the head in seven and MRI of the brain in eight. CONCLUSION: Many patients with "syncope of unknown origin" may have psychogenic pseudosyncope, but most such patients do not undergo EEG-video monitoring, which is the only way to demonstrate a psychogenic etiology. Psychogenic pseudosyncope is not simply a diagnosis of exclusion, and can be firmly diagnosed. As is usually recommended for seizure-like events, patients with syncope-like events and a negative evaluation should undergo EEG-video monitoring with induction, specifically looking for a possible psychogenic etiology.     

Nonepileptic Seizures After Head Injury

Summary: Purpose: To examine the role of head injury as a risk factor in the development of nonepileptic seizures (NES). Specifically, we will determine the relative frequency of head injury among NES patients referred to our center and will describe several pertinent clinical features and personal characteristics.
Methods: Retrospective record review of patients referred to our center for evaluation of seizures over a 4-year period. All patients with NES were evaluated as in a previously described protocol, which included intensive video EEG monitoring, provocation by suggestion, and psychiatric interview. All NES patients with a history of head injury were extracted for this report.
Results: Of 102 patients with NES, nearly one-third (32%) had an antecedent head injury; 52% were male, mean age was 34 years, and 12% had coexisting epilepsy. Multiple psychiatric disorders were not uncommon (79%), and a history of abuse was found in 35%. All but four patients had documented financial gain from their injury. Follow-up at 1 year found poor long-term outcome with lasting disability; despite that, the majority (91%) of head injuries were minor.
Conclusions: Our preliminary findings suggest that prior head injury is associated with the development of NES and may contribute to the pathogenesis of NES in vulnerable patients. Head injury and sexual or physical abuse appear to occur in comparable proportions in patients with NES. This suggests that head injury and abuse may be equally important risk factors in the development of NES.     

Provocation of Nonepileptic Seizures by Suggestion in a General Seizure Population

Summary: Nonepileptic seizures (NES) are common and are often diagnosed at epilepsy centers by video-EEG recording of both spontaneous and suggestion-induced episodes, but no study has evaluated provocative testing in a general seizure population. We studied consecutive patients with a tentative diagnosis of epilepsy using saline provocation during video–EEG recording, suggesting that this could produce a typical seizure. Of 52 patients, 40% had no response, 23% had responses unlike their seizures, and 37% had typical episodes (positive test). Patients whose usual episodes resembled complex partial seizures (CPS) were more likely to have NES than were patients with a history of generalized tonic-clonic seizures (GTC). Of patients with positive provocations, the primary physician predicted NES in 68% of cases. This preliminary study suggests that NES are frequent in a general neurology setting, and that saline provocation is a sensitive method of identifying NES.     

Events Calendar

Observation of psychogenic nonepileptic seizures (PNESs) during video-EEG represents the diagnostic gold standard for PNESs. Different provocative techniques have been used to increase PNES frequency during EEG. These techniques include placebo administration, suggestion strategies, or both. In order to avoid the appearance of deception, we investigated the following hypothesis: If patients with PNESs were informed about the possible reduction of seizure threshold caused by hyperventilation and photic stimulation prior to EEG without any other suggestive strategies, PNESs would occur more frequently. In total, 34 inpatients with a diagnosis of PNESs, who had been informed prior to EEG about the increased seizure risk during hyperventilation and photic stimulation (study group), and 80 “noninformed” patients (control group) were enrolled. Psychogenic nonepileptic seizures occurred significantly more often in the study group compared to controls (38% vs. 10.0%, p = 0.001). Our results imply that simply providing correct and explicit information about provocation techniques substantially increased the PNES rate.     

Improving diagnostic procedure and treatment in patients with non-epileptic seizures (NES).

The purpose of this study was to examine the incidence of patients with NES vs. NES and concomitant epilepsy in an epilepsy centre and to present a diagnostic algorithm. We collected and reviewed the data of 322 patients consecutively referred to the adult ward of our epilepsy centre in 1 year. The results of our study reveal that 44 (14%) of all patients referred had NES. Of these, nine proved to have concomitant epilepsy. Of 44 patients with NES, 20 were treated with AED on admission. In 14 cases this unnecessary antiepileptic drug treatment was stopped. In six remaining patients with NES and concomitant epilepsy, the total number of AEDs could be reduced until discharge. The maximum duration of AED treatment among patients with NES only, had been longer than 360 months (median 72 months).Much has been written about whether the diagnosis of psychogenic non-epileptic events is overused. According to our experience however, the fact that many patients with so-called 'pharmacoresistant epilepsy', suspected NES or other diagnoses are referred to a centre of excellence much too late, proves to be the key problem in diagnosis and treatment of NES.We conclude that early admission of so-called 'pharmacoresistant epilepsy' to an epilepsy centre, establishing a standard work-up and clarifying the medical terminology will improve diagnosis and lead to adequate therapy of NES as well as prevent unnecessary drug treatment.     

Stereotactic surgery for refractory epilepsy complicated by mental disorders☆ A retrospective case analysis

BACKGROUND： Anti-epilepsy and anti-psychosis drugs have traditionally been used in the clinic to treat epilepsy complicated by mental disorders. However, there is still no effective therapy for refractory epilepsy patients suffering from persistent mental disorders. OBJECTIVE： To explore the therapeutic effects of stereotactic multi-element localization and multi-target radiofrequency ablation on patients with refractory primary epilepsy and mental disorders. DESIGN： A retrospective case analysis. SETTING： Department of Neurosurgery, the 454 Hospital of Chinese PLA. PARTICIPANTS： Between June and November 2004, 13 patients with refractory primary epilepsy complicated by persistent mental disorders were admitted to the Department of Neurosurgery, the 454 Hospital of Chinese PLA. The patient group consisted of nine males and four females, with an average age of 25 years （range 18-39 years）, and a course of disease ranging 3-11 years. Diagnosis of mental disorders was in accordance with Chinese Classification of Mental Disorders. Written informed consent was obtained from all patients and their families, and the treatment protocol was approved by the Ethics Committee of the Hospital. METHODS： Under venous inhalation anesthesia, the disease targets, including bilateral corpus callosum, bilateral amygdala, and bilateral medial septal area, as well as unilateral Forel-H area, were coagulated by RFG-3CF radiofrequency thermocoagnlation at 75-80 ℃ for 60-70 seconds. During thermocoagulation, the targets were identified using deep-brain microelectrodes and localized according to electrophysiology and electric resistance values. MAIN OUTCOME MEASURES： One year post-surgery, epileptic seizures were assessed on the basis of the Tan classification, and psychogenic （non-epileptic） seizures were evaluated using a 5-grade system. RESULTS： All enrolled 13 epileptic patients were included in the final analysis. The results of follow-up evaluations demonstrated that epilepsy was well-controlled. In total,     

Headaches and other pain symptoms among patients with psychogenic non-epileptic seizures.

Studies of patients with psychogenic non-epileptic seizures (NES) typically focus upon the phenomenology and outcome of NES episodes. Little is known, however, about the frequency and nature of other somatic symptoms such as pain, in this population. To assess the frequency, location and severity of symptoms of pain among NES patients, we administered structured interviews to 56 patients, 6 or more months following the diagnosis of psychogenic non-epileptic seizures (NES). Patients were recruited from a tertiary hospital-based epilepsy monitoring unit. Seventy-seven percent of patients suffered from moderate to severe pain, most commonly headache (61%), while neck pain and backache were also common. Twenty-six of 27 patients with persistent NES vs. 17 of 29 patients whose NES resolved experienced moderate to severe pain (P < 0.001). Pain is an under-recognized problem that occurs frequently and with significant severity among NES patients. Pain symptoms are more common among patients with persistent NES than those whose NES resolve.     

Interictal EEG abnormalities in patients with psychogenic nonepileptic seizures

PURPOSE: To examine interictal EEG abnormalities in patients with psychogenic nonepileptic seizures (PNESs). METHODS: (a) Retrospective study of EEG reports of 187 consecutive patients with PNES seen at the Department of Epileptology, Bonn, Germany; (b) Blinded, multirater comparison of EEGs of all PNES patients with no other clinically recognizable cause of EEG disturbance (n = 50) and healthy controls (n = 50). RESULTS: Of 187 consecutive patients with PNESs, 57 patients had PNESs and epilepsy (PNES+E), and 130 patients, PNESs alone. The diagnosis of additional epilepsy was based on ictal (video-) EEG or on the critical assessment of all clinical data by an experienced epileptologist. Retrospective review of all available EEG reports showed that 92.9% of patients in the PNES+E and 53.8% in the PNES-only group had one or more abnormal EEGs (median number of EEGs per patient, three; range, one to 42). In the PNES-only group, EEG changes were nonspecific in 42.3% of patients. Only 50 of 130 patients with PNESs alone had no other clinically recognizable cause of EEG disturbance and entered the controlled study. In this study, 18% of patients and 10% of controls had abnormal EEGs. The frequency of epileptiform EEG changes was similar to that in previous population studies in both groups (2.0%). CONCLUSIONS: PNESs often occur in patients with organic brain disease. Even in patients with PNESs alone and no clinically recognizable cause of EEG disturbance, nonspecific abnormalities are found 1.8 times as often as in healthy controls. Interictal EEG changes are common in patients with PNESs and, in isolation, should not be interpreted as evidence of epilepsy.     

Non-epileptic seizures: delayed diagnosis in patients presenting with electroencephalographic (EEG) or clinical signs of epileptic seizures.

The clinical differentiation between epileptic seizures (ES) and non-epileptic seizures (NES) is often difficult and mostly based on the presence or absence of widely recognized features of ES such as tongue biting, falling, incontinence or concomitant epileptic abnormalities in the electroencephalogram (EEG). We retrospectively analysed the records of all patients referred to our Epilepsy Centre for refractory epilepsy and finally diagnosed with NES between 1980 and 1999 ( n= 103), half of them also exhibiting ES. The mean time-lapse between first attack and NES diagnosis was 8.7 +/- 1.3 years and 16.5 +/- 1.4 years for the NES and NES + ES groups respectively. At least one of the usual signs associated with generalized tonic-clonic seizures (tongue biting, falling or incontinence) was reported by 66% and 60% of patients with NES or NES + ES respectively. Interictal EEG abnormalities were recorded in 16% of NES patients vs. 80% of NES + ES patients. In the NES group, delay before establishing the correct diagnosis was significantly longer when the patients exhibited > or =1 symptom(s) of generalized seizures, or when patients exhibited interictal EEG abnormalities. Upon admission, 72% of NES patients and all NES + ES patients were being treated with antiepileptic drugs (AEDs).We conclude that EEG or clinical abnormalities suggestive of epileptic seizures are common in undiagnosed NES patients. Such diagnostic pitfalls, besides considerably delaying NES diagnosis, also considerably delay appropriate treatment implementation.     

De Novo Nonepileptic Seizures after Cranial Surgery for Epilepsy: Incidence and Risk Factors

We evaluated the incidence of de novo nonepileptic seizures (NES), confirmed by EEG monitoring, after cranial surgery for intractable epilepsy in 228 surgery patients. Eight patients (3.5%) developed de novo NES at 6 weeks to 6 years (mean, 23 months) after surgery. Six had undergone a resection and two complete callosotomy. They did not differ from a larger surgical group with respect to sex, side of surgery, age at onset, or duration of epilepsy, Full Scale Intelligence Quotient, seizure outcome, or preoperative interictal dysphoric disorder (IDD), but there was a significant excess of postoperative IDD and operative complications (bone flap infections); the callosotomy patients had marked hemisphere disconnection syndromes. Repeat EEG videotelemetry monitoring is important to detect postoperative NES so that inappropriate therapeutic measures may be avoided. Risk factors may be exacerbation or persistence of IDD and surgical complications. The etiology of NES is discussed.