The diagnosis of pseudoseizures, a case report and a review of the literature

Incidence of psychogenic seizures in adults: a population-based study in Iceland

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 > or = 15 years. For people aged 15-24 years, the incidence of NES is equal to approximately 5% of the incidence of epilepsy. Half the patients also had epilepsy.

Dipole modeling in epilepsy surgery candidates

PURPOSE

The validity and clinical significance of dipole modeling in epilepsy surgery candidates is not fully established.

PATIENTS AND METHODS

Interictal and ictal dipole modeling was performed in 43 patients with refractory complex partial seizures (CPS) and intracranial structural abnormalities demonstrated with optimum magnetic resonance imaging (MRI: space-occupying, n = 15; atrophic, n = 26; dysplastic, n = 2). Video-EEG monitoring showed CPS in all patients. In 12 patients, additional intracranial EEG monitoring demonstrated hippocampal seizure onset in 11 patients and medial occipital ictal onset in 1.

RESULTS

Spatiotemporal dipole mapping of averaged interictal spikes and epochs of early ictal discharges revealed two distinct dipole patterns. Patients with lesions located in the medial (+/-lateral) temporal lobe (n = 34) and medial occipital lobe (n = 1) uniformly presented a combined interictal dipole that consisted of a radial and a tangential component with a high degree of elevation relative to the axial plane. Eight of 9 patients with extratemporal lesions had a less stable dipole with a predominant radial component. Ictal dipole modeling identified the ictal onset zone correctly as compared with intracranial EEG recordings from bilateral hippocampal depth electrodes. Ictal dipoles showed a striking correspondence with the interictal dipoles in individual patients.

CONCLUSIONS

Interictal and ictal dipole mapping provided additional, reliable, and relevant localizing information in surgical candidates for refractory CPS. Ictal dipole analysis may limit the number of patients who require intracranial electrodes.

Clinical and neurophysiological correlations in patients with refractory partial epilepsy and intracranial structural lesions

Twenty patients (13 males, 7 females), who presented with refractory partial epilepsy and a CT and/or MR detected intracranial intra-axial structural lesion were admitted to the University of Gent Epilepsy Monitoring Unit. Mean duration of the epilepsy was 17 years (2-47 years). All patients were enrolled in a comprehensive presurgical protocol including neurological examination, video-scalp-EEG monitoring with prolonged interictal and ictal recording, neuropsychological assessment and positron emission tomography (PET). Intracranial EEG monitoring was performed in 5 patients in whom discrepancies between different tests were found during the non-invasive evaluation. Clinical neurological examination was normal in 16 patients; 4 patients had a mild contralateral hemiparesis. Lesions were mainly located in the temporal lobe (55%). Most patients presented with complex partial seizures (90%). Clinical seizure characteristics correlated well with the lesion location in 55% of patients. Interictal EEG showed focal epileptic activity and focal slowing in respectively 85% and 30% of patients. Interictal EEG lateralization was congruent with the side of the lesion in 17 patients (85%). Interictal EEG localization was congruent with the lobe of the lesion in 13 patients (65%). Ictal EEG lateralized correctly in 14 patients (70%) and localized correctly in 10 patients (50%). Neuropsychological assessment lateralized and localized congruently in respectively 8/17 (47%) and 7/17 (41%) of patients. Interictal PET showed focal interictal hypometabolism, congruent with the lesion, in 13/16 (81%) of patients. Intracranial EEG was congruent with the lesion location in 3 patients but non-congruent in 2 patients. All patients underwent surgical procedures: average follow-up was 14 months (6-24 months). Complete surgical removal of the lesion with free margins resulted in a more than 90% reduction of seizures without postoperative neurological deficit in 12/13 patients.

The diagnosis of pseudoseizures

Increasing experience with intensive monitoring of patients with intractable seizures has shown that a significant number of patients presents with pseudoseizures (psychogenic seizures). While in a majority of the patients differential diagnosis should be obvious, in some patients diagnostic error may occur. This is the case if the physician is unfamiliar with uncommon seizures, if the patient presents with atypical or bizarre attacks, and if interictal and/or ictal EEG are normal. Comparative studies of patients with true convulsive seizures and patients with pseudoseizures have revealed some 'typical' ictal features of pseudoseizures. Of these, longer ictal duration, less stereotypy, asynchronous extremity movements, atypical vocalization, alternating head movements and pelvic thrusting are the most characteristic. Many exceptions exist, however, since many patients with complex partial seizures (mostly of frontal origin) may present with similar ictal features. The final diagnosis of pseudoseizures is based upon integration of numerous data including careful seizure history, results of intensive video EEG monitoring and electroclinical correlation by experienced observers. Psychiatric and personality examination, different techniques of suggestion and determination of serum prolactin may provide additional diagnostic evidence.