Difficulties in Diagnosing Nonepileptic Seizures in Patients Who Also Have Epile
May 1, 1998
Difficulties in Diagnosing Nonepileptic Seizures in Patients Who Also Have Epilepsy
ABSTRACT & COMMENTARY
Source: Henry T, Drury I. Ictal behaviors during nonepileptic seizures differ in patients with temporal lobe interictal epileptiform EEG activity and patients without interictal epileptiform abnormalities. Epilepsia 1998;39:175-182.
A skilled neurologist can usually diagnose complex partial seizures accurately based on the clinical features of the attacks as described by patients and observers (including features such as abnormal motor activity, duration, and postictal state). Epileptic seizures typically differ from nonepileptic seizures (NES) of psychogenic origin, which tend to include long-lasting waxing and waning, feature chaotic agitated motor activity, and do not have a postictal state. However, some patients with epilepsy also have NES, and their epilepsy experiences may affect the ictal semiology of their NES. Henry and Drury now report that NES in patients with epilepsy more closely resemble epileptic seizures than do NES in patients who do not have concomitant epilepsy.
The authors describe 177 patients they studied in the University of Michigan video-EEG laboratory between 1988 and 1992. All had medication-resistant seizures and were undergoing evaluation for possible epilepsy surgery. None was referred for assessment of suspected NES. Based on the video-EEG findings, patients were segregated into three groups: 1) a "mixed group" (epileptic + NES seizures recorded, n = 20), 2) an "epileptic group" (epileptic seizures only recorded, n = 133), and 3) a purely "nonepileptic group" (NES only recorded, n = 24).
NES occurring in the purely nonepileptic group featured convulsive activity in half the cases, often characterized by waxing and waning jerking movements that cycled more than once during a single period of "unconsciousness." In contrast, NES in the mixed group and in the epileptic group featured convulsive movements in only 10%, 5%, and 14% of cases, respectively (P < 0.001). Hypotonic behaviors, such as gradual postural declines into limp unresponsiveness, occurred only in NES in the purely nonepileptic group (P < 0.05).
The duration of ictal unresponsiveness was long for NES in both the mixed seizures and the purely nonepileptic group. In the mixed seizures group, the mean duration of NES unresponsiveness was 6.1 minutes. In the purely nonepileptic group, the mean duration of NES unresponsiveness was 7.3 minutes. In contrast, no actual epileptic seizure in any group lasted more than two minutes (P < 0.001).
After NES in the mixed seizures and purely nonepileptic groups, 40% of patients exhibited an abnormal post-ictal behavioral state, 40% did not exhibit post-ictal abnormalities, and 20% had variable post-ictal states after multiple recorded seizures. In contrast, all actual epileptic seizures were followed by a post-ictal state (P < 0.001).
COMMENTARY
The current findings of Henry and Drury demonstrate that NES in patients who also have epilepsy are similar to bona fide epileptic seizures. Both of these seizure types typically featured unresponsive motionless staring and lacked convulsive activity and hypotonic features. These seizures differed from NES in patients who did not also have epilepsy, and expressed chaotic jerking movements and gradual loss of muscle tone were seen.
All NES, however, had certain common features, which differed from bona fide epileptic seizures. These common features were found in NES from patients both with and without associated documented epilepsy. NES were longer, and had absent or more variable post-ictal states than did physiologically engendered epileptic seizures.
Several hypotheses may be offered to explain these findings. Patients with epilepsy plus NES may have different underlying psychiatric diagnoses compared to patients with only NES. However, that did not appear to be the case in this series. Among the 20 patients in the mixed seizures group, 18 had depression, five had anxiety, five had somatization, and six reported childhood sexual abuse. Among the 24 patients in the purely NES group, 20 had depression, five had anxiety, five had somatization, and six reported childhood sexual abuse.
Patients with epilepsy may recall their auras and the contents of their complex partial seizures. Patients with epilepsy have often been questioned pointedly by physicians about certain ictal symptoms. Self-help patient groups, such as the Epilepsy Foundation, have developed and distributed to the public extensive printed material about seizures and their manifestations. These data all may be internalized and expressed as components of NES. Thus, when patients have both NES and epileptic seizures, differentiating between the two can be difficult. Video-EEG is often required for accurate diagnosis. -drl
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