Generalized Periodic Epileptiform Discharges— To Treat or Not to Treat?

abstract & commentary

Source: Husain AM, et al. Generalized periodic epileptiform discharges: Etiologies, relationship to status epilepticus, and prognosis. J Clin Neurophysiol 1999;16(1):51-58.

Few studies have investigated the underlying mechanisms and clinical importance of periodic epileptiform discharges, whether lateralized (PLEDs), bilateral independent (BiPEDs), or generalized (GPEDs). Conflicting statements have frequently resulted in hesitation to treat GPEDs as epileptic events, unless prompted by the clinical behavior of the patient.

Husain and colleagues review the etiologies and clinical course of 25 patients who demonstrated GPEDs on EEG. Patients with lateralized or bilateral independent PEDs were excluded. Despite the small number of patients, the lack of reference to the immediate cause of death, or the effect of treatment, the study offers some useful observations.

As the table indicates, age older than 70 years and the presence of GPEDs following anoxia strongly predicted death. Among the 25 patients, eight were found to be in status epilepticus (SE), which was defined as: 1) recognition of unambiguous electrographic seizure patterns; 2) tonic-clonic activity during the EEG; or 3) electrographic or clinical improvement following administration of an antiepileptic medication—surprisingly offered a somewhat better prognosis. Half of the eight SE patients survived compared to five of the 17 non-SE patients. Examining outcomes in the entire group of 25 patients, six of nine survivors had a history of seizures whereas the remaining three did not. In contrast, of the 16 nonsurvivors, only four had a history of seizures.

    Table
    Outcome by Age, Etiology, and the Presence of SE in 25 Patients with GPEDs_________
    n
    Outcome
    Age Older than 70 years 
    8
    8 died
    (100%)
    Younger than 70 years
    17
    8 died
    (47%)
    Etiology Anoxic encephalopathy
    10
    9 died
    (90%)
    Toxic-metabolic encephalopathy
    7
    4 died
    (43%)
    Primary neurological diseases 
    (seizures, stroke, hemorrhage, head trauma)
    8
    3 died
    (37%)
    Status Epilepticus Present
    8
    4 died
    (50%)
    Absent
    17
    5 died
    (29%)
    _________________________________________________________________________

Husain et al also attempt to identify EEG features that might foretell the presence of SE. They describe a statistically significant correlation (P < 0.05) between the presence of SE and with increasing GPED amplitude, duration, and with higher inter-GPED amplitude on EEG. Closer examination of the data, however, reveals that these EEG features have a low predictive value. For instance, a GPED amplitude greater than 100 µV (62.5% of SE patients) has a positive predictive value for the presence of SE equal 44% only. Similarly, the positive predictive value for a GPED duration of more than 0.4 seconds (62.5% of SE patients) is only 41.66%, and for an inter-GPED amplitude equal to or greater than 35 µV (50% of the SE patients) is only 66%.

Commentary

This study has serious limitations: small numbers, retrospective design, and lack of information on immediate cause of death or quality of outcome. Nevertheless, it describes one of the few available attempts to study the clinical usefulness of GPEDs in predicting SE and outcome. It may turn out that the presence of seizures or even SE confers a relatively favorable overall prognosis, which cannot be explained completely by age range, or less grave underlying comorbid condition. The reasons for the improved survival in patients with SE are unclear. It may be that the absence of seizures is a marker for more extensive neuronal damage or dysfunction. Alternatively, the presence of seizures and SE may have resulted in more aggressive treatment that improved survival. The question of whether to treat GPEDs as seizures or as SE remains open. An additional prospective study needs to answer this question and that of the eventual quality of life following GPEDs. —fl, aristea s. galanopoulou, solomon l. moshé (Dr. Galanopoulou is EEG Fellow, Department of Neurology, Montefiore Medical Center-Albert Einstein College of Medicine, Bronx, NY. Dr. Moshé is Professor and Director, Pediatric Neurology and Clinical Neurophysiology, Department of Neurology, Montefiore Medical Center-Albert Einstein College of Medicine, Bronx, NY.)

The most reliable predictor of a fatal outcome in patients with generalized epileptiform discharges (GPEDs) on EEG is/are:

    a. high amplitude and duration of the GPED bursts on EEG.
    b. age older than or equal to 70 years.
    c. presence of status epilepticus clinically or electrographically.
    d. a and b
    e. b and c