A unique presentation of atypical SREDA pattern in a young healthy woman

Abstract

Subclinical rhythmic electrographic discharge of adults (SREDA) is an EEG pattern seen in normal individuals and others with different diseases. we report a case of healthy young woman with alleged epilepsy but normal responsiveness during sustained SREDA. SREDA is a rare EEG variant with variable clinical significance. This is the first report of atypical SREDA in a 25 year-old woman.

Introduction

A 25-year-old woman took levetiracetam extended release formulation (LEV-XR) for presumed seizures. She wished to discuss LEV taper prior to planning a pregnancy.

She has two types of spells: Generalized shaking and staring spells.

A 4-day video-electroencephalography (VEEG) study performed 2 years earlier depicted 10–50 s frequent runs of bilateral frontotemporal spikes and sharp-and-slow wave complexes with no typical spells. LEV-XR dosage was increased to 2,000 mg twice daily with no benefit for spells. She had a second admission to the epilepsy-monitoring unit (EMU) for characterization of her episodes.

EEG analysis showed frequent bursts of high voltage sharply contoured rhythmic theta activity with bilateral temporofrontal predominance, intermixed with runs of 5Hz sharp-and-slow-wave activity [Figures 1–4]. An evolution of this EEG activity into a higher voltage, generalized rhythmic delta activity occurred in sleep.

Figure 1.

Bilateral sharp activity (red arrows) predominantly seen in the temporal regions (red arrows) during a normal conversation

Figure 4.

Sharp activity, seen predominantly in the temporal regions, evolves into a generalized rhythmic sharply contoured activity during drowsiness

Figure 2.

Bilateral sharp activity on the EEG (red arrows), predominantly in the temporal regions. Patient is texting on her phone and watching TV

Figure 3.

Patient is reading. EEG shows a high voltage rhythmic sharply contoured delta activity that stops abruptly (red arrow) with no clinical change

Such bursts were seen during normal behaviors (talking on the phone; playing with her child) and triggers included hyperventilation, exercise, and mental activity (watching TV or reading). Extensive examinations including administration of standardized tests of attention span, registration and recall, and orientation questions showed no abnormalities at all.

Two months following discharge on LEV-XR, she denied any generalized seizures, but the daily subjective spells continued.

This patient's initial presentation led to an initial VEEG monitoring recording that failed to record any spell. A second VEEG monitoring session was needed due to lack of clinical improvement and demonstrated the presence of subclinical rhythmic electrographic discharge of adults (SREDA). To our knowledge, a similar SREDA pattern has not been reported in a young healthy adult during normal functioning.

Naquet et al., first described SREDA in 1961.[1] It was later defined in 1981, with a series of 65 patients by Westmoreland and Klass demonstrating a normal distinctive EEG variant. This pattern consisted of rhythmic sharply contoured waves that merge into a monorhythmic sinusoidal theta pattern, without subsequent evolution in frequency, distribution, or morphology. It was predominant over the parietal and posterior temporal regions.[2]

SREDA was also found in patients with transient global amnesia[3,4] syncope, generalized tonic-clonic seizures, and temporal lobe epilepsy. It also appears to demonstrate morphological EEG change in response to benzodiazepines.[5]

In 1997, Westmoreland and Klass identified the characteristics of atypical SREDA consisting of predominant delta frequency, frontal/focal distribution, notched waveforms, prolonged duration, or occurrence during sleep. These features were separately reported in different patients older than 35 years of age and in three children aged 5, 10, and 11 years.[6,7] Further, within the identified clinical diagnoses, only two of the atypical SREDA patients had seizures and other epileptiform abnormalities that were distinct from SREDA.[2]

A careful examination of SREDA using Laplacian frequency spectral analysis demonstrated a complicated mix of frequency peaks with maximal activity in the parietocentrotemporal regions.[8]

In summary, this unique case represents all described features of an atypical SREDA, but in a healthy young adult female. Despite the lack of a clear physiological explanation, in this case, SREDA seems to represent a benign EEG phenomenon.