Variantes normales de aspecto epileptiforme en el electroencefalograma. Revisión de la bibliografía e implicaciones clínicas / Normal variants with an epileptiform appearance in electroencephalograms. A literature review and clinical implications

Las variantes normales de aspecto epileptiforme, o variantes epileptiformes benignas, son un reto diagnóstico en la interpretación de los electroencefalogramas que requiere su conocimiento y una amplia experiencia por parte de los responsables del informe electroencefalográfico. Incluyen un grupo heterogéneo de hallazgos, algunos muy infrecuentes, que inicialmente se relacionaron con epilepsia y patologías neurológicas diversas. En la actualidad, la mayoría se consideran variantes sin significado patológico, y su sobreinterpretación habitualmente acarrea diagnósticos erróneos y tratamientos innecesarios. Los datos de prevalencia de estas variantes son muy diversos y proceden habitualmente de poblaciones seleccionadas, por lo que son difícilmente extrapolables a población sana. No obstante, estudios con electrodos invasivos y series más recientes vuelven a asociar algunas de estas variantes con epilepsia. Nuestro objetivo es revisar las características y la prevalencia de las principales variantes epileptiformes benignas y actualizar su significado clínico. (AU)

SREDA: An Uncommon and Misleading EEG Rhythm.

Subclinical Rhythmic Electroencephalographic Discharges of Adults (SREDA) is a benign EEG variant characterized by sharply contoured rhythmic theta activity occurring bilaterally with maximum activity over the parietal or the posterior head region. These paroxysms are not associated with any objective or subjective clinical manifestations. SREDA, the rarest and last reported benign EEG pattern with no known clinical significance yet, is detailed in this case report. We provide the case of a gentleman with epilepsy who underwent vEEG recording in our lab. The described case is interesting due to its EEG characteristics as well as its clinical picture, which misled us for at least a while. It provides an illustration of how over interpretation of normal EEG patterns may result in an incorrect diagnosis.

Prevalence of benign epileptiform variants from an EEG laboratory in India and frequency of their misinterpretation.

OBJECTIVE: To prospectively study the prevalence of benign epileptiform variants (BEVs) and their impact on epilepsy misdiagnosis. METHODS: Consecutive patients, older than one year, who underwent EEG from January 2016 to December 2019 were prospectively studied for the presence of BEVs. We used descriptions of Klass and Westmoreland (1985) to categorize the BEVs. We reviewed old EEG reports and records in patients with BEV to determine whether they were interpreted as abnormal. RESULTS: Of the 1862 subjects included, 1474 (79 %) patients had epilepsy while 388 (21 %) had other diagnoses. The mean age of the subjects was 23.1 ± 15.3 years and 1111 (60 %) were males. BEVs were noted in 223 (12 %) subjects undergoing EEG. The most common BEVs were wicket waves (n = 127, 6.8 %) and small sharp spikes (n = 69, 3.7 %) while 6 Hz spike-wave discharges (0.9 %), 14 and 6 Hz positive spikes (0.6 %), rhythmic mid-temporal theta burst of drowsiness (0.4 %) and subclinical rhythmic epileptiform discharges in adults (0.2 %) were less common. Patients with BEVs were older and were more likely to have normal EEG (68.2 % vs. 55.8 %; p < 0.001). BEVs were not mentioned in any of the 282 previous EEG reports. BEVS were considered to be over-interpreted as epileptiform abnormalities in 31 of 101 (30 %) records available for review. CONCLUSION: BEVs are present in 12 % of subjects undergoing EEG. BEVS are largely unrecognized and are misdiagnosed as epileptiform discharges in one third of the patients by the general neurologists.

Atypical SREDA During Wakefulness, NREM and REM Sleep in a Young Teenager: A Diagnostic Challenge.

Subclinical rhythmic electrographic discharges of adult (SREDA) is a rare variant considered to be normal in EEG. It consists of sharp-contoured or sinusoidal waveforms in the theta frequency range (usually 5-7 Hz), occurring in a widespread distribution, often maximal over the parietotemporal regions. SREDA is usually bilateral but could be unilateral (atypical SREDA). Compared with true ictal activities, SREDA has little change in frequency, morphology, and distribution. It has been described in adults and is extremely rare in children/adolescents. There are only 5 cases published in children. We report a case of atypical SREDA in a child that may have occurred in wakefulness, non-rapid eye movement (NREM) sleep, and REM sleep. This finding was initially misdiagnosed as epilepsy. Inpatient video-EEG demonstrated that during periods of SREDA in quiet wakefulness the patient did not have any signs or symptoms with the SREDA pattern; SREDA abated whenever the patient was alerted or if he spontaneously initiated some activities. SREDA with same morphology was noted in NREM and REM sleep. The patient had no true epileptogenic abnormalities and hence antiepileptic medication was discontinued and stopped uneventfully. This case illustrates the importance of recognizing this rare variant, avoiding a misdiagnosis of epilepsy as it occurred in our case.

Unilateral SREDA in a Patient With Stroke.

Subclinical rhythmic electrographic discharges in adults (SREDA) is a well-known benign EEG phenomenon. However, the occurrence of SREDA is rare, and atypical forms are even more elusive, with only few cases reported in the literature. Herein, we describe a case of a 77-year-old woman with a left middle cerebral artery stroke and paroxysms of rhythmic, sharply contoured activity over the right central head region, mimicking focal seizures on EEG, that were determined to represent atypical SREDA. To our knowledge, no case of SREDA with a contralateral structural cerebral abnormality has been described, and its occurrence offers some limited insight as to the mechanisms underlying this mysterious entity.