SREDA: A Rare but Confusing Benign EEG Variant

Four Atypical Cases of Subclinical Rhythmic Electroencephalogram Discharge of Adults: Case Series and Review

SUMMARY

Subclinical rhythmic EEG discharge of adults is an uncommon variant that represents a diagnostic challenge in the clinical practice because it can be mistaken for an electrographic seizure. We present a case series of four patients who underwent EEG because of suspicious events or an unclear medical history of epilepsy. In all cases, the EEG revealed atypical features including focal and asymmetric distribution, presentation during NREM and REM sleep, rhythmic activity in the delta range with a notched appearance and blocked by eyes opening.

Pitfalls in scalp EEG: Current obstacles and future directions

Although electroencephalography (EEG) serves a critical role in the evaluation and management of seizure disorders, it is commonly misinterpreted, resulting in avoidable medical, social, and financial burdens to patients and health care systems. Overinterpretation of sharply contoured transient waveforms as being representative of interictal epileptiform abnormalities lies at the core of this problem. However, the magnitude of these errors is amplified by the high prevalence of paroxysmal events exhibited in clinical practice that compel investigation with EEG. Neurology training programs, which vary considerably both in the degree of exposure to EEG and the composition of EEG didactics, have not effectively addressed this widespread issue. Implementation of competency-based curricula in lieu of traditional educational approaches may enhance proficiency in EEG interpretation amongst general neurologists in the absence of formal subspecialty training. Efforts in this regard have led to the development of a systematic, high-fidelity approach to the interpretation of epileptiform discharges that is readily employable across medical centers. Additionally, machine learning techniques hold promise for accelerating accurate and reliable EEG interpretation, particularly in settings where subspecialty interpretive EEG services are not readily available. This review highlights common diagnostic errors in EEG interpretation, limitations in current educational paradigms, and initiatives aimed at resolving these challenges.

Aphasic Status Epilepticus Associated with Alzheimer's Disease: Clinical and Electrographic Characteristics

In aphasic status epilepticus (ASE), aphasia is the sole manifestation of seizure in patients with this disorder. Alzheimer's disease (AD) is one of neurological disorders causing ASE. Herein, we report two cases of ASE associated with AD, and discuss their clinical characteristics. Patient 1 presented Broca's aphasia, and patient 2 presented global aphasia during the ictal period. Both patients exhibited atypical ictal electroencephalographic (EEG) patterns, which improved after antiepileptic drug administration. ASE was the presenting symptom of AD in patient 1. ASE can develop at any stage of AD. Alterations in clinical symptoms and EEG patterns after treatment with antiepileptic drug are the key to diagnosis. Prompt diagnosis and treatment are critical for preventing further consciousness dysfunction.

Normal variants and artifacts: Importance in EEG interpretation

Overinterpretation of EEG is an important contributor to the misdiagnosis of epilepsy. For the EEG to have a high diagnostic value and high specificity, it is critical to recognize waveforms that can be mistaken for abnormal patterns. This article describes artifacts, normal rhythms, and normal patterns that are prone to being misinterpreted as abnormal. Artifacts are potentials generated outside the brain. They are divided into physiologic and extraphysiologic. Physiologic artifacts arise from the body and include EMG, eyes, various movements, EKG, pulse, and sweat. Some physiologic artifacts can be useful for interpretation such as EMG and eye movements. Extraphysiologic artifacts arise from outside the body, and in turn can be divided into the environments (electrodes, equipment, and cellphones) and devices within the body (pacemakers and neurostimulators). Normal rhythms can be divided into awake patterns (alpha rhythm and its variants, mu rhythm, lambda waves, posterior slow waves of youth, HV-induced slowing, photic driving, and photomyogenic response) and sleep patterns (POSTS, vertex waves, spindles, K complexes, sleep-related hypersynchrony, and frontal arousal rhythm). Breach can affect both awake and sleep rhythms. Normal variants or variants of uncertain clinical significance include variants that may have been considered abnormal in the early days of EEG but are now considered normal. These include wicket spikes and wicket rhythms (the most common normal pattern overread as epileptiform), small sharp spikes (aka benign epileptiform transients of sleep), rhythmic midtemporal theta of drowsiness (aka psychomotor variant), Cigánek rhythm (aka midline theta), 6 Hz phantom spike-wave, 14 and 6 Hz positive spikes, subclinical rhythmic epileptiform discharges of adults (SREDA), slow-fused transients, occipital spikes of blindness, and temporal slowing of the elderly. Correctly identifying artifacts and normal patterns can help avoid overinterpretation and misdiagnosis. This is an educational review paper addressing a learning objective of the International League Against Epilepsy (ILAE) curriculum.

Temporal intermittent rhythmic theta activity (TIRTA): A marker of epileptogenicity?

Objective

To describe a novel EEG rhythm, temporal intermittent rhythmic theta activity (TIRTA), and its potential association with epilepsy.

Methods

We report TIRTA on scalp EEG in a series of 12 patients, all of whom were found to have epilepsy. The clinical and electroencephalographic characteristics of each patient were reviewed. In addition, features that may distinguish TIRTA from benign EEG patterns, including rhythmic temporal theta bursts of drowsiness (RTTBD), were identified.

Results

TIRTA was unilateral in all cases. For all patients, TIRTA was seen in the awake and drowsy states. Eight patients also had TIRTA observed during N2 sleep. The average frequency of TIRTA was 5.5 Hz and the average duration of a train of TIRTA was 5.25 s. In seven cases the morphology was notched in appearance. Temporal intermittent rhythmic delta activity (TIRDA) was seen in seven patients on the same side as TIRTA. Eleven patients also had ipsilateral temporal sharp waves. Abnormal MRI (6/12) and or PET (5/5) findings were ipsilateral to TIRTA.

Conclusions

In this preliminary report we suggest that TIRTA may be a novel marker of potential epileptogenicity, possibly representing a higher frequency variant of TIRDA.