# Breach rhythm-induced asymmetric post-arousal hypersynchrony mimicking ictal EEG in coma

## TL;DR

This paper discusses how EEG patterns in comatose patients can be misinterpreted as seizures when they are actually normal arousal reactions.

## Contribution

The study highlights the risk of misinterpreting EEG patterns in comatose patients as nonconvulsive status epilepticus due to breach rhythm and arousal phenomena.

## Key findings

- Stimulation-induced rhythmic delta waves in comatose patients can mimic focal seizures.
- Benzodiazepine responsiveness in EEG patterns may indicate arousal rather than seizures.
- Breach rhythm can cause asymmetrical delta waves that are misread as ictal activity.

## Abstract

•SIRPIDs are rhythmic, periodic, or ictal discharges triggered by alerting stimuli.•The word “ictal” in the acronym complicates the interpretation of EEGs.•In coma, identify physiologic arousals to avoid misreading these patterns as seizures.

SIRPIDs are rhythmic, periodic, or ictal discharges triggered by alerting stimuli.

The word “ictal” in the acronym complicates the interpretation of EEGs.

In coma, identify physiologic arousals to avoid misreading these patterns as seizures.

To highlight the risk of misinterpreting stimulation-related EEG patterns as seizures in the ICU, and to illustrate how awakening hypersynchrony and breach rhythm can mimic a focal seizure, leading to an erroneous diagnosis of nonconvulsive status epilepticus (NCSE).

A single patient case observation of a 17-year-old male with a severe traumatic brain injury, resulting in a left depressed skull fracture and coma. A continuous EEG was analyzed during repeated auditory/somatosensory stimulations. Pharmacologic reactivity was assessed with IV clonazepam.

Several episodes of awakening hypersynchrony were initially misinterpreted as subclinical focal seizures, leading to a diagnosis of NCSE. The EEGs displayed asymmetrical, sharply contoured rhythmic delta waves after stimulations, showing evolution and lasting more than 10 s. These delta waves demonstrated reactivity to IV-clonazepam, resulting in an improved EEG. Although no clinical improvement was observed, the patient returned to sleep immediately. The EEGs were reinterpreted as representing arousal reactions during the awakening process. The asymmetry of the rhythmic delta waves corresponded to a breach rhythm.

In comatose or sedated ICU patients, stimulation-induced rhythmic delta waves with apparent evolution, and even benzodiazepine responsiveness, may represent normal arousal phenomena amplified by a breach rhythm rather than ictal activity. Significance: As stimulus-induced rhythmic, periodic, or ictal discharges (SIRPIDs) strictly describe EEG morphology and evolution without reference to the cause, normal arousals/awakenings and their variations must be recognized in comatose patients. Due to the ambiguity of the term “ictal” and its clinical implications, “ictal” could be replaced with “intermittent”: Stimulus-Induced Rhythmic or Periodic Intermittent Discharges.