Association between EEG metrics and continuous cerebrovascular autoregulation assessment: a scoping review.

OBJECTIVE: Cerebrovascular autoregulation is defined as the capacity of cerebral blood vessels to maintain stable cerebral blood flow despite changing blood pressure. It is assessed using the pressure reactivity index (the correlation coefficient between mean arterial blood pressure and intracranial pressure). The objective of this scoping review is to describe the existing evidence concerning the association of EEG and cerebrovascular autoregulation in order to identify key concepts and detect gaps in the current knowledge. METHODS: Embase, MEDLINE, SCOPUS, and Web of Science were searched considering articles between their inception up to September 2023. Inclusion criteria were human (paediatric and adult) and animal studies describing correlations between continuous EEG and cerebrovascular autoregulation assessments. RESULTS: Ten studies describing 481 human subjects (67% adult, 59% critically ill) were identified. Seven studies assessed qualitative (e.g. seizures, epileptiform potentials) and five evaluated quantitative (e.g. bispectral index, alpha-delta ratio) EEG metrics. Cerebrovascular autoregulation was evaluated based on intracranial pressure, transcranial Doppler, or near infrared spectroscopy. Specific combinations of cerebrovascular autoregulation and EEG metrics were evaluated by a maximum of two studies. Seizures, highly malignant patterns or burst suppression, alpha peak frequency, and bispectral index were associated with cerebrovascular autoregulation. The other metrics showed either no or inconsistent associations. CONCLUSION: There is a paucity of studies evaluating the link between EEG and cerebrovascular autoregulation. The studies identified included a variety of EEG and cerebrovascular autoregulation acquisition methods, age groups, and diseases allowing for few overarching conclusions. However, the preliminary evidence for the presence of an association between EEG metrics and cerebrovascular autoregulation prompts further in-depth investigations.

Comparison of Continuous Intracortical and Scalp Electroencephalography in Comatose Patients with Acute Brain Injury.

BACKGROUND: Depth electroencephalography (dEEG) is a recent invasive monitoring technique used in patients with acute brain injury. This study aimed to describe in detail the clinical manifestations of nonconvulsive seizures (NCSzs) with and without a surface EEG correlate, analyze their long-standing effects, and provide data that contribute to understanding the significance of certain scalp EEG patterns observed in critically ill patients. METHODS: We prospectively enrolled a cohort of 33 adults with severe acute brain injury admitted to the neurological intensive care unit. All of them underwent multimodal invasive monitoring, including dEEG. All patients were scanned on a 3T magnetic resonance imaging scanner at 6 months after hospital discharge, and mesial temporal atrophy (MTA) was calculated using a visual scale. RESULTS: In 21 (65.6%) of 32 study participants, highly epileptiform intracortical patterns were observed. A total of 11 (34.3%) patients had electrographic or electroclinical seizures in the dEEG, of whom 8 had both spontaneous and stimulus-induced (SI) seizures, and 3 patients had only spontaneous intracortical seizures. An unequivocal ictal scalp correlate was observed in only 3 (27.2%) of the 11 study participants. SI-NCSzs occurred during nursing care, medical procedures, and family visits. Subtle clinical manifestations, such as restlessness, purposeless stereotyped movements of the upper limbs, ventilation disturbances, jerks, head movements, hyperextension posturing, chewing, and oroalimentary automatisms, occurred during intracortical electroclinical seizures. MTA was detected in 18 (81.8%) of the 22 patients. There were no statistically significant differences between patients with MTA with and without seizures or status epilepticus. CONCLUSIONS: Most NCSzs in critically ill comatose patients remain undetectable on scalp EEG. SI-NCSzs frequently occur during nursing care, medical procedures, and family visits. Semiology of NCSzs included ictal minor signs and subtle symptoms, such as breathing pattern changes manifested as patient-ventilator dyssynchrony.

Subacute encephalopathy with seizures in alcoholics (SESA) syndrome.

PURPOSE: To describe four patients with subacute encephalopathy with seizures in alcoholics (SESA) syndrome and to review its clinical, electroencephalogram (EEG), neuroimaging and diagnostic criteria. METHODS: We conducted a retrospective analysis of a series of prospectively collected patients who met the previously established criteria for SESA syndrome. Subsequently, we reviewed all cases published in the English language from the initial description to the present. RESULTS: We found 34 patients diagnosed with SESA syndrome to date, including the four cases of SESA in this report. Fourteen out of 34 (41.1 %) patients were over 60 years of age. Twelve (35.2 %) were abstinent from alcohol and in 4 (11.7 %) there was excessive alcohol consumption. Triggering causes were unknown in 18 cases (53.0 %). All cases (100 %) presented with an altered mental status. Fourteen (41.1 %) subjects had a history of epileptic seizures in the context of acute withdrawal syndrome (AWS). Twenty (58.8 %) patients had focal motor seizures (FMSs), 24 (70.5 %) bilateral tonic-clonic seizures (BTCSs), and 15 (44.1 %) focal impaired awareness seizures (FIASs). In 8 (23.5 %), criteria for focal nonconvulsive status epilepticus (NCSE) were met. Twenty-eight (82.3 %) subjects had transient neurological deficits. In 29 (85.2 %) subjects, lateralized periodic discharges (LPDs) were observed in the EEG. Areas of increased T2/FLAIR signal and restricted diffusion were mentioned in 22 subjects (64.7 %). Transfer to the intensive care unit (ICU) was necessary in 8 (23.5 %) subjects. Thirteen (38.2 %) had recurrent episodes. Enduring cerebral sequelae had been mentioned in 9 (26.4 %) cases. The most used anti-seizure medication (ASM) was levetiracetam, followed by phenytoin and lacosamide. CONCLUSION: SESA syndrome represents a well-defined subtype of focal NCSE in patients with chronic alcoholism. Its prompt recognition can facilitate the initiation of early ASM therapy and help implement a video-EEG evaluation and neuroimaging strategy.

Bispectral index monitoring to detect delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage.

PURPOSE: Evaluate the bispectral index (BIS) monitoring to detect delayed cerebral ischemia (DCI) after aneurysmal subarachnoid hemorrhage (aSAH). MATERIALS AND METHODS: A single-center prospective study in patients with aSAH. BIS monitoring was recorded during 25-120 min in two periods, within the initial 72 h (BIS1) and between days 4 and 6 (BIS2) from admission. The median for each exported BIS parameter was analyzed. Transcranial Doppler (TCD) sonography was simultaneously performed with BIS1 (TCD1) and BIS2 (TCD2) monitoring. A multivariate logistic regression model was built to identify the variables associated with DCI. RESULTS: Sixty-four patients were included and 16 (25%) developed DCI. During BIS2 monitoring, significant differences were found in BIS value (left, p = 0.01; right, p = 0.009), 95% spectral edge frequency (left and right, p = 0.04), and total power (left and right, p = 0.04). In multivariable analysis, vasospasm on TCD2 (OR 42.8 [95% CI 3.1-573]; p = 0.005), a median BIS2 value <85 in one or both sides (OR 6.2 [95% CI 1.28-30]; p = 0.023), and age (OR 1.08 [95% CI 1.00-1.17]; p = 0.04) were associated with the development of DCI. CONCLUSIONS: BIS value is the most useful BIS parameter for detecting DCI after aSAH. Pending further validation, BIS monitoring might be even more accurate than TCD.