Counterpoint: Emergency (“Stat”) EEG in the Era of Nonconvulsive Status Epilepticus

The Cost of After-Hour Electroencephalography

Background and Objectives

High costs associated with after-hour electroencephalography (EEG) constitute a barrier for financially constrained hospitals to provide this neurodiagnostic procedure outside regular working hours. Our study aims to deepen our understanding of the cost elements involved in delivering EEG services during after-hours.

Methods

We accessed publicly available data sets and created a cost model depending on 3 most commonly seen staffing scenarios: (1) technologist on-site, (2) technologist on-call from home, and (3) a hybrid of the two.

Results

Cost of EEG depends on the volume of testing and the staffing plan. Within the various cost elements, labor cost of EEG technologists is the predominant expenditure, which varies across geographic regions and urban areas.

Discussion

We provide a model to explain why access to EEGs during after-hours has a substantial expense. This model provides a cost calculator tool (made available as part of this publication in eAppendix 1, links.lww.com/CPJ/A513) to estimate the cost of EEG platform based on site-specific staffing scenarios and annual volume.

A Simplified Electroencephalogram Monitoring System in the Emergency Room

OBJECTIVES

The study aims to assess the clinical usefulness and related limitations of our simplified emergency electroencephalography (eEEG) as an assessment tool of lethal abnormal brain waves in the emergency room (ER).

METHODS

Electrodes were placed on 4 places: bilateral frontal poles and parietal regions. The derivations to judge consisted of only 2 bipolar leads on the left and right. Abnormal wave was defined as either persistent rhythmic waves or persistent high-amplitude slow waves (<2 Hz). The indications of eEEG were as follows: prolonged impairment of consciousness, suspected subclinical or subtle seizure, and requirement of evaluation of consciousness or seizure during administration of muscle relaxants for endotracheal intubation.

RESULTS

We performed eEEG for 86 patients between July 2013 and February 2014. The persistent rhythmic waves were observed in 7 (8.1%), whereas high-amplitude slow waves were observed in 10 (11.6%). Among 69 patients with normal eEEG, 2 were diagnosed with encephalopathy after hospitalization. The mean time taken to attach electrodes was 5.4 minutes.

CONCLUSIONS

For the ER physician, the simple EEG, such as eEEG, is useful as a biological monitor because it enables quick assessment of lethal abnormal brain waves in the ER. The clinical usefulness and limitations of our eEEG method should be investigated further in a large population.

Emergency electroencephalogram: Usefulness in the diagnosis of nonconvulsive status epilepticus by the on-call neurologist

INTRODUCTION

We aim to describe the use of emergency electroencephalogram (EmEEG) by the on-call neurologist when nonconvulsive status epilepticus (NCSE) is suspected, and in other indications, in a tertiary hospital.

SUBJECTS AND METHODS

Observational retrospective cohort study of emergency EEG (EmEEG) recordings with 8-channel systems performed and analysed by the on-call neurologist in the emergency department and in-hospital wards between July 2013 and May 2015. Variables recorded were sex, age, symptoms, first diagnosis, previous seizure and cause, previous stroke, cancer, brain computed tomography, diagnosis after EEG, treatment, patient progress, routine control EEG (rEEG), and final diagnosis. We analysed frequency data, sensitivity, and specificity in the diagnosis of NCSE.

RESULTS

The study included 135 EEG recordings performed in 129 patients; 51.4% were men and their median age was 69 years. In 112 cases (83%), doctors ruled out suspected NCSE because of altered level of consciousness in 42 (37.5%), behavioural abnormalities in 38 (33.9%), and aphasia in 32 (28.5%). The EmEEG diagnosis was NCSE in 37 patients (33%), and this was confirmed in 35 (94.6%) as the final diagnosis. In 3 other cases, NCSE was the diagnosis on discharge as confirmed by rEEG although the EmEEG missed this condition at first. EmEEG performed to rule out NCSE showed 92.1% sensitivity, 97.2% specificity, a positive predictive value of 94.6%, and a negative predictive value of 96%.

CONCLUSIONS

Our experience finds that, in an appropriate clinical context, EmEEG performed by the on-call neurologist is a sensitive and specific tool for diagnosing NCSE.

Novel screen printed electrode set for routine EEG recordings in patients with altered mental status

There is a growing need for an easy to use screening tool for the assessment of brain's electrical function in patients with altered mental status (AMS). The purpose of this study is to give a brief overview of the state-of-the-art in electrode technology, and to present a novel sub-hairline electrode set developed in our research group. Screen-printing technology was utilized to construct the electrode set consisting of ten electroencephalography (EEG) electrodes, two electrooculography (EOG) electrodes, two ground electrodes and two reference electrodes. Electrical characteristics of hydrogel-coated silver ink electrodes were found adequate for clinical EEG recordings as assessed by electrical impedance spectroscopy (EIS). The skin-electrode impedances remain stable and low enough at least two days enabling high-quality long-term recordings. Due to the proper material selection, thin ink layers and detachable zero insertion force (ZIF) - connector, electrode was observed to be CT- and MRI-compatible allowing imaging without removing the electrodes. Pilot EEG recordings gave very promising results and an on-going clinical trial with larger number of patients will show the true feasibility of this approach.

Electroencephalography leads placed by nontechnologists using a template system produce signals equal in quality to technologist-applied, collodion disk leads

The purpose of this study was to compare the quality of the electroencephalographic (EEG) data obtained with a BraiNet template in a practical use setting, to that obtained with standard 10/20 spaced, technologist-applied, collodion-based disk leads. Pairs of 8-hour blocks of EEG data were prospectively collected from 32 patients with a Glasgow coma score of ≤9 and clinical concern for underlying nonconvulsive status epilepticus over a 6-month period in the Neurocritical Care Unit at the Duke University Medical Center. The studies were initiated with the BraiNet template system applied by critical care nurse practitioners or physicians, followed by standard, collodion leads applied by registered technologists using the 10/20 system of placement. Impedances were measured at the beginning and end of each block recorded and variance in impedance, mean impedance, and the largest differences in impedances found within a given lead set were compared. Physicians experienced in reading EEG performed a masked review of the EEG segments obtained to assess the subjective quality of the recordings obtained with the templates. We found no clinically significant differences in the impedance measures. There was a 3-hour reduction in the time required to initiate EEG recording using the templates (P < 0.001). There was no difference in the overall subjective quality distributions for template-applied versus technologist-applied EEG leads. The templates were also found to be well accepted by the primary users in the intensive care unit. The findings suggest that the EEG data obtained with this approach are comparable with that obtained by registered technologist-applied leads and represents a possible solution to the growing clinical need for continuous EEG recording availability in the critical care setting.

The utility of EEG, SSEP, and other neurophysiologic tools to guide neurocritical care

Neuromonitoring is an emerging field that aims to characterize real-time neurophysiology to tailor therapy for acute injuries of the central nervous system. While cardiac telemetry has been used for decades among patients requiring critical care of all kinds, neurophysiology and neurotelemetry has only recently emerged as a routine screening tool in comatose patients. The increasing utilization of electroencephalography in comatose patients is primarily due to the recognition of the common occurrence of nonconvulsive seizures among comatose patients, the development of quantitative measures to detect regional ischemia, and the appreciation of electroencephalography phenotypes that indicate prognosis after cardiac arrest. Other neuromonitoring tools, such as somatosensory evoked potentials have a complementary role, surveying the integrity of the neuroaxis as an indicator of prognosis or illness progression in both acute brain and spinal injuries.

A low-impedance, skin-grabbing, and gel-free EEG electrode

Inspired by the extraordinary object grabbing ability of certain insects (e.g., a grasshopper), we have developed a novel dry EEG electrode, called the skin screw electrode. Unlike the traditional disc electrode which requires several minutes to install, the installation of the skin screw electrode can be completed within seconds since no skin preparation and electrolyte application are required. Despite the drastic improvement in the installation time, our experiments have demonstrated that the skin screw electrode has a similar impedance value to that of the disc electrode. The skin screw electrode has a wide range of applications, such as clinical EEG diagnosis, epilepsy monitoring, emergency medicine, and home-based human-computer interface.

Nonconvulsive status epilepticus

Nonconvulsive status epilepticus (NCSE) refers to a prolonged seizure that manifests primarily as altered mental status as opposed to the dramatic convulsions seen in generalized tonic-clonic status epilepticus. There are 2 main types of NCSE, each of which has a different presentation, cause, and expected outcome. In the first type of NCSE, patients present with confusion or abnormal behavior, suggesting the diagnosis of absence status epilepticus (ASE) or complex partial status epilepticus (CPSE). The second type of NCSE (subtle status epilepticus [SSE]) must be considered in comatose patients who present after a prolonged generalized tonic-clonic seizure and who may have only subtle motor manifestations of a seizure, such as facial or hand twitchings. Whereas the morbidity and mortality in patients with prolonged ASE or CPSE is low, the mortality associated with SSE can exceed 30% if the seizure duration is greater than 60 minutes.