Guidance for clinical neurophysiology examination throughout the COVID-19 pandemic. Latin American chapter of the IFCN task force - COVID-19

On 31st December 2019, China notified the World Health Organization of an outbreak of atypical pneumonia from patients at a local seafood market in Wuhan, Hubei, China, responsible for a new coronavirus called Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) that caused COVID-19 disease, which spread rapidly around the world. WHO declared a state of pandemic (11th March, 2020), which has caused more than 1 million infected and more than 110,000 deaths; it was observed that up to 29% of those infected were health care personnel. The main route of transmission of SARS-CoV2 is through respiratory secretions and direct contact with contaminated surfaces and material. The pandemic induced an international saturation of health care services and a rupture in the supply chain of protective equipment for healthcare personnel, which poses a high occupational risk to all. Based on the different healthcare systems, human resources, infrastructure and medical emergencies that will warrant the conduct of clinical neurophysiology studies and the lack of a guide for the management of the situation, it was decided by an expert task force of the Latin American Chapter of the International Federation of Clinical Neurophysiology to carry out these guidelines for the protection of patient and healthcare professionals conducting clinical neurophysiological studies.

Diagnosis of covert hepatic encephalopathy: a multi-center study testing the utility of single versus combined testing

Covert hepatic encephalopathy (CHE) affects cognition in a multidimensional fashion. Current guidelines recommend performing Psychometric Hepatic Encephalopathy Score (PHES) and a second test to diagnose CHE for multi-center trials. We aimed to determine if a two-test combination strategy improved CHE diagnosis agreement, and accuracy to predict overt hepatic encephalopathy (OHE), compared to single testing. Cirrhotic outpatients without baseline OHE performed PHES, Inhibitory Control Test (ICT), and Stroop EncephAlapp (StE) at three centers. Patients were followed for OHE development. Areas under the receiver operation characteristic curve (AUROC) were calculated. We included 437 patients (399 with follow-up data). CHE prevalence varied with testing strategy: PHES+ICT 18%, ICT + StE 25%, PHES+StE 29%, ICT 35%, PHES 37%, and StE 54%. Combination with best test agreement was PHES+StE (k = 0.34). Sixty patients (15%) developed OHE. Although CHE by StE showed the highest sensitivity to predict OHE, PHES and PHES+StE were more accurate at the expense of a lower sensitivity (55%, AUROC: 0.587; 36%, AUROC: 0.629; and 29%, AUROC: 0.623; respectively). PHES+ICT was the most specific (85%) but all strategies including ICT showed sensitivities in the 33-45% range. CHE diagnosis by PHES (HR = 1.79, p = 0.04), StE (HR = 1.69, p = 0.04), and PHES+StE (HR = 1.72, p = 0.04), were significant OHE predictors even when adjusted for prior OHE and MELD. Our results demonstrate that combined testing decreases CHE prevalence without improving the accuracy of OHE prediction. Testing with PHES or StE alone, or a PHES+StE combination, is equivalent to diagnose CHE and predict OHE development in a multi-center setting.

Critical flicker frequency test predicts overt hepatic encephalopathy and survival in patients with liver cirrhosis

BACKGROUND

A critical flicker frequency (CFF) ≤39 Hz identifies cirrhotic patients with minimal hepatic encephalopathy (mHE) and predicts the risk of both overt hepatic encephalopathy (oHE) and mortality in patients with previous episodes of decompensation and/or oHE.

AIMS

Herein, we evaluated the effectiveness of CFF in predicting the first episode of oHE and survival in cirrhotics who had never experienced an episode of oHE.

METHODS

Our cohort study of 134 patients and 150 healthy subjects were examined. A CFF > 39 Hz was considered normal and pathological when ≤39 Hz. The median follow up was 36 months.

RESULTS

At baseline, all controls had CFF > 39 Hz. Ninety-three patients had a CFF > 39 Hz and 41 had a CFF ≤ 39 Hz. The prevalence of CFF ≤ 39 Hz significantly increased with the progression of the Child-Pugh class (p = 0.003). Moreover, the risk of oHE was increased by CFF ≤ 39 (p < 0.001, by log-rank test) [HR = 7.57; CI(3.27-17.50); p < 0.0001, by Cox model] and ammonia [HR = 1.02 CI(1.01-1.03), p = 0.0009]. Both a CFF value ≤ 39 Hz and Child-Pugh class were independent predictors of mortality by Cox model [HR = 1.97; CI(1.01-3.95), p = 0.049; HR = 3.85 CI(1.68-8.83), p = 0.003].

CONCLUSIONS

CFF predicts the first episode of oHE in cirrhotics that had never experienced oHE, and predicts mortality risk. These findings suggest that cirrhotic patients should be routinely screened by CFF.

Analysis of correlation between white matter changes and functional responses in thalamic stroke: a DTI & EEG study

Diffusion tensor imaging (DTI) allows in vivo structural brain mapping and detection of microstructural disruption of white matter (WM). One of the commonly used parameters for grading the anisotropic diffusivity in WM is fractional anisotropy (FA). FA value helps to quantify the directionality of the local tract bundle. Therefore, FA images are being used in voxelwise statistical analyses (VSA). The present study used Tract-Based Spatial Statistics (TBSS) of FA images across subjects, and computes the mean skeleton map to detect voxelwise knowledge of the tracts yielding to groupwise comparison. The skeleton image illustrates WM structure and shows any changes caused by brain damage. The microstructure of WM in thalamic stroke is investigated, and the VSA results of healthy control and thalamic stroke patients are reported. It has been shown that several skeleton regions were affected subject to the presence of thalamic stroke (FWE, p < 0.05). Furthermore the correlation of quantitative EEG (qEEG) scores and neurophysiological tests with the FA skeleton for the entire test group is also investigated. We compared measurements that are related to the same fibers across subjects, and discussed implications for VSA of WM in thalamic stroke cases, for the relationship between behavioral tests and FA skeletons, and for the correlation between the FA maps and qEEG scores.Results obtained through the regression analyses did not exceed the corrected statistical threshold values for multiple comparisons (uncorrected, p < 0.05). However, in the regression analysis of FA values and the theta band activity of EEG, cingulum bundle and corpus callosum were found to be related. These areas are parts of the Default Mode Network (DMN) where DMN is known to be involved in resting state EEG theta activity. The relation between the EEG alpha band power values and FA values of the skeleton was found to support the cortico-thalamocortical cycles for both subject groups. Further, the neurophysiological tests including Benton Face Recognition (BFR), Digit Span test (DST), Warrington Topographic Memory test (WTMT), California Verbal Learning test (CVLT) has been regressed with the FA skeleton maps for both subject groups. Our results corresponding to DST task were found to be similar with previously reported findings for working memory and episodic memory tasks. For the WTMT, FA values of the cingulum (right) that plays a role in memory process was found to be related with the behavioral responses. Splenium of corpus callosum was found to be correlated for both subject groups for the BFR.