A Comprehensive Review and Practical Guide of the Applications of Evoked Potentials in Neuroprognostication After Cardiac Arrest.

Cardiorespiratory arrest is a very common cause of morbidity and mortality nowadays, and many therapeutic strategies, such as induced coma or targeted temperature management, are used to reduce patient sequelae. However, these procedures can alter a patient's neurological status, making it difficult to obtain useful clinical information for the reliable estimation of neurological prognosis. Therefore, complementary investigations are conducted in the early stages after a cardiac arrest to clarify functional prognosis in comatose cardiac arrest survivors in the first few hours or days. Current practice relies on a multimodal approach, which shows its greatest potential in predicting poor functional prognosis, whereas the data and tools to identify patients with good functional prognosis remain relatively limited in comparison. Therefore, there is considerable interest in investigating alternative biological parameters and advanced imaging technique studies. Among these, somatosensory evoked potentials (SSEPs) remain one of the simplest and most reliable tools. In this article, we discuss the technical principles, advantages, limitations, and prognostic implications of SSEPs in detail. We will also review other types of evoked potentials that can provide useful information but are less commonly used in clinical practice (e.g., visual evoked potentials; short-, medium-, and long-latency auditory evoked potentials; and event-related evoked potentials, such as mismatch negativity or P300).

Etiology matters for neuroprognostication: A multimodal electrophysiological investigation in a case of Bickerstaff's brainstem encephalitis.

We report the case of a 19-year-old patient with an acute-onset non-traumatic coma. Brain MRI scan was normal, CSF showed mild pleocytosis and moderately elevated protein, and continuous EEG-monitoring was compatible with spindle-coma. Cortical somatosensory evoked potentials (SSEPs) and middle-latency auditory evoked potentials (MLAEPs) were bilaterally absent, and brainstem auditory evoked potentials suggested a brainstem dysfunction. Serum anti-GQ1b and anti-GT1a IgG antibodies positivity suggested Bickerstaff's brainstem encephalitis (BBE). The clinical and functional outcomes were favorable and normal cortical SSEPs/MLAEPs reappeared in a few weeks. Based on this report, in cases of unexplained MRI-negative coma with neurophysiological evidence of brainstem dysfunction, BBE should be eliminated before considering withdrawal of life-sustaining therapy (WLST).

The Use of Middle Latency Auditory Evoked Potentials (MLAEP) as Methodology for Evaluating Sedation Level in Propofol-Drug Induced Sleep Endoscopy (DISE) Procedure.

To analyze the middle latency auditory evoked potential index (MLAEPi), compared to the standard bispectral index (BIS), as a method for evaluating the sedation level in drug-induced sleep endoscopy (DISE). In this controlled clinical study on a sample of 99 obstructive sleep apnea (OSA) or snoring patients, we compared the MLAEPi with the BIS after propofol infusion during the standard DISE technique in order to define the MLAEPi values within the observational window of the procedure. The DISE procedure was divided into eight steps, and we collected both MLAEPi and BIS data values from the same patient in every step. The MLAEPi showed a faster response than the BIS after propofol infusion during DISE. Therefore, the clinical use of the MLAEPi in evaluating the sedation level seems to be a good alternative to the current technological standards.

Recommendations for the use of electroencephalography and evoked potentials in comatose patients.

Predicting the outcome of a comatose or poorly responsive patient is a major issue for intensive care unit teams, in order to give the most accurate information to the family and to choose the best therapeutic option. However, determining the level of cortical activity in patients with disorders of consciousness is a real challenge. Reliable criteria are required to help clinicians in the decision-making process, especially in the acute phase of coma. In this paper, we propose recommendations for recording and interpreting electroencephalography and evoked potentials in comatose patients based on the literature and the clinical experience of a group of neurophysiologists trained in the management of comatose patients. We propose methodological guidelines and discuss prognostic value of each test as well as the limitations concerning recording and interpretation. Recommendations for the strategy and timing of neurophysiological assessments are also proposed according to various clinical situations.

The role of middle latency evoked potentials in early prediction of favorable outcomes among patients with severe ischemic brain injuries.

OBJECTIVE: To explore the role of middle latency evoked potentials (EPs) as predictors for favorable outcome in patients with severe ischemic brain injuries by comparing the prognostic ability of short latency somatosensory and auditory evoked potentials (SLSEP and BAEP) with middle latency somatosensory and auditory evoked potentials (MLSEP and MLAEP). METHODS: MLSEP, MLAEP, SLSEP and BAEP were recorded in 112 patients with severe ischemic brain injuries (Glasgow Coma Scale ≤ 8). Among them, 83 patients suffered from cerebral ischemic stroke and 29 suffered from anoxic-ischemic encephalopathy after cardiopulmonary resuscitation between 1 and 7 days after the onset of stroke. Outcomes were reviewed 6 months later using the Glasgow Outcome Scale (GOS). A GOS score of 4-5 was considered as a good outcome while a score of 1-3 was considered as poor. RESULTS: By using the prognostic authenticity analysis of predictors for good outcome, at least unilateral N20 of the SLSEP exit and at least unilateral N60 of the MLSEP exit showed the highest sensitivity which was 100% (95% CI: 86.7%-100%). The bilateral normal N60 showed a high specificity of 97.5% (95% CI: 90.4%-99.6%). It also showed the highest positive likelihood ratio of 6.25% (95% CI: 1.28%-30.59%), which was superior to N20 of SLSEP, V of BAEP, and Pa of MLAEP. The analysis demonstrated that the area under the curve for MLSEP grading was the highest (0.838) compared to that of SLSEP grading (0.784), MLAEP grading (0.659) and BAEP grading (0.621). CONCLUSIONS: Compared with using N20 of SLSEP analysis alone, adding MLSEP improves the outcome prediction in patients with severe ischemic brain injuries. When an outcome is uncertain after initial evaluation using short-latency EPs, MLSEP is valuable to be used from the first week to further improve prognostication in these patients.

Respostas auditivas evocadas de latência média em doenças neurológicas / Middle-latency auditory responses in neurological diseases

A presença das respostas auditivas evocadas de latência média permite-nos a avaliação da integridade do sistema auditivo periférico e central, incluindo os núcleos e vias auditivas existentes até ao nível da região subcortical. Desta forma, elas têm sido usadas para o estudo das alterações ocorridas em diferentes doenças neurológicas. OBJETIVOS: Verificar os valores dos períodos de latências destas respostas e detectar a presença das deflexões. CASUíSTICA E MÉTODO: Foram avaliados 20 pacientes portadores de doenças neurológicas existentes ao nível central, de diferentes etiologias, sendo analisadas as várias deflexões, positivas e negativas, geradas pelos potenciais auditivos evocados de latência média. Os sujeitos da pesquisa foram escolhidos por conveniência e os dados coletados foram avaliados levando-se em consideração a relação interindivíduos. FORMA DE ESTUDO: Foi adotado o estudo de Coorte, com avaliação contemporânea. RESULTADOS: Foram analisados estatisticamente e mostram alterações significativas da respostas evocadas de latência média em pacientes neurológicos. CONCLUSÃO: Nesses pacientes ou havia supressão das deflexões estudadas ou suas latências estavam aumentadas, quando comparadas com os padrões normais.

The presence of middle-latency evoked auditory potentials allows for integrity evaluation of both peripheral and the central auditory systems, and also, that of the nucleus and auditory pathways of sub-cortical region. They have also been used to study alterations of these structures in different neurological diseases. AIMS: the aim of this study is to verify the latency of the middle-latency evoked auditory potentials and detect the presence of any deflections in subjects with neurological diseases. MATERIALS AND METHODS: In a clinical and prospective trial, 20 patients having central neurological diseases of various etiologies were evaluated and, positive and negative deflections produced by the middle-latency evoked auditory potentials in these patients were analyzed. RESULTS: Data was statistically analyzed and showed significant modifications in middle-latency evoked auditory potentials. CONCLUSION: The authors concluded that patients with neurological disorders have either wave suppression or enlarged latency periods in relation to normal subjects.

Effect of Ephedrine on Middle Latency Auditory-Evoked Potentials During Light General Anesthesia / 听力学及言语疾病杂志

Objective To study the effect of ephedrine on middle latency auditory-evoked potentials (MLAEP) during light general anesthesia , and evaluate the influence of ephedrine on anesthesia level. Methods 10 patients (ASAⅠ-Ⅱ) undergoing elective upper abdominal operations were concerned. Anesthesia: epidural anesthesia in combination with light general anesthesia with N 2O-O 2 . After success of epidural anesthesia and tracheal intubation , when anesthesia was smooth , before operation 0.1% ephedrine(0.15 mg/kg) was injected intravenously. These data HR, SBP, DBP, MBP were measured continuously before injection, 3 min after injection, 10 min after injection; the latentcies Nb and P1 of MLAEP were measured and rescorded. Results HR?SBP?DBP?MBP increased significantly 3 min after injection, 10 min after injection compared with these data before injection (P