Skip to main content

Early latency evoked potentials can no longer be considered an infallible predictor of neurologic outcome

We read with great interest the recent article by Rothstein et al. who conclude that the absence of the SSEP N20 cortical wave remains one of the most reliable early prognostic tools for identifying unfavorable outcome in the patients with severe anoxic-ischemic encephalopathy, whether or not they have been treated with therapeutic hypothermia [1]. The reliability of SSEP as a predictor of poor outcome in the era of therapeutic hypothermia following cardiac arrest has been questioned [2]. A systematic review of the literature identified cases in which there was a good outcome despite bilateral absence of the cortical SSEP N20 response and concluded that SSEP can no longer be considered an infallible predictor of neurologic outcome [2]. Early latency evoked potentials may not always be the best tool to identify the prognosis of a coma after cardiac failure [3]. Middle latency evoked potentials are elicited by cortico-cortical projections and appear up to 100 ms following stimulation of the median nerve [3]. They are believed to better reflect functional connectivity and thus allow prognostication of awakening, but due to challenging technical and practical issues, they are used far less commonly than early latency potentials. An Austrian study before the therapeutic temperature management (TTM) era reported a positive predictive value for awakening as high as 97% [3]. Long-latency evoked potentials represent higher-order cortical reactions occurring more than 100 ms after stimulation of the primary sensory areas. It is a common practice, especially in comatose patients, to record these with auditory stimulations; response to deviant stimuli in a sequence of standard stimuli, also called “mismatch negativity,” has been described several years ago, in the pre-TTM era, to be strongly associated with awakening after a latency of several days to weeks following cardiac arrest [4]. More recently, this approach has been developed and refined though an automated voltage topography analysis of recordings performed during acute post-cardiac arrest coma, on a case-by-case basis: progression of auditory discriminations between the first and the second assessments (both recorded within the first 48 h after the arrival of the patient to the hospital) heralded good recovery for the vast majority of patients [5]. In the near future, middle and late latency evoked potentials and mismatch negativity may replace early latency SSEP and may provide much more accurate prognostication in patients in coma after cardiac arrest.

Availability of data and materials

Not applicable.



Somatosensory evoked potentials


Therapeutic temperature management


  1. Rothstein TL. SSEP retains its value as predictor of poor outcome following cardiac arrest in the era of therapeutic hypothermia. Crit Care. 2019;23(1):327.

    Article  PubMed  PubMed Central  Google Scholar 

  2. Amorim E, Ghassemi MM, Lee JW, et al. Estimating the false positive rate of absent somatosensory evoked potential in cardiac arrest prognostication. Crit Care Med. 2018;46:e1213–21.

    Article  Google Scholar 

  3. Rossetti AO. Clinical neurophysiology for neurological prognostication of comatose patients after cardiac arrest. Clin Neurophysiol Pract. 2017;2:76–80. eCollection 2017.

    Article  PubMed  PubMed Central  Google Scholar 

  4. Madl C, Kramer L, Domanovits H, Woolard RH, Gervais H, Gendo A, Eisenhuber E, Grimm G, Sterz F. Improved outcome prediction in unconscious cardiac arrest survivors with sensory evoked potentials compared with clinical assessment. Crit Care Med. 2000;28:721–6.

    Article  CAS  Google Scholar 

  5. Fischer C, Luaute J, Nemoz C, Morlet D, Kirkorian G, Mauguiere F. Improved prediction of awakening or nonawakening from severe anoxic coma using tree-based classification analysis. Crit Care Med. 2006;34:1520–4.

    Article  Google Scholar 

Download references


We would like to thank Dr. Melissa Jackson for the critical review of the manuscript.



Author information

Authors and Affiliations



PMH, SR, and DDB designed the paper. All authors participated in drafting and reviewing. All authors read and approved the final version of the manuscript.

Corresponding author

Correspondence to Patrick M. Honore.

Ethics declarations

Ethics approval and consent to participate

Not applicable.

Consent for publication

Not applicable.

Competing interests

The authors declare to have no competing interests.

Additional information

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated in a credit line to the data.

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Honore, P.M., Barreto Gutierrez, L., Kugener, L. et al. Early latency evoked potentials can no longer be considered an infallible predictor of neurologic outcome. Crit Care 24, 322 (2020).

Download citation

  • Received:

  • Accepted:

  • Published:

  • DOI: