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Quantitative Infrared Pupillometry in Nonconvulsive Status Epilepticus

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Abstract

Background

Nonconvulsive status epilepticus (NCSE) is a frequent disorder in neurocritical care and diagnosing it can be challenging. NCSE patients often show altered pupil function, but nature and extent may vary. Infrared pupillometry allows detection of subtle changes of pupil function. The neurological pupil index (NPi) is considered a surrogate marker of global pupil function which is supposed to be independent of absolute parameters such as the pupil diameter.

Objective

Cross-sectional observational study to assess whether NPi is altered in NCSE.

Methods

128 consecutive adult emergency patients who had experienced a suspected seizure, have not reached their prior functional level regarding level of consciousness, mental status or focal deficits, had no obvious clinical signs of status epilepticus and had an EEG indication as determined by the treating clinician for exclusion of NCSE were examined by routine EEG and pupillometry. Exclusion criteria were ocular comorbidity (n = 21) and poor EEG quality (n = 4). Pupillometry was performed once directly before the beginning of EEG recording. NCSE diagnosis (no NCSE, possible NCSE and confirmed NCSE) was established according to Salzburg consensus criteria blinded to pupillometry results. Group comparison was performed for right NPi, left NPi, lowest NPi of both sides (minNPi) and the absolute difference of both sides (diffNPi) applying non-parametric testing. In post-hoc analysis, receiver operating characteristics (ROC) of NCSE diagnosis (combined confirmed NCSE and possible NCSE) were performed for minNPi and diffNPi.

Results

From 103 patients included in the final analysis, 5 (4.9%) had confirmed NCSE, 7 (6.8%) had possible NCSE. Right NPi (p = 0.002), left NPi (p < 0.001) and minNPi (p < 0.001) were significantly lower in “confirmed NCSE” and “possible NCSE” compared to “no NCSE”; diffNPi was significantly higher in “confirmed NCSE” and “possible NCSE” compared to “no NCSE” (p < 0.001). There was no significant difference of minNPi and diffNPi between “confirmed NCSE” and “possible NCSE”. ROC analysis showed an optimal cut-off of minNPi for NCSE diagnosis of 4.0 (AUC = 0.93, 95% CI 0.86–0.99). Optimal ROC analysis cut-off of diffNPi for NCSE diagnosis was 0.2 (AUC = 0.89, 95% CI 0.80–0.99).

Conclusions

NPi was significantly reduced and the difference between left and right NPi was significantly higher in confirmed NCSE. An NPi < 4.0 on either side as well as an NPi difference of both sides > 0.2 may be potential indicators of NCSE. Infrared pupillometry may be a helpful diagnostic tool in the assessment of NCSE and should be studied further in larger populations.

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Authors and Affiliations

  1. Department of Neurology, Klinikum Kassel, Mönchebergstr. 41-43, 34125, Kassel, Germany

    Jana Godau, Claudia Bierwirth, Johannes Rösche & Julian Bösel

  2. Emergency Department, Klinikum Kassel, Kassel, Germany

    Jana Godau

  3. Department of Neurology, University of Rostock, Rostock, Germany

    Johannes Rösche

Authors
  1. Jana Godau
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  2. Claudia Bierwirth
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  4. Julian Bösel
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Contributions

Authorship requirements have been met by all authors. JG, JR and JB designed the study. JG, JR and CB participated in data acquisition. JG wrote up the first draft of the manuscript. All authors took part in data analysis, interpretation and critical review of the manuscript. The final draft of the manuscript was approved by all authors.

Corresponding author

Correspondence to Jana Godau.

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Conflicts of interest

JG has nothing to disclose. CB has nothing to disclose. JR reports personal fees from Eisai GmbH, outside the submitted work. JB reports personal fees from Medtronic, personal fees from Boehringer Ingelheim, personal fees from Zoll and grants from PCORI, all outside the submitted work.

Ethical Approval/Informed Consent

The study was performed in adherence to ethical guidelines. Ethical approval including a formal consent waiver for observational pupillometry was granted by the Hesse Medical Association Ethical Board.

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Godau, J., Bierwirth, C., Rösche, J. et al. Quantitative Infrared Pupillometry in Nonconvulsive Status Epilepticus. Neurocrit Care 35, 113–120 (2021). https://doi.org/10.1007/s12028-020-01149-1

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  • DOI: https://doi.org/10.1007/s12028-020-01149-1

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