Letter: Response to Verboon et al.: Integrating Somatosensory Evoked Potentials into EEG-Based Prognostication after TBI

Dear Editor,

We read with great interest the article by Verboon et al., “Prognostication after moderate-to-severe traumatic brain injury (TBI) in the ICU,” which provides a valuable systematic review of electroencephalography (EEG) as a prognostic tool in this complex setting. The authors compellingly demonstrate that specific EEG patterns—such as preserved reactivity, continuity, and sleep features—are associated with favorable neurological outcomes. Their work strengthens the role of EEG as a central pillar in neurocritical prognostication. ¹ Nonetheless, we believe that integrating somatosensory evoked potentials (SSEPs), particularly the presence and amplitude of the cortical N20 component, can further enhance prognostic accuracy and physiological insight into cortical recovery mechanisms.^2,3

SSEPs assess the functional integrity of the somatosensory pathways from the periphery to the cortex, offering a direct measure of thalamocortical transmission. The N20 potential, generated in cortical layers III–V of the primary somatosensory cortex, reflects excitatory postsynaptic potentials within pyramidal neurons. Its presence and amplitude are robust indicators of cortical viability and synaptic integrity, especially in patients with severely depressed or confounded EEG patterns. Decades of neurophysiological and clinical evidence, including our own studies, demonstrate that the bilateral absence of N20 predicts poor outcomes with near-absolute specificity, while preserved or increasing N20 amplitudes correlate strongly with awakening and meaningful recovery.^2–4

Verboon et al. emphasize the need for multimodal prognostication to mitigate the limitations of single-modality approaches and reduce bias. We fully concur. Combining quantitative EEG with SSEP monitoring can provide complementary perspectives: EEG captures global cortical dynamics and reactivity, whereas SSEPs probe specific afferent circuits and cortical excitability. This integration enables a hierarchical understanding of residual brain function—whether the cortex merely exhibits oscillatory activity or retains effective thalamocortical connectivity capable of supporting consciousness. ¹

Furthermore, the quantitative analysis of N20 amplitude dynamics can serve as an early biomarker of cortical plasticity. Serial SSEP assessments in TBI patients have shown that incremental N20 recovery often precedes clinical improvement and normalization of EEG patterns. Continuous or repeated SSEP monitoring could thus enhance the temporal granularity of prognostication, enabling clinicians to distinguish between transient suppression and irreversible injury. Importantly, SSEP findings remain interpretable under conditions that often obscure EEG interpretation, such as hypothermia, sedative use, or diffuse background slowing, making them particularly valuable in ICU practice.

Future research should focus on multimodal algorithms integrating EEG, SSEP, and advanced analytics, including artificial intelligence, to predict outcomes more precisely. Machine learning models incorporating amplitude, latency, and interhemispheric asymmetry of N20 potentials alongside EEG features may yield superior predictive performance compared to conventional clinical models alone. ⁵ In conclusion, Verboon et al. make an essential contribution by reaffirming the prognostic potential of EEG in TBI. ¹

We suggest that integrating SSEP N20 presence and amplitude measures into these frameworks could further refine prognostic models, thereby improving their physiological interpretability and clinical applicability. This combination bridges functional and structural perspectives of cortical recovery, moving the field toward a more complete and evidence-based neuroprognostic paradigm.^2,3