Prognostic value of somatosensory evoked potentials, neuron-specific enolase, and S100 for short-term outcome in ischemic stroke

Abstract

To predict short-term outcome in acute ischemic stroke, we analyzed somatosensory evoked potentials (SEP) and biochemical parameters [neuron-specific enolase (NSE) and S100 protein] in a prospective study with serial measurement. In 31 patients with 1st middle cerebral artery infarction, serum NSE and S100 protein were measured daily between days 1 and 6 poststroke. The N20 and N70 components of the SEP (SEP20 and SEP70) were determined on days 1 and 6. SEP and biochemical markers in stroke patients were compared with a control group. Short-term outcome was assessed by the modified Rankin Scale (mRS) at days 7-10 and was dichotomized between good (mRS 0-2) and poor (mRS ≥3) outcome. Specificity and positive predictive value (PPV) were high at day 1 for SEP (SEP20: 100% for both; SEP70: 93 and 88%, respectively) compared with lower values for NSE (67 and 50%) and S100 (23 and 57%). In contrast, S100 showed the highest sensitivity at day 1 with 77% compared with a relatively low sensitivity of NSE (31%) and SEP (SEP20: 35%, SEP70: 47%). The biochemical markers showed an improving sensitivity over time with best values (>90%) between days 3 and 4 at the expense of a lower specificity. Specificity and PPV of SEP on day 6 was still 100% with sensitivity increasing up to 53% (SEP20) and 60% (SEP70). SEP could early differentiate between good and poor outcome and reliably predict poor outcome. Since biochemical markers and SEP complement each other in the prognosis of stroke, a combined application of these markers seems promising.

Keywords: NSE; S100; SEP; ischemic stroke; outcome; prediction; somatosensory evoked potentials.

Fig. 1.

Size of middle cerebral artery (MCA) infarction stratified by outcome groups. Patients with large MCA infarction were more likely to have a poor outcome. However, infarct size on computed tomography (CT) scan could be reliably estimated only in the follow-up imaging.

Fig. 2.

Unfavorable N20 components of the somatosensory evoked potentials [SEP20; grades 3 and 4 (Grad III and Grad IV)] were invariably associated with poor outcome already at day 1, whereas grade 1 SEP20 were invariably associated with good outcome. Discriminatory power of SEP70 was high but inferior to SEP20.

Fig. 3.

A: comparison of mean neuron-specific enolase (NSE) values between the 2 outcome groups. NSE values increased over time in both groups and were generally higher in the group with poor outcome, but the difference between the groups did not reach statistical significance. *Statistically different from control group (P < 0.05). B: comparison of mean S100 protein values between the 2 outcome groups. S100 values were significantly higher in the group with poor outcome and peaked at day 4 (d 4). In contrast, S100 values were stable and did not increase over time in the group with good outcome. *Significantly different from control group (P < 0.05); #significant difference between outcome groups (P < 0.05).