Somatosensory evoked potential monitoring following severe closed head injury

This paper describes the results of somatosensory evoked potential (SSEP) monitoring in 65 patients with severe head injury. Intracranial pressure (ICP) monitoring data were available for 63 patients, and arterial-jugular oxygen content (AVDO2) data for 52 patients. Eighty-nine percent of patients with no SSEP activity beyond 50 msec post-stimulus in either hemisphere died or were vegetative survivors (3 month Glasgow Outcome Score). All 17 patients with a good or moderate outcome had long latency cortical activity (i.e. > or = 70 msec post-stimulus) in both hemispheres. Among patients with absent activity in 1 hemisphere, 53% died and 47% were severely disabled (chi 2 = 40, p = 0.0000). In the latter group, age was a significant factor among patients who died or were severely disabled (p < 0.02). Forty-four of 65 patients had either clear-cut deterioration or improvement in SSEPs over the course of monitoring. There were no significant differences in peak ICP between patients with improving or deteriorating SSEPs. In contrast, those with deteriorating SSEPs had a significant drop in AVDO2, compared with patients with improving SSEPs (p < 0.01). Long-term continuous monitoring of SSEPs shows that following severe injury, neurologic function may undergo significant change in approximately two-thirds of patients. Furthermore, ICP does not appear to play a prominent role in neurologic deterioration. AVDO2 measurements indicate that deterioration is more likely associated with perturbation of cerebral oxidative metabolism. SSEP monitoring following severe head injury has proven prognostic value, and is recommended for patients who must be pharmacologically paralyzed for ICP or ventilator management.