Increased incidence and impact of nonconvulsive and convulsive seizures after traumatic brain injury as detected by continuous electroencephalographic monitoring

Object. The early pathophysiological features of traumatic brain injury obs erved in the intensive care unit (ICU) have been described in terms of alte red cerebral blood flow, altered brain metabolism, and neurochemical excito toxicity. Seizures occur in animal models of brain injury and in human brai n injury. Previous studies of posttraumatic seizures in humans have been ba sed principally on clinical observations without a systematic approach to e lectroencephalographic (EEG) recording of seizures. The purpose of this stu dy was to determine prospectively the incidence of convulsive and nonconvul sive seizures by using continuous EEG monitoring in patients in the ICU dur ing the initial 14 days postinjury. Methods. Ninety-four patients with moderate-to-severe brain injuries underw ent continuous EEG monitoring beginning at admission to the ICU (mean delay 9.6 +/- 5.4 hours) and extending up to 14 days postinjury. Convulsive and non convulsive seizures occurred in 21 (22%) of the 94 patients, with six o f them displaying status epilepticus. In more than half of the patients (52 %) the seizures were nonconvulsive and were diagnosed on the basis of EEG s tudies alone. All six patients with status epilepticus died, compared with a mortality rate of 24% (18 of 73) in the nonseizure group (p < 0.001). The patients with Status epilepticus had a. shorter mean length of stay (9.14 +/- 5.9 days compared with 14 +/- 9 days [t-test. p < 0.03]). Seizures occu rred despite initiation of prophylactic phenytoin on admission to the emerg ency room, with maintenance at mean levels of 16.6 +/- 2.8 mg/dl. No differ ences in key prognostic factors (such as the Glasgow Coma Scale score, earl y hypoxemia, early hypotension, or I-month Glasgow Outcome Scale score) wer e found between the patients with seizures and those without. Conclusions. Seizures occur in more than one in five patients during the 1s t week after moderate-to-severe brain injury and may play a role in the pat hobiological conditions associated with brain injury.