Incidence and prognostic value of spindles in post-traumatic coma

One hundred and thirty-three EEGs were analysed from 80 comatose patients with signs of brain stem impairment due to head/brain injury. Seventy EEGs were taken in acute coma on day 1 or 2 after brain injury. Sixty-three EEGs were recorded in prolonged coma 3-12 days after brain injury. Brain stem involvement was divided by neurological signs and by CT scan into secondary lesions due to supratentorial mass displacement and primary lesions due do direct violence to the brain stem. Different EEG patterns were observed, but spindle activity was of special interest. Spindles were classified as typical (easily recognizable, well organized, 12-14 c/sec activity) or atypical (hardly recognizable, distorted form, 6-11 c/sec activity). Furthermore, asymmetries of spindles were noted. The spindles and their alterations were related to different stages of outcome. Spindles were seen in 91% of the EEGs in acute coma and in 30% in prolonged coma. In acute coma due to secondary brain stem involvement a good outcome was heralded by the occurrence of typical symmetrical spindles combined with early stages of secondary brain stem impairment at neurological examination. In cases of primary brain stem involvement typical spindles also suggested a good prognosis despite the observation of serious clinical signs (decerebrate posturing). The percentage of spindle activity decreased, and distortion and asymmetry of spindles increased with the worsening of outcome. Severe intracerebral lesions (confirmed by clinical and CT scan examinations) led to distortion, asymmetry and finally disappearance of spindles. In prolonged coma spindle activity was markedly reduced regardless of the final outcome. When spindles were present atypical and asymmetric forms significantly increased in patients with bad outcome. There were no significant differences in spindle activity in the different outcome categories, if primary and secondary brain stem lesions were compared.