The EEG in the diagnosis of subdural empyema.

The EEG findings in 9 patients with a subdural empyema are reported. In all cases the EEG, recorded before the diagnosis had been established, contained focal zeta waves, extensive unilateral depression of cortical activity and, in all but one, a diffuse slowing of the background activity. This combination has not been reported before in the literature and it is concluded that in its presence the existence of a subdural empyema should be seriously considered. Comparison with CT scan findings in 3 cases indicated that sometimes EEG may be more sensitive than CT scanning in the diagnosis of subdural empyema. The value of EEG and CT scan in the diagnosis of patients with an acute or subacute bacterial meningo-encephalitis is briefly discussed.