[Value of sphenoidal electrodes in the EEG diagnosis of herpes encephalitis]

EEG features in acute necrotizing encephalitis show periodic activity, localized in the temporal area with a slow background activity. Nevertheless, this periodic activity is transient and may lack. Sphenoidal electrodes study of the internal face of the temporal lobe could record such activity in herpes encephalitis. Sphenoidal electrodes were inserted in 4 patients known to have herpes encephalitis. In 2 cases, periodic discharges were observed both on the surface and sphenoidal electrodes, while in 2 cases, periodic discharge was observed under only sphenoidal electrodes. Faced with uncertain diagnosis of herpes encephalitis, it may be useful to insert sphenoidal electrodes to record deep periodic discharges, not seen on surface electrodes, in order to confirm the diagnosis.