Electroencephalography in lacunar infarction.

To determine the occurrence and clinical implications of electroencephalographic (EEG) abnormalities in patients with acute lacunar infarction, we conducted a single-blinded EEG study in 55 patients. Twenty-nine (53%) had mild EEG abnormalities, which were focal and ipsilateral to the side of infarction in 7 patients (13%). Abnormalities were more common in patients with evidence of a prior stroke (10 of 12 patients, 83%). However, 43% (16 of 37 patients) of those without historical or radiologic evidence of a prior stroke also had mild EEG abnormalities. This represents a higher incidence of routine EEG abnormalities in lacunar infarction than is generally assumed. Indeed, these findings are more consistent with recent quantitative EEG studies that consistently have shown high rates of abnormalities in lacunar infarction. We did not find major EEG abnormalities, such as continuous or nearly continuous focal delta activity, in any patient with first lacunar infarction. We conclude that within the first 48 h after a first ischemic infarction, when computed tomography often fails to show abnormalities, an EEG that shows lateralized major abnormalities is useful in excluding the diagnosis of either lacunar infarction or infarction limited to the brain stem. Mild abnormalities occur more often than previously thought in lacunar infarction and do not exclude this diagnosis.