Landau-Kleffner syndrome (LKS), or acquired epileptiform aphasia, is an epilepsy syndrome involving progressive neuropsychological impairment related to the appearance of paroxysmal electroencephalograph (EEG) activity.

William M Landau 1924-2017

Frank R Kleffner1925-2015

William Landau & Frank Kleffner in 1957^[1] described six patients who were diagnosed with “acquired largely receptive aphasia, sometimes recurrent with some association with a convulsive disorder.” These attacks began as partial, myoclonic, or absence seizures, which they called “petit mal,” but were not closely correlated with the aphasic symptoms. In cases with an epileptiform pattern, “a severe paroxysmal EEG abnormality” was seen, usually diffuse. Any EEG improvement paralleled the speech improvement, and the general prognosis was good with appropriate treatment.

EEGs in five cases showed “generalized spikes” in three patients, spikes on the right hemisphere in one patient, and, for the fifth patient, only slow waves in the left temporal area that later became generalized. One patient did not have an EEG. The “generalized spikes” described in this original report were not labeled ESES or CSWS, because these two EEG patterns had not yet been described in 1957. Also, this early report did not designate if the EEG abnormalities were found in the sleep or waking record.

• among patients with LKS, 40–50% show ESES, and focal discharges were seen, especially in the frontal and temporal areas, in 70–100% of patients with behavior disorders
• LKS may evolve into ESES/CSWS patterns with the prognosis for LKS better than

the prognoses for these two EEG waveforms.

• regional spikes ar observed especially in the fronto-, centro-, or posterior-temporal areas^[2].