Abnormal fast activity in infancy with paroxysmal downwards gaze.

We report here on 8 infants who showed paroxysmal downwards gaze (PDG). The time of initial appearance of PDG ranged from one month to five months (mean: 2.7 months) of corrected age. Seven out of eight patients showed interictal spikes in EEG, so they were started on prophylactic therapy with antiepileptic drugs. In five of the eight patients, PDG ceased, either spontaneously or with antiepileptic drug treatment, by four to eight months of corrected age. Six out of eight patients showed localized spikes and peculiar abnormal fast activity (AFA) in the occipital area and five of these patients later developed West syndrome. These AFA were observed on EEGs recorded at the time of initial PDG appearance, before hypsarrhythmia was observed and before tonic spasms appeared. We were able to exclude the possibility that PDG was a subtle epileptic seizure by confirming the temporal discordance between individual episodes of PDG and AFA with video-EEG monitoring. Yet topographic data showed that AFA in these patients was characteristically located in the occipital area, with a distribution similar to that of the fast activity which accompanied the tonic spasms that later developed in these patients. As a risk factor for developing WS, we propose the clinical symptom of PDG with characteristic occipital AFA visible in the EEG, both of which represent damage to the occipital region including the optic radiation.