EEG subclinical paroxysmal rhythmic activity

We studied 33 non-epileptic adults presenting with subclinical paroxysmal rhythmic activity (SPRA) on EEG examination. Sixteen patients showed the psychomotor-variant pattern described by GIBBS et al. in 1963. Seventeen patients presented a Naquet-type pattern (Naquet et al., 1961). Regardless of SPRA type, patients had similar non-specific neuropsychiatric symptoms. Only 3 patients were diagnosed as having a neurological disorder, this being dementia. Mode of onset, appearance and location of SPRA, amplitude, duration and response to sensory stimuli were identical in all patients studied. Several patients with Naquet-type discharges presented Gibbs' patterns as well. Gibbs' pattern is analogous to the longer lasting, intermediate phase of Naquet-type SPRA. We believe that both these types of SPRA may manifest a common electro-encephalographic phenomenon, and are not necessarily related to cerebral circulatory insufficiency.