[Clinico-electroencephalographical significance of small sharp spikes]

Clinical and electroencephalographical investigations were made on the 234 patients with neuropsychiatric disorders, showing small sharp spikes (sss) on EEG. Incidence of sss was significantly higher in patients with epilepsy (8.6%) than in the non-epileptic cases (2.5%), especially in early age groups (11-35 years). Some differences in clinical features and in characteristics of sss were found between the epileptic patients and the non-epileptic patients; namely, 1) In majority of the subjects (97%), sss were observed exclusively in stage 1 and 2 of sleep, however, 8 epileptic patients exhibited sss in deep sleep (stage 3) or in awake state, as well as in light sleep. 2) In the non-epileptic group, females (3.4%) showed significantly higher incidence of sss than males (1.7%), while there was no sex difference in the epileptic group. 3) Of the non-epileptic patients, 45% had autonomic symptoms, such as headache, dizziness, tinnitus, nausea and vomiting, while there was no significant correlation between particular neuropsychiatric diagnosis and the EEG pattern. Among the non-epileptics, 72% showed normal EEG except for sss and in 89% sss appeared bilaterally but commonly bilaterally independently. 4) As to relation of sss to seizure types of epilepsy, complex partial seizures showed significantly higher incidence of sss (25.2%) than simple partial seizures (7.5%) and generalized tonic-clonic seizures (6.5%). In the patients with epilepsy, sss were often observed unilaterally predominantly (49%), especially in the patients with complex partial seizure (57%). In complex partial seizure, unilateral sss coincided with laterality of anterior-temporal seizure discharges in 68%. According to the results, the authors suggested that sss has some electroencephalographical significance, probably on mechanisms relating to epileptogenic dysfunction, particularly that of complex partial seizures.