Abstracts

Cingulate seizures are poorly understood because their patterns of propagation may confound both the classification of clinical semiology and attempts at seizure localization. The anterior cingulate gyrus is known to have anatomic connections to temporal lobe structures, but projections from the posterior cingulate area are less established. We present a detailed analysis of seizure dynamics from intracranial recordings of repetitive seizures originating from the right posterior cingulate region and producing secondary seizure activity in the right mesial temporal structures. Depth electrode recordings were made of complex partial seizures (CPS) in a 22 year-old man with one year history of medically intractable epilepsy. His seizures were characterized by staring, automatisms, and incomprehensible speech. MRI revealed an 8.5 X 7 mm lesion of the right parietal cingulate region. PET revealed decreased activity of the right lateral temporal lobe. With scalp EEG, his CPS revealed a buildup of right temporal rhythmic spikes at 8-9 Hz. Depth electrode arrays were then placed in the right amygdala, hippocampus and cingulate lesion. Three stereotyped CPS were recorded. Ictal recordings were analyzed using the matching pursuit method which allows for detailed time-frequency decomposition of rapidly changing signals. In addition the Gabor atom density (GAD) was calculated for all seizures. GAD is a composite measure of signal complexity that has been shown to increase during epileptic seizures. Each of the seizures had a stereotyped pattern of ictal dynamics. The seizures began with a right cingulate sentinel spike followed by low voltage, 40-hz activity. After 20-30 seconds, the mesial temporal depth contacts developed prominent secondary organized rhythmic activity of 6-8 Hz frequency, typical for mesial temporal lobe generators. The patient continued normal activities until the secondary right temporal involvement. GAD revealed a significant change of complexity from baseline during the earliest phase of the cingulate gamma activity and also a consistent pattern of complexity changes from both cingulate and mesial temporal contacts. These recurrent seizures did not produce clinical symptoms until secondary involvement of ipsilateral mesial temporal structures. This suggests connectivity between posterior cingulate regions and the temporal lobe and supports previous observations that cingulate seizures may not produce clinical symptoms without propagation to other brain regions. The dynamic analysis of the seizures revealed a stereotyped pattern of both time-frequency changes and complexity. The mesial temporal ictal evolution was a secondary pattern distinct from but always following the cingulate ictal onset. This activity can be clearly delineated by dynamical analyses. The patient is presently seizure free early after resection of this benign lesion. (Supported by NIH grant NS 33732.)