Abstracts

Rationale: The various human brain networks were recently elicited by electrical cortical stimulation (ECS) employing different techniques. ECS remains the gold standard for identifying brain functions in neurosurgical patients. Cingulate cortex is densely connected, it receives and projects wide-spread afferents/efferents, and it modulates several functions. To our knowledge, there is no systematic review of the literature on the functions of Cingulate studied by ECS.  Methods:  PubMed search for the studies that investigated cingulate cortex by ECS. We also identified book chapters and review-articles. Of a total of 553 articles identified, eighteen articles met our inclusion criteria. We searched Yale Brain-Mapping Program database for cases that undergone electrical stimulation in electrodes placed in the Cingulate. We identified symptomatology not-previously reported.  Results: A total of 456 patients were identified, mean per study: 25.3 ± 40.9-range: 1-164), six studies (33.3%) were prospective. Twelve (66.7%) employed standard 50Hz stimulation, and 6(33.3%) employed other stimulation parameters ( 0.1-200 Hz). The mean age was 30.6 ± 11.1 year (6-68 year). The stimulation was performed in drug-resistant epilepsy patients in 72.4% of the patients and in other disorders including major depression, schizophrenia, obsessive-compulsive disorder, and Parkinson's disease in 27.6% of the patients. On average, 41 electrodes were implanted per patient (7-110 electrodes). Depth electrodes were used in 15 studies; subdural electrodes were used in 3. The mode pulse width and train duration were 300 µs (12-1500 µs), and 5s (1.8-1500 s), respectively. Stimulation intensities were (0.2-15 mA), or (1 mV-25 V). Epilepsies studied included frontal series 28.6%, temporal 28.6%, parietal 7.1%, mixed 35.7%. The median ratio of negative-to-positive hits was 0.47  (0.15 – 1.69). Simple motor responses were reported in 45 of 96 patients (46.9%)  in 5 studies (27.8%). Hypermotor responses were obtained 46 out of 180 patients (25.6%) in 4 studies (%22.2).  Two studies (11.1%) reported gelastic responses without mirth after anterior cingulate stimulation. Somatosensory responses were obtained in 5 studies (%27.8). In these studies, 40 out of 333 patients (12%) developed somatosensory responses, three of them used anterior cingulate stimulation, and two of them used posterior cingulate stimulation. Autonomic responses including bradyarrhythmia, tachycardia, mydriasis, increased blood pressure and breathing, and hot flashes were obtained in 5 studies (27.8%), In these studies, 27 out of 52 patients (51.9%) developed autonomic responses, one of the studies reported on findings in posterior cingulate. Psychic symptoms including perceptual and behavioral changes, euphoria, and fear were obtained in 19 out of 129 patients (14.7%) in 3 studies (16.7%). K-like evoked complexes following stimulation of non-epileptic cingulate were identified based on low-frequency stimulation (1Hz). Conclusions: 1. Symptomatology obtained with the stimulation of the anterior cingulate overlaps with previously reported Cingulate epilepsy syndromes. 2. Although profound hyper-motor responses have been reported in Cingulate epilepsy, the motor symptomatology is less spectacular with cingulate electrical stimulation.3. The Cingulate exhibits remarkable connectivity with wide-spread brain regions including the limbic and paralimbic networks. Unique “K-like” evoked responses have been reported in some patients from non-epileptic cingulate regions. 4. Future research may continue to demonstrate additional symptomatology not previously reported.  Funding: AES/ACTS/Epilepsy & Swebilius Foundation