Hippocampal CA1 gamma power predicts the precision of spatial memory judgments.

The hippocampus plays a critical role in spatial memory. However, the exact neural mechanisms underlying high-fidelity spatial memory representations are unknown. We report findings from presurgical epilepsy patients with bilateral hippocampal depth electrodes performing an object-location memory task that provided a broad range of spatial memory precision. During encoding, patients were shown a series of objects along the circumference of an invisible circle. At test, the same objects were shown at the top of the circle (0°), and patients used a dial to move the object to its location shown during encoding. Angular error between the correct location and the indicated location was recorded as a continuous measure of performance. By registering pre- and postimplantation MRI scans, we were able to localize the electrodes to specific hippocampal subfields. We found a correlation between increased gamma power, thought to reflect local excitatory activity, and the precision of spatial memory retrieval in hippocampal CA1 electrodes. Additionally, we found a similar relationship between gamma power and memory precision in the dorsolateral prefrontal cortex and a directional relationship between activity in this region and in the CA1, suggesting that the dorsolateral prefrontal cortex is involved in postretrieval processing. These results indicate that local processing in hippocampal CA1 and dorsolateral prefrontal cortex supports high-fidelity spatial memory representations

Mesial temporal lobe epilepsy and hippocampal sclerosis associated with BRAFV600E mutant neurons in the Cornu Ammonis: an uncertain pathogenesis and a diagnostic challenge.

Mesial temporal lobe epilepsy (MTLE) is a common cause of seizures, and hippocampal sclerosis (HS) is the predominant subtype. BRAFV600E mutations in MTLE-HS have only been reported infrequently. Herein, we illustrate the neurologic, radiological, and histopathological details of a patient with MTLE-HS and BRAFV600E mutant neurons. A 31-year-old male with medically refractory epilepsy presented with magnetic resonance imaging (MRI) and electroencephalography (EEG) findings typical of mesial temporal sclerosis without a mass lesion. The surgical specimens showed ILAE Type 1 HS with neurons immunopositive for BRAFV600E mutant protein distributed along the Cornu Ammonis (CA) curvature. Instead of the normal mostly perpendicular orientation of pyramidal neurons relative to the hippocampal surface, the BRAF mutant neurons were often oriented in a parallel manner. On CD34 immunostaining, sparse clusters or nodules of CD34+ stellate cells and single immunopositive stellate cells were identified. BRAFV600E or CD34 immunopositive cells were less than 1 % of total cells. The patient responded well to surgery with no further seizures after 2 years and occasional auras. Hippocampal BRAF mutant non-expansive lesion (HBNL) has been used to describe such lesions with preserved cytoarchitecture and without overt tumor mass. Others may argue for the dual pathology of HS with early ganglioglioma. Whether pre-neoplastic lesions or early tumors, these cases are important for understanding early glioneuronal tumorigenesis and suggest that BRAFV600E studies should be routinely performed on MTLE-HS cases in the setting of clinical trials. With next-generation sequencing, a FANCL deletion was detected in almost half of the alleles in our case, suggesting that many of the histologically normal-appearing cells of the hippocampus contain this alteration. FANCL mutations can result in cytogenetic anomalies and defective DNA repair and therefore may underlie the development of a low frequency BRAF alteration

Multifaceted utilization of a cortical stimulator during tumor resection

Background: Neurosurgeons use Ojemann cortical stimulators to map and localize cortical and subcortical regions of the brain to map functional areas intraoperatively to avoid resecting or damaging functional tissue. Here we describe a technique where, rather than using a separate retracting tool, a handheld Ojemann cortical stimulator was used to retract cerebral parenchyma while simultaneously stimulating descending white matter tracts to prevent accidental damage to white matter tracts involved with motor function. Case description: A 48-year-old patient developed intractable seizures and preoperative workup showed a left frontal brain mass close to her motor region. Subdural grid electrodes were implanted to localize the patient's ictal onset zone. The electrodes were then removed and the tumor was resected along with the ictal onset zone. During the resection, the neurosurgeon (S. Vadera) successfully utilized the Ojemann cortical stimulator to stimulate descending white matter tracts to prevent accidental injury to the patient and also retract cerebral parenchyma during resection. Four weeks post-operative, the patient had made a complete recovery and had no unforeseen deficits or weaknesses. Conclusion: Here we show that the Ojemann cortical stimulator can be used as an effective retraction tool as well as a cerebral parenchyma stimulator, effectively preventing accidental injury to functional tissue while concurrently giving the neurosurgeon a free hand to perform other tasks

Minimally invasive surgical approaches for temporal lobe epilepsy

Surgery can be a highly effective treatment for medically refractory temporal lobe epilepsy (TLE). The emergence of minimally invasive resective and nonresective treatment options has led to interest in epilepsy surgery among patients and providers. Nevertheless, not all procedures are appropriate for all patients, and it is critical to consider seizure outcomes with each of these approaches, as seizure freedom is the greatest predictor of patient quality of life. Standard anterior temporal lobectomy (ATL) remains the gold standard in the treatment of TLE, with seizure freedom resulting in 60-80% of patients. It is currently the only resective epilepsy surgery supported by randomized controlled trials and offers the best protection against lateral temporal seizure onset. Selective amygdalohippocampectomy techniques preserve the lateral cortex and temporal stem to varying degrees and can result in favorable rates of seizure freedom but the risk of recurrent seizures appears slightly greater than with ATL, and it is not clear whether neuropsychological outcomes are improved with selective approaches. Stereotactic radiosurgery presents an opportunity to avoid surgery altogether, with seizure outcomes now under investigation. Stereotactic laser thermo-ablation allows destruction of the mesial temporal structures with low complication rates and minimal recovery time, and outcomes are also under study. Finally, while neuromodulatory devices such as responsive neurostimulation, vagus nerve stimulation, and deep brain stimulation have a role in the treatment of certain patients, these remain palliative procedures for those who are not candidates for resection or ablation, as complete seizure freedom rates are low. Further development and investigation of both established and novel strategies for the surgical treatment of TLE will be critical moving forward, given the significant burden of this disease

Rare complication of ventriculoperitoneal shunt. Early onset of distal catheter migration into scrotum in an adult male: Case report and literature review

© 2014 The Authors. Presentation of case 65-year-old male underwent shunt placement for normal-pressure hydrocephalus-like symptoms. On post-operative day seven patient developed right testicular edema, for which ultrasound was performed, revealing hydrocele along with the presence of distal catheter in the scrotum. On post-operative day nine patient underwent distal catheter trimming via laparoscopic approach with general surgery, with post-operative imaging showing satisfactory location of distal catheter in the peritoneal cavity.Discussion/Conclusion Early onset of distal catheter migration into scrotum in an adult male is a unique case, as most cases are reported in pediatric patients, and it is the first case reported in the English literature to have occurrence at an early onset during the peri-operative period. As our case demonstrates, early occurrence and detection of scrotal migration of the distal catheter prevent shunt malfunction. Prompt surgical management of catheter repositioning is therefore recommended to avoid the risk of further complications.Introduction The role of shunt placement is to divert cerebrospinal fluid from within the ventricles to an alternative location in the setting of hydrocephalus. One of the rare shunt complications is distal catheter migration, and various body sites have been reported, including the scrotum. Although cases of scrotal migration of distal catheter have been reported in pediatric patients, cases in adult patients are rare due to obliterated processus vaginalis. Furthermore, there has not been a case reported for scrotal migration in an adult at an early onset