The Neural Representation of Events Is Dominated by Elements that Are Most Reliably Present

An episodic memory is specific to an event that occurred at a particular time and place. However, the elements that comprise the event—the location, the people present, and their actions and goals—might be shared with numerous other similar events. Does the brain preferentially represent certain elements of a remembered event? If so, which elements dominate its neural representation: those that are shared across similar events, or the novel elements that define a specific event? We addressed these questions by using a novel experimental paradigm combined with fMRI. Multiple events were created involving conversations between two individuals using the format of a television chat show. Chat show “hosts” occurred repeatedly across multiple events, whereas the “guests” were unique to only one event. Before learning the conversations, participants were scanned while viewing images or names of the (famous) individuals to be used in the study to obtain person-specific activity patterns. After learning all the conversations over a week, participants were scanned for a second time while they recalled each event multiple times. We found that during recall, person-specific activity patterns within the posterior midline network were reinstated for the hosts of the shows but not the guests, and that reinstatement of the hosts was significantly stronger than the reinstatement of the guests. These findings demonstrate that it is the more generic, familiar, and predictable elements of an event that dominate its neural representation compared with the more idiosyncratic, event-defining, elements.

Posterior midline cleft of the atlas – a crucial anatomical variation in vertebral fractures

The anatomy of the first vertebra, namely atlas, has significant clinical implications. Atlas is situated between the occipital bone and the second cervical vertebra (axis) and is one of the main points of head movement. Most congenital anomalies of the vertebra are diagnosed incidentally during imaging investigations and can be associated with cervical spine anomalies. The neurological symptoms may include weakness in the four limbs, acute neurologic deficits such as transient quadriparesis, paraparesis, Lhermitte's sign, chronic neck pain, and headache. This anomaly is also commonly seen in gonadal dysgenesis, Klippel-Feil syndrome, Arnold-Chiari malformations, and Turner and Down syndrome. Unlike other variations, which arise due to disturbances of ossification posterior midline clefts of the atlas, are different since they are a developmental failure of chondrogenesis. We therefore present an anatomical case and analysis of the literature about posterior arch clefts of atlas.

Endoscopic Harmonic Midline Partial Glossectomy in Obstructive Sleep Apnea

Aim: Our study was done to evaluate the role of Endoscopic posterior midline partial glossectomy as a surgical modality for the hypopharyngeal collapse in obstructive sleep apnea patients. Study design: Prospective case series study. Place and Duration of Study: Tanta university hospital, otolaryngology department, from October 2017 till March 2019. Methodology: This was a prospective case series study, conducted on 10 patients from 2017 -2019 with tongue base collapse and normal craniofacial angles, the patients were evaluated preoperative and 6 months postoperative subjectively by Epworth sleepiness scale (ESS) and objectively by polysomnography and lateral cephalometry. Results: Our study included 10 patients with age (mean ± SD48.70±4.08), BMI( mean ±SD24.45±1.56), 5 patients showed a significant reduction in AHI with a success rate of 50% with a significant change in ESS and the non-significant changes in cephalometric parameters. Conclusion: Transoral endoscopic posterior midline partial glossectomy can improve the surgical outcomes of obstructive sleep apnea patients.

Posterior Midline Approach for a C2 Schwannoma: 2-Dimensional Operative Video

C2 schwannomas are rare lesions that may develop in the spinal canal, in the area of the C2 ganglion situated posterior to the C1C2 articulation, in the extraspinal area or in a combination of these 3 sectors.1,2 The surgical removal of these lesions is delicate because of the intimate relationships the schwannomas develop with the V3 segment of the vertebral artery. A variety of lateral, far-lateral, or extreme lateral approaches have been described in order to tackle these lesions. We use a posterior midline approach that takes advantage of the predominantly extradural development of C2 schwannomas. In this technique, the main step is the debulking of the posterior articular sector of the tumor, which is easily accessible through a midline posterior approach and necessitates minimal bone removal. In most cases, removal of the homolateral posterior arch of C1 is sufficient in order to create an adequate access. These maneuvers create the necessary space for dissecting both the intradural and extraspinal sectors of the schwannoma. We present this technique through a case with a minimal intradural component exerting mainly a lateral compression of the spinal cord. The tumor was operated through the midline mini-invasive posterior approach with a favorable result. We demonstrate the surgical technique in video and discuss the nuances.

The Neuropsychological Correlates of Brain Perfusion and Gray Matter Volume in Alzheimer’s Disease

Background: Neuropsychological tests, structural neuroimaging, and functional neuroimaging are employed as diagnostic and monitoring biomarkers of patients with Alzheimer’s disease (AD) Objective: We aimed to elucidate the similarities and differences in neuropsychological tests and neuroimaging with the use of the Mini-Mental State Examination (MMSE), Alzheimer’s Disease Assessment Scale cognitive subscale (ADAS-cog), structural magnetic resonance image (MRI), and perfusion single photon emission computed tomography (SPECT), and parametric image analyses to understand its role in AD. Methods: Clinically-diagnosed AD patients (n = 155) were scanned with three-dimensional T1-weighted MRI and N-isopropyl-p-[123I] iodoamphetamine SPECT. Statistical parametric mapping 12 was used for preprocessing images, statistical analyses, and voxel-based morphometry for gray matter volume analyses. Group comparison (AD versus healthy controls), multiple regression analyses with MMSE, ADAS-cog total score, and ADAS-cog subscores as variables, were performed. Results: The AD group showed bilateral hippocampal volume reduction and hypoperfusion in the bilateral temporo-parietal lobe and posterior midline structures. Worse MMSE and ADAS-cog total score were associated with bilateral temporo-parietal volume loss and hypoperfusion. MMSE, but not ADAS-cog, was associated with the posterior midline structures. The ADAS-cog subscores were associated with the temporal volume, while perfusion analyses were linked to the left temporo-parietal region with the language function and right analogous region with the constructional praxis subscore. Conclusion: MMSE and ADAS-cog are associated with temporo-parietal regions, both in volume and perfusion. The MMSE score is associated with posterior midline structures and linked to an abnormal diagnostic AD pattern. Perfusion image analyses better represents the cognitive function in AD patients

Stereotactic posterior midline approach under direct microscopic view for biopsy of medulla oblongata tumors: technical considerations

Background Open and stereotactic transfrontal or transcerebellar approaches have been used to biopsy brainstem lesions. Method In this report, a stereotactic posterior and midline approach to the distal medulla oblongata under microscopic view is described. The potential advantages and limitations are discussed, especially bilateral damage of the X nerve nuclei. Conclusion This approach should be considered for biopsy of distal and posterior lesions. We strongly recommend the use of direct microscopic view to identify the medullary vessels, confirm the midline entry point, and avoid potential shift of the medulla. Further experience is needed to confirm safety and success rate of this approach.

Ergonomics of surgical microscopes for the sitting position as determined by ocular-corpus length

Background: The sitting position is favorable for microsurgical procedures applied to posterior midline pathologies in both the supra- and infratentorial regions. The dimensions of the microscope corpus affect the device’s comfort and handling in the hands of the microneurosurgeon for such procedures. A shorter microscope corpus provides more favorable intraoperative ergonomics for surgical practice. Methods: Evaluation of the most comfortable microscope for its application in microsurgical procedures in the sitting position as determined by ocular-corpus length. Results: Six modern surgical microscopes were tested and evaluated regarding their ocular-corpus lengths and working distances: the Mitaka MM90, Zeiss Kinevo 900, Zeiss Pentero 900, Leica M530, Zeiss Neuro NC4, and Möller-Wedel Hi-R 1000. The ocular-corpus lengths vary between 270 and 380 mm. The Mitaka MM90 microscope has the shortest ocular-corpus length at 270 mm. Conclusion: The ocular-corpus length determines the predominant part of the lever arm, which affects the fatigue of the surgeon. By virtue of its short ocular-corpus length, the Mitaka MM90 is currently the most favorable microscope for microsurgical procedures using a sitting position.