Summary Low-frequency (delta/theta band) hippocampal neural oscillations play prominent roles in computational models of spatial navigation but their exact function remains unknown. Some theories propose they are primarily generated in response to sensorimotor processing while others suggest a role in memory-related processing. We directly recorded hippocampal EEG activity in patients undergoing seizure monitoring while they explored a virtual environment containing teleporters. Critically, this manipulation allowed patients to experience movement through space in the absence of visual and self-motion cues. The prevalence and duration of low-frequency hippocampal oscillations were unchanged by this manipulation, indicating that sensorimotor processing was not required to elicit them during navigation. Furthermore, the frequency-wise pattern of oscillation prevalence during teleportation contained spatial information capable of classifying the distance teleported. These results demonstrate that movement-related sensory information is not required to drive spatially informative low-frequency hippocampal oscillations during navigation and suggest a specific function in memory-related spatial updating.

Purpose The positive rate of head CT in non-trauma patients presenting to the Emergency Department (ED) is low. Currently, indications for imaging are based on the individual experience of the treating physician, which contributes to overutilization and variability in imaging utilization. The goals of this study are to ascertain the predictors of positive head CT in non-trauma patients and demonstrate feasibility of a clinical scoring algorithm to improve yield. Methods We retrospectively reviewed 500 consecutive ED non-trauma patients evaluated with non-contrast head CT after presenting with headache, altered mentation, syncope, dizziness, or focal neurologic deficit. Medical records were assessed for clinical risk factors: focal neurologic deficit, altered mental status, nausea/vomiting, known malignancy, coagulopathy, and age. Data was analyzed using logistic regression and receiver operator characteristic (ROC) curves and 3 derived algorithms. Results Positive CTs were found in 51 of 500 patients (10.2%). Only two clinical factors were significant. Focal neurologic deficit (adjusted OR 20.7; 95% CI 9.4–45.7) and age >55 (adjusted OR 3.08; CI 1.44–6.56). Area under the ROC curve for all 3 algorithms were of 0.73–0.83. In proposed Algorithm C, only patients with focal neurologic deficit (major risk factor) or ≥2 of the five minor risk factors (altered mental status, nausea/vomiting, known malignancy, coagulopathy, and age) would undergo CT imaging. This may reduce utilization by 34% with only a small decrease in sensitivity (98%). Conclusion Our simple scoring algorithm utilizing multiple clinical risk factors could help to predict the non-trauma patients who will benefit from CT imaging, resulting in reduced radiation exposure without sacrificing sensitivity.

Accurate interpretation of cervical spine imagining can be challenging, especially in children and the elderly. The biomechanics of the developing pediatric spine and age-related degenerative changes predispose these patient populations to injuries centered at the craniocervical junction. In addition, congenital anomalies are common in this region, especially those associated with the axis/dens, due to its complexity in terms of development compared to other vertebral levels. The most common congenital variations of the dens include the os odontoideum and a persistent ossiculum terminale. At times, it is necessary to distinguish normal development, developmental variants, and developmental anomalies from traumatic injuries in the setting of acute traumatic injury. Key imaging features are useful to differentiate between traumatic fractures and normal or variant anatomy acutely; however, the radiologist must first have a basic understanding of the spectrum of normal developmental anatomy and its anatomic variations in order to make an accurate assessment. This review article attempts to provide the basic framework required for accurate interpretation of cervical spine imaging with a focus on the dens, specifically covering the normal development and ossification of the dens, common congenital variants and their various imaging appearances, fracture classifications, imaging appearances, and treatment options.

Decubitus CT myelography is a reported method to identify CSF-venous fistulas in patients with spontaneous intracranial hypotension. One of the main advantages of decubitus CT myelography in detecting CSF-venous fistulas is using gravity to dependently opacify the CSF-venous fistula, which can be missed on traditional myelographic techniques. Most of the CSF-venous fistulas in the literature have been identified in patients receiving general anesthesia and digital subtraction myelography, a technique that is not performed at all institutions. In this article, we discuss the decubitus CT myelography technique and how to implement it in daily practice.

The lumbosacral plexus is a complex anatomic area that serves as the conduit of innervation and sensory information to and from the lower extremities. It is formed by the ventral rami of the lumbar and sacral spine which then combine into larger nerves serving the pelvis and lower extremities. It can be a source of severe disability and morbidity for patients when afflicted with pathology. Patients may experience motor weakness, sensory loss, and/or debilitating pain. Primary neurologic processes can affect the lumbosacral plexus in both genetic and acquired conditions and typically affect the plexus and nerves symmetrically. Additionally, its unique relationship to the pelvic musculature and viscera render it vulnerable to trauma, infection, and malignancy. Such conditions are typically proceeded by a known history of trauma or established pelvic malignancy or infection. Magnetic resonance imaging is an invaluable tool for evaluation of the lumbosacral plexus due to its anatomic detail and sensitivity to pathologic changes. It can identify the cause for disability, indicate prognosis for improvement, and be a tool for delivery of interventions. Knowledge of proper MR protocols and imaging features is key for appropriate and timely diagnosis. Here we discuss the relevant anatomy of the lumbosacral plexus, appropriate imaging techniques for its evaluation, and discuss the variety of pathologies that may afflict it.