Hippocampal gamma-slow oscillation coupling in macaques during sedation and sleep.

Behavioral and neurophysiological evidence suggests that the slow (≤1 Hz) oscillation (SO) during sleep plays a role in consolidating hippocampal (HIPP)-dependent memories. The effects of the SO on HIPP activity have been studied in rodents and cats both during natural sleep and during anesthetic administration titrated to mimic sleep-like slow rhythms. In this study, we sought to document these effects in primates. First, HIPP field potentials were recorded during ketamine-dexmedetomidine sedation and during natural sleep in three rhesus macaques. Sedation produced regionally-specific slow and gamma (∼40 Hz) oscillations with strong coupling between the SO phase and gamma amplitude. These same features were seen in slow-wave sleep (SWS), but the coupling was weaker and the coupled gamma oscillation had a higher frequency (∼70 Hz) during SWS. Second, electrical stimuli were delivered to HIPP afferents in the parahippocampal gyrus (PHG) during sedation to assess the effects of sleep-like SO on excitability. Gamma bursts after the peak of SO cycles corresponded to periods of increased gain of monosynaptic connections between the PHG and HIPP. However, the two PHG-HIPP connectivity gains during sedation were both substantially lower than when the animal was awake. We conclude that the SO is correlated with rhythmic excitation and inhibition of the PHG-HIPP network, modulating connectivity and gamma generators intrinsic to this network. Ketamine-dexmedetomidine sedation produces a similar effect, but with a decreased contribution of the PHG to HIPP activity and gamma generation.

Improved Postoperative Metrics with Modified Myofascial Closure in Fetal Myelomeningocele Repair.

BACKGROUND: The effect of modifications in fetal myelomeningocele (fMMC) closure techniques has not been extensively studied. OBJECTIVE: To study the effect of a modified closure technique on fMMC postnatal patient outcomes: hydrocephalus, hindbrain herniation, and cyst development. METHODS: We performed single-center retrospective study of a subset of post-MOMS (Management of Myelomeningocele Study) trial patients who underwent fMMC closure. After January 2015, the fetal myofascial closure technique was modified. Needlepoint monopolar cautery was used to raise dural lined myofascial flaps to create a more robust closure. Outcomes between the pre- and postmodification groups were compared with regard to hindbrain herniation, hydrocephalus, and cyst development. Families who transitioned care to local institutions were contacted via telephone for outcome information. RESULTS: From January 2011 to May 2016, data were reviewed from 119 fMMC closure patients. Patients without full follow-up data were excluded from the final analysis. Cerebrospinal fluid diversion was seen in 32 of 74 patients with the standard technique compared to 14 of 45 with the modified closure and was significantly decreased in postmodification when compared to that of the MOMS trial (P = .01). Hindbrain herniation resolution was significantly decreased in both the pre- and postmodification groups compared to that of the MOMS trial (P < .01). Prior to January 2015 with standard closure, 23 cysts required resection whereas no cysts required resection in the modified repair group (P < .01). CONCLUSION: Modified myofascial closure for fMMC closure is safe and feasible. The new approach reflects a decreased rate of cyst development requiring surgical resection, and a trend for improved rates of hindbrain herniation and hydrocephalus.

The effect and evolution of patient selection on outcomes in endoscopic third ventriculostomy for hydrocephalus: A large-scale review of the literature.

Endoscopic third ventriculostomy (ETV) has become a popular technique for the treatment of hydrocephalus, but small sample size has limited the generalizability of prior studies. We performed a large-scale review of all available studies to help eliminate bias and determine how outcomes have changed and been influenced by patient selection over time. A systematic literature search was performed for studies of ETV that contained original, extractable patient data, and a meta-analytic model was generated for correlative and predictive analysis. A total of 130 studies were identified, which included 11,952 cases. Brain tumor or cyst was the most common hydrocephalus etiology, but high-risk etiologies, post-infectious or post-hemorrhagic hydrocephalus, accounted for 18.4%. Post-operative mortality was very low (0.2%) and morbidity was only slightly higher in developing than in industrialized countries. The rate of ETV failure was 34.7% and was higher in the first months and plateaued around 20months. As anticipated, ETV is less successful in high-risk etiologies of hydrocephalus and younger patients. Younger patient age and high-risk etiologies predicted failure. ETVs were performed more often in high-risk etiologies over time, but, surprisingly, there was no overall change in ETV success rate over time. This study should help to influence optimal patient selection and offer guidance in predicting outcomes.

Intraoperative Navigation Is Associated with Reduced Blood Loss During C1-C2 Posterior Cervical Fixation.

OBJECTIVE: Traumatic injuries, degenerative/rheumatologic conditions, tumors, or infections of the upper cervical spine may in certain circumstances require surgical stabilization. C1 lateral mass screws (Harms technique) in combination with C2 instrumentation (pars, pedicle, translaminar screws) have become a mainstay of surgical treatment. The surgical anatomy of the C1 lateral mass can be challenging especially with the robust venous plexus that often causes significant bleeding with exposure of the C1-C2 articular complex. The purpose of this study was to examine whether the use of navigation reduced intraoperative blood loss during atlantoaxial fixation. METHODS: We reviewed our institutional experience with atlantoaxial instrumentation with and without navigation from 2007 to 2016. We limited our cases to those requiring C1-C2 stabilization in traumatic and degenerative cases and not as part of more extensive surgical stabilizations. We identified 45 consecutive patients and compared intraoperative blood loss, need for transfusion, and time of procedure with and without the use of navigation. RESULTS: There was a significant reduction in the amount of intraoperative blood loss in the navigated (n = 20) versus non-navigated cases (n = 25). In addition, although the navigated cases initially were longer, currently there is no significant difference in the length of the cases. CONCLUSIONS: In our series, surgical navigation significantly reduced blood loss compared with non-navigated cases without increasing surgical time or risk of complication. Furthermore, navigation has the potential to reduce operative times due to a reduction in blood loss.

Ultrasonography Detects Ulnar Nerve Dislocation Despite Normal Electrophysiology and Magnetic Resonance Imaging.

BACKGROUND: Dislocation of the ulnar nerve (UN) occurs in a subset of patients with ulnar neuropathy. Electrodiagnostic and magnetic resonance imaging (MRI) studies are performed to support the clinical diagnosis. We report the case of a patient with ulnar neuropathy with normal electrodiagnostic and MRI studies but with ultrasonography (US) showing UN dislocation, which prompted successful treatment by UN submuscular transposition. CASE DESCRIPTION: A healthy 15-year-old female softball player presented with right medial elbow pain and paresthesias of the fourth and fifth digits. She had 4+/5 strength in the right hand intrinsic muscles and a Tinel sign at the right elbow. A snap was palpated at the elbow upon flexion. MRI showed mild common flexor tendonitis, and electrodiagnostic studies showed normal motor responses and no conduction block at the elbow. High-resolution US showed dislocation of the UN over the medial epicondyle. UN dislocation was confirmed intraoperatively, and, after UN submuscular transposition, the patient reported complete resolution of her preoperative symptoms at 6-week follow-up and continued resolution at 1 year. CONCLUSIONS: Normal findings on electrodiagnostic or MRI studies should not immediately dissuade surgeons from operating on a symptomatic patient with a clinical examination supporting ulnar neuropathy and with US evidence of UN dislocation, because such a patient may experience postoperative symptom relief. Furthermore, the dynamic capability of US imaging complements data obtained from electrodiagnostic and MRI studies, especially when these tests are normal, and it should be considered by clinicians when evaluating patients with medial elbow pain or signs of ulnar neuropathy.

NMDA receptor-independent control of transcription factors and gene expression.

Consolidation of synaptic plasticity seems to require transcription, but how the nucleus is informed in this context remains unknown. As NMDA receptor antagonists have been shown to interfere with action potential generation, the issue of whether or not a synaptically generated signal is required for nuclear signaling is currently unresolved. Here, we show that pharmacological maintenance of action potentials during NMDA receptor blockade allows for NMDA receptor-independent transcription factor binding and arc gene expression, both of which were previously thought to be NMDA receptor dependent. These data suggest that types of signaling in the nucleus previously attributed to NMDA-receptor-dependent synapse-to-nucleus signals can be initiated in the absence of NMDA receptor-dependent synaptic plasticity.