Adult Hippocampal Neurogenesis and Memory Enhancement

Hippocampal neurogenesis continues throughout life in mammals. These adult-generated dentate granule cells (DGCs) are generally believed to contribute to hippocampal memory processing and are generated at varying rates in response to neuronal network activity. Deep brain stimulation (DBS) allows clinicians to influence brain activity for therapeutic purposes and raises the possibility of targeted modulation of adult hippocampal neurogenesis. It has recently been shown that DBS may ameliorate cognitive decline associated with Alzheimer’s disease (AD), and while underlying mechanisms are unknown, one possibility is activity-dependent regulation of hippocampal neurogenesis. To this end, whether or not adult-generated DGCs can assume functional roles of developmentally-generated neurons, and stimulation-induced enhanced neurogenesis can benefit memory function in the normal and diseased brain, warrant study. First, we examined separate cohorts of developmentally- and adult-generated DGCs in intact mice and demonstrated similar rates of activation during hippocampus-dependent spatial memory processing, suggesting functional equivalence. Second, we examined the neurogenic and cognitive effects of targeted entorhinal cortex (EC) stimulation in mice using parameters analogous to clinical high frequency DBS. Stimulation increased the generation of DGCs. Moreover, stimulation-induced neurons were functionally recruited by hippocampal spatial memory processing in a cell age-dependent fashion that is consistent with DGC maturation. Importantly, stimulation facilitated spatial memory in the same maturation-dependent manner, and not when stimulation-induced promotion of adult neurogenesis was blocked, suggesting a causal relationship. Finally, we are in the process of testing whether similar stimulation facilitates spatial memory in a transgenic (Tg) disease model of AD that exhibits amyloid neuropathology and cognitive impairment. Preliminary results suggest stimulation promotes neurogenesis and rescues impaired spatial memory in Tg animals. When considered in the context of promising clinical results, this body of work suggests stimulation-induced neurogenesis could provide a novel therapeutic modality in settings where functional hippocampal regenerative therapy is desirable.Ph

Occipital-Cervical Fusion and Ventral Decompression in the Surgical Management of Chiari-1 Malformation and Syringomyelia: Analysis of Data From the Park-Reeves Syringomyelia Research Consortium

Background: Occipital-cervical fusion (OCF) and ventral decompression (VD) may be used in the treatment of pediatric Chiari-1 malformation (CM-1) with syringomyelia (SM) as adjuncts to posterior fossa decompression (PFD) for complex craniovertebral junction pathology. Objective: To examine factors influencing the use of OCF and OCF/VD in a multicenter cohort of pediatric CM-1 and SM subjects treated with PFD. Methods: The Park-Reeves Syringomyelia Research Consortium registry was used to examine 637 subjects with cerebellar tonsillar ectopia ≥ 5 mm, syrinx diameter ≥ 3 mm, and at least 1 yr of follow-up after their index PFD. Comparisons were made between subjects who received PFD alone and those with PFD + OCF or PFD + OCF/VD. Results: All 637 patients underwent PFD, 505 (79.2%) with and 132 (20.8%) without duraplasty. A total of 12 subjects went on to have OCF at some point in their management (PFD + OCF), whereas 4 had OCF and VD (PFD + OCF/VD). Of those with complete data, a history of platybasia (3/10, P = .011), Klippel-Feil (2/10, P = .015), and basilar invagination (3/12, P < .001) were increased within the OCF group, whereas only basilar invagination (1/4, P < .001) was increased in the OCF/VD group. Clivo-axial angle (CXA) was significantly lower for both OCF (128.8 ± 15.3°, P = .008) and OCF/VD (115.0 ± 11.6°, P = .025) groups when compared to PFD-only group (145.3 ± 12.7°). pB-C2 did not differ among groups. Conclusion: Although PFD alone is adequate for treating the vast majority of CM-1/SM patients, OCF or OCF/VD may be occasionally utilized. Cranial base and spine pathologies and CXA may provide insight into the need for OCF and/or OCF/VD

Socioeconomic and demographic factors in the diagnosis and treatment of Chiari malformation type I and syringomyelia

OBJECTIVE The goal of this study was to assess the social determinants that influence access and outcomes for pediatric neurosurgical care for patients with Chiari malformation type I (CM-I) and syringomyelia (SM). METHODS The authors used retro-and prospective components of the Park-Reeves Syringomyelia Research Consortium database to identify pediatric patients with CM-I and SM who received surgical treatment and had at least 1 year of follow-up data. Race, ethnicity, and insurance status were used as comparators for preoperative, treatment, and postoperative characteristics and outcomes. RESULTS A total of 637 patients met inclusion criteria, and race or ethnicity data were available for 603 (94.7%) patients. A total of 463 (76.8%) were non-Hispanic White (NHW) and 140 (23.2%) were non-White. The non-White patients were older at diagnosis (p = 0.002) and were more likely to have an individualized education plan (p < 0.01). More non-White than NHW patients presented with cerebellar and cranial nerve deficits (i.e., gait ataxia [p = 0.028], nystagmus [p = 0.002], dysconjugate gaze [p = 0.03], hearing loss [p = 0.003], gait instability [p = 0.003], tremor [p = 0.021], or dysmetria [p < 0.001]). Non-White patients had higher rates of skull malformation (p = 0.004), platybasia (p = 0.002), and basilar invagination (p = 0.036). Non-White patients were more likely to be treated at low-volume centers than at high-volume centers (38.7% vs 15.2%; p < 0.01). Non-White patients were older at the time of surgery (p = 0.001) and had longer operative times (p < 0.001), higher estimated blood loss (p < 0.001), and a longer hospital stay (p = 0.04). There were no major group differences in terms of treatments performed or complications. The majority of subjects used private insurance (440, 71.5%), whereas 175 (28.5%) were using Medicaid or self-pay. Private insurance was used in 42.2% of non-White patients compared to 79.8% of NHW patients (p < 0.01). There were no major differences in presentation, treatment, or outcome between insurance groups. In multivariate modeling, non-White patients were more likely to present at an older age after controlling for sex and insurance status (p < 0.01). Non-White and male patients had a longer duration of symptoms before reaching diagnosis (p = 0.033 and 0.004, respectively). CONCLUSIONS Socioeconomic and demographic factors appear to influence the presentation and management of pa- tients with CM-I and SM. Race is associated with age and timing of diagnosis as well as operating room time, estimated blood loss, and length of hospital stay. This exploration of socioeconomic and demographic barriers to care will be useful in understanding how to improve access to pediatric neurosurgical care for patients with CM-I and SM