Despite aggressive management, CM II continues to cause various devastating neurological dysfunctions in patients with spinal open ONTD. The aim of the present study was to validate a CM II model in late-stage chick embryos with surgically induced ONTD developed by authors [6]. The authors evaluated the pathophysiology of CM II associated with spinal ONTD by using MRI and histopathological examination.

MRI evaluation of the posterior fossa in embryos with ONTDs showed that the bony posterior fossa was smaller than that in the control group, with a rather flattened curvature. The cerebrospinal fluid signal was also apparently absent or barely visible owing to overcrowding in the surgically induced ONTD group. The cerebellum was located caudally; however, no herniation into the vertebral column was observed. Morphological changes were more prominent in the postoperative day (POD) 17–18 group than in the POD 14–15 group. Embryos with ONTD also showed distinct histomorphological changes, similar to the MRI findings. The cerebellum was located at the lower levels, with a shorter distance between the posterior end of the cerebellum and the upper margin of the posterior arch of C1. The spaces between the cerebellar cortex, anterior to the dorsal surface of the upper brain stem, and posterior to the inner table of the skull were narrower and smaller in the surgically induced ODNT group. The subarachnoid spaces around the cerebellar cortex were narrower.

These characteristic results of the posterior fossa on MRI and histological examination in chick embryos with surgical ONTD demonstrated progressive pathological changes in CM II with morphological similarity to those in humans. Therefore, this model can serve as an important tool for understanding the pathogenesis of CM II and can be applied in future investigations of various fetal therapeutic strategies.

Little information exists on the incidence of VS worldwide; however, several studies have reported a national incidence rate of VS ranging from approximately 0.6 to 3.3 per 100000 populations [1]. Population-based studies on VS have not been conducted in Korea, similar to most other countries. This study aimed to investigate the incidence of VS, associated demographic characteristics, and risk factors for VS in Korea using population-based National Health Insurance Service data.

Overall, from 2005 to 2020, there were 5751 patients with VS, with an overall annual incidence rate of 0.71 per 100000. The VS group included 2456 male patients (42.7%) and 3295 female patients (57.3%). The mean age of the VS group was 53.42, and that of the control group was 53.35. The annual incidence in females was higher than that in males for all ages except those aged 80 years or older. The overall female-to-male incidence ratio was 1.225, and the sex difference in the VS was statistically significant. Regarding treatment modalities, patients who received radiosurgery (46.64%) were the most common, followed by the wait-and-scan group (37.96%), the microsurgery group (12.85%), and those who received both (2.56%). In the multivariate Cox regression analysis, VS was associated with diabetes mellitus and dyslipidemia. Interestingly, alcohol consumption increased the risk of VS; in contrast, smoking was associated with a decreased risk.

The significance of this study is the presentation of population-based data, including the entire Korean, and investigated the incidence and risk factors for VS. One of the limitations of this study is the possible misclassification or misdiagnosis of VS. Nonetheless, this epidemiological study of VS could be used by clinicians to investigate and treat brain tumors, including VS.