1Department of Surgery and Translational Medicine, Neurosurgery Unit, Tuscany School of Neurosurgery, University of Florence.
2Department of Surgery and Translational Medicine, Ophthalmic Unit, University of Florence.
J Neurosurg. 2018 Oct;129(4):1078-1084. doi: 10.3171/2017.5.JNS163062. Epub 2017 Nov 17.
Changes in the pressure gradient between intraocular and intracranial compartments at the lamina cribrosa level are a possible explanation of normal tension glaucoma (NTG). Shunt-treated normal pressure hydrocephalus (NPH) is a model for testing whether the increase (time from disease onset to CSF shunt placement, i.e., "protection period") and decrease (time from shunt placement to observation, i.e., "exposure period") in intracranial pressure (ICP) are glaucoma protective or risk factors, respectively. The authors estimated the prevalence of NTG in patients with shunt-treated NPH and calculated the extent of optic nerve exposure to changes in the trans-lamina cribrosa gradient.
Data obtained in patients with NPH who had undergone ventriculoperitoneal (VP) shunt placement were analyzed. Patients with more than 6 months' follow-up, no pathologies associated with ICP changes or CSF dynamics disturbances, and no surgical or valve-related complications were scheduled for ophthalmic evaluation.
Nine of 22 patients had NTG, which is about a 40-fold increase in rate compared with the rate in the general elderly population without hydrocephalus (p < 0.001). The median protection period was 12.0 months in patients with NTG and 18.0 months in those without NTG (p = 0.033). The median ICP decrease multiplied by duration of exposure in months was 76.0 mm Hg × months in the NTG group and 24.1 mm Hg × months in the no-NTG group (p = 0.048). The patients' median adjusted age (adjusted for "protection" and "exposure" times) was 85.1 years in the NTG group and 78.8 years in the no-NTG group (p = 0.001).
A crucial risk factor for development of NTG in patients with shunt-treated NPH is the duration of optic nerve exposure to the lowering of ICP. Patients with NPH who are candidates for CSF shunting should be informed of the risk of incurring glaucoma. Longitudinal studies could provide estimates of tolerated times for a given ICP decrease.
在视盘筛板水平，眼内压和颅内压之间压力梯度的变化可能是正常眼压性青光眼（NTG）的一个解释。分流治疗的正常压力脑积水（NPH）是测试颅内压升高（从发病到 CSF 分流放置的时间，即“保护期”）和降低（从分流放置到观察的时间，即“暴露期”）是否分别是青光眼保护或危险因素的模型。作者估计了分流治疗的 NPH 患者中 NTG 的患病率，并计算了视神经暴露于穿过筛板梯度变化的程度。
分析了接受脑室-腹腔（VP）分流术的 NPH 患者的数据。有 6 个月以上随访、无与 ICP 变化或 CSF 动力学紊乱相关的病理学、无手术或阀门相关并发症的患者被安排进行眼科评估。
22 例患者中有 9 例患有 NTG，这比没有脑积水的一般老年人群的发病率高约 40 倍（p<0.001）。NTG 患者的中位保护期为 12.0 个月，无 NTG 患者为 18.0 个月（p=0.033）。NTG 组中 ICP 降低乘以暴露时间的中位数为 76.0mmHg×月，无 NTG 组为 24.1mmHg×月（p=0.048）。NTG 组患者的中位校正年龄（校正“保护”和“暴露”时间）为 85.1 岁，无 NTG 组为 78.8 岁（p=0.001）。
分流治疗的 NPH 患者发生 NTG 的一个关键危险因素是视神经暴露于 ICP 降低的时间。接受 CSF 分流的 NPH 患者应被告知发生青光眼的风险。纵向研究可以提供给定 ICP 降低允许的时间估计。
