Division of Neurosurgery, Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia.
Med Hypotheses. 2013 Oct;81(4):686-9. doi: 10.1016/j.mehy.2013.07.027. Epub 2013 Aug 6.
Normal pressure hydrocephalus (NPH) is a poorly understood entity as well as a source of continuous controversy in the neuroscientific community. The surgical management of this disease requires that intracranial pressure (ICP), also referred to as the cerebrospinal fluid pressure (CSFP), be lowered using a cerebrospinal fluid (CSF) diversion procedure. Numerous complications are linked with this procedure; we believe that new evidence suggests that the induction or acceleration of glaucomatous optic neuropathy are possible sequelae that warrant further investigation. We also suggest potential solutions derived from the increased understanding of the disease's pathophysiology and new advances in imaging of the optic nerve head complex. The recent inclusion of the translaminar gradient (TLG) (the difference between the intraocular pressure (IOP) and the ICP/CSFP across the thickness of the lamina cribrosa in the optic nerve head complex) in the pathogenesis of normal tension glaucoma (NTG) suggests that the disease may be a complication encountered during the treatment of NPH with CSF diversion procedures. The significant decrease in CSFP required to treat NPH increases this gradient. In addition, there have been recent observations of an increased prevalence of NTG, as well as other forms of glaucoma, among patients with NPH, thought to be due to inherently fragile neurons in these patients. This new data suggest that patients who undergo ICP lowering therapy for their NPH may be at a higher risk of developing or accelerating already present NTG. We present the clinical and theoretical basis for our hypothesis after reviewing the relevant literature linking the two entities. We also propose a possible solution, as we believe that treatment guidelines for NPH should take the TLG into account. Indeed, recent advances in the imaging of the optic nerve head complex may provide an opportunity to detect the mechanical sequelae of an increased TLG in the preclinical stage, i.e., prior to optic nerve damage. If we are able to determine safe parameters for the TLG in this population, we may be able to recommend the initiation of prophylactic glaucoma therapy for selected patients.
正常压力脑积水（NPH）是一个尚未被充分理解的病症，也是神经科学界持续存在争议的根源。该疾病的手术治疗需要通过脑脊液（CSF）分流术来降低颅内压（ICP），也称为脑脊液压力（CSFP）。该手术存在多种并发症，我们认为新证据表明，诱导或加速青光眼性视神经病变可能是需要进一步研究的后果。我们还提出了一些潜在的解决方案，这些方案源自对疾病病理生理学的深入理解以及视神经头复合体成像方面的新进展。最近，将跨层梯度（TLG）（视神经头复合体中穿过筛板的眼内压（IOP）与 ICP/CSFP 之间的差异）纳入正常眼压型青光眼（NTG）的发病机制中，提示该疾病可能是 CSF 分流术治疗 NPH 时出现的并发症。为了治疗 NPH 而需要显著降低 CSFP 会增加这种梯度。此外，在患有 NPH 的患者中，最近观察到 NTG 以及其他类型的青光眼的患病率增加，这被认为是由于这些患者的神经元本来就脆弱。这些新数据表明，接受 ICP 降低治疗的 NPH 患者可能有更高的风险患上或加速已经存在的 NTG。在回顾了将这两种病症联系起来的相关文献后，我们提出了我们的假设的临床和理论依据。我们还提出了一个可能的解决方案，因为我们认为 NPH 的治疗指南应该考虑 TLG。实际上，视神经头复合体成像方面的最新进展可能为在临床前阶段（即在视神经损伤之前）检测 TLG 增加的机械后果提供机会。如果我们能够确定该人群中 TLG 的安全参数，我们也许能够为选定的患者推荐预防性青光眼治疗。
